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Variations of body composition, growth and efficiency of nutrient utilization among wild and domesticated… Ming, Frederick Warren 1985

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VARIATIONS OF BODY COMPOSITION, GROWTH AND EFFICIENCY NUTRIENT UTILIZATION AMONG WILD AND DOMESTICATED STRAINS OF RAINBOW TROUT, SALMO GAIRDNERI by FREDERICK WARREN MING B.Sc , The Univ e r s i t y of Ottawa, 1975 M.Sc, The University of Guelph, 1978 A THESIS SUBMITTED IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF DOCTOR OF PHILOSOPHY i n THE FACULTY OF GRADUATE STUDIES (Department of Poultry Science, I n t e r d i s c i p l i n e ) We accept t h i s t h e s i s as conforming to the required standard THE UNIVERSITY OF BRITISH COLUMBIA October 1985 (c) Frederick Warren Ming, 1985 In presenting this thesis in partial fulfilment of the requirements for an advanced degree at the University of British Columbia, I agree that the Library shall make it freely available for reference and study. I further agree that permission for extensive copying of this thesis for scholarly purposes may be granted by the head of my department or by his or her representatives. It is understood that copying or publication of this thesis for financial gain shall not be allowed without my written permission. Department The University of British Columbia 1956 Main Mall Vancouver, Canada V6T 1Y3 Date DE-6(3/81) ABSTRACT S t r a i n differences i n e f f i c i e n c y of u t i l i z a t i o n of dietary protein and energy were investigated using rainbow trout (Salmo gairdneri) from Pennask and Premier Lakes ( w i l d s t r a i n s ) and a t r o u t farm (Sun V a l l e y s t r a i n ) . Endogenous l o s s e s of p r o t e i n and energy v a r i e d among the s t r a i n s . Sun Valley f i s h were concluded to have a higher basal metabolic r a t e and maintenance requirement, based on s l o p e s of r e g r e s s i o n (g or kcal loss / f i s h / day versus i n i t i a l dry weight) for endogenous losses of protein and energy. E f f i c i e n c y of protein and energy u t i l i z a t i o n were examined i n two feeding t r i a l s conducted a year apart using a non-replicated f a c t o r i a l design c o m p r i s i n g thre e s t r a i n s ( s t ) , two f e e d i n g l e v e l s ( f l ) , two dietary protein sources (pr) and two protein concentrations (co). Feed consumption (appetite) at ages 0 and 1 showed s i g n i f i c a n t s t r a i n - r e l a t e d v a r i a t i o n as d i d r e l a t i v e growth (R), and a number of e f f i c i e n c y t r a i t s : Feed C o n v e r s i o n E f f i c i e n c y (FCE), P r o t e i n E f f i c i e n c y R a t i o (PER), P r o d u c t i v e P r o t e i n Value (PPV), Net P r o t e i n E f f i c i e n c y (NPE), Energy Conversion (EC), and Net Conversion of Energy (NCE). Age 0 s t r a i n ranking was consistently Sun Valley > Premier > Pen-nask for appetite, R and a l l e f f i c i e n c y t r a i t s except NCE . FCE and PER indicated a s i m i l a r r e l a t i o n s h i p among yearlings. Maintenance-corrected t r a i t s (NPE and NCE) i n yearlings varied l i t t l e among s t r a i n s . S t r a i n X diet i n t e r a c t i o n s were s i g n i f i c a n t (p<0.05) or near s i g -n i f i c a n t f o r s e v e r a l t r a i t s , i n d i c a t i n g v a r i a b l e s t r a i n response to changes i n l e v e l s of p r o t e i n c o n c e n t r a t i o n or source. S t a t i s t i c a l l y s i g n i f i c a n t or near s i g n i f i c a n t i n t e r a c t i o n s for e f f i c i e n c y t r a i t s at age 0 were: s t x f l (PPV, and NCE); s t x pr (FCE, PER, PPV, and NCE); - i i i -and s t x co (FCE, NPE, and EC). Age 1 s i g n i f i c a n t i n t e r a c t i o n s were: s t x f l (PPV), s t x pr (NCE), s t x co (FCE, PER and NPE). S i g n i f i c a n t or near s i g n i f i c a n t s t x pr and s t x co i n t e r a c t i o n s were observed f o r appetite (both years) and dry tissue growth (st x pr, age 0). Ammonia e x c r e t i o n , r e s u l t i n g from o x i d a t i o n of amino a c i d s , was evaluated for i n d i r e c t comparison of s t r a i n s for e f f i c i e n c y of protein u t i l i z a t i o n i n a four-day assay at age 1. Ammonia-N excretion rate (mg NHg/ kg BW / g d i e t ) f o l l o w i n g consumption of one h i g h - p r o t e i n meal d a i l y c o r r e l a t e d i n v e r s e l y i n rank w i t h FCE and PER, having v a l u e s of 0.30, 0.31 and 0.44 for Sun Valley, Premier and Pennask, respectively. TABLE OF CONTENTS Page ABSTRACT i i TABLE OF CONTENTS i v LIST OF TABLES v i i i LIST OF FIGURES x i LIST OF APPENDIX TABLES x i i i ACKNOWLEDGEMENTS xv 1. INTRODUCTION 1 2. LITERATURE REVIEW 3 2.1 Stock V a r i a t i o n i n Rainbow Trout (Salmo  gairdneri) 3 2.2 Phenotypic and Genotypic V a r i a t i o n i n P r o d u c t i o n T r a i t s 6 2.2.1 Body Composition and Condition Factor 6 2.2.2 Feed Consumption 7 2.2.3 Growth Rate 8 2.2.3.1 Measurement of Growth Rate 8 2.2.3.2 E f f e c t s of S t r a i n and Dietary Environment on Growth Rate 10 2.2.4 E f f i c i e n c y of Nutrient U t i l i z a t i o n 12 2.3 P h y s i o l o g i c a l Basis of S t r a i n Differences 14 2.3.1 Digestion and Absorption of Nutrients 15 2.3.2 Protein Metabolism 17 2.3.2.1 Maintenance Protein Requirements and Endogenous-N Losses 17 2.3.2.2 E f f e c t of Dietary Components on the Evaluation of Energy and Protein U t i l i z a t i o n 19 A. Dietary Protein: Level and Source 19 - V -B. Dietary Carbohydrate 21 2.3.2.3 Protein as an Energy Source and the Production of Ammonia 23 2.3.2.4 Ammonia Excretion as an Index o f P r o t e i n U t i l i z a t i o n 24 3. EXPERIMENTAL, PART I : STRAIN DIFFERENCES IN PRODUCTION-RELATED TRAITS 27 3.1 Introduction 27 3.2 Materials and Methods 28 3.2.1 Stock 28 3.2.1.1 Source and History 28 3.2.1.2 Laboratory Acclimation 29 3.2.2 Experimental Populations and Conditions 30 3.2.3 Variation of Endogenous Losses in Fish during a Period of Feed Withdrawal 31 3.2.3.1 Chemical Analysis of Carcasses....33 A. Age 0 Fish 33 B. Age 1 Fish 35 3.2.4 Estimation of Growth and Efficiency Traits by Feeding Trials 36 3.2.4.1 Preparation of Diets 36 3.2.4.2 Pre-experimental Treatment 36 3.2.4.3 Experimental Phase 37 3.2.4.4 Chemical Analysis of Diets 41 3.2.5 Numerical Analysis 41 3.2.5.1 Mortality 41 3.2.5.2 Feed Consumption 42 3.2.5.3 Relative Growth 43 - v i -3.2.5.4 Compositional Gains 43 3.2.5.5 Efficiency and Net Efficiency of Nutrient Utilization 44 3.2.5.6 Stat i s t i c a l Analysis 45 4. RESULTS, PART 1 47 4.1 Variation of Endogenous Losses among Strains of Rainbow Trout 47 4.1.1 Endogenous Losses as Live and Dry Matter...47 4.1.2 Endogenous Losses among Strains: Carcass Protein and Gross Energy 59 4.2 Variation in Feed Consumption, Growth and Body Composition, among Strains of Rainbow Trout 69 4.2.1 Variation of Feed Consumption 69 4.2.1.1 Strain x Diet interactions for Consumption 73 4.2.2 Variation of Growth Rate 77 4.2.2.1 Strain x Diet Interactions for growth 85 4.2.3 Variation of Carcass Composition and Condition Factor 91 4.2.3.1 Carcass composition 91 4.2.3.2 Condition factor 103 4.3 Variation of Efficiency of Nutrient Utilization among Strains of Rainbow Trout 103 4.3.1 Strain Effects 103 4.3.2 Strain x Diet Interactions for Efficiency Traits 107 5. DISCUSSION, PART 1 121 A. Metabolic Losses 121 B. Feed Consumption, Growth, Composition and Conversion 123 - v i i -6. EXPERIMENTAL, PART II : STRAIN DIFFERENCES IN EFFICIENCY OF PROTEIN UTILIZATION BY ANALYSIS OF AMMONIA EXCRETION 131 6.1 Introduction 131 6.2 Materials and Methods 131 6.2.1 Acclimation and Selection of Experimental Populations 131 6.2.2 Experimental Protocol 132 6.2.3 Water Sampling and Ammonia Analysis 133 6.2.4 St a t i s t i c a l Analysis 134 6.3 RESULTS, PART II 136 6.4 DISCUSSION, PART II 143 7. SUMMARY AND CONCLUSIONS 150 8. REFERENCES 153 9. APPENDIX TABLES 162 - v i i i -LIST OF TABLES I Selection of experimental populations of rainbow trout 32 I l a Experimental dietary treatments for rainbow trout of three s t r a i n s during three-week growth t r i a l s * 38 l i b Proximate composition of experimental d i e t s fed to rainbow trout of three s t r a i n s during three week growth t r i a l s 39 III I n i t i a l and f i n a l body weights of groups of rainbow trout subjected to 21 (age 0) or 32 (age 1) days of feed withdrawal 48 IV Mean dry feed consumption per 21 days as a function of i n i t i a l dry body weight f o r rainbow trout of three s t r a i n s f e d to s a t i a t i o n 72 V S i g n i f i c a n t e f f e c t s and i n t e r a c t i o n s i n v o l v i n g s t r a i n i n the analysis of variance of feed consumption for rainbow trout 74 VI Analysis of d a i l y feed consumption i n r e l a t i o n to source of dietary protein f o r three s t r a i n s of rainbow trout 75 VII Analysis of t o t a l feed consumption i n r e l a t i o n to dietary protein concentration f o r s t r a i n s of rainbow trout 76 VIII Mean weights and lengths of rainbow trout of three s t r a i n s i n a 21-day feeding t r i a l 78 IX S i g n i f i c a n t main e f f e c t s and i n t e r a c t i o n s i n v o l v i n g s t r a i n i n the analysis of variance of r e l a t i v e growth i n rainbow trout under eight dietary environments 79 X Relative growth i n weight and length for age 0 and age 1 rainbow trout of three s t r a i n s fed four d i e t s at two feeding l e v e l s or 21 days 86 Xia E f f e c t of feeding l e v e l on r e l a t i v e growth as l i v e or dry t i s s u e i n age 0 and age 1 rainbow trout of three s t r a i n s , fed four d i e t s at two feeding l e v e l s for 21 days 87 - i x -Xlb Effect of feeding level on relative growth as fork length in age 1 rainbow trout of three strains fed one of four diets for 21 days 88 XII Effect of protein source on relative growth as liv e or dry tissue in age 0 and age 1 rainbow trout of three strains, fed four diets at two feeding levels for 21 days 89 XIII Effect of dietary protein concentration on relative growth as live or dry tissue in age 0 and age 1 rainbow trout of three strains fed four diets at two feeding levels for 21 days 90 XIV Proximate composition of carcasses of rainbow trout of three strains at the start of feeding t r i a l s conducted at age 0 and age 1 92 XV Final carcass moisture content of age 0 and age 1 rainbow trout of three strains fed four experimental diets at two feeding levels for 21 days 94 XVI Final carcass crude protein content of age 0 and age 1 rainbow trout of three strains fed four experimental diets at two feeing levels for 21 days...95 XVII Final carcass crude fat content of age 0 and age 1 rainbow trout of three strains fed four experimental diets at two feeding levels for 21 days 96 XVIII Final carcass ash content of age 0 and age 1 rainbow trout of three strains fed four experimental diets at two feeding levels for 21 days 97 XIX Mean change in percent carcass protein, fat, ash and moisture in age 0 and age 1 rainbow trout of three strains fed four diets to satiation for 21 days 98 XX Change of condition factor in three strains of age 1 rainbow trout fed four diets at two feeding levels for 21 days 100 XXI Effect on condition factor of strain of rainbow trout and diet at age 1 101 XXII Change of coefficient of variation for condition factor in three strains of age 1 rainbow trout fed four diets for 21 days 102 XXIII Strain means and rankings for various efficiency-related t r a i t s in rainbow trout fingerlings (age 0) and yearlings (age 1) of three strains, receiving -X-four d i e t s at two feeding l e v e l s f o r 21 days 104 XXIV S t a t i s t i c a l s i g n i f i c a n c e of main e f f e c t s and in t e r a c t i o n s i n v o l v i n g s t r a i n f o r various e f f i c i e n c y - r e l a t e d t r a i t s i n age 0 and age 1 rainbow trout of d i f f e r e n t s t r a i n s , receiving four d i e t s at two feeding l e v e l s for 21 days 106 XXV Interaction of s t r a i n and feeding l e v e l e f f e c t s on Protein Productive Value i n age 0 and age 1 r a i n -bow trout 109 XXVI Interactions of s t r a i n and feeding l e v e l e f f e c t s on Net Conversion of Energy i n age 0 rainbow trout 110 XXVII Interaction of s t r a i n and protein source e f f e c t s on Feed Conversion E f f i c i e n c y i n age 0 rainbow t r o u t . . . . I l l XXVIII Interaction of s t r a i n and protein source e f f e c t s on Protein E f f i c i e n c y Ratio i n age 0 rainbow trout...112 XXIX Interaction of s t r a i n and protein source e f f e c t s on Protein Productive Value i n age 0 rainbow trout...113 XXX Interaction of s t r a i n and protein source e f f e c t s on Net Conversion of Energy i n age 0 and age 1 rainbow trout 114 XXXI Interaction of s t r a i n and protein concentration e f f e c t s on Feed Conversion E f f i c i e n c y i n age 0 and age 1 rainbow trout 115 XXXII Interaction of s t r a i n and protein concentration e f f e c t s on Protein E f f i c i e n c y Ratio i n age 1 rainbow trout 118 XXXIII Interaction of s t r a i n and protein concentration e f f e c t s on Net Protein E f f i c i e n c y i n age 0 and age 1 rainbow trout 119 XXXIV Interaction of s t r a i n and protein concentration e f f e c t s on Energy Conversion i n age 0 rainbow trout 120 XXXV Body weights and feed consumption of three s t r a i n s of rainbow trout over a four-day period 135 - x i -LIST OF FIGURES Figure Page 1 Change i n l i v e body weight at age 1 with days a f t e r feed withdrawal i n large and small sized rainbow trout of three s t r a i n s 50 2 Mean l i v e weight loss during 21 days of feed withdrawal versus mean i n i t i a l l i v e weight i n three s t r a i n s of age 0 and age 1 rainbow trout 52 3 Estimated d a i l y weight l o s s as l i v e t i s s u e i n r e l a t i o n to i n i t i a l weight of fasted rainbow trout of three s t r a i n s 54 4 Estimated d a i l y weight loss as dry ti s s u e i n r e l a t i o n to i n i t i a l dry weight of fasted rainbow trout of three s t r a i n s 56 5 Linear regression of d a i l y dry weight loss on mean i n i t i a l dry weight i n three s t r a i n s of fasted rainbow trout 58 6 Mean change i n percent body protein and f a t i n rainbow trout of three s t r a i n s a f t e r a period of feed withdrawal l a s t i n g 21 days and 32 days at ages 0 and 1, re s p e c t i v e l y 61 7 Mean change i n percent body moisture and ash i n rainbow trout of three s t r a i n s a f t e r a period of feed withdrawal l a s t i n g 21 days and 32 days at ages 0 and 1, res p e c t i v e l y 63 8 Regression of 21-day protein losses on mean i n i t i a l dry weight i n f a s t i n g rainbow trout of three s t r a i n s 66 9 Regression of 21-day gross energy losses on mean i n i t i a l dry weight i n f a s t i n g rainbow trout of three s t r a i n s 68 10 Dry feed consumed at s a t i a t i o n , r e l a t i v e to mean i n i t i a l body weight, i n age 0 and age 1 rainbow trout of three s t r a i n s 71 11 Relative growth as l i v e weight (% body weight/ day) i n age 0 and age 1 rainbow trout of three s t r a i n s 82 12 Relative growth as dry weight (% body weight/ day) i n age 0 and age 1 rainbow trout of three s t r a i n 84 - x i i -13 Dynamics of ammonia-N accumulation with a l t e r n a t i n g hourly periods of fl u s h i n g (replacement) and standing water i n a tank containing a group of yearling rainbow trout of the Sun Valley s t r a i n 138 14 Dynamics of ammonia-N accumulation with a l t e r n a t i n g hourly periods of flu s h i n g (replacement) and standing water i n a tank containing a group of yearling rainbow trout of the Pennask s t r a i n 140 15 Dynamics of ammonia-N accumulation with a l t e r n a t i n g hourly periods of fl u s h i n g (replacement) and standing water i n a tank containing a group of yearling rainbow trout of the Premier s t r a i n 142 16 Change i n rate of excretion of ammonia-N with time a f t e r feeding wild (Pennask and Premier) and domesticated (Sun Valley) s t r a i n s of r a i n -bow trout 145 - x i i i -LIST OF APPENDIX TABLES Table Page IA Water q u a l i t y data f o r the West Vancouver Laboratory, the Department of F i s h e r i e s and Oceans, Canada 163 IIA Estimation of water flow rate i n experimental tanks containing age 0 rainbow trout 164 IIIA Weight changes over 32 days f o r age 1 rainbow trout of three s t r a i n s subjected to feed withdrawal 165 IVA F i n a l carcass composition as protein, f a t , ash, and moisture i n age 0 and age 1 rainbow trout of three s t r a i n s withdrawn from feed f o r 21 and 32 days, r e s p e c t i v e l y 166 VA Vitamin and mineral premix formulation f o r d i e t s fed to rainbow trout s t r a i n s during experiments on growth and nutrient u t i l i z a t i o n 167 VIA Analysis of variance table f o r feed consumption by groups of age 0 and age 1 rainbow trout fed one of four d i e t s at s a t i a t i o n f o r 21 days 168 VILA Mean body weights f o r groups of rainbow trout fed one of four d i e t s (Table II) to s a t i a t i o n (100) or 50 % of s a t i a t i o n f o r 21 days at age 0 169 VIIB Mean body weights and fork lengths f o r groups of rainbow trout fed one of four d i e t s (Table II) to s a t i a t i o n (100) or 50 % of s a t i a t i o n (50) for 21 days at age 1 170 VIIIA Analysis of variance table f o r r e l a t i v e growth as l i v e t i s s u e f o r groups of age 0 and age 1 rainbow trout fed one of four d i e t s to s a t i a t i o n f o r 21 days 171 IXA Analysis of variance table f o r r e l a t i v e growth as dry t i s s u e f o r groups of age 0 and age 1 rainbow trout fed one of four d i e t s to s a t i a t i o n f o r 21 days 172 XA Analysis of variance table f o r condition factor and c o e f f i c i e n t of v a r i a t i o n f o r condition factor of groups of age 0 and age 1 rainbow trout r e c e i v i n g one of eight dietary t r e a t -ments for 21 days 173 - x i v -XIA Mean conversion of feed, protein and energy i n groups of rainbow trout given one of four d i e t s (Table II) at s a t i a t i o n (100) or 50 % of s a t i a t i o n (50) f o r 21 days at age 0 174 XIB Mean conversion of feed, protein and energy i n groups of rainbow trout given one of four d i e t s (Table II) to s a t i a t i o n (100) or 50 % of s a t i a t i o n (50) f o r 21 days at age 1 175 XIIA Analysis of variance table f o r feed conver-sion e f f i c i e n c y f o r groups of age 0 and age 1 rainbow trout fed one of four d i e t s to s a t i a t i o n of 50 % of s a t i a t i o n f o r 21 days 176 XIIIA Analysis of variance table f o r Protein E f f i c i e n c y Ratio f o r groups of age 0 and age 1 rainbow trout fed one of four d i e t s to s a t i a t i o n or 50 % of s a t i a t i o n f o r 21 days 177 XIVA Analysis of variance table f o r Productive Protein Value f o r groups of age 0 and age 1 rainbow trout fed one of four d i e t s to s a t i a t i o n or 50 % of s a t i a t i o n f o r 21 days 178 XVA Analysis of variance table f o r Energy Conversion f o r groups of age 0 and age 1 rainbow trout fed one of four d i e t s to s a t i a t i o n or 50 % of s a t i a t i o n f o r 21 days 179 XVIA Analysis of variance f o r Net Protein E f f i c i -ency f o r groups of age 0 and age 1 rainbow trout fed one of four d i e t s to s a t i a t i o n or 50 % of s a t i a t i o n f o r 21 days 180 XVIIA Analysis of variance f o r Net Conversion of Energy f o r groups of age 0 and age 1 rainbow trout fed one of four d i e t s to s a t i a t i o n or 50 % of s a t i a t i o n f o r 21 days 181 XVIIIA Measurement of dissolved oxygen made during analysis of ammonia excretion by s t r a i n s of age 1 rainbow trout 182 - X V -ACKNOWLEDGMENTS No words can adequately express the g r a t i t u d e I f e e l towards the numerous i n d i v i d u a l s who have helped i n various ways to make t h i s t h e s i s a r e a l i t y . To a l l of you I express my deepest f e e l i n g s of o b l i g a t i o n . I e s p e c i a l l y acknowledge the e f f o r t s of P r o f . B.E. March who granted me the opportunity to pursue t h i s study, and moreover provided an example of s c h o l a r l y p r o f i c i e n c y which I have admired and sought to emulate. The other members of my s u p e r v i s o r y committee are no l e s s out-s t a n d i n g i n t h i s r e s p e c t . So I thank Dr. David A. Higgs (Dept. of F i s h e r i e s and Oceans, Canada) and h i s colleagues at the West Van Labora-tory for t h e i r support and provision of f a c i l i t i e s during the prepara-t i o n and execution of experiments. As well, Professors D.B. Bragg (Poul-t r y S c i e n c e Dept.), D.J. R a n d a l l (Zoology Dept.), CC. L i n d s a y ( I n s t . Animal Resource Ecology), as members of my supervisory committee, a l l provided valuable assistance. For t h e i r help with s t a t i s t i c a l analysis I thank Dr. Malcome Greig (Computer Science) and Dr. Jo and h i s a s s i s t a n t s i n the Dept. of S t a t i s -t i c s at UBC. A l l of my colleagues i n the Department of Poultry Science have been a great help; among them: Mr. Raymond Soong, Ms. C a r o l M a c M i l l a n and Dr. Matt Wolde-Tsadick f o r t e c h n i c a l a s s i s t a n c e ; Dr. Ian McCallum and h i s wife L e s l i e for helping to transport f i s h , et cetera; and Mrs. Betty Carlson, the departmental secretary. I also acknowledge te c h n i c a l help received from Mr. Peter Garnett i n the Dept. of Plant Science. Research f u n d i n g p r o v i d e d by the Dept. of F i s h e r i e s and Oceans, Canada and a s c h o l a r s h i p from the Bank of Bermuda made p o s s i b l e the completion of t h i s study. -xvi-I dedicate t h i s work to Jocelyn, my wonderful wife, and to my beloved children, Alfa, Nzingha and Nabil. -1-1. INTRODUCTION Detection, f i r s t l y of the p a r t i c u l a r character to be improved, and secondly of the va r i a t i o n s i n that character e x i s t i n g i n the a v a i l a b l e population, are the i n i t i a l steps i n genetic improvement. Detection, as a p r e - c u l t i v a t i o n a c t i v i t y that i s c a r r i e d out before any genetic mani-pulations are done, circumscribes the scope of t h i s study. The focus of genetic improvement programs i n f i n f i s h production has to some extent been l i m i t e d by a v a i l a b l e methodology for the evaluation of t r a i t s . Thus, among n u t r i t i o n - r e l a t e d production t r a i t s i n cultured f i s h , growth rate has received much attention while those t r a i t s which r e f l e c t the e f f i c i e n c y of n u t r i e n t u t i l i z a t i o n have been v i r t u a l l y ignored. Growth rate, and the strain-rank c o r r e l a t i o n between t h i s t r a i t and e f f i c i e n c y t r a i t s were of i n t e r e s t i n t h i s study, as was i t s r e -l a t i o n s h i p to "apparent metabolic rate." Compared with omnivores l i k e the channel c a t f i s h (Ictalurus puncta- tus), rainbow trout (Salmo gairdneri) and other salmonid f i s h e s require a high l e v e l of protein i n the diet. The pattern of protein u t i l i z a t i o n i n salmonids i s based upon the interdependent biochemical phenomena of excessive catabolism of dietary amino a c i d s ( f o r g l u c o n e o g e n e s i s ) , on the one hand, and l i m i t e d c a p a c i t y f o r carbohydrate u t i l i z a t i o n as a source of dietary energy, on the other. At the biochemical l e v e l , there-fore, s t r a i n s e l e c t i o n i n rainbow trout could be aimed at a l t e r i n g the pattern of protein and carbohydrate metabolism toward greater reliance on the l a t t e r energy source. One aim of t h i s t h e s i s was to consider, at a p r e l i m i n a r y l e v e l , s t r a i n d i f f e r e n c e s i n e f f i c i e n c y of p r o t e i n and gross energy u t i l i z a t i o n . -2-Complementary to s e l e c t i v e reduction i n quantitative nutrient r e -quirements for production of f i s h f l e s h i s the lowering of unit cost of d i e t a r y p r o t e i n sources, such as by the replacement of f i s h m e a l w i t h o i l s e e d p r o t e i n (soybean or c a n o l a meal). The q u e s t i o n posed i n t h i s instance was whether there i s evidence for s t r a i n x n u t r i t i o n i n t e r a c -tions to suggest the p o s s i b i l i t y of s e l e c t i n g for a s t r a i n better able to u t i l i z e soybean meal as a protein source. Soybean meal was i n t e r e s t -ing and appropriate for t h i s study because i t d i f f e r s from fishmeal not only i n amino a c i d c o m p o s i t i o n , but a l s o i n having a l a r g e a s s o c i a t e d carbohydrate f r a c t i o n . Three k i n d s of experiment were used i n the f o l l o w i n g r e s e a r c h to answer the s e r i e s of questions given above. Feed withdrawal experiments served to provide i n s i g h t s i n t o differences among s t r a i n s i n endogenous l o s s e s from the major body components (dry matter, p r o t e i n and gross energy), and i n d i r e c t l y of m e t a b o l i c r a t e . Secondly, f e e d i n g t r i a l s were conducted to explore differences i n u t i l i z a t i o n of dietary protein and energy among s t r a i n s of rainbow trout, i n response to d i e t s varying i n source and c o n c e n t r a t i o n of d i e t a r y p r o t e i n and energy. F i n a l l y , e f f i c i e n c y of p r o t e i n u t i l i z a t i o n was compared among s t r a i n s u s i n g a modified ammonia excretion procedure. Together these experiments were designed to define t r a i t s which f o r the most part have gone unconsidered by f i s h g e n e t i c i s t s , and to enable p r e l i m i n a r y d e c i s i o n s to be made about the f e a s i b i l i t y of a r i g o r o u s estimation of genetic parameters f o r those t r a i t s of i n t e r e s t . As impor-tantly, a d d i t i o n a l experiental tools were sought for screening popula-tions of rainbow trout for growth capacity and e f f i c i e n c y of nutrient u t i l i z a t i o n at the p r e - c u l t i v a t i o n phase of genetic s e l e c t i o n . -3-2. LITERATURE REVIEW 2.1 STOCK VARIATION IN RAINBOW TROUT (SALMO GAIRDNERI) Mayr (1963) d e f i n e s a s p e c i e s as c o n s i s t i n g of a l l i n d i v i d u a l s which are " a c t u a l l y or p o t e n t i a l l y i n t e r b r e e d i n g and r e p r o d u c t i v e l y i s o l a t e d from other such groups." In r e a l i t y , however, as Wilkins (1981) p o i n t s out, s p e c i e s themselves c o n s i s t of s m a l l e r , g e o g r a p h i c a l l y -i s o l a t e d populations which experience d i f f e r e n t b i o l o g i c a l and environ-mental h i s t o r i e s . D i f f e r e n t variants (genotypes) are favored by natural s e l e c t i o n , a r i s e f o r t u i t o u s l y or become l o s t i n the various populations, thereby creating c h a r a c t e r i s t i c genetic differences between stocks. The rainbow trout, Salmo gairdne r i , displays a tremendous degree of b i o l o g i c a l v a r i a t i o n over i t s n a t i v e range, which covers the e a s t e r n P a c i f i c from Mexico to Alaska. Included i n the s p e c i e s are r e s i d e n t f r e s h water and anadromous p o p u l a t i o n s ( S c o t t and Crossman, 1973). In ad d i t i o n to widely dispersed native populations, the numerous introduc-tions of the species both within and outside North America have made i t one of the most w i d e l y c u l t u r e d s p e c i e s of f i s h on a world wide b a s i s (Scott and Crossmnan, 1973). Most, i f not a l l d o m e s t i c a t e d s t o c k s throughout the world are believed to be descendant from rainbow trout o r i g i n a t i n g i n the McCloud River i n C a l i f o r n i a (Busack el; a l . , 1979). The species purity of domes-t i c a t e d rainbow t r o u t i s q u e s t i o n a b l e , as i t was common i n the e a r l y days of t r o u t c u l t u r e to mix s t r a i n s and even h y b r i d i z e rainbow t r o u t with the cutthroat trout, Salmo c l a r k i (Busack et^ a l . , 1979). The rainbow t r o u t ' s e x t r a o r d i n a r y a d a p t a b i l i t y as a s p e c i e s i s consistent with extensive genetic v a r i a b i l i t y throughout i t s genome, as -4-evidenced by large heterozygosity values for a number of l o c i (Allendorf and U t t e r , 1979). T h i s i n t u r n i s i n d i c a t i v e of l a r g e a d d i t i v e ( m e t r i -cal) genetic variance for phenotypic t r a i t s of importance to f i s h c u l -t u r i s t s ( A l l e n d o r f and U t t e r , 1979). D o m e s t i c a t i o n , on the other hand has resulted i n l o s s of heterozygosity i n rainbow trout, due to intense s e l e c t i o n programs inv o l v i n g too few parental f i s h , and s e l e c t i n g for too few t r a i t s ; body s i z e , egg number, and age at maturity, being among the more common (Donaldson and Olson, 1955). Genetic improvement i s based on the existence of v a r i a t i o n f or the chosen character within or between a v a i l a b l e stocks of the species, and the design of breeding schemes which s e l e c t i v e l y a l t e r the expression of that character i n subsequent generations (Wilkins, 1981). "The under-l y i n g p r i n c i p l e i s cle a r , namely, v a r i a t i o n must normally be present i n the s p e c i e s at the o u t s e t and t h a t v a r i a t i o n must be measurable i f improvement i s to be effected and monitored" (Wilkins, 1981). Detection of v a r i a t i o n f o r the c h a r a c t e r to be improved, and secondly of the v a r i a t i o n s i n that character e x i s t i n g i n the a v a i l a b l e population, are the i n i t i a l s t e p s i n the g e n e t i c improvement program ( W i l k i n s , 1981). M e t r i c a l characters (such as mature s i z e and weight, growth rate, meat to s k e l e t o n r a t i o s , food c o n v e r s i o n e f f i c i e n c y , and f e c u n d i t y ) exhibit continuous v a r i a t i o n i n populations, and t h e i r variance usually r e f l e c t s both genetic and environmental influences (Wilkins, 1981). The presence of a s i g n i f i c a n t genotype X environment, and genotype X d i e t i n t e r a c t i o n s i s common for many production t r a i t s i n a v a r i e t y of farm animals (National Academy of Sciences, 1975) and salmonid f i s h e s (Ayles et a l . 1983; Gunnes, 1980; Austreng and R e f s t i e , 1979; R e f s t i e and Austreng, 1981). These i n t e r a c t i o n s are important and must be taken - 5 -account of i n genetic s e l e c t i o n , whether i n conjunction with lake stock-ing programs (Ayles, 1975), or i n s e l e c t i v e breeding f o r s t r a i n s showing s p e c i f i c n u t r i t i o n a l responses under i n t e n s i v e c u l t u r e (Austreng and Re f s t i e , 1979). The comparatively elevated quantitative requirements for e s s e n t i a l amino a c i d s by c a r n i v o r o u s f i s h e s l i k e the rainbow t r o u t ( N a t i o n a l Research Council, 1981) entrains the use of a large proportion of high q u a l i t y protein i n the diet of such species. T h e o r e t i c a l l y at least, to focus on e f f i c i e n t u t i l i z a t i o n of t h i s nutrient i n a r t i f i c i a l feeds f o r fis h e s under intensive culture may be economically advantageous. Gjed-rem (1983) has a l r e a d y s t r e s s e d the need f o r improvement of food conversion e f f i c i e n c y , though he did not s p e c i f i c a l l y address the poten-t i a l s i g n i f i c a n c e of protein u t i l i z a t i o n . To focus on feed e f f i c i e n c y a t the expense of growth r a t e may not produce genetic gains, at l e a s t not i n meat chickens (Pym and N i c h o l l s , 1979). However, r e s u l t s from chicken studies do in d i c a t e that economi-c a l l y s i g n i f i c a n t genetic gains could be made with the chicken by com-bined s e l e c t i o n for feed e f f i c i e n c y and growth rate. The d i f f i c u l t y of measuring feed consumption i s a primary reason for avoiding e f f i c i e n c y parameters r e l a t i n g to growth i n f i s h genetical studies; hence the need for suitable methodology f o r t h e i r measurement. In a thorough review of t h i s topic by Gjedrem (1983), only one published study appeared (Kinghorn, 1981) i n which feed e f f i c i e n c y had been con-s i d e r e d i n the context of g e n e t i c s e l e c t i o n i n rainbow t r o u t or any other f i n f i s h species. -6-2.2 PHENOTYPIC AND GENOTYPIC VARIATION IN PRODUCTION TRAITS In regard to genotypic v a r i a t i o n i n the use of ingested nutrients, f i s h have been studied far l e s s than t e r r e s t r i a l farm animals (Gjedrem, 1983). F i s h , because of t h e i r ample g e n e t i c d i v e r s i t y , among other fac t o r s , provide vast opportunity for genetic s e l e c t i o n (Wilkins, 1981). In the ensuing discussion, a number of the t r a i t s bearing on growth and e f f i c i e n c y of nutrient u t i l i z a t i o n w i l l be reviewed from the standpoint of s t r a i n differences. While the emphasis w i l l be on rainbow trout and other salmonids, reference w i l l be made to other species of farm animal where appropriate. 2.2.1 Body Composition and Condition Factor In a s e r i e s of s t u d i e s conducted i n p r a i r i e p o t h o l e l a k e s i n western Canada, A y l e s and co-workers have i n v e s t i g a t e d i n t e r - s t r a i n differences i n body composition of the rainbow trout, and the r e l a t i v e c o n t r i b u t i o n s of genotype, environment and t h e i r i n t e r a c t i o n on body co m p o s i t i o n . In a two-part experiment (Ayl e s et a l . , 1979), two w i l d s t r a i n s (Pennask and Tunkwa l a k e ) , two domestic s t r a i n s (Idaho and Nisqually) and t h e i r hybrids were compared. In one lake, Idaho, Pennask and N i s q u a l l y s t r a i n s and t h e i r h y b r i d s were stocked. In t h r e e other lakes, Idaho, Tunkwa and t h e i r hybrids were planted. E f f e c t s of genetic s t r a i n , lake and t h e i r i n t e r a c t i o n e f f e c t s on carcass proximate composi-t i o n were analyzed. There was s i g n i f i c a n t difference between s t r a i n s f or percent dry matter ( a d j u s t e d f o r s i z e ) and percent l i p i d . In a s i n g l e l a k e , v a l u e s ranged from 28.5-31.5%, and 32.5-46% f o r dry matter and l i p i d , r e s p e c t i v e l y . F i s h of the Pennask s t r a i n (both parents) had - 7 -lowest content of f a t and dry matter, while those of a domestic s t r a i n (Idaho) had the highest values f o r both parameters. The progeny of crosses between Pennask and eit h e r of the domestic s t r a i n s were intermediate i n body composition f o r l i p i d . Carcass l i p i d content was p o s i t i v e l y c o r r e l a t e d w i t h growth r a t e f o r a l l s t r a i n s , i n d i c a t i n g the two t r a i t s would be s e l e c t e d f o r tog e t h e r . In other words, l e a n but f a s t growing s t r a i n s w i l l be d i f f i c u l t to breed. When s t r a i n e f f e c t s on composition were separated s t a t i s t i c a l l y from l a k e e f f e c t s and s t r a i n x lake i n t e r a c t i o n components, the r e s u l t s indicated that phenotypic differences i n body composition have a strong genetic component. Also using a s e r i e s of wild and domestic s t r a i n s and t h e i r crosses (rainbow t r o u t ) , but i n l a b o r a t o r y experiments, R e i n i t z e t a l . (1979) observed a s i g n i f i c a n t difference among s t r a i n s i n carcass composition at a weight of 1.5 grams, and p o s i t i v e c o r r e l a t i o n between protein, ash and moisture content. Eggs f or a l l crosses and pure s t r a i n s were f e r t i -l i z e d the same day and r e a r e d i n a s t a n d a r d i z e d environment. Austreng and R e f s t i e (1979) observed a s i g n i f i c a n t e f f e c t of genotype on condi-t i o n f a c t o r (K= 100 . weight i n g / ( l e n g t h i n cm)3), i n d i c a t i n g a d i f f e r e n t body c o n f o r m a t i o n among the d i f f e r e n t f a m i l i e s and inbred l i n e s of rainbow trout tested. 2.2.2 Feed Consumption Feed consumption i s to a l a r g e extent determined by the energy d e n s i t y of the d i e t . A c c o r d i n g l y , an animal w i l l eat to s a t i s f y i t s energy requirements. However, l i k e body composition , feed consumption also appears to have both genetic and environmental components. Results -8-of feeding experiments with beef c a t t l e (e.g., Warwick and Cobb, 1975, for review) and chickens (Lepore, 1965; Pym and N i c h o l l s , 1979) support the theory of a g e n e t i c b a s i s f o r feed consumption i n those s p e c i e s . Warwick and Cobb (1975) review a number of genetics studies showing the h e r i t a b i l i t y for t h i s t r a i t to be high. The only comparable study of feed consumption i n f i n f i s h i s that of Kinghorn (1981; c i t e d by Gjedrem, 1983) w i t h rainbow t r o u t . Kinghorn used i n d i r e c t calorimetry to study feed consumption through considera-t i o n of energy metabolized and the energy component of growth. He con-cluded that young rainbow trout which consume more food, grow fas t e r but are not better converters of feed. 2.2.3 Growth Rate 2.2.3.1 Measurement of Growth Growth has many working d e f i n i t i o n s and numerous methods have been devised to measure growth i n f i s h (see Ricker, 1979, for a review of the s u b j e c t ) . Gerking, i n a s e r i e s of s t u d i e s (1952; 1955; 1971) and o t h e r s such as Savitz (1971) considered protein synthesis or protein deposition to be the preferable method to measure growth i n f i s h for the purpose of analyzing i t s e f f i c i e n c y . However, i n the genetic analysis of growth i n f i s h , absolute increase i n body weight or rate of increase ( l i v e or dry weight) appear to be the most commonly used indic e s (see Gjedrem, 1976; 1983, for reviews). The c h o i c e of method and parameter f o r e s t i m a t i n g growth v a r i e s considerably, due i n some cases to genuine b i o l o g i c a l c o n s i d e r a t i o n s . Where there i s a d i f f e r e n c e i n the i n i t i a l weight of i n d i v i d u a l s or - 9 -group of i n d i v i d u a l s being compared i t i s commonplace to use r e l a t i v e growth (Zeitoun e_t a l . , 1973; Brett, 1979). Other expressions of growth applicable to genetical studies include time to a c e r t a i n body weight (Reinitz et a l . 1979). Duration of growth t r i a l s also varies considerab-l y , depending on a number of f a c t o r s and what appears to be no more than s u b j e c t i v e p r e f e r e n c e . S t u d i e s of n u t r i e n t r e q u i r e m e n t s i n d i f f e r e n t s p e c i e s of f i s h , or w i t h i n a s p e c i e s maintained under v a r i o u s con-d i t i o n s , are generally of a few months duration (see review by M i l l i k i n , 1982). A few workers have found t h a t a s h o r t (three-week) e v a l u a t i o n p e r i o d was s u f f i c i e n t f o r a n a l y s i s of growth i n the a d u l t red hind (Epinephelus g u t t a t u s ) , a warmwater s p e c i e s (Menzel, 1961) and i n j u v e n i l e rainbow t r o u t , a c o l d w a t e r s p e c i e s ( G a r c i a ejt a l . , 1981). Studies (Ming and March, 1982) conducted i n our laboratory have already established that three week growth assays with rainbow trout f i n g e r l i n g s (age 0) are a time e f f i c i e n t means for analysis of feed conversion and e f f i c i e n c y of energy and protein deposition, and for the assay of pro-t e i n q u a l i t y of diets. Garcia et a l . (1981) used four three-week growth periods, separated by shorter f a s t i n g periods, to compare growth and e f f i c i e n c y of p r o t e i n u t i l i z a t i o n f o r rainbow trout weighing approxi-mately 50 grams, under various dietary regimes. Duration of growth t r i a l s i s also subject to change where v a r i a t i o n i n growth rate among g e n e t i c a l l y d i s t i n c t populations i s the parameter under measurement. Studies conducted i n a natural environment (Cordone and N i c o l a , 1970; A y l e s , 1975; A y l e s et_ al. 1979) are g e n e r a l l y of s e v e r a l months d u r a t i o n . Even controlled-environment t e s t s of genetic -10-d i f f e r e n c e s may extend over s e v e r a l months ( R e i n i t z et a l . , 1979). Other g e n e t i c a l s t u d i e s of growth v a r i a t i o n have compared d i f f e r e n t s t r a i n s (Klupp , 1979; Chevassus, 1976) i n time course experiments, observing v a r i a t i o n i n the h e r i t a b i l i t y of growth with age. 2.2.3.2 E f f e c t s of S t r a i n and Dietary Environment on Growth Rate. The sources of v a r i a t i o n i n growth can be p a r t i t i o n e d by the appropriate experimental design into genotypic, environnmental and the i n t e r a c t i o n terms. Ayles (1975) and Ayles et a l . (1979) tested wild and domesticated s t r a i n s of rainbow trout under t o t a l l y natural conditions. Matched plantings c o n s i s t i n g of one w i l d - e i t h e r Pennask or Tunkwa -and one domestic s t r a i n (Idaho) were made i n a number of l a k e s at constant stocking density with the f i s h being allowed to grow for sever-a l months without supplemental f e e d i n g . During both years f i s h of the domestic s t r a i n grew l a r g e r than the w i l d s t r a i n s , but t h e r e was a greater component of environmental variance than genetic variance mea-sured each time. Not s u r p r i s i n g l y t h e r e was a l s o a s i g n i f i c a n t l a k e X s t r a i n i n t e r a c t i o n , p a r t i c u l a r l y i n the second year. S t r a i n e f f e c t s were a t t r i b u t e d to g e n e t i c d i f f e r e n c e s i n r e c o g n i t i o n of the s i z e -s p e c i f i c i t y of growth r a t e ( B r e t t e t a l . , 1969), and the f a c t t h a t the f i s h of the d i f f e r e n t s t r a i n s had equal mean s t a r t i n g weights. In a c o n t r o l l e d environment, R e i n i t z et^ a l . (1979) examined growth as a function of genotype using s i x pure s t r a i n s of rainbow trout (wild and domesticated populations) and t h e i r crosses. Time to the same weight (1.5g) was s i g n i f i c a n t l y d i f f e r e n t f o r d i f f e r e n t s t r a i n s spawned the same day, as was weight gained during 180 rearing days from the time of -11-having a c h i e v e d t h a t weight. Other s t u d i e s w i t h rainbow t r o u t under co n t r o l l e d conditions have looked at both v a r i a b i l i t y f o r growth and i t s h e r i t a b i l i t y ( A u l s t a d t ejt a l . , 1972; Chevassus, 1976; Klupp, 1979). Aulstadt measured a good h e r i t a b i l i t y f o r weight and length and detected a s i g n i f i c a n t environmental variance - two dens i t i e s were used - for both t r a i t s . Chevassus (1976) found that variance among d i f f e r e n t f u l l -s ib f a m i l i e s of domesticated rainbow t r o u t was l e s s than i n t r a f a m i l y variance f o r body weight and length. S t r a i n differences were s u f f i c i e n t -l y high to suggest l a r g e h e r i t a b i l i t y v a l u e s at the s t r a i n l e v e l , though not being the case f o r the d i f f e r e n t f a m i l i e s within s t r a i n s . He a t t r i b u t e d a good p a r t of the w i t h i n - f a m i l y v a r i a n c e to a g g r e s s i v e i n t e r a c t i o n s between i n d i v i d u a l s . In other experiments u s i n g two s t r a i n s , Klupp (1979) found t h a t e s t i m a t e s of h e r i t a b i l i t y of body weight v a r i e d depending on age, w i t h the l o w e s t v a l u e s o c c u r r i n g i n youngest f i s h . Chevassus ^it a l . (1979) found no s i g n i f i c a n t environment (density) X s t r a i n i n t e r a c t i o n , though the d e n s i t y e f f e c t was g r e a t e r than the s t r a i n e f f e c t . The same p r i n c i p l e h e l d f o r l a k e and s t r a i n e f f e c t s (Ayles, 1975). Austreng and R e f s t i e (1979) found extensive v a r i a t i o n i n r e l a t i v e growth of d i f f e r e n t f a m i l i e s and inbred l i n e s of rainbow trout i n laboratory experiments using d i e t s d i f f e r i n g i n protein concentration (from 25 - 51% crude p r o t e i n ) . In a r e l a t e d experiment ( R e f s t i e and Austreng, 1981) r e l a t i v e growth d i f f e r e d among the s t r a i n s where carbo-hydrate c o n c e n t r a t i o n was v a r i e d between 15 and 49%. A s i g n i f i c a n t genotype X d i e t e f f e c t was observed i n the f i r s t instance f o r growth i n l e n g t h and c o n d i t i o n f a c t o r , and a n e a r l y s i g n i f i c a n t i n t e r a c t i o n f o r weight. However, where carbohydrate concentration was varied there was -12-no s t r o n g genotype X d i e t i n t e r a c t i o n f o r any of these t r a i t s . I t was concluded that while s e l e c t i o n for f a m i l i e s or inbred l i n e s better able to u t i l i z e dietary protein seems p r o m i s i n g , i n t e r - f a m i l i a l s e l e c t i o n for a b i l i t y to u t i l i z e higher dietary carbohydrate concentrations does not. In summary the f o l l o w i n g statements can be made about growth t r a i t s such as gain i n weight and length for the rainbow trout. Rate of growth i s a h e r i t a b l e t r a i t which varies s i g n i f i c a n t l y among s t r a i n s , whether these be wild or domestic. Furthermore, h e r i t a b l e v a r i a t i o n for these t r a i t s has been found i n t r a - and i n t e r - f a m i l i a l l y . F i n a l l y , the e x i s -tence of genotype X d i e t i n t e r a c t i o n s f o r growth i n l e n g t h , and near s i g n i f i c a n t i n t e r a c t i o n f o r growth i n weight i s encouraging evidence that s t r a i n s can be s e l e c t i v e l y bred for improved a b i l i t y to u t i l i z e a p a r t i c u l a r l e v e l of dietary protein. 2.2.4 E f f i c i e n c y of Nutrient U t i l i z a t i o n While growth rate i s probably the most important economic deter-minant i n the production of t e r r e s t r i a l farm animals such as the meat c h i c k e n (Nesheim, 1975), e f f i c i e n c y of protein u t i l i z a t i o n f or growth could be of comparable s i g n i f i c a n c e i n the commercial culture of s a l -monid f i s h . In comparing chicken and carnivorous f i s h e s , Cowey (1980) i d e n t i f i e d poikilothermy and lower maintenance requirements for energy as the most s i g n i f i c a n t b i o l o g i c a l factors contributing to a more e f f i -c i e n t energy u t i l i z a t i o n i n f i s h . On the other hand, greater quantita-t i v e requirements for e s s e n t i a l amino acids - meaning large requirement f o r p r o t e i n sources of high q u a l i t y i n the d i e t - r e s u l t s i n l e s s e f f i c i e n t protein (or amino acid) u t i l i z a t i o n by carnivorous fishes , i n -13-comparison to the broiler chicken. And since protein i s the most expen-sive and abundant macro-nutrient in salmonid diets, i t s efficient use deserves attention in genetic selection programs. Gjedrem (1983) was in basic agreement with this analysis in stating that feed efficiency was a p r i o r i t y for genetic selection programs geared to production of f i s h through a r t i f i c i a l feeding. Evidence against production gains being made by selecting for feed e f f i c i e n c y i s not altogether conclusive. While e f f i c i e n c y of food conversion i s p o s i t i v e l y correlated with body weight i n chickens (Nesheim, 1975; Pym and Nicholls, 1979) there remains nonetheless considerable variation in feed efficiency not accounted for by variation i n body weight (Pym and Nicholls, 1979). And whereas selection for efficiency alone i s not expected to yield any improvement i n economics of broiler production, combined selection for body weight and efficiency should (Pym and Nicholls, 1979). The only pertinent data available on fish for efficiency of nutri-ent u t i l i z a t i o n come from Kinghorn (1981, c i t e d by Gjedrem, 1983). Kinghorn used an indirect method - based on indirect calorimetry - to estimate feed consumption in 33 tanks at a time from sires of 34 fami-l i e s of rainbow trout. According to this technique, food consumption in each tank was estimated by consideration of energy metabolized (via oxygen consumption) and the energy conponent of growth. The study showed that for the rainbow trout e f f i c i e n c y of feed u t i l i z a t i o n i s a heritable t r a i t . Gjedrem concluded that feed e f f i c i e n c y i s worthy of consideration for selectively breeding rainbow trout, pending the fur-ther development of methods of measuring i t , both directly and indirect-ly. -14-Protein u t i l i z a t i o n e f f i c i e n c y has received r e l a t i v e l y l i t t l e a t -tention as a prospective t r a i t for genetic s e l e c t i o n , even for t e r r e s -t r i a l farm animals. In p o u l t r y t h i s may be e x p l a i n e d by the f a c t t h a t t h e r e i s l i t t l e d i f f e r e n c e i n u t i l i z a t i o n (requirement) between the d i f f e r e n t poultry s t r a i n s or even species when expressed as grams gain i n body weight per gram of protein consumed. What differences do occur seem to be r e l a t e d to body c o m p o s i t i o n (Nesheim, 1975). Ducks, f o r example, with a higher f a t content gain more weight per gram of protein consumed than the other poultry species (Nesheim, 1975). S i m i l a r l y f or f i s h t h e r e i s a d i s t i n c t l a c k of data and methodology f o r e s t i m a t i n g differences among s t r a i n s of f i s h for e f f i c i e n c y of protein u t i l i z a t i o n for growth or maintenance. 2.3 PHYSIOLOGICAL BASIS OF STRAIN DIFFERENCES Given t h a t a p r o d u c t i o n t r a i t i s the net outcome of numerous p h y s i o l o g i c a l p r o c e s s e s o p e r a t i n g i n c o n c e r t , i n f o r m a t i o n u s e f u l to future genetic s e l e c t i o n for e f f i c i e n c y t r a i t s may be gained by consid-ering key underlying p h y s i o l o g i c a l processes themselves; a view shared by Nesheim (1975). Should i t be possible to c o r r e l a t e e f f i c i e n c y t r a i t s w i t h s i n g l e b i o c h e m i c a l or p h y s i o l o g i c a l processes, measurement of s t r a i n v a r i a t i o n f o r these t r a i t s may be c o n s i d e r a b l y shortened and s i m p l i f i e d . Gerking's (1971) choice of protein retention as an index of growth i n sunfish i s an example of the a p p l i c a t i o n of t h i s p r i n c i p l e i n a more general context. Nesheim (1975) discusses a number of other more of l e s s d i s t i c t functions that underly net expression of growth t r a i t s ; included are digestion and absorption, energy deposition, maintenance and energy l o s s e s d u r i n g metabolism. In the comparison of s t r a i n s f o r -15-e f f i c i e n c y of protein u t i l i z a t i o n , and of carbohydrate and energy u t i l i -zation, a s i m i l a r approach may be developed. 2.3.1 Digestion and Absorption of Nutrients A number of studies of genotypic e f f e c t s on digestive and absorp-t i v e e f f i c i e n c y of dry matter, f a t and nitrogen appear i n the l i t e r a -t u r e f o r p o u l t r y (Nesheim, 1975), wi t h only one such study i n v o l v i n g t e l e o s t s (Austreng and R e f s t i e , 1979). S l i g h t g e notypic d i f f e r e n c e s e x i s t and i n some instances s i g n i f i c a n t genotype X di e t and genotype X environment i n t e r a c t i o n s have been observed. Some of these genotypic or s t r a i n e f f e c t s and t h e i r i n t e r a c t i o n s with other factors w i l l be con-sidered b r i e f l y . Poultry s t r a i n s d i f f e r only s l i g h t l y i n the a b i l i t y to digest and absorb nutrients (Nesheim, 1975). Over a l l , the major nutrients are very e f f i c i e n t l y absorbed, though younger birds digest f a t l e s s e f f i c i e n t l y than older birds. Katongole (1978), reported large age-dependent v a r i a -t i o n f o r f a t d i g e s t i b i l i t y among three d i f f e r e n t s t r a i n s of domestic chicken, which disappeared i n older birds. In contrast to f a t , however, digestion and absorption of dietary protein i n common feed ingredients, undamaged by p r o c e s s i n g and i n mixed d i e t s , i s 80% - 90% e f f i c i e n t i n the chicken and appears to show no s i g n i f i c a n t v a r i a b i l i t y among d i f f e r -ent genotypes (Nesheim, 1975). Austreng and R e f s t i e (1979) found s i g n i f i c a n t differences i n appar-ent protein d i g e s t i b i l i t y among d i f f e r e n t f a m i l i e s and inbred l i n e s of rainbow trout, but the amount of v a r i a t i o n between genotypes declined w i t h i n c r e a s i n g d i e t a r y p r o t e i n c o n c e n t r a t i o n . At the same time mean d i g e s t i b i l i t y for a l l s t r a i n s improved with the higher dietary concen--16-t r a t i o n , to a maximum of 93% with 50% crude protein i n the diet. Factors r e l a t e d to both d i g e s t i b i l i t y and metabolism contribute to the rather l i m i t e d u t i l i z a t i o n i n carnivorous f i s h compared to omnivor-ous mammals. D i g e s t i b i l i t y of carbohydrate i n salmonids i s influenced by the type of carbohydrate fed - d e c l i n i n g i n the more complex and higher molecular weight carbohydrates (Buhler and Halver, 1961, c i t e d by M i l l i -k i n , 1982) - and i n v e r s e l y r e l a t e d to d i e t a r y c o n c e n t r a t i o n , at l e a s t f o r s t a r c h ( N a t i o n a l Research C o u n c i l , 1981). T h i s r e l a t i o n s h i p of concentration to d i g e s t i b i l i t y i s reversed i n the case of dietary pro-t e i n ( Austreng and R e f s t i e , 1979). P r o t e i n and carbohydrate a l s o i n t e r a c t i n the die t , so that high carbohydrate l e v e l s depresses protein d i g e s t i b i l i t y (Kitamikado j2t a l . 1964). These authors r e p o r t e d t h a t d i g e s t i b i l i t y of the protein f r a c t i o n decreased from a high of 81% i n a low (10%) s t a r c h d i e t , to a low 32% i n high (20%) s t a r c h d i e t . P r o t e i n concentration i n the above s e r i e s of die t s was confounded with carbohy-d r a t e l e v e l , going from 63% i n the low s t a r c h d i e t down to 56% i n the high s t a r c h d i e t . T h e r e f o r e , i t i s tempting to a t t r i b u t e a p a r t of the depression i n protein d i g e s t i b i l i t y to the e f f e c t of protein concentra-t i o n per se i n the h i g h s t a r c h d i e t , b e a r i n g i n mind the d i r e c t r e -la t i o n s h i p between protein concentration and apparent protein d i g e s t i -b i l i t y (Austreng and Ref s t i e , 1979). S t r a i n by d i e t i n t e r a c t i o n s have been reported for metabolizable energy v a l u e s of d i f f e r e n t f e e d s t u f f s i n p o u l t r y (review by Nesheim, 1975), but no s i m i l a r data have appeared f o r f i s h . ME val u e of a h i g h energy d i e t was d i f f e r e n t by 1.6 % f o r a c r o s s b r e d b r o i l e r s t r a i n and the white l e g h o r n ( S l i n g e r et a l . 1964; c i t e d by Nesheim, 1975), but -17-were the same for the two strains on a low energy diet. Turkeys compared at the same time , as well as l a t e r experiments conducted with different s t r a i n s of po u l t r y using more than one d i e t (March and B i e l y , 1971) also yielded a genotype X diet interaction for ME. These differences due to s t r a i n or species of po u l t r y are often i n c o n s i s t e n t and at best quantitatively too small to be important for genetic selection. 2.3.2 Protein Metabolism 2.3.2.1 Maintenance Protein Requirements and Endogenous-N Losses The f a t e of energy entering the body as absorbed and re t a i n e d metabolites determines the e f f i c i e n c y of u t i l i z a t i o n of energy f o r productive purposes. E f f i c i e n c y of production i s a f u n c t i o n of the difference between maintenance energy and the net energy intake (Smith et a l . (1978a). Some metabolizable energy i s l o s t as heat due to the heat increment of feeding, and the net energy remaining can be used for maintenance and productive purposes. The maintenance f r a c t i o n i s r e l a -t i v e l y s m a l l i n f i s h (Nijkamp et a l . , 1973) owing to a number of f a c -tors: poikilothermy, low rate of metabolism and growth, and the ammono-t e l i c mode of nitrogen e x c r e t i o n . The low l e v e l of heat production associated with biosynthesis of excretory products and th e i r concentra-tion (Smith eit a l . , 1978a, b), and the physical support provided by the aquatic medium (Cowey, 1980) result i n substantial energetic savings to the animal. Maintenance requirements for dietary energy have been investigated i n f i s h by d i r e c t and i n d i r e c t means. Keslo (1972) and others (e.g. Gerking, 1955, 1971; Brett and Zala, 1975) have investigated maintenance -18-in a direct manner in various carnivorous species of fishes, including salmonids, by feeding a ration that just maintained body weight. Others (Cho et a l . , 1976; Smith et al . , 1978a) have used d i r e c t or i n d i r e c t calorimetry with fasted or fed rainbow trout. A f i s h deprived of food obtains maintenance energy (the energy required for those functions of the body immediately necessary for maintaining l i f e ) by catabolizing body reserves of fat and protein. A major portion of maintenance energy in poikilotherms i s spent for basal metabolism, and a smaller portion for involuntary or resting a c t i v i t y (Cho ejt a l . , 1982). Noting the relationship between maintenance requirements and basal metabolic rate (BMR), Nesheim (1975) concludes from studies with poultry that clear evidence i s lacking for variations i n BMR that are due to differences of genotype. No studies i n the current literature deal with strain effects on maintenance or metabolic rate in fish. The notion of nitrogen requirement for maintenance i n f i s h i s a concept in need of further development, this due mainly to the protein -non protein-energy interaction (Luquet and Kaushik, 1981). Several com-parative studies reviewed by Luquet and Kaushik ( 1981) confirm that fis h have greater losses of nitrogen to energetic ends than homeothermic farm animals. Estimates ranging from 3 to 8 times greater losses have been reported, translating into 7-20 mgN/ Kcal in fi s h compared to 2.3-2.9 mgN/ Kcal i n homeotherms (Luquet and Kaushik, 1981). In spite of t h i s species discrepancy f i s h have a lower maintenance N requirement than higher vertebrates, by virtue of a lower metabolic rate and asso-ciated energy requirement (Cowey, 1980; Luquet and Kaushik, 1981). Endogenous nitrogen loss i s an acceptable index of true mainten-ance requirement, although i t underestimates nitrogen requirements for -19-maintenance (e.g. Savitz, 1969). In turn, endogenous losses of nitrogen can be estimated by various methods i n v o l v i n g one or more of f a s t i n g the f i s h , feeding a N-free d i e t or a d i e t with low protein content (Luquet and Kaushik, 1981). Endogenous N-expenditure can a l s o be e s t i m a t e d by extrapolation — to zero N-intake — i n the regression of protein (N) consumption on nitrogen retention. The method of estimating endogenous N l o s s by c a r c a s s a n a l y s i s g e n e r a l l y produces h i g h e r v a l u e s than the l a t t e r procedure, since c e r t a i n minor excretory products (e.g. purines, pyrimidines, and c r e a t i n i n ; Smith, 1929) are not analyzed by the d i r e c t method. Overall, however, there i s reasonable s i m i l a r i t y between values obtained f o r non-fecal endogenous N by the carcass ( i n d i r e c t ) and excre-t i o n ( d i r e c t ) methods i n f i s h , though c a r c a s s a n a l y s i s i s s t i l l the p r e f e r r e d method f o r e s t i m a t i n g maintenance r e q u i r e m e n t s as p r o t e i n (Luquet and Kaushik, 1981). There are no published data on s t r a i n or genotypic differences i n maintenance requirements e s t i m a t e d by e i t h e r the d i r e c t or i n d i r e c t procedures. Nor have maintenance requirements appeared among the recent r e v i e w s on p o s s i b i l i l i t i e s f o r g e n e t i c improvement i n salmonids (Gjedrem, 1976) or f i n f i s h e s i n general (Gjedrem, 1983). Gjedrem, how-ever, has speculated that v a r i a t i o n s i n maintenance requirements among d i f f e r e n t genotypes of f i n f i s h species w i l l l i k e l y be small, i n view of the f a c t that the absolute maintenance requirement i s i t s e l f low. 2.3.2.2 E f f e c t of D i e t a r y Components on the E v a l u a t i o n of Energy and Protein U t i l i z a t i o n A. Dietary Protein: Level and Source Nitrogen metabolism i n f i s h i s a f f e c t e d by a number of environmen--20-t a l parameters and d i e t , as w e l l as by the b i o l o g i c a l s t a t u s of the a n i m a l ( S a v i t z , 1969; Gerking, 1955, 1971; Cowey, 1980). As such, ex-perimental conditions must take account of these f a c t o r s when observing u t i l i z a t i o n of d i e t a r y p r o t e i n , and be c a r e f u l l y d e f i n e d to address p a r t i c u l a r questions. F i s h may have t h e i r greatest protein conversion e f f i c i e n c i e s when fe d d i e t a r y p r o t e i n c o n c e n t r a t i o n s t h a t are s u b - o p t i m a l f o r maximum growth and feed e f f i c i e n c y . For example, Cho et a l . (1976) reported that reducing the protein l e v e l i n the d i e t of rainbow trout from 40% to 25% i n a herring and soybean containing d i e t tended to reduce the amount of p r o t e i n needed per gram of p r o t e i n d e p o s i t e d i n the c a r c a s s , though increasing the amount of dietary energy used per k c a l of energy deposit-ed. For the carp, Ogino and Chen (1973) determined t h a t 10% crude pro-t e i n was the optimal concentration of protein for measurement of protein b i o l o g i c a l value. This l e v e l of protein i n the d i e t i s well below that required by carp for maximum growth (National Research Council, 1981). In consideration of e f f i c i e n c y of p r o t e i n u t i l i z a t i o n alone, however, use of a low concentrations of t h i s ingredient would seem to be p r e f e r -able. Rainbow t r o u t appear to be e x c e p t i o n a l l y s e n s i t i v e to t r y p s i n i n h i b i t o r s present i n soybean meal as w e l l (review by P f e f f e r , 1982). But more important to the q u a l i t y of heated soybean meal i s content of e s s e n t i a l amino a c i d s , some of which are d e f i c i e n t i n t h i s p r o t e i n source. Experiments with y e a r l i n g rainbow trout weighing 32 g have shown that supplementation with a sulphur-containing amino acid (cystine) and t r y ptophan was necessary to m a i n t a i n growth r a t e when the r a t i o of percent f i s h meal to soybean meal was changed from 28:10 i n the c o n t r o l -21-d i e t to 17:26 i n t e s t d i e t s (Dabrowska and Wojno, 1977). In rainbow trout f r y , Rumsey and Ketola (1975) have also demonstrated the need for exogenous amino acids to improve the q u a l i t y of soybean meal. Cho et a l . (1974) have shown, however, that one ha l f of the herring meal ( i n i t i a l l y 35% of the t o t a l diet) could be replaced by soybean meal without d e t r i -mental r e s u l t s . More r e c e n t l y , Cho et a l . (1976) observed a s m a l l but r e a l growth suppression i n rainbow trout fed d i e t s containing soybean and herring meal, compared to those with herring meal alone. B. Dietary Carbohydrate Carbohydrate intolerance i n salmonids i s not merely the outcome of the d i g e s t i b i l i t y problems outlined above (section 2.3.1). While glucose i s s t i l l the main source of m e t a b o l i c energy f o r f i s h , i t s o r i g i n i s predominantly gluconeogenic (Brett and Groves, 1979). As a consequence, there i s a greater r e l i a n c e on protein and f a t to meet energy require-ments. V a r i a t i o n among genotypes f o r carbohydrate u t i l i z a t i o n c o u l d , therefore, have important i m p l i c a t i o n s f or s e l e c t i n g i n d i r e c t l y f o r the a b i l i t y to u t i l i z e dietary protein more e f f i c i e n t l y i n the growing f i s h . A d i r e c t consequence of such a unique m e t a b o l i c c a p a c i t y , were i t to e x i s t , would be the p o s s i b i l i t y of replacing most or a l l of the animal protein sources with plant sources (e.g., soybean meal or canola meal). P l a n t products, i n c o n t r a s t to a n i m a l sources, c o n t a i n c o n s i d e r a b l e amounts of carbohydrate as well as protein, thus enabling economies of production through lower feed costs. The l i m i t e d metabolic capacity of salmonids to use carbohydrate as an energy source was i l l u s t r a t e d by Luquet et a l . (1975). They observed a growth d e p r e s s i o n i n rainbow t r o u t f e d a d i e t w i t h a high l e v e l of -22-carbohydrate, but r e l a t i v e l y low i n protein (35 % crude protein), com-pared to another low-sugar d i e t of 55 % crude protein. Given the almost t o t a l d i g e s t i b i l i t y of sucrose (the major source of ME i n the former d i e t ) the authors concluded t h a t sucrose ( composed of glucose and fructose subunits) was metabolically i n e f f e c t i v e i n meeting exogenous energy demands, r e s u l t i n g i n the catabolism of dietary amino acids. To support t h i s c o n c l u s i o n they drew a t t e n t i o n to a complementary study (Lee and Putnam, 1973) i n which no growth depression occurred when f a t l e v e l s - i n s t e a d of sucrose l e v e l s - were i n c r e a s e d i n a 35% crude protein d i e t i n order to meet the energy demand. The i n c l u s i o n of soybean meal i n f i s h d i e t s appears to have the a d d i t i o n a l advantage of providing a good supply of non-protein energy. Approximately 42% of the a i r dry weight of soybean meal c o n s i s t s of carbohydrate (National Research Council, 1981). However, the presence of t h i s carbohydrate component might help to explain some of the c o n f l i c t -i n g f i n d i n g s on the b i o l o g i c a l v a l u e of soybean meal to f i s h . For ex-ample, Cowey and Sargent (1979) i n reviewing studies by Andrews and Page (1974) and Rumsey and Ketola (1975), f a i l e d to explain growth responses s i m p l y i n terms of the p r i n c i p l e of l i m i t i n g ( f i r s t , or f i r s t and second) amino a c i d s . In the former study, s u p p l e m e n t a t i o n of c a t f i s h d i e t s containing soybean as the protein source with the f i r s t and second l i m i t i n g amino acids (l y s i n e , and the sulphur containing amino acids, respectively) did not improve i t s quality. On the other hand, Rumsey and Ketola reported improved growth i n rainbow trout fed soybean based d i e t s supplemented with f i v e or eight e s s e n t i a l amino acids at once. Genetic v a r i a b i l i t y i n a b i l i t y of rainbow trout to u t i l i z e dietary carbohydrate has already received some att e n t i o n (Edwards et^ a l . , 1977; -23-Austreng et_ a l . , 1977; Ref s t i e and Austreng, 1981), but the r e s u l t s are not very p r o m i s i n g from the s t a n d p o i n t of s e l e c t i o n . D i e t s v a r y i n g i n the concentration of carbohydrate (starch alone or starch plus sucrose) were fed ad l i b i t u m to several f a m i l i e s and inbred l i n e s , and genotype X die t i n t e r a c t i o n s on growth and some other production t r a i t s evaluated. The absence of any s i g n i f i c a n t i n t e r a c t i o n of t h i s type on growth i n the lower carbohydrate concentration range (31-43% of the die t ) , (Edwards et  al . , 1977) was l a t e r confirmed f o r an even broader range of carbohy-drate concentrations (15 - 49%)(Refstie and Austreng, 1981). From t h i s , i t was concluded that there e x i s t s no p o s s i b i l i t y of s e l e c t i v e l y breed-ing among f a m i l i e s of rainbow trout f o r the a b i l i t y to u t i l i z e carbohy-drate i n the die t (Refstie and Austreng, 1981). 2.3.2.3 Protein as an Energy Source and the Production of Ammonia The possible existence of exploitable differences i n protein meta-bolism among s t r a i n s of rainbow trout and other salmonids i s increased by the f a c t of a high d i e t a r y requirement f o r t h i s component. Both exogenous and endogenous protein sources serve to meet the energy needs of f i s h , each to a degree dependent on the a n i m a l s requirement f o r energy i n r e l a t i o n to the metabolizable energy provided i n the diet, as w e l l as to the o v e r a l l plane of n u t r i t i o n ( B r e t t and Z a l a , 1975; B r e t t and Groves, 1979). Krebs cycle i s the common s i t e for the oxidation of sugars, l i p i d s and amino acids. In f i s h , which use large quantities of amino acids to meet energy requirements, modulation of the Krebs cycle i s achieved by unique mechanisms (Kutty, 1972; i n G a r i n and Damael, 1981), and, as previously stated blood glucose may derive more r e a d i l y through gluco--24-neogenesis than d i r e c t l y from dietary carbohydrate. Ammonotelism, and the biochemical adaptations to t h i s mode of nitrogen excretion i n f i s h , r e s u l t s i n e f f i c i e n t e n e r g e t i c s of amino a c i d u t i l i z a t i o n (Cowey and Sargent, 1972; i n Garin and Damael, 1981). In a l l organisms the f i r s t s t e p s i n ammonia p r o d u c t i o n are, i n a g e n e r a l sense, very s i m i l a r . Walton and Cowey (1977; i n V e l l a s , 1981) have shown also that the transamination process i n l i v e r and kidney of f i s h i s the major process i n ammonia formation. Substrates of ammonia p r o d u c t i o n , i n a d d i t i o n to amino a c i d s , i n c l u d e amides (glutamine, asparagine), purines, pyrimidines, nucleotides, and nucleosides (Vellas, 1981). D e t a i l s of the m e t a b o l i c pathways l e a d i n g to the p r o d u c t i o n of ammonia i n f i s h a r e as y e t u n c l e a r ( G a r i n and Damael, 1981). Considerable evidence points to glutamate dehydrogenase as a key enzyme i n the process, however, ammonia s y n t h e s i s from d i r e c t enzymatic conversion of glutamic acid appears not to occur (Vellas, 1981). The bulk of ammonia excreted by the f i s h i s produced i n the l i v e r , with a l e s s e r amount coming from the kidney (Pequin and Serfaty, 1963; Ve l l a s , 1981). The free ammonia so produced i s e i t h e r excreted d i r e c t l y i n t o the aqueous environment, or, converted i n t o a n o n - t o x i c form. In t e l e o s t f i s h , free ammonia can be trapped as glutamine i n a r e v e r s i b l e r e a c t i o n w i t h g l u t a m i c a c i d (Pequin and S e r f a t y , 1966, 1967, 1968; i n V e l l a s , 1981). 2.3.2.4 Ammonia Excretion as an Index of Protein U t i l i z a t i o n Simple e f f e c t i v e methodology f o r estimating v a r i a b i l i t y , p a r t i c u -l a r l y that of e f f i c i e n c y of nutrient u t i l i z a t i o n , are lacking (Gjedrem, 1983). In the case of rainbow trout and other salmonid species, protein r e q u i r e m e n t s are very high and t h e i r e f f i c i e n t u t i l i z a t i o n should be considered f o r genetic s e l e c t i o n . As the predominant form of nitrogen excretion by carp (Smith 1929) and rainbow trout (Burrows 1964, Forster and Goldstein 1969; Beamish and Thomas, 1984) and other salmonid species (Brett and Zala 1975), ammonia has f e a t u r e s which appear to make i t a p o t e n t i a l l y u s e f u l index of p r o t e i n u t i l i z a t i o n a p p l i c a b l e to g e n e t i c s e l e c t i o n s t u d i e s . Among these, are a consistent and stable d i u r n a l pattern of excretion related to time of feed i n t a k e . Moreover, i n sockeye salmon a sharp peak i n excretion rate occurred at 4 to 4.5 hours post-prandially at 150C (Brett and Z a l a , 1975). A c c o r d i n g to B r e t t and Z a l a (1975) the l a r g e pulse i n ammonia excretion was due to exogenous protein catabolism. In the r a i n -bow t r o u t , the p r o p o r t i o n of N H 3-N e x c r e t e d r e l a t i v e to i n g e s t e d N increases with dietary protein concentration; i n contrast the proportion of urea-N excreted remains constant (Beamish and Thomas, 1984). While ammonia i s the p r i n c i p a l nitrogenous excretory product f o r rainbow trout, urea has a s i m i l a r status i n the rat. Munchow and Bergner (1968, c i t e d i n Eggum 1970) reported a high negative c o r r e l a t i o n between b i o l o g i c a l v a l u e of the feed (of r a t s ) and blood urea content. Blood urea also increased with protein content of the diet. These r e s u l t s were confirmed by Eggum (1970) who also demonstrated the s i g n i f i c a n c e of time a f t e r f e e d i n g on blood urea content i n p i g : urea l e v e l s i n c r e a s e d f o r the f i r s t 3-4 hours a f t e r f e e d i n g b e fore r e a c h i n g a p l a t e a u . Based on t h i s inverse r e l a t i o n s h i p , Eggum (1970) proposed the use of blood urea content, under standardized conditions with respect to d i e t and sampling time, to serve as a predictor of b i o l o g i c a l value of feedstuffs. In ammonia excretion studies with rainbow trout a dietary e f f e c t on ammonia e x c r e t i o n l e v e l s has been observed (Rychly and Marina, 1977; G a r c i a et a l . , 1981). G a r c i a e t a l . (1981) used t o t a l ammonia e x c r e t e d over 20 hours to compare ca t a b o l i c use made of die t s containing high or low p r o t e i n or f a t . The amount of ammonia e x c r e t e d served to i n d i c a t e r e l a t i v e amount of dietary protein used f o r energetic purposes (Garcia -27-3. EXPERIMENTAL PART I: STRAIN DIFFERENCES IN PRODUCTION RELATED TRAITS 3.1 INTRODUCTION This s e r i e s of experiments was c a r r i e d out to measure v a r i a t i o n i n p r o d u c t i o n - r e l a t e d t r a i t s among the t h r e e s t r a i n s of rainbow t r o u t . S i m i l a r experiments were conducted i n two successive years, both times using f i s h sampled from the same, o r i g i n a l populations. Concurrent feed w i t h d r a w a l and f e e d i n g experiments were run, the former designed to inve s t i g a t e differences i n the r a t e of endogenous or m e t a b o l i c l o s s e s of carcass components. Starvation losses (expressed as wet or dry t i s -sue, p r o t e i n or gross energy d u r i n g s t a r v a t i o n ) were c o n s i d e r e d as an approximation of maintenance requirements (Luquet and Kaushik, 1981; Cho et a l . , 1982), and thus were used as a m e t a b o l i c c o r r e c t i o n i n the determination of net e f f i c i e n c y of protein and energy conversion, from gross e f f i c i e n c y data. Feed consumption, growth and e f f i c i e n c y of con-v e r s i o n of feed, p r o t e i n and gross energy were determined f o r e i g h t dietary treatments i n a f a c t o r i a l experiment based on two l e v e l s protein (20 or 30% of the d i e t ) , two p r o t e i n sources ( f i s h meal or f i s h meal p l u s soybean meal), w i t h each of these f o u r d i e t s being f e d at two feeding l e v e l s ( s a t i a t i o n or 50% of s a t i a t i o n ) . -28-3.2 MATERIALS AND METHODS 3.2.1 Stock 3.2.1.1 Source and History The f i s h used i n a l l experiments, i n both years (i.e. f i s h aged 0 and 1 respectively), were selected from a single hatched population in the case of each strain. A l l were hatched in the f a l l of 1981, and i n i -t i a l numbers of individuals received comprised about 4000 fish of each strain. The two wild strains, Pennask Lake (PK) and Premiere Lake (PL), obtained through the Provincial Hatchery at Abbotsford B.C., originated in British Columbia lakes bearing their respective names. The domestic stock (Sun Valley or SV) was obtained from the Sun Valley Trout Farms Ltd., Mission, B.C. Body weight ranges, based on a random sample (n=150 fish) of each of the three strains on landing, were as follows : S.V. 0.15-0.25g (mean 0.20g) ; P.N. 0.66 - 4.03g (mean 1.75g); and PL 1.00 -3.85g (mean 2.06g). The domesticated strain used i n the study was bred from a number of d i f f e r e n t domesticated stocks o r i g i n a t i n g i n Washington State, and subjected to further genetic s e l e c t i o n by personnel of the Sun Valley Trout Farms l t d . The Sun Valley stock had been hatched and reared i n wellwater at 9°C-10°C, and fed a dry, commercial trout diet. Pennask Lake stock are a native s t r a i n with no history of introductions from other sources (Larry Lemke, personal communication). Typically, broodstock ( about 3000 males and the same number of females) are trapped during the upstream spawning migration each year for random breeding, i.e. on a f i r s t come, f i r s t served basis. Each female i s mated with a single male. Hatchery water temperature for hatching and rearing -29-Pennask l a k e f i s h i s 10-11°C year round. Only dry d i e t s are used i n rearing (L. Lemke, personal communications). Premier Lake stock are probably of mixed domestic and wild h e r i -tage. A domesticated stock was introduced to the lake from Washington State i n the 1960's, followed some years l a t e r by introductions of wild s t o c k from Pennask and Beaver l a k e s (L. Siemens, p e r s o n a l communica-tions). During any given spawning season eggs from 1500 females are f e r t i -l i z e d by m i l t from an equal number of males. Spawning males and females are trapped i n an i n l e t stream and sorted to remove small "precocious" males. F e r t i l i z e d eggs are hatched and reared i n the Kootenay Hatchery, Kootenay, B.C. between 7°C and 12°C. Currently Premier Lake i s restocked when a portion of these f i n g e r l i n g s are returned to the lake, t h i s being the only known source of rainbow trout to Premier lake f o r the past 13-14 years. The f i s h used i n these experiments were i n a l l cases progeny of the 'pure' s t r a i n s ; no c r o s s e s of the t h r e e s t r a i n s were used. F i s h were ordered from respective suppliers according to s i z e , with the objective of having s i m i l a r i n i t i a l weights. 3.2.1.2 Laboratory Acclimation At the West Vancouver L a b o r a t o r y , Department of F i s h e r i e s and Oceans, Canada, a l l f i s h (age 0, f i n g e r l i n g s ) were p l a c e d i n 110 1 holding tanks supplied with plastic-mesh (2.5 cm) covers, and an empty tank separating those containing f i s h . Aerated w e l l water was supplied at a flow rate of 1-2 1/min., at a constant 10-10.5oC. Water chemistry data are given i n the Appendix (Table IA). A 14h p h o t o p e r i o d (08.00-22.00 h) was enforced, and the d i e t consisted of a mixture of moist and -30-dry commercial trout feeds: Oregon Moist P e l l e t s (Moore-Clarke Co. Ltd., La Conner , WA, USA) and S i l v e r c u p T r o u t Chow (Murray E l e v a t o r s , S a l t Lake C i t y , Utah, USA). Age 1 ( y e a r l i n g ) f i s h were e i t h e r h e l d over at the West Vancouver Laboratory from the o r i g i n a l stocks received (wild s t r a i n s ) or obtained anew from the s u p p l i e r one year l a t e r , i n time f o r a one month p e r i o d of acclimation under laboratory conditions. According to the suppliers, these f i s h were from the same hatching as those obtained the year before (age-0 SV) and, s i m i l a r l y to the other s t r a i n s , were r e a r e d at 9-10°C on a dry d i e t during the intervening year. Photoperiod during the one-year h o l d i n g p e r i o d f o r the w i l d s t r a i n s was a u t o m a t i c a l l y a d j u s t e d according to the natural cycle. 3.2.2 Experimental Populations and Conditions F i s h were weighed i n d i v i d u a l l y to a p r e c i s i o n of O.Olg u s i n g a t o p l o a d i n g , e l e c t r o n i c balance a f t e r being a n a e s t h e t i z e d i n a e r a t e d water containing 2- phenoxyethanol (0.5ml/l), and dabbed with a c l o t h to remove excess moisture. F i s h were weighed at no l e s s than 12 hours a f t e r the previous meal. The procedures f o l l o w e d i n s e l e c t i n g e x p e r i m e n t a l a n i m a l s from among the stock on hand were s i m i l a r at both ages. Body weight frequency d i s t r i b u t i o n of each population was f i r s t estimated from a random sample of f i s h , o b t a i n e d by p a s s i n g a d i p n e t v e r t i c a l l y through each tank c o n t a i n i n g f i s h of t h a t s t r a i n . S i z e s of samples f o r the d i f f e r e n t s t r a i n s are shown i n Table I. In s e l e c t i n g experimental populations, optimal uniformity of body weight was d e s i r e d , w i t h i n and between s t r a i n s . However, s i g n i f i c a n t -31-differences i n body weight (mean and range) necessitated the acceptance of d i f f e r e n t l i m i t s on weight ranges f o r f i s h of the v a r i o u s s t r a i n s (Table I). Limited numbers of f i s h was an a d d i t i o n a l constraint on the choice of weight ranges, p a r t i c u l a r l y at age 1. The t o t a l number of f i s h used i n each tank was 30 at age-0, and 15 at age-1. S e l e c t e d i n d i v i d u a l s from each s t r a i n were p l a c e d i n a s i n g l e holding tank before being randomly d i s t r i b u t e d f i v e at a time to experi-mental tanks. D i s t r i b u t e d groups of f i s h were reweighed i n d i v i d u a l l y the same day and returned to t h e i r respective tanks. Experimental tanks were prepared i n advance by d i s i n f e c t i n g , scrubbing, and flushing with w e l l water for at l e a s t 24h. A l l tanks were f i t t e d with an outside standpipe of adjustable height, thus enabling equalization of water l e v e l among tanks, and periodic f l u s h i n g with minimal disturbance to the f i s h . The standard f l o w r a t e was a p p r o x i m a t e l y 1.5 1/m (Appendix T a b l e IIA) and dissolved oxygen was 9.8 - 9.9 p.p.t. during several spot checks (Model 57 Oxygen Meter, Yellow Springs Instrument Co., Ohio). 3.2.3 Determination of Endogenous Losses i n F i s h During a Period of Feed Withdrawal In the f i r s t year a seven day pre-experimental period preceded the a c t u a l experiment. During t h i s time a l l f i s h were fed s t r i c t l y to s a t i a t i o n on a commercial dry d i e t ( S i l v e r c u p , see above). The body weight recorded a f t e r d i s t r i b u t i o n of f i s h to e x p e r i m e n t a l tanks was thus the pre-experimental weight, and the time 0 (starting) weight was recorded at the end of t h i s p r e - e x p e r i m e n t a l p e r i o d , when feed was withdrawn. At t h i s time 36 of the undistributed f i s h from each s t r a i n , also having received the pre-experimental s a t i a t i o n r a t i o n of Silvercup -32-Table I. Selection of experimental populations of rainbow t r o u t . S t r a i n Sun Valley Pennask Premier F i n g e r l i n g s (age 0) I n i t i a l population Size of sample BW range, sample (g) BW mean, sample (g) BW range, experimental (g) 5,000 228 0.20-0.86 0.44 Standard deviation (g) 0.14 0.40-0.60 4,000 159 0.98-3.51 1.92 0.38 1.65-2.00 4,000 157 1.51-4.05 2.72 0.70 2.30-2.80 Yearlings (age 1)' I n i t i a l population 400 Size of sample 34 BW range, sample (g) 23.6-63.5 BW mean, sample (g) 41.87 Standard deviation (g) 11.22 40.0-60.0 BW range, experimental (g) 2,000 66 4.8-83.2 26.39 18.19 30.0-60.0 2,000 55 6.9-70.9 27.88 19.12 30.0-60.0 Using body weight data, obtained for each s t r a i n from a random sample from each year class. Yearling Premier and Pennask f i s h were held i n the laboratory from the f i n g e r l i n g stage. Age 1 Sun V a l l e y f i s h , d e r i v e d from the same o r i g i n a l population as t h e i r age 0 counterparts, were obtained anew from the hatchery for the second year's experiments. -33-feed, were weighed i n d i v i d u a l l y and frozen f or l a t e r chemical analysis as the Experimental time 0 groups. The feed withdrawal period was 21 days at age 0 and 32 days at age 1. The l a t t e r part of the experiment was divided into two periods of 11 days and 21 days r e s p e c t i v e l y , r e w e i g h i n g f i s h at the end of each p e r i o d . At the end of the e x p e r i m e n t a l p e r i o d a l l f i s h were reweighed and frozen f or chemical analysis. 3.2.3.1 Chemical Analysis of Carcasses A. Age 0 F i s h The procedures f o r chemical analysis of carcasses were those of the AOAC (1972), or m o d i f i c a t i o n s of these methods, as d e s c r i b e d below. Because of a diffe r e n c e i n s i z e of f i n g e r l i n g and y e a r l i n g trout, some of the procedures for carcass analysis also d i f f e r e d between the two. Dry matter was determined on l o t s of f i s h i n a two step d r y i n g procedure: l y o p h y l i z a t i o n f o r 72h , immediately followed by oven drying i n p e t r i dishes at 80°C to constant weight (less than 24 h). In d i v i d u a l dry weights were also determined. Crude p r o t e i n , crude f a t and ash were determined from c a r c a s s e s a f t e r g r i n d i n g the dry m a t e r i a l i n an A n a l y t i c a l M i l l (Tekmar Co., C i n c i n n a t i , Ohio) and thoroughly mixing by hand with a spatula . Mois-t u r e (ca. 2%) c o n t a i n e d i n ground samples was determined d u r i n g the procedure of f a t analysis, and subtracted from the t o t a l dry matter i n a l l a n a l y s e s (i . e . , p r o t e i n , f a t and ash). Crude f a t was estimated on ground, dry samples of 0.4-0.5 g by the i n d i r e c t method (AOAC, 1972), but combined with ash determination accor--34-ding to the fo l l o w i n g procedure. Carcass samples were weighed from the desiccator into alundum thimbles which had been previously i g n i t e d at 600 °C and stored at 80°C i n a drying oven. Thimbles were cooled i n a desiccator, l a b e l l e d and weighed j u s t p r i o r to adding sample. Thimbles c o n t a i n i n g samples were oven-dried o v e r n i g h t (80 ±2 %) , c o o l e d i n a d e s i c c a t o r and reweighed to determine the weight of dry sample, and m o i s t u r e content of samples a f t e r g r i n d i n g and mixing (see above). E x t r a c t i o n time w i t h d i e t h y l e t h e r (50 ml/ sample) was 4 h u s i n g the G o l d f i s c h F a t E x t r a c t i o n Apparatus (Labconco Corp., Kansas C i t y , Mo.). Thimbles c o n t a i n i n g e x t r a c t e d sample were oven-dried overnight a f t e r a l l o w i n g excess s o l v e n t to evaporate ( i n a fume hood), c o o l e d i n a d e s i c c a t o r and weighed. Et h e r e x t r a c t was determined as the l o s s i n weight of the oven-dry, ground sample during extraction. T o t a l ash i n the c a r c a s s was determined u s i n g e t h e r - e x t r a c t e d samples i n alundum thimbles a f t e r the f i n a l weighing f o r f a t determina-tion. Thimbles containing f a t - f r e e sample were ashed at 600°C f o r 5h, or u n t i l a white ash was obta i n e d , c o o l e d i n a d e s i c c a t o r and weighed. After removing the ash, thimbles were stored i n the drying oven at 80°C i n preparation f or the next s e r i e s of crude f a t and ash determinations. K j e l d a h l - n i t r o g e n (% crude p r o t e i n = % N x 6.25) was determined on ground samples of 0.25 g. Samples were weighed on 11.0 cm a s h l e s s f i l t e r paper c i r c l e s (Watman No. 541), digested i n concentrated sulphur-i c a c i d (25 ml) w i t h 10.3 g c a t a l y s t (0.3 g CuSo4, and 10.0 g Na2S04)» using a Buchi 430 digestor (Buchi Laboratoriums - Technik AG, Schweiz). D i s t i l l a t i o n of the d i g e s t was c a r r i e d out a c c o r d i n g to the standard procedure using a Buchi 325 d i s t i l l a t i o n unit. -35-B. Age 1 F i s h The main differ e n c e i n the procedures used f o r carcass analysis at age 1 was rela t e d to the larger sized f i s h . Thus f i s h were ground before drying instead of a f t e r , and t h i s necessitated the f o l l o w i n g changes i n preparation of samples f o r determination of dry matter, protein, f a t and ash content. Each l o t of p a r t i a l l y thawed f i s h was weighed to the near-e s t 0.01 g, passed through a g r i n d e r p l a t e ( 1.17 mm di a m e t e r ) , and homogenized i n an o s t e r i z e r , adding the equivalent of 20 % of l o t weight as deionized water to f a c i l i t a t e blending. True weight of the homogenate was determined by d i v i d i n g d i l u t e homogenate weight by 1.20. A l l mate-r i a l from each l o t was s t o r e d i n a l a b e l l e d p l a s t i c c o n t a i n e r w i t h a l i d . Moisture determinations from the same sample containers gave accep-tably s i m i l a r r e s u l t s (±5 % ) , with or without a fr e e z i n g period between analyses. Samples were stored at 5oC i n a r e f r i g e r a t o r f o r t y p i c a l same day use for moisture determinations. Dry sample f o r protein f a t and ash determination was obtained by l y o p h i l i z i n g about 20 g of frozen, d i l u t e homogenate i n aluminium weighing dishes, followed by oven drying over-n i g h t (80°C). Percent dry matter of homogenates was determined according to AOAC (1972) u s i n g a l i q u o t s of a p p r o x i m a t e l y 2g. Ash was determined on the same oven-dry samples used f o r dry matter analysis, using l i g h t weight (7 g) porcelain dishes. Kjeldahl-N was determined as before (above) on samples of 1.2 - 1.3 g. Crude f a t was determined by i n d i r e c t method (see above, Age 0 f i s h ) using about 1 g of oven-dried, l y o p h i l i z e d sample. -36-3.2.4 Estimation of Growth and E f f i c i e n c y T r a i t s by Feeding T r i a l s 3.2.4.1 Preparation of Diets The procedure used f o r p r e p a r a t i o n of i n g r e d i e n t s and mixing of d i e t s was the same both years. Table 2 shows that the type of f i s h meal used d i f f e r e d s l i g h t l y i n the two years. Diets f or age 0 and age 1 f i s h used a meal prepared from f i l l e t s of cod or pollack, respectively. Both are 'white f i s h ' species with a low muscle f a t content. O i l content also d i f f e r e d s l i g h t l y between age 0 and 1 d i e t s , and p e l l e t s i z e s were adjusted according to s i z e of f i s h . Formulations for experimental d i e t s are shown i n Table I l a . Where necessary, i n g r e d i e n t s were ground i n a W i l e y m i l l to pass through a U.S. No 30 s i e v e (.60mm mesh). P r e s s cod or p o l l a c k f i l l e t , ( B r i t i s h Columbia Packers, Ltd., Richmond, B.C.) were thawed and pressure cooked ( l l O ^ C , 15 p.s.i.) i n an a u t o c l a v e f o r 25 min., and d r i e d o v e r n i g h t i n a convection oven at 80-90°C. Ingredients f o r each d i e t were mixed i n a 30 1 c a p a c i t y Hobart mixer (Model D300) f o r l h . H a l f the o i l was added during mixing and the remainder a f t e r dry p e l l e t i n g (3/64" die). P e l l e t s were stored at -20o C and crumbled as required. Crumbles were stored f o r l e s s than a week at room temperature p r i o r to feeding. Optimum crumble si z e s were determined during a pre-experimental feeding phase: 1.00-1.18 mm (U.S. No 16-18 s i e v e ) f o r SV and PN, and 1.00-1.70 mm (U.S. No 12-18 s i e v e ) f o r PL f i s h a t age 0, and at age 1, 1.70 - 2.38 mm (U.S. 12-8 sieves) crumbles were used for a l l s t r a i n s . 3.2.4.2 Pre-experimental Treatment Once d i s t r i b u t e d each tank of f i s h was fed to s a t i a t i o n on the same -37-d i e t s (Table IIa,b) as they would r e c e i v e , e i t h e r at s a t i a t i o n l e v e l (100%) or at 50% of s a t i a t i o n , during the subsequent 3 week experimental phase. Pre-experimental feeding began the morning a f t e r d i s t r i b u t i o n and c o n t i n u e d up u n t i l r e w e i g h i n g at the s t a r t of the e x p e r i m e n t a l phase (seven days). The p r e - e x p e r i m e n t a l p e r i o d l a s t e d f o r 10 days at age 1, since most groups of w i l d f i s h f a i l e d to take food any sooner. 3.2.4.3 Experimental Phase Age 0 f i s h were reweighed i n l o t s of 10 ( t h r e e l o t s per treatment group) at the s t a r t of the experimental phase (day 8). F i s h were return-ed to t h e i r respective tanks immediately a f t e r weighing and given an o v e r n i g h t 'maintenance' r a t i o n (25 % of s a t i a t i o n r a t i o n ) . Regular experimental feeding (see below) began the f o l l o w i n g morning. An experi-mental time 0 sample of 30 f i s h from each s t r a i n (see section II.B.) was taken at the end of the pre-experimental period and frozen a f t e r weigh-ing. These f i s h had received a commercial trout chow at s a t i a t i o n during the p r e - e x p e r i m e n t a l p e r i o d , and thus served as a c o n t r o l group f o r carcass composition at time 0 f o r a l l dietary treatments. Age 1 f i s h were reweighed and measured (fork length) i n d i v i d u a l l y at the s t a r t of the e x p e r i m e n t a l p e r i o d . A sample of 15 f i s h of each s t r a i n was taken at the beginning of the pre-experimental period, frozen and a n a l y z e d f o r proximate c o m p o s i t i o n . No samples were taken at the beginning of the experimental period. Some systematic error i n the estimation of compositional losses and gains would have resulted from the f a i l u r e of some groups of age 1 wild s t r a i n s to feed d u r i n g the f i r s t nine days of the p r e - e x p e r i m e n t a l period, and the lack of representative c o n t r o l groups f o r body composi-- 3 8 -T a b i e I l a . E x p e r i m e n t a l d i e t a r y t r e a t m e n t s f o r rainbow t r o u t of t h r e e s t r a i n s d u r i n g three-week growth t r i a l s . Experimental Diets^ AGE 0 AGE l 2 Protein Source: F i s h Meal Soybean Meal F i s h Meal Soybean Meal Name of Die t : FM.l FM.2 SBM.l SBM. 2 FM.ll. FM.12 SBM.11 SBM.12 Formulation (g/ kg di e t ) Cod meal 215.3 338.2 150.0 150.0 Pollack meal 181.2 284.8 126.3 126.3 Soybean meal 110.6 319.2 110.6 327.0 Wheat middlings 200.0 200.0 200.0 200.0 234.0 234.0 234.0 234.0 Dextrin 438.9 327.8 399.4 213.5 439.0 335.4 383.3 166.9 Salmon o i l 105.8 97.7 109.0 106.9 105.8 105.8 105.8 105.8 Bone f l o u r 5.0 1.3 5.0 5.0 5.0 5.0 5.0 5.0 Carboxymethyl-c e l l u l o s e Vit/Min premix^ 20.0 20.0 20.0 20.0 20.0 20.0 20.0 20.0 15.0 15.0 15.0 15.0 15.0 15.0 15.0 15.0 ^ Eight treatments i n each year; each d i e t being fed to s a t i a t i o n or 50 % of s a t i a t i o n . 2 Tested one year a f t e r age 0 f i s h were tested. 3 Refer to Appendix Table VA. -39-Table l i b . Proximate composition of experimental diets fed to rainbow trout of three strains during three-week growth t r i a l s . Experimental Diets^" Age 0 Age 1 Protein Source: Fish Meal Soybean Meal Fish Meal Soybean Meal Name of Diet: FM.l FM.2 SBM.l SBM.2 FM.ll FM.12 SBM.11 SBM.12 Proximate Analysis Moisture (%) Crude protein (%) Fat (ether extract) (%) Ash (%) Carbohydrate (X) 2 Gross Energy (kcal/kg) 8.66 8.25 8.52 8.57 9.34 9.64 10.15 10.10 19.59 29.84 20.02 28.33 18.42 27.21 18.29 28.41 9.65 10.54 10.44 10.62 12.11 11.26 11.91 12.49 2.69 2.49 3.04 4.24 2.19 2.66 2.55 3.82 59.41 48.88 57.98 48.24 57.94 48.83 57.10 45.18 4,520 4,746 4,548 4,660 4,561 4,641 4,500 4,638 * A l l diets were fed to satiation or to 50 % of satiation to fi s h in both years. 2 By difference. Determined by bomb calorimetry (age 0) or by computation (age 1), using 5.65 kcal/j protein, 9.45 kcal/g fat, and 4.10 kcal/g carbohydrate. -40-t i o n at time 0. During the same period Sun Valley f i s h consumed food and increased i n weight. Age 0 f i s h were fed by hand three times d a i l y (at 08.30 h, 12.45 h and 15.00 h), and age 1 f i s h t w i c e (09.00 h and 13.30 h). Feeding sessions l a s t e d about one hour on average, making three or four rounds of a l l tanks. Time spent per v i s i t at each tank v a r i e d from about 30 seconds to a minute or more. Feed v i a l s assigned to s a t i a t i o n feeding were r e f i l l e d d a i l y or as r e q u i r e d and a l l r e s i d u a l feed l e f t a f t e r t h r e e or f o u r days was d i s c a r d e d . Groups of f i s h a s s i g n e d to 50 % s a t i a t i o n groups were given a measured quantity of feed, calculated by halving the previous day's consumption for the 100 % group correspon-ding i n d i e t and s t r a i n . Feed was broadcast uniformly over the water surface using a spatu-l a to minimize bias i n feeding opportunities. F i s h on 50 % r a t i o n were allo c a t e d approximately equal amounts of the d a i l y r a t i o n at each of the two (age-1) or t h r e e (age 0) d a i l y f e e d i n g s . F i s h were s a i d to be s a t i a t e d i f on two s u c c e s s i v e passes of a tank c e r t a i n behaviours were evident: s p i t t i n g without r e t r i e v a l , hovering near the tank bottom or avoiding p e l l e t s . Care was taken to reduce the rate of feeding as signs of s a t i a t i o n became more obvious to m i n i m i z e feed wastage and con-sequent severe errors i n estimating feed consumption. Tanks were f l u s h -ed once weekly to remove accumulated feces. F i n a l l i v e weights at age 0 were measured on l o t s of 8-10 f i s h . Each tank of f i s h ( treatment group) was d i v i d e d i n t o t h r e e such l o t s , with equal numbers of f i s h i n each l o t except where deaths occurred. At age 1, a l l f i s h from each tank were weighed i n d i v i d u a l l y , as previously d e s c r i b e d ( a f t e r f i r s t b l o t d r y i n g on absorbent t o w e l l i n g ) , to an -41-accuracy of O.Olg and frozen immediately i n p l a s t i c bags. Carcass analy-s i s was c a r r i e d out as explained i n 3.2.3.1 (above). 3.2.4.4 Chemical Analysis of Diets. Feed samples were subjected to proximate analysis generally accor-ding to the procedures of the AOAC (1972). Percent f a t was determined as d e s c r i b e d p r e v i o u s l y f o r c a r c a s s e s ( u s i n g 1 g of feed) , and ash determination was combined with that of f a t as done with carcasses of age 0 f i s h . Gross energy of d i e t s was determined by Oxygen Bomb c a l o r i -metry, using a p l a i n jacket, oxygen bomb calorimeter (Series 1300; Parr Instrument Co., Moine, 111.) i n conjunction with a Hewlett-Packard e l e c -t r o n i c thermometer (Model 2801A, Hew l e t t Packard, P a l o A l t o , Ca.) and d i g i t a l recorder (Model 562A, Hewlett Packard, Palo Alto, Ca.). 3.2.5 Numerical Analysis 3.2.5.1 M o r t a l i t y Six deaths occurred i n the age 0 experiment, and f i v e were recorded at age 1. A l s o i n the age 1 e x p e r i m e n t a l groups t h e r e was one i n s t a n c e of a f i s h of the Pennask s t r a i n jumping i n t o an a d j a c e n t tank, a l s o occupied by Pennask f i s h r e c e i v i n g a s i m i l a r dietary treatment (FM.l and SBM.l, r e s p e c t i v e l y , both a t 50% s a t i a t i o n ; T a b l e l i b ) . A few tanks of age 0 f i s h showed some s i g n s of a m i l d white spot i n f e c t i o n and t h r e e deaths - w i t h two of these o c c u r r i n g i n a s i n g l e tank - were r e c o r d e d from i n f e c t e d tanks. Only one death occured i n any sing l e tank at age 1. Age 0 deaths were immediately evident, and dead f i s h were weighed on the day that death occurred. At age 1, the carcass of only one dead f i s h was -42-recovered, the date of death and body weight recorded. M i s s i n g weights ( c a r c a s s not recovered) were r e p l a c e d w i t h an e s t i m a t e d value. In each case, t h i s was the e s t i m a t e d mean weight at half-time f o r the corresponding treatment tank, i.e. the average of the mean i n i t i a l and mean f i n a l f i s h weights. The assumption was t h a t the f i s h had disappeared at the halfway point of the experiment. Where the dead carcass could be weighed, t h i s weight was merely added to the t o t a l biomass at the end of the experiment, and a corrected mean body weight c a l c u l a t e d w i t h the l a r g e r biomass and number of f i s h . In the one i n -stance where a f i s h (Pennask on 50% SBM.11 ration) jumped from one tank to another containing f i s h of the same s t r a i n (on 50% FM.ll), adjustment was made on the assumption t h a t the t r a n s f e r had o c c u r r e d halfway through the experiment. The mean f i n a l weight of a f i s h i n the r e c e i v i n g tank was added to the f i n a l biomass of f i s h i n the tank l o s i n g an i n d i v i d u a l , and subtracted from the former. 3.2.5.2 Feed Consumption T o t a l feed consumption had to be c a l c u l a t e d on a per f i s h b a s i s because some f i s h died during the experiment. Thus, knowing the weight of the f i s h at death, date of death, tank number and treatment, i t was possible to estimate the average consumption of food per fish-day. Where date of death was not known (as o c c u r r e d a t age 0), i t was assumed to have o c c u r r e d at the halfway p o i n t of the experiment (day 11), and adjustments were made to feed consumption as done f o r body weight (above). -43-3.2.5.3 Relative Growth In both years of experimentation there were large differences i n i n t i t i a l body weight and fork length among the three s t r a i n s of trout. Hence, r e l a t i v e growth r a t e ( i . e . , as a % of body weight or f o r k l e n g t h per day), and not rate of weight gain, were used to compare the d i f f e r -ent s t r a i n s for growth rate. The mathematical expression f o r r e l a t i v e growth, from Fisher (1958), i s as follows: R„ (% BW per day) = ( l n W2 - In W x). 100/ days (equation 1) Where Wi_ and W2 represent i n i t i a l and f i n a l body weight, r e s p e c t i v e l y . Relative growth i n fork length ( R ^ w a s computed by s u b s t i t u t i n g fork length f o r body weight i n equation 1, according to Riker (1979). 3.2.5.4 Compositional Gains The method used to c a l c u l a t e mean (per f i s h ) gains or l o s s e s as crude protein, f a t , ash, and gross energy i s given i n equation 2, below: Gain =[(mean dry weight . % Y ) f i n a l _ ( m e a n dry weight . % Y ) i n i t i a l ] / 1 0 0 (equation 2). Where Y = Crude protein, f a t or ash on a dry weight basis. Carcass gain i n crude energy was estimated using published combustible energy values ( L l o y d e t a l . , 1978) f o r p r o t e i n and f a t ( 5.7 k c a l and 9.5 k c a l / g dry t i s s u e , r e s p e c t i v e l y ) , ignoring the carbohydrate f r a c t i o n . I n i t i a l dry weights (i . e . , at e x p e r i m e n t a l time-0) f o r a l l e x p e r i m e n t a l groups within a strain-year were based on dry matter and proximate composition of a s i n g l e (time-0) group of 30 (age 0) or 15 (age 1) f i s h . - 4 4 -3.2.5.5 E f f i c i e n c y and Net E f f i c i e n c y of Nutrient U t i l i z a t i o n The standard n u m e r i c a l procedures were used to c a l c u l a t e feed conversion e f f i c i e n c y (FCE), protein e f f i c i e n c y r a t i o (PER), productive protein value (PPV), energy conversion (EC). In addition two other non-standard indi c e s of conversion - with corrections f o r 'maintenance r e -quirements' - were estimated: v i z . net conversion of energy (NCE), and net p r o t e i n c o n v e r s i o n (NPC). The l a t t e r i n d i c e s were e s t i m a t e d by making the appropriate c o r r e c t i o n i n gross e f f i c i e n c y of nutrient (pro-t e i n and energy) u t i l i z a t i o n , using s t a r v a t i o n losses at comparable body weight as an estimate of endogenous losses. The g e n e r a l e q u a t i o n f o r net e f f i c i e n c y by t h i s procedure was as follows: Net E f f i c i e n c y = (Gain + E ) / C (equation 3) Where Gain (per f i s h per 21 days) i s expressed i n terms of dry matter (g / f i s h ) , protein (g/ f i s h ) , or gross energy ( k c a l / f i s h ) ; E = endogenous l o s s e s ( i . e . , l o s s e s i n c u r r e d d u r i n g s t a r v a t i o n , i n terms of the same carcass components), and C = grams of dry d i e t or protein or k c a l gross energy consumed. Exact formulae f o r the d i f f e r e n t net e f f i c i e n c y parame-ters are given i n tables containing such data (Results). Endogenous losses i n the fed f i s h were estimated by i n t e r p o l a t i o n i n equations f o r regression of s t a r v a t i o n l o s s (as l i v e or dry matter, p r o t e i n , or gross energy ) on i n i t i a l body weight. Mean e x p e r i m e n t a l body weight ( [ i n i t i a l + f i n a l ] / 2) was used as the independent v a r i a b l e fo r estimating losses i n treatment groups from the regression equations based on 'untreated' (i.e., unfed) f i s h . -45-3.2.5.6 St a t i s t i c a l Analysis The mathematical model used for a l l analysis of variance was based o n a 3 X 2 X 2 X 2 non-replicated f a c t o r i a l design. The inherent 'hidden' r e p l i c a t i o n of the f a c t o r i a l arrangement (Ostle, 1963, p.272) was relied upon for replication effects. The pooled second- and third-order interaction terms in the analysis of variance was thus used as a measure of experimental error, according to Cornish (1936, p.80). This approach seemed justi f i e d after taking into account previous experience with the same tank system, where l i t t l e tank e f f e c t was observed. The design had the advantage of enabling the inclusion of a larger number of dietary environments, under conditions where the number of experimental tanks available was limited, in testing strain responses. The general model was: Y i j k l =/k + Ai + Bj + (AB)i-j + C k + ( A C ) i k + ( B C ) j k + D x + (AD) ± 1 + (BD)j 1 + (CD) k l + Residuals Where: ^ i j k l = the i * " * 1 feeding l e v e l of the j t n protein source of the k t n protein concentration for the l t n strain. J4 = overall mean A i = effect of the i th feeding level Bj= effect of the j th protein source ^= effect of the k th protein concentration j)j= effect of the 1 th strain Residuals= pooled three and four way interactions used as an estimate of independent normal random variable with mean 0 and variance <f^  (Ostle, 1963). -46-The U n i v e r s i t y of B r i t i s h Columbia computer program GENLIN was used f o r ANOVA. A l l e f f e c t s were considered as fixed, and a l l but protein concen-t r a t i o n (quantitative) were considered as q u a l i t a t i v e factors. The Neu-man-Keuls range t e s t (Hicks, 1973) was used to d i s t i n g u i s h between means that were s t a t i s t i c a l l y s i g n i f i c a n t . The Neuman-Keuls te s t i s conserva-t i v e i n t h a t the p r o b a b i l i t y t h a t no erroneous c l a i m of s i g n i f i c a n c e w i l l be made i s >0.95. Decisions regarding transformation of the raw data were based on the p l o t of r e s i d u a l sums of squares a g a i n s t p r e d i c t e d v a l u e s f o r the dependent v a r i a b l e (Y) from the a n a l y s i s of v a r i a n c e . T h i s t e s t i s an o p t i o n of the G e n l i n program. A l o g a r i t h m i c t r a n s f o r m a t i o n of feed consumption was effected because the r e s i d u a l sum of squares increased with the value of Y i n the ANOVA model. -47-4. RESULTS 4.1 VARIATION OF ENDOGENOUS LOSSES AMONG STRAINS OF RAINBOW TROUT 4.1.1 Endogenous Losses as Live and Dry Matter Feed withdrawal experiments lasted 21 days (age-0) or 32 days (age-1). Two fasted groups of different i n i t i a l body weight were used in the experiment for age 1 f i s h , and a single group for each s t r a i n at age 0 (Table III). Mean weight of feed withdrawal groups was unavoidably different among strains at the start of the t r i a l s conducted with each age group of fish. Table III shows i n i t i a l and f i n a l l i v e and dry weights (g/ f i s h ) for the three size groups of f i s h tested at two ages (0 and 1). A t h i r d (day 11) l i v e weight measurement was taken for age 1 f i s h (Figure 1). Figure 1 indicates s i m i l a r , p a r a l l e l responses among st r a i n s as l i v e weight loss over time (days) from the beginning of feed withdrawal for this age group. Live weight losses on a 21-day or a per day basis are shown i n Figures 2 and 3 respectively. Mean daily losses as dry matter are pre-sented i n Figure 4. Data for age 0 and age 1 f i s h were combined i n the l a t t e r figures which compare starvation weight loss among str a i n s i n relation to a given i n i t i a l weight. The two upper points on each graph came from age 1 fish, and the other from the age 0 group. Absolute loss of body weight increased with starting weight for a l l strains. However, from the plots of live weight losses there appears to be no consistency in this response among strains. Thus Figures 2 and 3 show that Premier f i s h l o s t more weight per unit of time at low to intermediate body -48-Table III. I n i t i a l and f i n a l body weights of groups of rainbow trout subjected to 21 (age 0) or 32 (age 1) days of feed withdrawal. Strain Age Class I n i t i a l Weight Final Weight (g/ fish) (g/ fish) Live Weights Sun Valley 0 0.61 0.47 1 30.85 29.51 1 60.25 57.42 Pennask 0 2.03 1.70 1 . 30.18 28.94 1 49.50 48.03 Premier 0 2.82 2.32 1 32.25 30.81 1 51.61 50.06 Dry Weights Sun Valley 0 0.12 0.08 1 8.41 7.18 1 16.43 14.22 Pennask 0 0.43 0.32 1 7.74 7.09 1 12.70 11.93 Premier 0 0.62 0.47 1 8.76 7.59 1 14.01 12.87 -49-F i g u r e 1. Change i n l i v e b o d y w e i g h t a t age 1 w i t h d a y s a f t e r f e e d w i t h d r a w a l i n l a r g e and s m a l l s i z e d r a i n b o w t r o u t o f t h r e e s t r a i n s . T I M E A F T E R F E E D W I T H D R A W A L ( d a y . ) -51-Figure 2. Mean l i v e weight loss during 21 days versus mean i n i t i a l l i v e weight i n three s t r a i n s of age 0 and age 1 rainbow t r o u t . Feed withdrawal was for 21 days at age 0 and 32 days at age 1. -53-F i g u r e 3. E s t i m a t e d d a i l y weight l o s s as l i v e t i s s u e i n r e l a t i o n to i n i t i a l weight of f a s t e d rainbow t r o u t of three s t r a i n s . Feed w i t h -drawal was for 21 days at age 0 and 32 days at age 1. - 5 4 --55-F i g u r e 4. E s t i m a t e d d a i l y weight l o s s as dry t i s s u e i n r e l a t i o n to i n i t i a l dry weight of f a s t e d rainbow t r o u t of three s t r a i n s . Feed withdrawal was for 21 days at age 0 and 32 days at age 1. -57-F i g u r e 5. L i n e a r r e g r e s s i o n of d a i l y dry weight l o s s on mean i n i t i a l dry weight i n three s t r a i n s of fasted rainbow trout. Feed withdrawal was for 21 days at age 0 and 32 days at age 1. Regression Equations: Sun Valley y= 6 + 5x , R 2= 0.99 Pennask y= 9 + 3x , R 2= 0.89 Premier y= 4 + 3x , R 2= 1.00 -58-M E A N DRY W E I G H T L O S S ( m g / f i s h / d a y ) s i -59-weight, and less than the other s t r a i n s when the s t a r t i n g weight was highest. Dry weight losses, in contrast, were of a consistent rank over the range of starting weights employed (Figure 4). Linear regressions of mean weight loss (Y) on i n i t i a l weight (X) were computed for each strain from the data plotted i n Figure 4. These regression l i n e s are shown i n Figure 5, along with th e i r respective equations and coefficients of determination (R^). Only in the vicinity of the smallest i n i t i a l body weight did crossing over of regression l i n e s occur, a f f e c t i n g the ranks of Premier and Sun Valley strains. Slopes of the regressions r e l a t i n g dry weight losses to i n i t i a l dry weight were s i m i l a r for the wild s t r a i n s (b= 3 mg/ g i n i t i a l dry weight) and greatest for the domesticated strain (b= 5 mg/ g i n i t i a l dry weight; Figure 5). C o e f f i c i e n t s of determination were high for a l l strains, with values of 0.99, 0.89, and 1.00 for Sun Valley, Premier and Pennask respectively. Thus, at any mean dry carcass weight above 3 g, the ranking for endogenous losses as g dry matter/ g i n i t i a l dry weight of carcass, increase i n magnitude as follows: Sun Valley, Premier, Pennask. 4.1.2 Endogenous Losses among Strains; Carcass Protein and Gross Energy Changes in carcass composition over the fasting period were defined as % Xf^ n a-L - % X^n^t-^a^, where X represents carcass protein, f a t , or ash on a dry matter basis, or carcass moisture on a l i v e weight basis. Mean change in these components at age 1, as represented in the Figures 6 and 7, are the pooled means for small and large groups. Data for the individual size groups at the end of the experimental period are given in the appendix (Table IVA). -60-Figure 6. Mean change i n percent body protein and f a t i n rainbow trout of three s t r a i n s a f t e r a period of feed withdrawal l a s t i n g 21 days and 32 days at ages 0 and 1, r e s p e c t i v e l y . 10 A G E 0 PROTEIN F A T -10 A G E 1 P R O T E I N F A T HHJSUN V A L L E Y | | P E N N A S K I PREMIER -62-F i g u r e 7. Mean change i n p e r c e n t body m o i s t u r e and ash i n rainbow t r o u t of t h r e e s t r a i n s a f t e r a p e r i o d of f e e d w i t h d r a w a l l a s t i n g 21 days and 32 days a t ages 0 and 1, r e s p e c t i v e l y . -64-Percent carcass fat declined in a l l strains during feed withdrawal. Changes i n % fat were greater i n f i n g e r l i n g s than i n older f i s h of a l l s t r a i n s (Fig. 6). Protein increased as a percentage of t o t a l dry mat-ter, however. At age 0 Sun Valley experienced the greatest net increase in percent protein, r e l a t i v e to other components, coupled with the largest decline i n percent fat. The wild s t r a i n s were s i m i l a r to each other i n changes of percent protein and f a t at age 0, but i n f e r i o r to Sun Valley. The sharp distinction between domesic and wild strains for change i n % fat and protein was not evident at age 1, however, yearlings of a l l s t r a i n s exhibited r e l a t i v e l y lower reduction i n % fa t , but % increase i n protein was larger i n the yearling wild strains compared to their age 0 values. In fact, Pennask increased i n % carcass protein by a greater amount, on average, than both Sun Valley and Premier at age 1. No obvious patterns were evident for change i n % moisture or ash during starvation , but a l l strains increased i n the relative amount of these components at both fingerling and yearling stages. Figures 8 and 9 show the linear regressions of losses for protein and gross energy i n relation to i n i t i a l weight. Protein was determined as N X 6.25, and gross energy using 5.65 kcal and 9.45 kcal per g of protein and fat respectively. Three observations were obtained for each strain, as described previously for weight losses. Regression equations and coefficients of determination (R^) are also given i n Figures 8 and 9. The r e l a t i o n s h i p of carcass protein loss to i n i t i a l dry weight indicates a larger slope of regression for Sun valley, compared to the wild s t r a i n s (Fig. 8). Premier had the larger slope of the l a t t e r pair. Within the weight range tested Pennask f i s h indicated no increase i n -65-F i g u r e 8. R e g r e s s i o n of 21-day p r o t e i n l o s s e s on mean i n i t i a l dry weight i n f a s t i n g rainbow trout of three s t r a i n s . Regression equations: Sun Valley y = 0.55 + 0.032 x ; R 2 = 0.94 Pennask y = 0.061 + 0.001 x ; R 2 = 0.02 Premier y = 0.019 + 0.024 x ; R 2 = 0.79 0 5 10 15 2 0 I N I T I A L D R Y W E I G H T t g / f i s h ) -67-Figure 9. Regression of 21-day gross energy losses on mean i n i t i a l dry weight i n f a s t i n g rainbow trout of three s t r a i n s . Regression equations: Sun Valley y = 0.293 + 0.631 x ; R 2 = 1.00 Pennask y = 0.572 + 0.262 x ; R 2 = 0.95 Premier y = 1.530 + 0.315 x ; R 2 = 0.56 protein loss (g/ f i s h / 21 days) with increasing i n i t i a l weight; however the f i t of t h i s regression was poor - hence the low c o e f f i c i e n t of determination for t h i s s t r a i n (R = .02) - i n comparison to the two other strains (R z 0.79 - 0.94, Fig. 9). Rankings for protein losses were the same, therefore, as for dry weight loss: Sun Valley > Premier > Pennask. A l l strains showed an increase i n gross energy losses over the 21-day period as i n i t i a l dry weight increased (Fig. 9). As previously observed for overall ranking of strains based on slope of regressions of gross energy, losses were the same as before: Sun Valley > Premier > Pennask. C o e f f i c i e n t s of determination for the regressions of gross energy loss ranged from 0.56 for Premier to 1.0 for Sun Valley, with 0.95 for Pennask (Fig. 9). 4.2 VARIATION IN FEED CONSUMPTION, GROWTH AND BODY COMPOSITION AMONG STRAINS OF RAINBOW TROUT 4.2.1 Variation of Feed Consumption Figure 10 shows the mean consumption rate for each strain as g dry feed/100 g l i v e weight/ day. Each of these values i s the mean of four dietary treatments. Age 0 fish consumed, at the satiation level, two to three times as much dry feed per day as did yearlings. Rankings for rate of consumption, based on these average values, were also consistent at the different ages. Accordingly, Sun Valley consistently consumed at a rate of two to three times that of the wild strains, with Pennask always consuming feed at about one-half to three quarters the rate of Premier. These relationships are further illustrated i n Table IV where the same quantities are compared in relation to dry weight of fi s h and diet. -70-F i g u r e 10. Dry f e e d consumed a t s a t i a t i o n r e l a t i v e t o mean i n i t i a l body w e i g h t i n age 0 and age 1 r a i n b o w t r o u t o f t h r e e s t r a i n s . Age 0 f i s h were f e d t h r e e t i m e s , and age 1 f i s h t w i c e d a i l y t o s a t i a t i o n . V a l u e s show a r e t h e means and s t a n d a r d e r r o r s f o r f o u r d i e t a r y t r e a t m e n t s ( T a b l e H a ) . F E E D C O N S U M E D a g e o HISUN V A L L E Y | | P E N N A S K l l l l P R E M I E R -72-Table IV. Mean dry feed consumption per 21 days as a function of i n i t i a l dry body weight for rainbow trout of three s t r a i n s fed to satiation. Strain Amount Consumed (g dry feed/ g dry BW/ 21 days) Age 0 Diet: FM.l FM.2 SBM.l SBM. 2 Sun Valley 1.36 1.10 1.35 1.08 Pennask 0.23 0.26 0.39 0.36 Premier 0.50 0.38 0.58 0.52 Age 1 Diet: FM.ll FM.12 SBM.11 SBM.12 Sun Valley 0.33 0.34 0.40 0.34 Pennask 0.14 0.10 0.10 0.10 Premier 0.11 0.15 0.16 0.17 Age 0 f i s h were fed three times daily to s a t i a t i o n , and age 1 f i s h twice. The analysis of variance of log^g g dry feed consumed/ g average live experimental weight i s summarized in Table V. Average experimental body weight was the mean of mean i n i t i a l and mean f i n a l weights. A l l eight dietary treatments (i.e. 4 diets X 2 feeding le v e l s ) were i n -cluded in this analysis. Based on ANOVA and comparison of means, the o v e r a l l ranking for strains was the same at both ages. Consumption rates for Pennask, Pre-mier, and Sun Valley, i n order of increasing rate of consumption were, respectively: at age 0, 0.22, 0.32 and 0.61 g dry feed/ g average l i v e experimental weight and at age 1, .07, .10, and 0.24. In both age groups the means were a l l significantly different from each other. The preference for SBM diets over FM diets was significant at age 0, but there was also a significant strain X protein (st X pr) interac-ti o n (Tables V,VI). Mean consumption of diets based on the SBM and FM sources of protein were 0.38 and 0.32 g dry feed/ g average experimental weight, respectively. At age 1 these two kinds of diet had a s i m i l a r rate of consumption (about 0.12 g; Table VI). With respect to protein concentration, Age 0 trout preferred 20 % protein diets (mean = 0.43 g) to 30% protein diets (.34 g dry d i e t / g average l i v e weight), while no preferance was observed among age 1 strains (Table VII). 4.2.1.1 Strain X Diet Interactions for Consumption Tables VI and VII i l l u s t r a t e why s i g n i f i c a n t or near s i g n i f i c a n t i n t e r a c t i o n s were observed for s t r a i n x protein source and s t r a i n x protein concentration (Table V). However, i n spite of the s i g n i f i c a n t i n t e r a c t i o n at both ages no change of rank ac t u a l l y took place among -74-Table V. S i g n i f i c a n t e f f e c t s and interactions involving s t r a i n in the analysis of variance of feed consumption for rainbow trout. Source of Variation Test of Significance^ Age 0 Age 1 Main Effects Strain *** *** Feeding level *** *** Protein Source *** NS Protein Concentration *** NS Interactions 2 St X F l NS NS St X Pr ** * St X Co * 0.052 ANOVA was carried out on log-transformed data (g dry feed/ g average l i v e experimental weight/ 21 days) . S t a t i s t i c a l s i g n i f i c a n c e at the 5%, 1% and 0.1% l e v e l of probability i s indicated by *, **,and ***, respectively. Refer to appendix (Table VIA) for complete ANOVA table. -75-Table VI. Analysis of daily feed consumption i n relation to source of dietary protein for three strains of rainbow trout . Strain Amount Consumed^ (g dry diet/ g average li v e weight/ 21 days) FM2 SBM Age 0 Sun Valley Pennask Premier 0.61 a 0.18 e 0.29 c 0.60 a 0.25 d 0.35 b Age 1 Sun Valley Pennask Premier 0.24 a 0.08 c 0.10 c 0.24 a 0.07 c 0.11 b Significant strain x protein source interaction: p<0.01 (age 0), p<0.05 (age 1). Standard error of the mean: 0.11 (age 0), 0.01 (age 1). Means having the same l e t t e r subscript were not significantly different. Fishmeal prepared from white f i s h f i l l e t s (age 0), or a combination of fishmeal and soybean meal were the major sources of dietary protein in FM and SBM diets, respectively. -76-Table VII. Analysis of t o t a l feed consumption i n r e l a t i o n to d i e t -ary protein concentration f o r s t r a i n s of rainbow trout.^ S t r a i n Amount Consumed (g dry d i e t / g average l i v e weight/ 21 days) 20% protein 30% protein Age 0 Sun Valley Pennask Premier 0.70 a 0.22 e 0.36 c 0.52 b 0.21 e 0.29 d Age 1 Sun Valley Pennask Premier 0.25 a 0.08 c,d 0.09 b,c 0.23 a 0.07 d 0.11 b S i g n i f i c a n t s t r a i n x p r o t e i n c o n c e n t r a t i o n i n t e r a c t i o n : p<0.05 (age 0).Near s i g n i f i c a n t p=0.052 (age 1). Standard error of the mean: 0.11 (age 0), 0.01 (age 1). Means having the same l e t t e r subscript were not s i g n i f i c a n t l y d i f f e r e n t . -77-strains. Table VI shows that Sun Valley did not respond to a change of protein source at age 0. On the other hand Pennask as well as Premier f i s h increased t h e i r mean consumption by 0.6-0.7 g d i e t / g average BW in response to a change from FM to SBM at age 0. Consumption by Sun Valley and Pennask f i s h was l i t t l e affected by a change i n protein source at age 1. Consumption did not change as much with changing protein concentra-t i o n at age 1, as i t did at age 0, where both SV and PL ate s i g n i f i -cantly less feed of 30 % protein than the 20 % crude protein diet (Table VII). At age 1 there was a near-significant strain X concentration (st X co) interaction due to the increased rate of consumption of 30% protein diets by Premier. It should be noted (Table II), that GE of 30 % protein diets was only slightly higher than comparable 20 % diets - by 5 % for FM, and by 2.5 % for SBM diets. Meanwhile, age 0 consumption declined by 25 % and 19.4 % for SV and PL, respectively, i n going from diets of lower to higher concentration of crude protein. The Pennask consumption rate remained constant under, the effect of the same experimental va r i -able (Table VII). Pennask consumption of diet remained low and constant with changing concentration in both age classes. 4.2.2 Variation of Growth Rate Growth rate was expressed as relative growth (% body weight or fork length per day) to enable direct comparison among strains differing in mean i n i t i a l body weight. Mean i n i t i a l and f i n a l body weights (live and dry), and fork lengths (age 1 fish only) for each strain, averaged over a l l dietary treatments, are presented in Table VIII. Table IX summarizes the results of analysis of variance of relative growth for main effects -78-Table VIII. Mean weights and lengths of rainbow trout of three strains in a 21-day feeding t r i a l . Strain Mean Weight or Length Live Weight Dry Weight I n i t i a l Final I n i t i a l Final Age 0 mg mg mg mg Sun Valley 587 1,045 122 218 (9) (60) (2) (U) Pennask 1,769 1,895 378 379 (16) (43) (3) (12) Premier 2,691 3,301 580 765 (15) (106) (3) (27) Age 1 8 g g g Sun Valley 52.76 61.19 14.39 16.41 (1.29) (2.27) (0.35) (0.68) Pennask 39.62 40.86 10.16 10.41 (0.77) (0.82) (0.20) (0.27) Premier 40.18 42.12 10.91 10.92 (0.83) (i.oi) (0.22) (0.30) Fork Length (cm) Age 1 I n i t i a l Final Sun Valley 16.6 17.3 (0.1) (0.1) Pennask 16.3 16.3 (0.1) (0.1) Premier 16.3 16.4 (0.1) (0.1) Standard error in parentheses; N=8 treatment groups per strain. -79-Table IX. S i g n i f i c a n t main e f f e c t s and i n t e r a c t i o n s i n v o l v i n g s t r a i n i n the analysis of variance of r e l a t i v e growth i n rainbow trout under eight dietary environments. Source of V a r i a t i o n Test of S i g n i f i c a n c e f o r Relative Growth L i v e T i s s u e Dry T i s s u e Fork Length Age 0 Age 1 Age 0 Age 1 Age 1 Main E f f e c t s S t r a i n *** *** *** Feeding l e v e l *** *#* Protein Source # ns * * ns Protein Concentration ns * ns ns ns I n t e r a c t i o n s 2 St X F l •5BS- ### * * St X Pr ns ns * ns ns St X Co ns ns ns ns ns * f ** > *** i n d i c a t e s t a t i s t i c a l s i g n i f i c a n c e at the 5%, 1% and 0.1% l e v e l of p r o b a b i l i t y , respectively. Refer to appendix (Table VIIIA, and VIIIB) for complete ANOVA tables . -80-and s t r a i n - r e l a t e d i n t e r a c t i o n s of the f i r s t order. Table IX shows that s t r a i n and feeding l e v e l both exerted a consis-tent and highly s i g n i f i c a n t e f f e c t on r e l a t i v e growth, expressed ei t h e r as weight (R w) or as fork length (R^). The i n t e r a c t i o n of these f a c t o r s ( s t X f l ) was a l s o h i g h l y s i g n i f i c a n t , p a r t i c u l a r l y f o r age 0 f i s h . In l i v e and dry tissue growth age 0 f i s h had co n s i s t e n t l y higher l e v e l s of s i g n i f i c a n c e f o r t h i s i n t e r a c t i o n . At the other extreme, Table IX shows that protein concentration (co) was s i g n i f i c a n t f o r r e l a t i v e growth only i n one case, i.e. l i v e t i s s u e growth at age 1. Moreover, the s t X co i n t e r a c t i o n was not s i g n i f i c a n t f o r e i t h e r age group. Protein source had a more moderate e f f e c t than those mentioned above on r e l a t i v e growth, being s i g n i f i c a n t a t the 5 % l e v e l f o r both age groups, i n a d d i t i o n to producing a s i g n i f i c a n t s t X pr i n t e r a c t i o n f o r age 0 growth as dry t i s s u e . Responses to i n d i v i d u a l dietary treatments are shown i n Figures 11 and 12. In g e n e r a l , age 0 f i s h had a g r e a t e r c a p a c i t y f o r growth (both as l i v e and dry t i s s u e ) than y e a r l i n g s of the same s t r a i n , and s t r a i n rankings were generally consistent over the two ages. At 2.77 % and 0.69 % BW per day a t ages 0 and 1, r e s p e c t i v e l y , Sun V a l l e y f i s h had an o v e r a l l t h r e e times g r e a t e r mean growth r a t e than i t s n e a r e s t r i v a l (Premier, a t 0.96 % and 0.22 %, r e s p e c t i v e l y ) when r e l a t i v e growth was expressed as l i v e t i s s u e (Table X). Table XIa also shows the s i g n i f i c a n t main e f f e c t s and i n t e r a c t i o n s f o r r e l a t i v e growth as fork length (R^. S t r a i n and feeding l e v e l were s i g n i f i c a n t as main e f f e c t s and only the only s i g n i f i c a n t i n t e r a c t i o n was f o r s t X f l . T a b l e X shows t h a t R^ was c o n s i s t e n t l y l e s s t h a t R w. Rankings among the t h r e e s t r a i n s f o r l i n e a r growth (R^) a t age 1 d i d , -81-Figure 11. Relative growth as l i v e weight (% body weight/ day) i n age 0 and age 1 rainbow trout of three strains. 50% SATIATION-FED (AGEO) Legend (21 Son v j v , Ka r»cnUr Lain 9 a. K 9 > I J • 1 i I FM-1 FV4-2 SBM-1 S B M - 2 Dietary Vvabnenl 50% SATIATION-FED (AGE 0 a <U-§i 0.J-0.0--0.1 J FM-H ru-12 SBM-n SBMH2 Dietary fmhnent SATIAT10N-rTD (AGE 0) FM-1 FM-2 SBM-1 SBM-2 Dietary treatment SATIATION-FED (AGE D 111! S I 5 ^ i FM-H F M I 2 semt Dietary Teatmenl SBM 12 -83-F i g u r e 12. R e l a t i v e growth as dry weight (% body weight per day) i n age 0 and age 1 rainbow t r o u t o f t h r e e s t r a i n s . - 8 4 -Relativ* growth (7. pur day) it a p 8 ft ? 2 i R«loltv« growth (Z par day) o CO o IS o Relotlvs growth (JJ p«r doy) ? 5 Ralotlv* growth (55 par day) 72 777A o f -85-however, conform to the age 0 pattern for Rw, but apparently not for the age 1 pattern based on dry tissue growth. There i s a strong possibility that the lack of a proper time 0 carcass analysis at age 1 has produced this inconsistency of growth ranks for l i v e and dry tissue at age 1. 4.2.2.1 Strain X Diet Interactions for Growth Table Xia shows that, i n a l l s t r a i n s , a doubling of feed intake (i.e., from 50 % to 100 % satiation) resulted i n a marked increase i n Rw, although not to the same degree i n a l l s t r a i n s . Thus the s t r a i n X feeding l e v e l (st X f l ) i n t e r a c t i o n was s i g n i f i c a n t for both l i v e and dry measures of Rw at both ages. This interaction was stronger in age 0 fish, however, as indicated by the higher associated significance levels (Table Xia). The lack of a significant growth response in Pennask, when feeding l e v e l was increased at age 0, i s what caused the s i g n i f i c a n t i n t e r a c t i o n to occur as l i v e and dry growth. In absolute terms the increase i n R w was always greater i n Sun Valley, the s t r a i n with the highest rate of feed consumption (Fig. 10). Therefore, the significant interactions observed, being based on absolute increase - which in turn i s related to feed intake - may not r e f l e c t a more e f f i c i e n t physio-l o g i c a l response i n Sun Valley. Indeed i f one looks at the r a t i o of growth at 50 % satiation to growth at 100 % satiation, i t appears as i f there was a more positive response in the wild fish. Table Xlb shows that both Sun Valley and Premier (high consumers) responded with increased R^  with a doubling of ration. Pennask yearlings failed to respond to the increase in ration, which in fact represented less additional feed than for other strains (Figure 10). The interaction of strain with protein source (st X pr) was signi--86-Table X. Relative growth i n weight and length for age 0 and age 1 rainbow trout of three strains fed four diets at two feeding levels for 21 days. 1 Strain Relative Growth2 % Body Weight per day Live Tissue Dry Tissue % Fork Length per day Age 0 Sun Valley 2.77 (0.06) a 2.98 (0.08) Pennask 0.32 (0.06) c 0.22 (0.08) Premier 0.96 (0.06) b 1.30 (0.08) Age 1 Sun Valley 0.69 (0.03) a 0.60 (0.04) Pennask 0.15 (0.03) b 0.11 (0.04) Premier 0.22 (0.03) b 0.00 (0.04) 0.17 (0.01) a -0.02 (0.01) c 0.02 (0.01) b 1 Each age group, and length/ weight group was analyzed by different ANOVA, indicated by a different standard error. 9 Means having the same letter subscript were not significantly d i f f e r -ent. Standard error of the mean (of 8 dietary treatments) shown in parenthesis. -87-Table Xia. E f f e c t of feeding l e v e l on r e l a t i v e growth as l i v e or dry tissue in age 0 and age 1 rainbow trout of three st r a i n s , fed four diets at two feeding levels for 21 days. Strain Relative Growth (% BW / day) Live Tissue Dry Tissue 50' 100 50 100 Age 0 Sun Valley Pennask Premier Age 1 Sun Valley Pennask Premier 2.08 b (0.08) 0.21 e (0.08) 0.61 d (0.08) 0.42 b (0.04) 0.05 d (0.04) 0.08 d (0.04) 3.45 a (0.08) 0.43 d,e (0.08) 1.30 c (0.08) 0.96 a (0.04) 0.24 c (0.04) 0.36 b,c (0.04) 2.19 b (0.11) 0.08 e (0.11) 0.94 d (0.11) 0.29 b (0.06) -0.04 c (0.06) -0.20 c (0.06) 3.77 a (0.11) 0.37 e (0.11) 1.67 c (0.11) 0.92 a (0.06) 0.25 b (0.06) 0.20 b (0.06) 1 Age groupings for li v e or dry tissue growth were analyzed by separate ANOVA. Standard error of means (of four dietary treatments) in paren-thesis. 2 Percentage of satiation feeding for the respective strains. -88-Table Xlb. Effect of feeding level on relative growth as fork length in age 1 rainbow trout of three strains fed one of four diets for 21 days. Strain Relative Growth^ Feeding Level (% Satiation) 50 100 Sun Valley Pennask Premier 0.10 b 0.0 c 0.0 c 0.24 a 0.0 c 0.05 b Means having the same letter subscript were not significantly d i f f e r -ent. Standard error of the mean = 0.02. -89-Table XII. E f f e c t of protein source on r e l a t i v e growth as l i v e or dry tissue in age 0 and age 1 rainbow trout of three strains, fed four diets at two feeding levels for 21 days. Strain Relative Growth''" (% BW / day) Live Tissue Dry Tissue FM2 SBM FM SBM Age 0 Sun Valley 2.75 a (0.08) 2.78 a (0.08) 3.01 a (0.11) 2.95 a (0.11) Pennask 0.13 d (0.08) 0.51 c (0.08) -0.08 d (0.11) 0.53 c (0.11) Premier 0.90 b (0.08) 1.01 b (0.08) 1.25 b (0.11) 1.35 b (0.11) Age 1 Sun Valley 0.61 b (0.04) 0.78 a (0.04) 0.56 a (0.06) 0.66 a (0.06) Pennask 0.16 c (0.04) 0.13 c (0.04) 0.03 b (0.06) 0.18 b (0.06) Premier 0.18 c (0.04) 0.27 c (0.04) -0.07 b (0.06) 0.07 b (0.06) 1 Different age groups and liv e and dry tissue growth were analyzed by separate ANOVA. Standard error of means (of four dietary treatments) in parenthesis. 2 Dietary protein sources: FM, fishmeal ; SBM, soybean meal/fishmeal. -90-Table XIII. Effect of dietary protein concentration on relative growth as li v e or dry tissue in age 0 and age 1 rainbow trout of three strains fed four diets at two feeding levels for 21 days. Strain Relative Growth (% BW / day) Live Tissue Dry Tissue 20%2 30% 20% 30% Age 0 Sun Valley 2.66 a (0.08) 2.88 a (0.08) 2.84 a (0.11) 3.11 a (0.11) Pennask 0.25 c (0.08) 0.39 c (0.08) 0.18 c (0.11) 0.27 c (0.11) Premier 1.02 b (0.08) 0.89 b (0.08) 1.38 b (0.11) 1.23 b (0.11) Age 1 Sun Valley 0.69 a (0.04) 0.69 a (0.04) 0.65 a (0.06) 0.56 a (0.06) Pennask 0.10 c (0.04) 0.19 b,c (0.04) 0.09 b (0.06) 0.13 b (0.06) Premier 0.15 b,c (0.04) 0.30 b (0.04) -0.07 b (0.06) 0.06 b (0.06) Different age groups and live or dry tissue growth were analyzed by separate ANOVA. Standard error of means (of four dietary treatments) in parenthesis. 2 Percent crude protein of diet. -91-f i c a n t only for R w a s dry tissue i n age 0 f i s h (Table XII). While Sun Valley and Premier strains responded similarly, and without any change i n R w» to the a change of dietary protein source, age 0 Pennask f i s h significantly increased growth rate under diets based on soybean. Growth as dry tissue increased from a negative rate (mean= -0.08 % / day) on fishmeal diets to a value of 0.53 % BW per day on SBM/FM-containing d i e t s (Table XII). On a l i v e t i s s u e b a s i s , these values were, respectively, 0.13 % and 0.51 % BW per day. Si m i l a r increases did not occur for t h i s s t r a i n within the experimental period when f i s h were tested at age 1, although a l l strains showed some increased growth rate. The overall response to increasing protein concentration were un-clear when considering both age groups, and l i v e and dry R w (Table XIII). At age 0 there was a clear trend towards higher relative growth ( l i v e and dry) for Sun Valley and Pennask on the higher protein diets. The opposite was true for Premier. This pattern was totally obscured in age 1 fish, where Premier appeared to show the reverse trend to i t s age 0 counterpart, Pennask remained as before, and Sun Valley showed e v i -dence of declining growth with increased dietary protein concentration (Table XIII). There were no significant strain X protein concentration (st X co) interactions for R w (Table IX). 4.2.3 Variation of Carcass Composition and Condition Factor 4.2.3.1 Carcass Composition Table XIV shows the i n i t i a l carcass composition i n terms of % moisture, % crude protein, % fat (ether extract), and % ash, for age 0 and age 1 rainbow trout. Tables XV-XVIII inclusive show results of car-Table XIV. Proximate composition of carcasses of rainbow trout of three strains at the start of feeding t r i a l s conducted at age 0 and age 1. Strain Percent of Dry Matter^ Moisture 2 Crude Protein Crude Fat Ash Age 0 Sun Valley 80.57 64.99 18.95 9.17 (-) (0.07) (0.62) (0.10) Pennask 78.66 65.89 17.71 10.72 (-) (0.74) (0.82) (0.21) Premier 78.45 65.74 18.89 10.25 (-) (1.01) (0.63) (0.06) Age 1 Sun Valley 72.73 61.84 24.53 9.79 (0.10) (0.67) (0.01) (0.26) Pennask 74.35 63.49 22.76 8.16 (0.11) (0.63) (0.15) (0.34) Premier 72.85 64.22 22.10 9.74 (0.02) (0.47) (0.20) (0.33) 1 Standard error i n parentheses; N=2 l o t s per s t r a i n , except Pennask and Premier, age 0 (N=3 lots). 2 Age 0 samples were handled as a single lot for moisture determination. -93-cass analysis at the end of the 21-day feeding t r i a l s for each age group. Only data from s a t i a t i o n - f e d groups have been included i n t h i s analysis. Sun Valley trout had a higher mean % moisture than the wild strains (80.6 % versus 78.5-78.7 %) at age 0 but not at age 1, where i t equalled Premier and was actually inferior to Pennask. Size differences among fish of the different strains (Table XIV) w i l l account for much of this variation; predictably, moisture content was inversely proportional to body weight according to the data in this table. Between 93 and 94 % (age 0) and 94-96 % (age 1) of total dry matter consisted of protein, f a t and ash (Table XIV). On a dry matter basis, s l i g h t but inconsistent differences were d i s c e r n i b l e i n percent com-posit i o n as protein, f a t and ash. This inconsistency might be due, i n part, to the variable s i z e - r e l a t i o n s h i p among st r a i n s at the two d i f -ferent ages. At age 0 the smallest s t r a i n , Sun Valley , had lower protein and ash content and a higher fat content. The higher f a t and lower percent protein obtained at the start of the experiment at age 1 also. Percent ash did not , however, conform to the age 0 pattern. Differences among strains with respect to the three major compo-nents of the dry carcass were more consistent at the end of feeding to s a t i a t i o n for 21 days. This was so i n both ages as indicated i n the Tables XVI-XVIII i n c l u s i v e . F i n a l moisture content appeared, as i n i n i t i a l composition, to be size-related according to an inverse function (table XV). Smaller fish consistently had higher moisture content both i n the comparison of s t r a i n s within an age/size group and i n the com-parison of the different age/size groups. Table XVI shows that f i n a l % -94-Table XV. Final carcass moisture content of age 0 and age 1 rainbow trout of three strains fed four experimental diets at two feeding levels for 21 days. Strain Percent of Dry Matter Fish Meal Diets Soybean Meal Diets 20% l 30% 20% 30% Mean Age 0 Sun Valley 78.86 78.36 78.98 78.74 78.74 Pennask 79.70 79.20 78.06 78.43 78.75 Premier 76.05 76.69 76.34 76.07 76.29 Age 1 Sun Valley 72.40 72.20 72.84 73.84 72.82 Pennask 74.19 75.19 73.38 74.31 74.27 Premier 73.84 74.02 73.58 73.66 73.78 Concentration of crude protein in the diet. Age 0 and age 1 diets were similar (Table I l a ) . -95-Table XVI. Final carcass crude protein content of age 0 and age 1 rainbow trout of three strains fed four experimental diets at two feeding levels for 21 days. Strain Percent of Dry Matter Fish Meal Diets Soybean Meal Diets 20%! 30% 20% 30% Mean Age 0 Sun Valley 55.70 55.71 56.31 57.21 56.23 Pennask 62.66 63.46 60.85 62.74 62.43 Premier 57.23 59.81 58.00 59.01 58.51 Age 1 Sun Valley 56.83 55.82 56.69 60.30 57.41 Pennask 63.63 65.07 63.63 63.89 64.06 Premier 65.24 61.73 63.31 62.99 63.32 Concentration of dietary crude protein; age 0 and age 1 diets were similar (Table I l a ) . Table XVII. Final carcass crude fat content of age 0 and age 1 rainbow trout of three strains fed four experimental diets at two feeding levels for 21 days. Strain Percent of Dry Matter Fish Meal Diets Soybean Meal Diets - 20%1 30% 20% 30% Mean Age 0 Sun Valley 27.55 27 .98 28 .18 28. ,78 28 .12 Pennask 17.95 17 .86 21 .15 20. ,07 19 .26 Premier 24.98 23 .87 25 .07 26. ,32 25 .06 Age 1 Sun Valley 30.64 30 .94 31 .79 27. ,88 30 .31 Pennask 23.91 21 .20 25 .43 23. ,11 23 .41 Premier 23.32 24 .41 23 .46 24. ,92 24 .03 Concentration of dietary crude protein; age 0 and age 1 diets were similar (Table I l a ) . -97-Table XVIII. Final carcass ash content of age 0 and age 1 rainbow trout of three strains fed four experimental diets at two feeding levels for 21 days. Strain Percent of Dry Matter Mean Fish Meal Diets Soybean Meal Diets 20%! 30% 20% 30% Age 0 Sun Valley 5.86 5.38 5.82 5.56 5.66 Pennask 10.71 10.56 9.45 9.51 10.06 Premier 8.02 8.37 7.87 7.81 8.02 Age 1 Sun Valley 8.35 7.04 7.36 8.28 7.76 Pennask 8.85 9.80 8.28 9.93 9.22 Premier 9.41 8.92 8.93 9.33 9.15 Concentration of dietary crude protein; age 0 and age 1' diets were similar (Table I l a ) . -98-Table XIX. Mean change i n percent carcass protein, fat, ash and mois-ture in age 0 and age 1 rainbow trout of three s t r a i n s fed four diets to satiation for 21 days. Strain Percent Change Protein Fat Ash Moisture Age 0 Sun Valley -8.78 9.17 -3.52 -1.80 (0.36) (0.26) (0.11) (0.15) Pennask -3.46 1.55 -0.66 0.19 (0.56) (0.81) (0.34) (0.37) Premier -7.23 6.17 -2.23 -2.16 (0.57) (0.50) (0.13) (0.15) Age 1 Sun Valley -4.43 5.78 -2.03 0.09 (0.99) (0.85) (0.33) (0.37) Pennask 0.57 0.65 1.06 -0.08 (0.34) (0.88) (0.39) (0.37) Premier -0.90 1.93 -0.59 0.93 (0.73) (0.38) (0.13) (0.10) 1 Standard error in parenthesis; N= 4 dietary treatments (Table I l a ) . -99-protein was always lowest i n Sun Valley fish, regardless of body weight, and largest in Pennask. Percent fat i n the carcass, on the contrary, was highest always in Sun Valley by 3-9 % and least i n Pennask (Table XVII). Ash content varied i n direct relation to protein under the same circum-stances (Table XVIII). Table XIX shows changes in carcass protein, fat, moisture and ash which occurred during the 3-week feeding period. Q u a l i t a t i v e l y , the responses at both ages were similar for protein and fat, but more var i -able for the change in percent moisture and ash. Quantitatively, age 0 and age 1 populations differed by the latter changing less i n percentage protein, fat, moisture and ash. Means change in body composition shown in Table XIX were each calculated from the values for the four dietary treatments under satiation feeding (Table l i b ) . In both fingerling and yearling trout, percent protein decreased by about the same amount as carcass fat increased (Table XIX); the one exception was age 1 Pennask, whose percent carcass protein increased. Negative changes i n percent carcass ash i n a l l other s t r a i n s and ages indicate that soft tissue growth occurred, or that the amount of soft tissue growth exceeded that of hard tissue. Changes in moisture content were small (age 1) to negligible (age 0) (Table XIX). Strain-dependent responses, shown i n Table XIX, appear to be i n d i r e c t response to feed consumption (see Fig. 10). Thus the absolute changes occurring in % protein and fat, both at age 0 and at age 1, were greatest i n Sun Valley and least i n Pennask despite d i f f e r e n t size relationships (as mean body weight) among the three strains. -100-Table XX. Change of condition factor in three strains of age 1 rainbow trout fed four diets at two feeding levels for 21 days. Strain Condition Factor^ I n i t i a l Final Sun Valley 1.13 b 1.17 a Pennask 0.90 c 0.94 c Premier 0.92 c 0.95 c Condition factor = 1000 . body weight (g)/ fork length (cm) J. Standard error of the mean (of 4 dietary treatments) = 0.01. Means having the same letter subscript were not significantly different. -101-Table XXI. Effect on condition factor of strain of rainbow trout and diet at age l . 1 9 Strain Condition Factor Diet FM.ll FM.12 SBM.11 SBM.12 Sun Valley 1.10 b Pennask 0.94 c Premier 0.92 c 1.20 a 1.18 a 1.12 b 0.93 c 0.90 c 0.92 c 0.95 c 0.94 c 0.94 c There was a significant strain X diet interaction (p<0.05). Mean of four dietary treatments including two feeding levels ( s a t i -ation and 50% satiation). Standard error = 0.02. FM.ll, and FM.12 = Fishmeal based diets containing 20% and 30% crude protein, respectively; SBM = Fishmeal plus soybean meal. -102-Table XXII. Change of coefficient of variation for condition factor in three strains of age 1 rainbow trout fed four diets for 21 days. Strain Coefficient of Variation''' I n i t i a l Final Sun Valley 9.06 a 6.68 b Pennask 5.81 b 6.57 b Premier 5.70 b 6.31 b Standard error of the mean =0.57; N= 8 ( 4 diets x 2 feeding levels. Diets are shown in Table I l a . Means having the same letter subscript were not significantly different. -103-4.2.3.2 Condition Factor Differences in condition factor (CF), calculated as 1,000 times the r a t i o of body weight (g) to fork length (cm) raised to the cubic power (Table XX), indicated a distinction between wild and domestic strains. Table XX shows that condition factor for SV d i f f e r e d s i g n i f i c a n t l y , both at the s t a r t and end of the 21 day feeding period, from that for the wild strains. The latter had almost identical CF at both times. A non-significant time X s t r a i n i n t e r a c t i o n (p=0.84) showed that a l l strains increased i n condition by a similar proportion over the 21 day period. There was however, a significant strain X diet interaction (p <.05) caused by a more positive response of condition factor i n SV to diets FM-2 and SBM-1 (p <.05), compared with other strains (Table XXI). Coefficients of variation for condition factor were i n i t i a l l y s i g -n i f i c a n t l y d i f f e r e n t (p <0.05; Table XXII) , however, by the end of the 21-day period a l l strains had a similar variation i n condition factor. There was a s i g n i f i c a n t (p < .05) s t r a i n x diet (st X di) i n t e r a c t i o n for coefficient of variation of condition factor. This was caused by a large reduction i n c o e f f i c i e n t of v a r i a t i o n among the Sun Valley f i s h r e l a t i v e to the wild strains (Table XXII). The l a t t e r experienced a s l i g h t increase i n c o e f f i c i e n t of v a r i a t i o n for t h i s t r a i t over the feeding period at age 1. 4.3 VARIATION OF EFFICIENCY OF NUTRIENT UTILIZATION AMONG STRAINS OF RAINBOW TROUT 4.3.1 Strain Effects The re s u l t s of analysis of variance for a number of e f f i c i e n c y parameters i s shown i n Table XXIII. For feed conversion e f f i c i e n c y -104-Table XX I I I . Strain means and rankings for various efficiency-related traits in rainbow trout fingerlings (age 0) and yearlings (age 1) of three strains, receiving four diets at two feeding levels for 21 days. Trait 1 Feed Protein Productive Conversion Efficiency Protein Efficiency Ratio Value (FCE) (PER) (PPV) Net Energy Net Protein Conversion Conversion Efficiency of Energy (NPE) (EC) (NCE) Age 0 Sun Valley 0.91 I,a 3.42 I,a 0.39 I,a (0.04) (0.18) (0.01) 0.88 I,a (0.02) 0.26 I,a (0.01) 0.43 II,b (0.01) Pennask Premier Age 1 0.26 III.c 0.95 I I I.c 0.03 I I I.c 0.68 III.c 0.04 III.c 0.38 I I I.c (0.04) (0.18) (0.01) (0.02) (0.01) (0.01) 0.58 II,b 2.23 II,b 0.27 II,b 0.79 Il.b 0.22 II,b 0.60 I,a (0.04) Sun Valley 0.56 I,a (0.04) (0.18) 2.29 I.a (0.17) (0.01) (0.02) (0.02) 0.21 II,a 0.38 II,a 0.21 I,a (0.04) (0.04) (0.03) (0.01) 0.36 I,a (0.03) Pennask Premier 0.35 III,b 1.31 III,b 0.31 I,a 0.41 I,a (0.04) (0.17) (0.04) (0.04) 0.09 II,b 0.33 II,a (0.03) (0.03) 0.37 II,b 1.41 II,b Il l . b 0.34 III,a 0.00 III.c 0.25 III,a (0.04) (0.17) (0.04) (0.04) (0.03) (0.03) 1 Strain ranks are indicated by roman numerals; means having the same letter subscript were not significantly different. Standard error of the mean (of 8 dietary treatments) is indicated in parenthesis. -105-(FCE), and protein efficiency ratio (PER) rankings for the strain means were consistent over the two ages. For other efficiency t r a i t s there was a change i n s t r a i n rank with age; though i n some of these cases, e.g. net protein e f f i c i e n c y (NPE) and net conversion of energy (NCE), there was no s t a t i s t i c a l strain difference. Table XXIII shows significant difference among a l l strains for feed conversion e f f i c i e n c y , and protein e f f i c i e n y r a t i o at age 0. For both tr a i t s Sun Valley fish had the highest mean value, followed i n order by Premier and Pennask. At age 1 the difference between the wild strains for these t r a i t s was no longer s t a t i s t i c a l l y s i g n i f i c a n t , while the domestic s t r a i n maintained a s t a t i s t i c a l margin over the l a t t e r two. There was roughly a 2:1 ratio i n feed conversion efficiency between the age 0 st r a i n s of successive rank, and a nearly s i m i l a r quantitative r e l a t i o n s h i p for PER. These differences i n means were considerably smaller at age 1 (Table XXIII). A maximum e f f i c i e n c y of feed conversion approaching unity (0.91) was recorded for Sun Valley at age 0. For t h i s s t r a i n and Premier the e f f i c i e n c y of feed conversion dropped at age 1 by about one half. In contrast, the mean feed conversion efficiency for Pennask fis h improved s l i g h t l y at age 1 (0.35) over the age 0 mean (0.26). For Sun Valley and Premier the f a l l in conversion efficiency of age 1 fish coincided with a similar reduction in feed intake at satiation (see Fig. 10). The similar degree of reduction i n feed intake was also noted for Pennask, but this did not translate into the corresponding decline i n feed conversion efficiency as observed elsewhere. The same pattern of strain response with age was observed in the behaviour of PER (Table XXIII). In regard to the actual conversion of dietary protein and energy -106-Table XXIV. Stat i s t i c a l significance of main effects and interactions invol-ving strain for various efficiency-related t r a i t s in age 0 and age 1 rain-bow trout of different strains, receiving four diets at two feeding levels for 21 days. Source of Variation Trait Age FCE PER PPV NPE EC NCE Test of Significance Main Effects Strain 0 *** ### 1 ** *** ns ns Feeding level 0 ns ns ** *** * *** 1 ** ns *** ns Protein Source 0 ns ns *** ns ns 1 ns ns * ns * * Protein Concentration 0 ns ns *## 1 ** ns ns .08 ns ns Interactions St X F l 0 ns ns ** ns ns * 1 ns ns * ns ns ns St X Pr 0 * .056 ns ns * 1 ns ns ns ns ns .073 St X Co 0 .067 ns ns .051 * ns 1 .059 ns .082 ns ns FCE, Feed Conversion Efficiency: mean BW gain (g)/g dry feed consumed; PER, Protein Efficiency Ratio: mean BW gain (g)/g protein consumed; PPV, Productive Protein Value: average gain in carcass protein (g)/g protein consumed; NPE, Net Protein Efficiency: (g gain in carcass protein + g loss in protein on fasting)/g protein consumed; EC, Energy Conversion: Kcal carcass energy gain/ Kcal energy consumed; NCE, Net Conversion of Energy: (Kcal carcass energy gained + Kcal carcass energy lost on fasting)/ Kcal gross energy consumed. #f ** > ##* indicate s t a t i s t i c a l significance at the 5%, 1% and 0.1% level of probability, respectively. Refer to appendices for complete ANOVA tables. -107-into the respective carcass components, a different picture emerged in the comparison of strains. Apart from net conversion of energy (NCE), age 0 strain rankings for these traits were exactly the same as for food conversion efficiency and PER for the same age of fish (Table XXIII). At age 1, on the other hand, many of these ranks reversed completely (PPV, NPE), or for the wild strains only (Energy Conversion, NCE). Pennask lake f i s h ranked l a s t at age 0 for PPV and NPE, but ranked f i r s t for these traits at age 1. For NPE and NCE , both parameters expressing e f f i c i e n c y with a correction for endogenous losses (i.e. an approximate correction for maintenance requirements for protein and energy, respectively), there was no s i g n i f i c a n t difference among str a i n s based on the mean values obtained at age 1. In the case of NPE, means ranged from 0.41 to 0.34 (SEM = .03), and for NCE, 0.25 to 0.36 (SEM = 0.03). 4.3.2 Strain X Diet Interactions for Efficiency Traits Table XXIV shows, for a number of efficiency traits , the complete l i s t of significant main effects and first-order interactions involving strain. Only those interactions which are s t a t i s t i c a l l y significant, or nearly so, have been discussed below (Tables XXV-XXXI). St X F l interactions were not observed for any t r a i t s other than PPV in age 1 fish, but significant interactions existed for PPV and NCE at age 0 (Table XXIV). As a main eff e c t at age 0, feeding l e v e l had a significant to highly significant effect on Protein and Energy conver-sion (gross and net), but not on FCE and PER. At age 1, a l l t r a i t s except net protein and energy conversion (NPE and NCE) were s i g n i f i -cantly affected by a change in feeding level. -108-The significant strain x feeding level interaction (p<.01) was due at age 0 to a decline i n mean PPV for Pennask, while for the other strains PPV remained constant over the two feeding levels. At age 1, a l l strains exhibited a decline in PPV at the lower feeding level, however, in this age group the Premier mean declined by a significantly greater extent (Table XXIV). In t h i s instance the i n t e r a c t i o n of st x f l was s i g n i f i c a n t at the 5% l e v e l . In conclusion the nature of the interac-tions was not consistent over the two age (size) categories of f i s h tested for PPV. There was no s i g n i f i c a n t or near s i g n i f i c a n t st x f l i n t e r a c t i o n for NCE at age 1 , although a s i g n i f i c a n t i n t e r a c t i o n was observed i n the age 0 fis h (Tables XXIV, XXVI). This latter interaction was due to a more dramatic increase i n net conversion of energy by Pennask from the satiation to 50 % satiation feeding. For SV and PL the mean increased by about one half, whereas for PN there was a doubling in NCE at the lower feeding level (Table XXVI). Table XXIV shows that there were five instances in which a s i g n i f i -cant or near s i g n i f i c a n t s t r a i n x protein i n t e r a c t i o n occurred for various measures of nutrient efficiency. Four out of the five occurred at age 0 (FCE, PER, PPV, and NCE). Only NCE had a near-significant interacton at age 1. Tables XXVII-XXX i l l u s t r a t e the nature of the interactions at age 0, and the age 1 i n t e r a c t i o n i s detailed i n Table XXXI. Fish of the Pennask strain had superior mean feed conversion e f f i -ciency on the SBM diets, compared to their performance on the FM diets: from 0.13 to 0.40 (Table XXVII). The other strains maintained a more or less constant rate of conversion over both protein sources. The same -109-Table XXV. Interaction of strain and feeding level effects on Protein Productive Value in age 0 and age 1 rainbow trout. Strain Protein Productive Value 1 Feeding Level (% Satiation) 100 50 Age 0 Sun Valley 0.38 Pennask 0.08 Premier 0.29 Age 1 Sun Valley 0.24 Pennask 0.39 Premier 0.12 a 0.39 a c -0.02 d b 0.25 b a,b 0.18 a,b a 0.23 a,b b -0.24 c Significant strain x feeding level interaction: p<0.01 (age 0), p<0.05 (age 1). Standard error of the mean: 0.01 (age 0), 0.05 (age 1). Means having the same letter subscript were not significantly different. -110-Table XXVI. Interaction of strain and feeding level effects on Net Conversion of Energy in age 0 rainbow trout. Strain 1 o Net Conversion of Energy Feeding Level (% satiation) 100 50 Sun Valley Pennask Premier 0.37 c 0.26 d 0.50 b 0.49 b 0.50 b 0.71 a Refer to Table XXIV for mathmatical expression. 2 Significant strain x feeding level interaction: p<0.05. Standard error of the mean (of 4 dietary treatments) 0.02. Means having the same letter subscript were not significantly different. - I l l -Table XXVII. Interaction of strain and protein source effects on Feed Conversion Efficiency in age 0 rainbow trout. Strain Feed Conversion Efficiency 1,2 Protein Source-^ FM SBM Sun Valley Pennask Premier 0.91 a 0.13 c 0.59 b 0.92 a 0.40 b 0.56 b Refer to Table XXIV for mathmatical expression. Significant strain x protein interaction, p<0.05. Standard error of the mean (of 4 dietary treatments) 0.05. Means having the same letter subscript were not significantly different. Fishmeal, FM; soybean meal/fishmeal, SBM (table Ila) -112-Table XXVIII. Interaction of strain and protein source effects on Pro-tein Efficiency Ratio in age 0 rainbow trout. Strain Protein Efficiency Ratio-*-*2 Protein Source^ FM SBM Sun Valley Pennask Premier 3.37 a 0.35 c 2.30 b 3.48 a 1.54 b 2.16 b 1 Refer to Table XXIV for mathmatical expression. Near significant strain x protein interaction, p=0.056. Standard error of the mean (of 4 dietary treatments) 0.025. Means having the same letter subscript were not significantly different. 3 Fishmeal, FM; soybean meal/fishmeal, SBM (table I l a ) . -113-Table XXIX. Interaction of strain and protein source effects on Protein Productive Value in age 0 rainbow trout. Strain Protein Productive Value 1' 2 Protein Source-FM SBM Sun Valley Pennask Premier 0.38 a -0.59 d 0.26 b 0.40 a 0.12 c 0.28 b 1 Refer to Table XXIV for mathmatical expression. Significant strain x protein interaction, p<0.001. Standard error of the mean (of 4 dietary treatments), 0.01. Means having the same letter subscript were not significantly different. 3 Fishmeal, FM; soybean meal/fishmeal, SBM (table I l a ) . -114-Table XXX. Interaction of strain and protein source effects on Net Conversion of Energy in age 0 and age 1 rainbow trout. Strain Net Conversion of Energy 1* 2 Protein Source-^ FM SBM Age 0 Sun Valley 0.43 c 0.44 c Pennask 0.36 c 0.40 c Premier 0.64 a 0.57 b Age 1 Sun Valley 0.36 a 0.36 a Pennask 0.21 a 0.45 a Premier 0.24 a 0.27 a 1 Refer to Table XXIV for mathmatical expression. 2 Significant strain x protein interaction, p<0.05, age 0; near s i g n i f i -cant at age 1 (p=0.073). Standard error of the mean (of 4 dietary treatments) 0.02, and 0.05 (ages 0 and 1 respectively. Means having the same letter subscript were not significantly different. 3 Fishmeal, FM; soybean meal/fishmeal, SBM (table I l a ) . -115-Table XXXI. Interaction of strain and protein concentration effects on Feed Conversion Efficiency in age 0 and age 1 rainbow trout. Strain Feed Conversion Efficiency ' Protein Concentration^ 20 % 30 % 1.07 a 0.37 c 0.59 b 0.57 a 0.51 a 0.49 a Age 0 Sun Valley Pennask Premier Age 1 Sun Valley Pennask Premier 0.76 b 0.16 d 0.56 b 0.55 a 0.20 b 0.24 b Refer to Table XXIV for mathmatical expression. 2 Near significant interaction for strain x protein concentration, p=0.67, age 0; p=0.059, age 1. Standard error of the mean (of 4 dietary treatments) 0.05 (ages 0 and 1). Means having the same letter subscript were not significantly different. 3 Formulated concentrations, see Table l i b for exact analysis. -116-kind of r e l a t i v e responses was responsible for the near-significant (p=0.056) and h i g h l y - s i g n i f i c a n t (p<.001) interactions for PER (Table XXVIII) and PPV (Table XXIX) at age 0, and for NCF (p=0.073) at age 1 (Table XXX). PER for Pennask f i s h increased about f i v e f o l d on soybean diets (from 0.35 to 1.54, Table XXVIII), and PPV t r i p l e d (0.06 to 0.12, table XXIX) under the same change from FM diets. Age 1 Pennask f i s h similarly doubled t h e i r net conversion of energy from 0.21 to 0.45 on soybean containing diets (Table XXX). Age 0 Pennask f i s h did not show t h i s pattern for net conversion of energy (Table XXX). Instead, the decline in the mean value of t h i s t r a i t for Premier, r e l a t i v e to the other strains was responsible for the significant interaction for NCE. Significant or near-significant interactions obtained in four d i f -ferent e f f i c i e n c y parameters (FCE, PER, NPE, and EC) with two of the traits (FCE and NPE) being equally affected at both ages (Table XXIV). Feed conversion efficiency had a n e a r - s i g n i f i c a n t i n t e r a c t i o n for ap-parently d i f f e r e n t reasons at the d i f f e r e n t ages (Table XXXI). Age 0 fish of both Sun Valley and Pennask strains were more efficient on the 30 % protein diet than on the 20 % crude protein diet, whereas Premier had a constant mean over these two classes of treatment. In contrast, f i s h of the Sun Valley s t r a i n had a constant rate of conversion at age 1, while f i s h of the two wild strains showed a dramatic increase in FCE on the higher protein diets (Table XXXI). The wild strains again responded i n a similar fashion to each other - as d i s t i n c t from Sun Valley - for three other t r a i t s ; i.e., PER (age 1, Table XXXII), NPE (age 0, Table XXXIII), and EC (age 0, Table XXXIV). In two of these cases (PER age 1, and EC age 0) the i n t e r a c t i o n of s t r a i n x concentration was s i g n i f i c a n t (p<0.05, Table XXIV), and very close to s i g n i f i c a n t i n the t h i r d (p=0.051; NPE, age 0). Sun valley had a decrease i n PER while the others showed a s l i g h t increase (Table XXXII). A l l strains declined in mean NPE with increasing concentration of dietary protein, at age 0, but Sun Valley did so to a lesser extent than the others (Table XXXIII). And while a l l strains increased i n energy conversion at age 0, Sun Valley did so to a significantly greater extent than Premier and Pennask (Table XXXIV). Pennask, on the other hand, showed a mean increase where the two other s t r a i n s declined i n mean value of NPE with increasing protein concentration,at age 1, a l -though the interaction was not significant (p=0.82). -118-Table XXXII. Interaction of s t r a i n and protein concentration e f f e c t s on Protein E f f i c i e n c y Ratio i n age 1 rainbow trout. S t r a i n Protein E f f i c i e n c y R a t i o 1 ' 2 Protein Concentration^ 20 % 30 % Sun Valley Pennask Premier 2.71 a 0.99 b 1.21 b 1.88 b 1.64 b 1.60 b 1 Refer to Table XXIV f o r mathmatical expression. 2 S i g n i f i c a n t i n t e r a c t i o n f o r s t r a i n x protein concentration at age 1, p<0.05. Standard error of the mean (of 4 dietary treatments) 0.25. Means having the same l e t t e r subscript were not s i g n i f i c a n t l y d i f f e r -ent . Formulated l e v e l s , for exact analysis see Table l i b . Table XXXIII. Interaction of strain and protein concentration effects on Net Protein Efficiency in age 0 and age 1 rainbow trout. Strain Net Protein E f f i c i e n c y 1 ' 2 Protein Concentration^ 20 % 30 % Age 0 Sun Valley Pennask Premier 0.92 a 0.79 b,c 0.86 a,b 0.85 a,b 0.56 d 0.73 c Age 1 Sun Valley Pennask Premier 0.43 a 0.38 a 0.46 a 0.33 a 0.44 a 0.23 a Refer to Table XXIV for mathmatical expression. 2 Near significant interaction for strain x protein concentration, p=0.051, age 0; p=0.082, age 1. Standard error of the mean (of 4 dietary treatments) 0.03, and 0.06 (ages 0 and 1, respectively). Means having the same letter subscript were not significantly different. ^ Formulated concentrations, see Table l i b for exact analysis. -120-Table XXXIV. Interaction of strain and protein concentration effects on Energy Conversion in age 0 rainbow trout. Strain Energy Conversion^»2 Protein Concentration^ 20 % 30 % Sun Valley Pennask Premier 0.22 b 0.03 c 0.21 b 0.30 a 0.04 c 0.23 b Refer to Table XXIV for mathmatical expression. Significant interaction for strain x protein concentration p<0.05. Standard error of the mean (of 4 dietary treatments) 0.01. Means having the same letter subscript were not significantly different. Formulated levels, for exact analysis see Table l i b . -121-5. DISCUSSION, PART I A. Metabolic losses as Gross Energy A f i s h deprived of food obtains the energy necessary to maintain e s s e n t i a l l i f e functions from catabolism of body reserves of fat and protein. The energy expenditure of fasting f i s h under resting conditions can be regarded as an approximation of basal metabolism (Cho et al., 1982). In the foregoing experiment on endogenous losses of body compo-nents, "apparent basal metabolism" was estimated and compared among the strains of rainbow trout by measurement of dry matter or gross energy losses from the carcass. Losses of dry matter and gross energy were not related to i n i t i a l weight by the same l i n e a r function i n the d i f f e r e n t strains (Figs. 5, 9). Sun Valley fish metabolized more of each of these components (had a higher coefficient of regression) at any given i n i t i a l dry weight above 3 or 4 grams, than did the other strains. This suggests a r e l a t i v e l y higher metabolic weight c o e f f i c i e n t "b" (from the equation for basal metabolism, measured as heat production = a.WD; see Smith, 1978a) for the Sun Valley strain. In the latter equation, "a" i s a constant, "W" i s body weight in kg, and "b" i s the metabolic weight exponent. Gross energy losses of a 40 g f i s h (10 g dry weight), based on the regression equations in Figure 9, ranged from 3.80 kcal/ kg/ day (15.88 k j / kg/ day) i n Pennask, to 7.86 k c a l / kg/ day (32.86 kJ/ kg/ day) for Sun Valley. In experiments conducted at 15°C, Smith e_t a l . (1978a) obtained values ranging from 54 to 136 kJ/ kg/ day for rainbow trout in the body weight range 0.85-57 g. Given that heat production of starving rainbow trout approximately doubles for every 10°C rise i n temperature, -122-the values for basal metabolic rate determined in this experiment con-ducted at 10°C are satisfactory. One may therefore conclude that there i s evidence of strain related differences in basal metabolic rate among the strains. To what extent such metabolic differences are due to body compo-s i t i o n , body shape or other factors cannot be answered i n the present study. Smith et al. (1978a) have indirect evidence that the surface area to volume r a t i o a f f e c t s metabolic heat loss i n a s i m i l a r manner as occurs in homeotherms. They observed an inverse relation between fis h weight and r e l a t i v e heat loss of starving rainbow trout of d i f f e r e n t sizes (0.85-57 g). This relationship was reflected i n the magnitude of the metabolic weight exponent "b" (above equation), which in the small-est f i s h (less than 4 g) the value of b was unity, while i n the larger category the value was 0.67. Stamina of brook trout, measured by the a b i l i t y to swim against a current, d i f f e r s between wild and domestic stocks; the former consistently outperformed the latter even when both populations were reared i n a hatchery (Vincent, 1960; Green, 1964). In relating these examples to the present experiments, reference can be made to clear differences between Sun Valley and the two wild strains i n terms of condition factor, which relates body weight to the cube of l i n e a r size. Table XX shows that at age 1 the domestic s t r a i n has more weight r e l a t i v e to the cube of fork length, and possibly a smaller surface area to volume ratio than the wild fish. Alternatively, the p o s s i b i l i t y of an e f f e c t of body composition on metabolic rate i s suggested by the parallelism of strain rank for fat content (Table XVII) and starvation losses of dry matter and gross energy (Sun Valley > Premier > Pennask). -123-Endogenous nitrogen excretion (ENE) provides only a conservative estimate of maintenance-N requirements i n carnivorous fishes (Savitz, 1969), since i t f a i l s to account for digestive and metablic losses incurred on ingestion of a protein containing meal (Luquet and Kaushik, 1981). In turn, carcass losses of protein i n the f a s t i n g f i s h approxi-mated endogenous losses of protein (Luquet and Kaushik, 1981). Protein losses in starving fish differed among the three strains (Fig. 8) when expressed in relation to i n t i a l body weight. The daily endogenous losses as protein or nitrogen, based on the regression equations i n Fig. 8 were, for a f i s h of 10 g dry weight (approximately 40 g l i v e weight, Table IVA) 17.86 mg protein day (2.857mg N) for Sun Valley, 3.381 mg protein day (0.541 mg N) for Pennask, and 12.33 mg protein day (1.97 mg N) for Premier. Converting this to mg N per day/ 100 g fish, we observe for Sun Valley, Pennask and Premier the values of 7.14, 1.35 and 4.93, respectively. These values compare favourably with values of 5-25 mg N / lOOg BW / day, reported by Nose (1971) for f i n g e r l i n g rainbow trout, assuming the strain of rainbow trout used in that study was more similar metabolically to the domesticated strain used in this study (Sun Valley) than to the native Pennask f i s h . Therefore, the greater demand for energy by f a s t i n g f i s h of the domestic s t r a i n concides with a greater degree of mobilization of carcass protein. B. Feed Consumption, Growth, Composition and Conversion The strain rankings for feed consumption support the hypothesis of metabolic differences among strains. At both ages (sizes), and i n spite of variable interstrain relationships for mean body weight (Table VIII), Sun Valley consistently ranked ahead of wild strains when feed consump--124-tion was expressed per 100 g body weight (Fig. 10). Protein source and protein concentration s i g n i f i c a n t l y affected feed consumption at age 0 - though not at age 1 (Table V). There were also s i g n i f i c a n t s t r a i n X protein source interactions (ages 0 and 1), and st X co (age 0, and nea r - s i g n i f i c a n t at age 1; Table V), i n d i c a t i n g that strains responded differently to changes in these dietary parame-ters. S i g n i f i c a n t s t r a i n v a r i a t i o n and s t r a i n X diet interactions for feed consumption suggest the potential for selectively breeding a strain capable of higher rate of consumption of diets having a lower protein concentration or a diet containing a higher concentration of soybean meal as the protein source. Thus while there was strong evidence for a metabolically dependent difference in appetite, there i s also indication of important dietary components, and exploitable interaction. The only other published study in which strain (or genotype) varia-tion has been considered i n terms of feed consumption (Kinghorn, 1981; c i t e d by Gjedrem, 1983), found that feed consumption i s a heritable t r a i t among families of rainbow trout. However, in contrast to present findings, feed consumption was not always related d i r e c t l y to feed conversion efficiency i n Kinghorn's indirect estimates of feed consump-tion by calorimetric techniques. The current study i s the f i r s t report-ed attempt to compare feed consumption directly for several genotypes. • Higher rates of feed consumption for Sun Valley translated into proportionately higher relative growth rates (% BW per day) as shown by Figures 11 and 12. Dietary protein concentration was less important to growth than was protein source (Table IX). Pennask had least capacity for growth in a l l nutritional environments, borne out by data on rela-t i v e growth as l i v e and dry tissue (Table X). However, wild strains -125-converged in growth rate at age 1, so that no significant difference was observed between them. Only in terms of l i v e tissue did Premier continue to exceed Pennask i n t h i s t r a i t (Table X). On a dry tissue basis, reversal of ranks for Premier and Pennask was observed. However, t h i s observation must be treated with caution i n view of a sampling error that would affect estimates of i n i t i a l dry weights at the beginning of age 1 growth t r i a l s (see below, e f f i c i e n c y of nutrient u t i l i z a t i o n ) . Klupp et a l . (1979) found an age e f f e c t on h e r i t a b i l i t y of body weight in rainbow trout. Considerable v a r i a t i o n among str a i n s for r e l a t i v e growth rate, coupled with more limited evidence of strain X dietary interactions for r e l a t i v e growth, support the conclusion that selective breeding among the strains could produce a strain capable of relatively superior growth at p a r t i c u l a r l e v e l s of the n u t r i t i o n a l parameters tested. Strain X protein source (dry tissue growth) at age 0, and st X f l at both ages and tissue types were significant (Table IX). The significance of the st X f l interaction i s d i f f i c u l t to inter-pret, however, because qualitatively defined levels of feeding (satia-t i o n or h a l f - s a t i a t i o n ) translated into d i f f e r e n t quantities of food (per unit BW) being consumed by different strains under the same treat-ment (Fig. 10). However, the significant strain x protein level interac-t i o n for feed consumption suggests that i t i s possible to s e l e c t i v e l y breed a s t r a i n with better growth capacity on diets of lower protein concentration. Austreng and Refstie (1979) measured significant genotype x protein concentration e f f e c t s on growth without looking at age ef-fects, and arrived at a similar conclusion for families and inbred lines of rainbow trout. -126-Poor rate of feed consumption by wild strains was responsible for the poor r e l a t i v e growth and deposition of protein and f a t i n both years. In cer t a i n cases consumption of feed was not even enough to maintain body weight in the wild strains (Table VIII). Palatability of the experimental diets may have been a factor, but probably only a minor one, since a similar strain-consumption pattern was observed for Oregon Moist P e l l e t s (a moist commercial diet) during the determination of optimal feeding rate for the ammonia excretion study (Part II). The s t r a i n e f f e c t on feeding thus appears to be a r e a l one. The fact that a similar consumption pattern among strains was observed in both age-0 and age-.l f i s h - the same population, assayed a year apart - further supports this conclusion. Table XVII shows that percent fat content of the whole body ranks in the same order as starvation losses of dry matter, protein and gross energy, as well as feed consumption and growth, among the three strains: i.e., Sun Valley > Premier > Pennask. Reinitz et a l (1979) demonstrated a negative correlation between growth rate and carcass percent protein, in the evaluation of strains of rainbow trout and their crosses. No data for fat was available from the l a t t e r study, but since percent f a t i s inversely related to percent protein in the body, a positive correlation between f a t content and growth would be predicted, as was the case i n the present study. One plausible genetical explanation for differences in fat content of domesticated and wild strains of trout derives from studies conducted on other species. Investigation of carcass composition of high and low weight lines of mice have shown that selection for rapid growth results in a marked contribution of fat to body weight (McPhee and Neil, 1976). -127-In the broiler chicken fat lines preferentially used feed energy above the maintenance requirement for l i p i d synthesis. A lean line used in the same experiment synthesized less l i p i d , and also tolerated feed re s t r i c -t i o n more e a s i l y . The authors (Leclercq and Saadoun, 1981) concluded that the a higher secretion of insulin by chickens belonging to the fat line was probably responsible for the deviation of dietary energy to fat synthesis. The i n a b i l i t y of salmonids (including the rainbow trout) to effectively u t i l i z e high levels of carbohydrate in the diet stems from low production of i n s u l i n i n response to glucose intake (Walton and Cowey, 1982). Variation in the capacity for insulin production may be a factor in strain differences in growth rate and fat deposition observed in this study. Strain rankings for efficiency of nutrient (feed, protein and gross energy) u t i l i z a t i o n generally agreed with the aforementioned trends observed for feed consumption and growth, as i l l u s t r a t e d by Table (XXXIII). Feed Conversion'Efficiency (FCE), PER, PPV, Net Protein Efficiency (NPE), Energy Conversion (EC), and Net Conversion of Energy (NCE) were a l l significantly different among strains at age 0, and a l l but NPE and NCE (indices corrected for endogenous losses of protein or gross energy, respectively) were significant at age 1 (Table XXIV). Evi-dently, at age 1, maintenance requirements would have consumed a larger fraction of the metabolizable energy according to the inverse relation-ship between growth rate and body size (Brett, 1979). Significant strain x nutrition interactions for efficiency tr a i t s , i n conjunction with s i g n i f i c a n t s t r a i n effects or phenotypic variance (Table XXIV), suggests the p o t e n t i a l for s e l e c t i v e l y breeding a strain(s) able to more e f f i c i e n t l y u t i l i z e a p a r t i c u l a r l e v e l of each -128-nutritional factor concerned. In age 1 fish, failure to obtain a sample of fish at the experimen-t a l time 0 (that i s , at the beginning of the experimental phase) caused a systematic error i n the estimation of proximate gains. Calculated gains in carcass protein and gross energy for this age group were based on data from carcasses sampled at the beginning of the pre-experimental phase (10 days before experimental time 0). This problem may explain the alteration, with increasing age, of ranks (Table XXIII) and pattern of s i g n i f i c a n t s t r a i n x n u t r i t i o n i n t e r a c t i ons (Table XXIV) for those t r a i t s to which t h i s data applies: PPV, NPE, and EC. Net conversion of energy (NCE), which was corrected for endogenous losses of gross energy from the carcass, differed in strain ranking from other t r a i t s even at age 0 (Table XXIII). It i s debatable whether the aforementioned sampling problem contributed to the lack of agreement, at age 1, between PPV or NPE (both determined by carcass analysis procedure), and efficiency of protein u t i l i z a t i o n as estimated by the ammonia-N excretion procedure (Part II, below). Lacking f u l l replication of the experimental treatments makes the results less conclusive than they otherwise might be. Genetical studies have f a i l e d to observe any large tank e f f e c t (Aulstad et a l . , 1972) or i n the design of the experiment ignored the tank e f f e c t altogether (Chevassus, 1976). The latter author did acknowledge that such a design might have increased the variance attributed to genotype, y i e l d i n g inflated he r i t a b i l i t y estimates. The same type of error must be assumed in the present experiments. In support of the large observed variance i n growth performance between the domesticated and Pennask strains of fi s h are data from Ayles -129-(1975) and Ayles et al . (1979, 1983). Their domestic fi s h grew s i g n i f i -cantly better than Pennasks i n an uncontrolled environment ( pothole lake). There was also a significant strain x lake variance component for growth. Moreover, growth of hybrid s t r a i n s (domestic X Pennask) was heterotic (Ayles and Baker, 1983). This result indirectly lends support to the rationale of Austreng and Refstie (1979) that a s i g n i f i c a n t interaction of strain with nutritional environment indicates the poten-t i a l for improved performance for the t r a i t i n question, under the specific environmental conditions defined. I have extended this ration-ale for the interpretation of nutrient efficiency and consumption data. In summary, therefore, based on the observed significant strain x diet i n f r a c t i o n s i n the present experiments, i t seems possible to improve a number of e f f i c i e n c y t r a i t s , previously not studied i n t h i s manner or context. Austreng and Refstie (1979) observed a significant or near-significant interaction for genotype (family or inbred line) and dietary protein concentration for condition factor and relative growth. Their conclusion was that an improved s t r a i n , better able to u t i l i z e lower protein concentrations (or higher carbohydrate concentrations) i n the diet was possible. However, a subsequent study that examined a s i m i l a r i n t e r a c t i o n for carbohydrate concentration failed to support hopes of breeding for improved carbohydrate u t i l i z a t i o n among families or inbred lines, based on low variance conmponents for interactions of genotype x carbohydrate level (Refstie and Austreng, 1981). Ability to u t i l i z e soybean meal as a protein source seems amenable to selection , based on significant strain x protein source interactions for feed consumption (Table V) and growth at age 0 (Table IX). It i s doubtful this result can be used to dispute existing knowledge on strain -130-x carbohydrate concentration (Edwards et al., 1977; Refstie and Austreng, 1981). However, i t would be constructive to explore the cause of t h i s interaction in future work in this area. This study was unique i n that e f f i c i e n c y - r e l a t e d t r a i t s and the basis of their differences among populations of fi s h had not previously been studied so extensively from the general standpoint of genetic or phenotypic variation. Pym and Nicholls (1979) have recommended including feed efficiency together with growth rate or body weight in selection prograns for the meat chicken; even though alone feed e f f i c i e n c y was considered a t r a i t incapable of yielding any significant gains of pro-d u c t i v i t y . Kinghorn (1981; c i t e d by Gjedrem, 1983) did, on the other hand, find feed efficiency to be worthy of direct selection in rainbow trout, contrary to what has been concluded about b r o i l e r and layer chickens (Nesheim, 1975; Pym and N i c o l l s , 1979). The r e s u l t s of the present study imply that other efficiency tr a i t s , notably those related to protein metabolism, warrant further investigation as potential candi-dates for genetic s e l e c t i o n i n rainbow trout, and perhaps i n other f i n f i s h species having a similarly high protein,requirement. -131-6. EXPERIMENTAL, PART II: STRAIN DIFFERENCES IN EFFICIENCY OF PROTEIN UTILIZATION BY ANALYSIS OF AMMONIA EXCRETION 6.1 INTRODUCTION The following study examined ammonia excretion by three strains of rainbow trout following consumption of a high protein meal. The strains were known to d i f f e r i n growth rate and e f f i c i e n c y of u t i l i z a t i o n of dietary protein (Part I, above). The objective of the experiment was to test a new technique for comparing efficiency of protein u t i l i z a t i o n by measurement of ammonia excretion rates in genetically distinct popula-tions of rainbow trout. This technique for open tanks was adapted from one developed by Brett and Zala (1975) for closed systems, using the chinook salmon (Oncorhynchus tshawytscha). For that species a consistent peak of ammonia-N excretion occurred between 4-4.5 h post-prandially. The modified technique appeared to promise a quicker, and simpler means than the carcass analysis procedure (Part 1) for analysis of i n t e r -strain variation in efficiency of protein utilization. 6.2 MATERIALS AND METHODS 6.2.1 Acclimation and selection of experimental populations The origins of the three strains of rainbow trout have already been discussed (Materials and Methods, Part I). Both wild strains were reared from the fingerling stage for a period of one year at the West Vancouver Laboratory of The Department of Fisheries and Oceans, Canada, where the experiment was conducted. Fish of the Sun Valley strain were obtained three months before the experiment from a local trout farm (Sun Valley -132-Trout Farms, Ltd). A l l strains were acclimated in oval fiberglas tanks with flowing aerated well water (6-6.5 1/min, pH 6.6-6.8, dissolved oxygen 8-9 ppm) under s i m i l a r conditions of photoperiod (08.00-20.00) and water temperature (10-11°C). A l l f i s h were fed twice d a i l y with a commercial trout diet. Starting one week before the experiment, the f i s h were fed once-daily (at 09.30) a commercial moist feed (Oregon Moist Pellets, Moore-Clarke Co., Laconner, WA). The feed was analyzed and found to have the following composition: crude protein 53.9%, ether-extractable l i p i d 14.9%, ash 10.2%, carbohydrate (by difference) 21.0%, a l l on a dry weight basis; moisture 27.5%. Selection of the three experimental populations (Table XXXV) was based on their respective modal weights estimated from the weight fre-quency distribution in a sample of 100 fi s h from each strain. The mean and standard deviation of body weights shown for each s t r a i n varied depending on the numbers of acclimated fi s h available in holding tanks and their respective weight frequency distributions. 6.2.2 Experimental protocol Three 700-litre capacity, oval, fiberglas tanks (without lids) were used , one for each strain. Water volumes were approximately equalized, and l a t e r measured: Sun Valley and Premier tanks contained 352 l i t r e s and that of Pennask, 364 l i t r e s . Ammonia-free compressed air was bubbled into each tank via a single air stone weighted in the middle of the tank bottom, providing both aeration and mixing during times when water flow was turned off experimentally (see below). Each tank was equipped with 2 overhead fluorescent lamps (F40 cool white, Sylvania XL l i f e l i k e ) at a -133-height of 1.5 m above the water surface. Fish were weighed individually on the day preceding the experiment, and returned to the same tank, which had been thoroughly cleaned. A l l weighings were done at least 12 h af t e r the previous meal, and af t e r fi s h were anaesthetized (2-phenoxyethanol, 0.5ml/l water and rolled in cloth to remove excess water. On the four t r i a l days the f i s h were fed the diet once daily (at 09.30) at a fixed percentage of i n i t i a l body weight (Table XXXV). Feed-ing was done with the water flow to the tanks turned o f f . Feeding activity could therefore be monitored carefully to assure total consump-tion of a l l the feed offered, and i t s even d i s t r i b u t i o n among a l l ex-perimental animals in each tank. Feeding of the fish in a l l three tanks was completed in about 10 min. Fecal matter was siphoned from a l l tanks at the end of the second day of the experiment. Sim i l a r to the method of Brett and Zala (1975), an al t e r n a t i n g water flow cycle (one hour on, and one hour off) was used to prevent excessive elevation of ammonia concentration during the daily six-hour experimental period (09.30-15.00). Water flow was on at a l l other times, and off during feeding (09.30-09.40). Ammonia excretion was only meas-ured during the one hour i n t e r v a l s when water flow was turned off, giving three daily measurements of ammonia production for each tank. On alternate days, the cycle was reversed. Over a two-day period, there-fore, ammonia excretion was determined for each of six, hourly inter-vals. The fi s h were reweighed at the termination of the four-day experi-ment. 6.2.3 Water sampling and ammonia analysis For determining ammonia production, two water samples of 125 ml -134-each were taken hourly from each tank, between 09.30 and 15.30, just before turning water flow on, or just after turning i t off. The f i r s t sample was taken immediately after feeding (at about 09.40) so as not to disrupt feeding behaviour. Samples were taken from either side of the cen t r a l stand pipe by moving the glass sampling bottle backwards i n a slow sweeping arc from the back of the tank to the front, about halfway to the bottom. The duplicate samples from each tank were mixed together, and two 10 ml aliquots were analyzed by the phenate method ( Taras et  al., 1971). A calibration curve prepared from ammonium chloride solution (0.025 mg/1 to 0.50 mg/1) was used for assessing the values for ammonia-nitrogen from the measured absorbances at 600 nm (Spectronic 20, Bausch and Lomb). Total ammonia-N excreted per hour was calculated using the follow-ing equation: mg NH3_N/h = V . ( [NH 3-N] t l - [NH 3-N] t 0 ) (equation 4) where, [NRVj-N]^ = ammonia-N concentration (mg/1) at time tx_ tO = beginning of a one-hour water-off period, t l = end of the same one hour period, V = total volume of water in the tank, l i t r e s . 6.2.4 S t a t i s t i c a l analysis Parabolic curves (Fig. 13) were f i t t e d by the method of least squares and compared s t a t i s t i c a l l y by a regression and covariance procedure (UBC REGC0V computer program). The program compares slopes and levels of the regressions. As a result of differences in growth rate among the three strains i t was not possible to standardize body weight in the experiment. How--135-Table XXXV. Body weights and feed consumption of three s t r a i n s of rain-bow trout over a four-day period. S t r a i n Sun Val l e y Pennask Premier Mean l i v e body wt (g) I n i t i a l 63.48 SD 7.40 F i n a l 63.99 SD 7.30 Number of f i s h 88 Feed Consumption Grams, as fed Day 1 38.2 Day 2 41.8 Day 3 33.9 Day 4 33.9 % of T o t a l F i s h Weight Day 1 .68 Day 2 .75 Day 3 .61 Day 4 .61 31.89 5.28 32.44 5.49 98 11.8 16.8 18.8 18.8 .38 .54 .60 .60 52.65 9.14 52.92 9.17 101 31.4 33.8 32.4 32.4 .59 .64 .61 .61 -136-ever, for reasons that are presented in the discussion i t i s believed that the e f f e c t of t h i s difference on ammonia excretion rate does not jeopardize the conclusions of the experiment. 6.3 RESULTS, PART II Table XXXV shows the number, mean body weight and feed consumption for each tank of f i s h (one tank per s t r a i n ) . There was considerable difference i n mean body weight for the three strains. Table XXXV also shows that there was a s l i g h t increase i n body weight i n a l l strains, during the four days of the experiment. Composition of the gain was not determined. Figures 13-15 show the timecourse of ammonia accumulation (mg NHg-N) i n tanks containing f i s h belonging to the Sun Valley, Pennask and Premier strains respectively. Alternating positive and negative slopes indicate times when there was no exchange of tank water (standing water conditions) and times of flushing, respectively. The absolute amount of ammonia-N excreted by Pennask f i s h was lower than for the other two strais. This coincided with a lower biomass of fi s h of the former strain in that tank (Table XXXV). Excretion patterns were clearly parallel on alternate days when the same water flow schedule was enforced (Figures 13-15). Appetite of both wild s t r a i n s , p a r t i c u l a r l y of Pennask, was less than had been determined (0.9 % of l i v e body weight/ day) i n the pre-t r i a l period. The planned l e v e l of experimental feeding was 0.8 % of live weight per day to a l l strains. Actual feed consumed per unit body weight per day was different for the different strains in the f i r s t two days of the t r i a l period (Table XXXV). After the second day, feeding -137-Figure 13. Dynamics of ammonia-N accumulation with a l t e r n a t i n g hourly p e r i o d s of f l u s h i n g (replacement) and s t a n d i n g water i n a tank containing a group of yearling rainbow trout of the Sun Valley s t r a i n . The single d a i l y r a t i o n was given between 09.30-09.40 h. H O U R S O F T H E D A Y -139-Figure 14. Dynamics of ammonia-N accumulation with alternating hourly periods of f l u s h i n g (replacement) and standing water i n a tank containing a group of yearling rainbow trout of the Pennask str a i n . The single daily ration was given between 09.30-09.40 h. I o 170 150 130 6 110 E h 9 0 Z z H 70 o 5 0 3 0 10 0 P E N N A S K D A Y I -D A Y 2-D A Y 3-D A Y 4 ' 0 9 3 0 10 3 0 1130 1 2 3 0 1 3 3 0 1 4 3 0 H O U R S O F T H E D A Y 15 3 0 -141-Figure 15. Dynamics of ammonia-N accumulation with a l t e r n a t i n g hourly p e r i o d s of f l u s h i n g (replacement) and s t a n d i n g water i n a tank containing a group of yearling rainbow trout of the Premier s t r a i n . The single d a i l y r a t i o n was given between 09.30-09.40 h. -142-T O T A L N H 3 - N . m g . - • U U i > 4 < 0 - « C i > U i N O O O O O O O O O O -143-rate for a l l strains had been standardized at 0.6 % of i n i t i a l weight per day. There was no apparent consistency in the ammonia excretion re-sponse within strains as a r e s u l t of the d i f f e r e n t rates of feed con-sumption between the f i r s t two days ( f i r s t run) and the l a s t two days (second run) of the experiment. Hourly rates of NHg-N excretion were expressed as mg ammonia-N excreted per kg body weight per gram of moist diet consumed (Figure 16). Duplicate hourly points on the graph for each strain represent measure-ments made on d i f f e r e n t days (days 1 and 3 , or days 2 and 4) . Ammonia excretion curves d i f f e r e d s i g n i f i c a n t l y for the different strains (p< 0.01), due to a difference i n l e v e l s (p< 0.01) between the graph for Pennask compared with those for the two other s t r a i n s . Graphs for Sun Valley and Premier did not differ significantly from each other. Slopes were s i m i l a r for a l l strains (p> 0.92). Maximum rates of excretion (Y max) and the corresponding times after feeding (X opt) as determined by differentiation of f i t t e d equations, are also shown in Figure 16. Based on Y max values, the increasing order of s t r a i n rank for ammonia excretion (and decreasing order of rank for N-retention e f f i -ciency) was: Sun Valley, Premier, and Pennask respectively, with l i t t l e difference in Y max between Premier and Sun Valley (Figure 16). The order in which fish of the three strains reached the calculated maximum rate of excretion was: Pennask, Sun Valley, and Premier. 6.4 DISCUSSION, PART II The post-feeding increase i n ammonia excretion i s considered to represent rapid oxidation of exogenous rather than endogenous amino-acids (Brett and Zala, 1975). Therefore, the inverse r e l a t i o n s h i p be--144-F i g u r e 16. Change i n r a t e of e x c r e t i o n of ammmonia-N w i t h time a f t e r feedingwild(Pennask •, and Premier o) and domesticated (Sun V a l l e y •) s t r a i n s of rainbow t r o u t . P o i n t s p l o t t e d i n d i c a t e ammonia e x c r e t i o n during the preceeding one-hour period. N=88-101 f i s h / tank, temperature= 10°C. Regression equations describing the graphs shown are as follows: Sun V a l l e y : y= -0.181 + 0.209x - 0.023x2, r = o.87 (Ymax=0.297, X=4.57h) Pennask : y= 0.040 + 0.185x - 0.205x 2, r= 0.73 (Ymax=0.442, X=3.65h) Premier : y= -0.066 + 0.140x - 0.103x2, r = 0 > 8 3 (Ymax=0.308, X=5.34h) The regression equation f o r Pennask d i f f e r e d s i g n i f i c a n t l y from those for Premier and Sun Valley (p < .01). Calculated maximum hourly excre-t i o n rates (Y max) and corresponding times (X) are shown i n parenthesis. A l a r g e Y max i n d i c a t e s a low e f f i c i e n c y ( s t r a i n rank) of d i e t a r y protein u t i l i z a t i o n . -145-Time a f t e r f e e d i n g (h) -146-tween body weight and rate of endogenous nitrogen excretion when expres-sed as mg-N per kg body weight per day (Savitz, 1969) i s not important in the present experiment. On the other hand, a direct r e l a t i o n s h i p exists between body weight and e f f i c i e n c y of nitrogen retention (Gerking, 1971) - and hence an inverse r e l a t i o n to exogenous N-excre-tion. On t h i s basis, one would predict a r e l a t i v e l y higher rate of ammonia excretion for the larger strains (Sun Valley and Premier, Table XXXV), in the absence of a strain effect. In fact, the opposite ranking occurred (Figure 16) supporting the hypothesis of a s t r a i n e f f e c t on protein retention. One may further conclude that the observed d i f f e r -ences in peak excretion rate between Pennask and the two larger strains, and between Premier and Sun Valley, underestimated the true s t r a i n difference, due to a masking effect of size. P r i n c i p a l end-products of nitrogen metabolism have been used to measure efficiency of dietary protein u t i l i z a t i o n i n t e r r e s t r i a l and aquatic species (Eggum, 1970; Miles and Featherston, 1974; Garcia «^ t al., 1981). Eggum (1970) found that, following consumption of different feedstuffs, the plateau concentration of blood urea i n the pig was negatively correlated with protein biological value (BV) for the feed-stuffs. Miles and Featherstone (1974) used the inflection point in the dose-response graph of uric acid excretion r e l a t i v e to dietary lysin e concentration to determine the optimum level of supplementation for that amino acid to the chick. Results obtained by this indirect method agreed with those based on weight gain. Moreover, Garcia et_ al.(1981) in comparing efficiency of protein u t i l i z a t i o n for different diets fed to groups of rainbow trout of the same strain, found agreement between PER (protein efficiency ratio) and PPV (productive protein value) rankings, and ranking based on total ammonia excreted in 24 hours. -147-In the present study, significant differences among curves (strains of rainbow trout) for excretion of ammonia-N versus time-after-feeding (Fig. 13) were the result of differences i n levels and not slopes of the regressions. Protein efficiency ranking of the strains, determined here as the inverse of peak NH3-N excretion ranking, agreed with PER (age 1), and PPV and net protein e f f i c i e n c y ranks (age 0) obtained i n a three-week growth study using experimental animals from the same o r i g i -nal laboratory populations. Peak (maximum) values are therefore a better parameter than slopes for expressing s t r a i n differences i n ammonia excretion rate. Furthermore, post-prandial times of peak ammonia excre-tion rate (Figure 16) are compatible with the six-hour appetite cycle reported for rainbow trout ( Fange and Groves, 1979), as well as the post-prandial time of peak ammonia excretion for sockeye salmon (Brett and Zala, 1975). Rankings based on maximum rate of excretion (Y max, Figure 16) are, therefore, a good indicator of the r e l a t i v e e f f i c i e n c y with which dietary protein i s used for growth, by the three strains of trout. Rychly and Marina (1977), i n a single 24-hour t r i a l , observed multiple peaks for ammonia excretion rate i n rainbow trout. However, their supernumerary peaks may have been an artifact of the experimental design, by which i n d i v i d u a l f i s h were tested i n standing water con-tinuously for 24 hours. Under s i m i l a r conditions (with the exception that the trout used were of a larger body weight, and fasted), the increase in ammonia concentration in the water appeared to suppress the normal rate of ammonia excretion within two hours. Rates returned to normal af t e r flushing the closed system with fresh water (Wright and Wood, 1984) . To minimize negative feedback of ammonia i n the current experiment, I have used an intermittent flushing/ standing water regimen -148-(see Materials and Methods), similar to that described by Brett and Zala (1975). The use of a high (53%) protein diet to evaluate protein u t i l i z a -tion had the important advantage of minimizing inter-strain differences i n f e c a l N-excretion. The observed differences i n ammonia excretion (Figure 16) are thus considered to reflect only differences in protein metabolism among the three strains. Austreng and Refstie (1975) measured large differences i n apparent protein d i g e s t i b i l i t y with low (25-35%) protein diets, but only very minor difference at high (51%) dietary protein. Mean protein dig e s t i b i l i t y for a l l families and inbred lines used was also maximal (about 92%) with the high protein diet. On t h i s premise the d i f f e r e n t X-max values (time postprandially corresponding to peak rate of ammonia-N excretion) observed for the strains in the present experiment (Figure 16) may represent differences in food passage rate or digestion rate. Time required to empty the stomach i s dependent on numerous factors including meal size, and f i s h size, both of which correlate positively with emptying time (Fange and Groves, 1979). Slight differences i n the size of f i s h (Table XXXV) should have no effect on passage time since feeding fish of a different size to a stated percentage of body weight w i l l f i l l the stomach to the same extent (Fange and Grove, 1979). However the s l i g h t , inadvertent differences i n feeding rate used on days 1 and 2 (Table XXXV) would predictably bias the ranking of X-max in favour of Pennask < Premier < Sun Valley. Since this was only vaguely observed for X-max values (Fig-ure 16, caption) other factors were probably involved. It i s possible that the rate of digestion may vary among str a i n s for genetic reasons without affecting the overall extent of digestion. This study indicates that peak ammonia excretion rate by rainbow -149-trout may be used as the basis f o r comparing the r e l a t i v e e f f i c i e n c y of d i e t a r y p r o t e i n u t i l i z a t i o n under s p e c i f i c d i e t a r y c o n d i t i o n s . Using t h i s technique d i f f e r e n t genotypes may be ranked f o r N-retention e f f i -ciency. -150-7. SUMMARY AND CONCLUSIONS Samples of three populations (one domesticated and two wild strains) of rainbow trout (Salmo gairdneri) were compared in two succes-sive years ( f i s h aged 0 and 1 years, respectively) of experimentation under hatchery conditions for i n t e r s t r a i n v a r i a t i o n i n a number of production and physiological t r a i t s . Endogenous losses ( l i v e or dry weight, protein and gross energy) were studied by feed withdrawal and carcass analysis. Feeding experiments - also i n combination with carcass analysis - incorporating eight dietary treatments, served to analyze i n t e r - s t r a i n v a r i a t i o n for body composition, growth and efficiency of nutrient u t i l i z a t i o n i n a factorial design. The second part of the study saw the testing of an ammonia excretion method for analysis of inter-strain variation i n efficiency of protein u t i l i z a t i o n , i n age 1 fish. The following results and conclusions were forthcoming from the series of experiments: 1. Starvation losses measured as li v e or dry matter, protein and gross energy were regressed i n d i v i d u a l l y on i n i t i a l dry weight (g/ f i s h ) . Regression equations (for Sun Valley, Pennask and Premier, respectively) were for mean dry-weight loss (mg/ f i s h / day) : y= 6 + 5x, y= 9 + 3x, and y= 4 + 3x; for mean protein loss (g/ f i s h / 21 days) : y= 0.55 + 0.032x, y= 0.061 + O.OOlx, and y= 0.019 + 0.024x; and for mean gross energy loss (Kcal/ f i s h / 21 days) : y= 0.293 + 0.631x, y= 0.572 + 0.262x, and y= 1.530 + 0.315x. Greater losses for Sun Valley (domestic) coupled with a consistently larger slope of regression compared to the wild strains, for a l l body components and over most of the weight range employed, indicates a greater metabolic weight exponent for the domestic strain. Premier ranked ahead of Pennask for a l l of the above parameters. -151-2. Feed consumption varied among strains in both years. Rates of feed consumption (% BW per day) at age 0 and age 1 ranked i n the same order as endogenous losses, viz., Sun Valley > Premier > Pennask. 3. Feed consumption was affected s i g n i f i c a n t l y by s t r a i n , feeding l e v e l , dietary protein source and concentration at age 0, and only by the f i r s t two of these dietary factors at age 1. There were significant (p< 0.05) or near s i g n i f i c a n t interactions of s t r a i n x protein source (st x pr) and protein concentration (st x co) in both years. 4. Strain, feeding l e v e l , and protein source a l l had a s i g n i f i c a n t effect on relative growth as dry weight (R w) at both ages, and s i g n i f i -cant interactions were observed only for s t r a i n x feeding l e v e l (st x f l ) , and st x pr; the l a t t e r only at age 0. Relative growth as fork length (Ri) a t a 8 e 1 followed a s i m i l a r pattern as dry tissue growth, with the exception of significant effects for protein source and protein concentration. 5. F i n a l carcass composition varied among str a i n s : percent crude protein and ash were least i n Sun Valley, and highest i n Pennask; the inverse rankings occurred with percent fat. Condition factor (age 1) varied i n rank with fat content. Coefficient of variation for condition factor decreased during feeding for Sun Valley (from 9-6 % ) , while increasing slightly for the other strains (from 5.8-6.5 % and from 5.7-6.3 % for Pennask and Premier, respectively). 6. S i g n i f i c a n t s t r a i n v a r i a t i o n was observed with a l l e f f i c i e n c y t r a i t s at age 0, and with a l l but the indices of net protein (NPE, Net Protein Efficiency) and energy (NCE, Net Conversion of Energy) eff i c i e n -cy at age 1. Stra i n rankings were the same as for growth and feed consumption for a l l but NCE at age 0, and for only FCE (Feed Conversion Efficiency), and PER (Protein Efficiency Ratio) at age 1. -152-7. There were more s i g n i f i c a n t or nearly s i g n i f i c a n t s t r a i n x n u t r i t i o n i n t e r a c t i o n s at age 0 than at age 1 f o r the v a r i o u s e f f i c i e n c y t r a i t s . 8. Based on the observed v a r i a t i o n s among s t r a i n s , a c c l i m a t e d and t e s t e d under s i m i l a r c o n d i t i o n s , I conclude t h a t t h e r e i s evidence of p o t e n t i a l f o r g e n e t i c s e l e c t i o n f o r r e l a t i v e growth r a t e (R), feed consumption (or appetite), feed conversion e f f i c i e n c y , and e f f i c i e n c y of p r o t e i n c o n v e r s i o n . Furthermore, p r e l i m i n a r y evidence - based on the aforementioned i n t e r a c t i o n s - suggests further examination of growth, consumption and e f f i c i e n c y t r a i t s as p o t e n t i a l bases f o r s e l e c t i v e breeding f o r growth, consumption or nutrient conversion at lower concen-t r a t i o n of d i e t a r y p r o t e i n , or on d i e t s c o n t a i n i n g soybean meal as a p r o t e i n source. 9. Peak hourly excretion of ammonia (mgNHg-N/ kg BW/ g d i e t consumed) provided a quick and r e l i a b l e method of detecting v a r i a t i o n f o r e f f i c i -ency of p r o t e i n u t i l i z a t i o n among the t h r e e s t r a i n s of rainbow t r o u t . This procedure may apply to genetic s e l e c t i o n among s t r a i n s and f a m i l i e s i n the d e t e c t i o n phase, and l a t e r i n e v a l u a t i n g the r e s u l t s of s e l e c -t i o n . I t i s a method t h a t may a l s o apply to brood s t o c k e v a l u a t i o n , given that the groups of f i s h tested need not be k i l l e d . -153-8. REFERENCES Allendorf, F.W. and F.M. Utter. 1979. Population genetics. In: Fish Physiology, vol 8 (W.S. Hoar, D.J. Randall, and J.R. Brett, eds ), pp 407-454, Academic Press, New York and London. Andrews, J.W. and J.W. Page. 1974. Growth factors in the fishmeal component of catfish diets. J. Nutr., 104: 1091-1096. Aulstad, D., T. Gjedrem and H. Skjerrold. 1972. 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Halver, D.E. U l l r e y and P.I. Tack. 1973. I n f l u -ence of salinity on protein requirements of rainbow trout (Salmo gairdneri) f i n g e r l i n g s . J. Fish. Res. Bd. Canada, 30:1867-1873. A P P E N D I X T A B L E S -163-Table IA. Water quality data for the West Vancouver Laboratory, the Department of Fisheries and Oceans, Canada. Hardness (mg/1 CaC03) pH 2 Calcium (mg/1) Magnesium (mg/1) Copper (mg/1) Zinc (mg/1) Lead (mg/1) 46-48 6.4-8.6 (6.3-6.5) 15-17 2.1-2.6 <0.01 <0.01-0.1 <0.02 Taken from Higgs et a l . 1979. Values recorded during these experiments. -164-Table IIA. Estimation of water flow rate in experimental tanks con-taining age 0 rainbow trout. No. of Sample F i l l Time,1 Combined 2 3 Mean Flow 2.77 l i t r e s Flow Rate per Tank (sec.) (ml/sec) (1/min) 1 4.4 630.2 1.45 2 4.4 630.2 1.45 3 4.3 644.9 1.49 4 4.2 660.2 1.52 5 4.4 630.2 1.45 6 4.3 644.9 1.49 7 4.1 676.3 1.56 8 4.3 644.9 1.49 9 4.2 660.2 1.52 1 Outflow from 26 tanks of approximately uniform individual flow rates adjusted manually; time required for f i l l i n g a bucket of 2.77 1 capa-city, placed at the end of common conduit for a l l tanks. For 26 tanks. Calculated overall mean, 1.49 1/min. -165-T a b l e IIIA. Weight changes over 32 days f o r age 1 rainbow t r o u t of t h r e e s t r a i n s subjected to feed withdrawl. S t r a i n Live Weight (g/ f i s h ) 1 Day 0 Day 11 Day 32 Sun Valley Pennask Premier Sun Valley Pennask Premier (S)2 (S) (S) (L) (L) (L) 32.19 31.30 33.72 61.89 51.69 53.34 30.85 30.18 32.25 60.25 49.50 51.61 29.51 28.94 30.81 57.42 48.03 50.06 d a i l y l o s s ( g / f i s h ) Period 1 Period 2 Sun Valley Pennask Premier (S) (S) (S) 0.120 0.102 0.134 0.064 0.059 0.069 Sun Valley Pennask Premier (L) (L) (L) 0.149 0.199 0.157 0.135 0.070 0.074 N=12-17 f i s h per group. Small (S) or large (L) body weight groupings within s t r a i n s . -166-Table IVA. Final carcass composition as protein, fat, ash and moisture in age 0 and age 1 rainbow trout of three strains withdrawn from feed for 21 and 32 days, respectively. Strain Percent of Dry Matter 1 Final BW (g / fish) Moisture Protein Fat Ash Age 0 Sun Valley 0.47 83.63 73.52 10.85 12.69 (-) (0.12) (0.17) (0.20) Pennask 1.70 81.26 68.57 13.23 12.62 (0.17) (0.33) (0.39) (0.18) Premier 2.32 79.82 69.06 14.80 12.16 (0.18) (0.41) (0.76) (0.15) Age 1 (Sma til) Sun Valley 29.51 75.67 66.86 21.58 10.90 (0.22) (0.67) (0.47) (0.26) Pennask 28.94 75.49 69.26 20.24 10.66 (0.27) (0.15) (0.64) (0.31) Premier 30.81 75.38 68.73 17.72 11.88 (0.00 (0.66) (0.32) (0.42) Age 1 (Large) Sun Valley 57.42 75.24 67.54 20.35 10.17 (0.62) (1.10) (0.70) (0.31) Pennask 48.03 75.16 70.20 20.41 9.31 (0.17) (0.85) (0.24) (0.25) Premier 50.06 74.30 67.81 21.86 9.76 (0.24) (0.42) (0.48) (0.44) 1 Standard error i n parenthesis; N= 3 l o t s per tank, except age 0 Sun Valley (N=l). - 1 6 7 -T a b l e VA. V i t a m i n and m i n e r a l premix f o r m u l a t i o n f o r d i e t s f e d to rainbow t r o u t s t r a i n s d u r i n g experiments on growth and n u t r i e n t u t i l i z a t i o n . Ingredient Amount 1 (mg/ kg di e t ) Calcium pantothenate 164 Pyridoxine hydrochloride 36 R i b o f l a v i n 60 Niacin 300 F o l i c a c i d 10 Thiamin hydrochloride 34 B i o t i n 3 Vitamin B 1 2 (0 .1%) 60 Menadione 80 Choline chloride (50%) 3456 Vitamin E (500 IU/g) 1200 Vitamin Do (500 ,000 ICU/g) 0 .4 ( 8 . 0 ) Vitamin A ( 500 ,000 IU/g) 20 Ascorbic acid 1200 I n o s i t o l 400 Sodium Chloride (Iodized) 5000 Modifications to the formulation at age 1 are shown i n parenthesis. -168-Table VIA. Analysis of variance table for feed consumption by groups of age 0 and age 1 rainbow trout fed one of four diets at satiation for 21 days. Age 0, Feed Consumption, 2 » Source of Variation d.f. Mean Square F-ratio Probability Strain 2 0.4098 617.44 0.0000 Feeding level 1 0.3788 570.66 0.0000 Protein source 1 0.0310 46.76 0.0000 Protein concentration 1 0.0363 54.65 0.0000 St x F l 2 0.0023 3.53 0.0740 St x Pr 2 0.0102 15.35 0.0013 St x Co 2 0.0050 7.53 0.0120 F l x Pr 1 0.0001 0.15 0.7069 F l x Co 1 0.0005 0.72 0.4185 Pr x Co 1 0.0007 1.08 0.3264 Residual 9 0.0007 Total 23 Age 1, Feed Consumption, 3 * Source of Variation d.f. Mean Square F-ratio Probability Strain 2 0.5364 239.52 0.0000 Feeding level 1 0.4936 220.41 0.0000 Protein source 1 0.0043 1.93 0.1983 Protein concentration 1 0.0014 0.62 0.4526 St x F l 2 0.0016 0.70 0.5214 St x Pr 2 0.0173 7.71 0.0112 St x Co 2 0.0093 4.17 0.0522 Fl x Pr 1 0.0001 0.05 0.8340 F l x Co 1 0.0002 0.07 0.7952 Pr x Co 1 0.0008 0.38 0.5554 Residual 9 0.0022 Total 23 1 Newman-Keuls multiple range test was performed on log-transformed data, uing a significance probability level of 0.05. 2 10 . l o g i o (100 . g dry feed / average experimental BW (g)), where average experimental weight = (mean i n i t i a l BW + mean f i n a l BW)/2. 3 100 . l o g i o (100 • 8 dry feed / average experimental BW (g)), where average experimental weight = (mean i n i t i a l BW + mean f i n a l BW)/2. Table VTIA. Mean body weights for groups of rainbow trout fed one of four diets (Table EE) to satiation (100) or 50 % of satiation for 21 days at age 0. Dietary Live Weight Live Weight Dry Weight Dry Weight Fork Length Fork Length Treatment Initial Final Initial Final Initial Final and Strain g / fish g / fish g / fish g / fish cm / fish an / fish Sun Valley FM. 1-103 0.58 1.12 0.116 0.237 FM.1-50 0.54 0.83 0.108 0.173 — — FM. 2-103 0.58 1.27 0.115 0.275 — FM.2-50 0.63 0.98 0.125 0.203 — — SEM. 1-103 0.58 1.16 0.115 0.245 — SBM.1-50 0.56 0.85 0.111 0.174 — — SBM.2-103 0.57 1.21 0.113 0.257 — — SBM.2-50 0.58 0.90 0.115 0.180 — — Pennask FM. 1-100 1.78 1.84 0.381 0.377 FM.1-50 1.80 1.75 0.385 0.361 — — FM. 2-103 1.73 1.82 0.369 0.380 — FM.2-50 1.74 1.83 0.371 0.363 — — SBM. 1-100 1.78 2.03 0.381 0.444 — — SBM.1-50 1.69 - 1.81 0.360 0.386 — — SBM. 2-100 1.82 2.08 0.388 0.446 — — SBM.2-50 1.81 1.97 0.387 0.420 — — Premier FM.1-103 2.69 3.66 0.580 0.814 _ _ FM.1-50 2.73 3.12 0.588 0.738 FM.2-100 2.70 3.34 0.583 0.781 — FM.2-50 2.68 2.96 0.578 0.669 — — SBM.1-103 2.67 3.57 0.575 0.845 SBM. 1-50 2.66 3.01 0.573 0.699 — — SBM.2-100 2.76 3.66 0.595 0.878 — — SBM.2-50 2.63 3.06 0.567 0.698 — — T a b l e V H B . Mean body w e i g h t s and f o r k l e n g t h s f o r groups o f ra inbow t r o u t f e d one o f f o u r d i e t s ( T a b l e I I ) t o s a t i a t i o n (103 ) o r 50 % o f s a t i a t i o n (50) f o r 21 days a t age 1 . D i e t a r y L i v e Weight L i v e Weight Dry Waight Dry Weight F o r k Leng th Fo rk L e n g t h Treatment I n i t i a l F i n a l I n i t i a l F i n a l I n i t i a l F i n a l and S t r a i n g / f i s h g / f i s h g / f i s h g / f i s h cm / f i s h cm / f i s h Sun V a l l e y FM.11-100 55.89 6 4 . 9 1 15.24 17.92 1 6 . 8 17 .5 FM.11-50 45 .36 49 .98 12.37 13.17 16 .2 1 6 . 5 FM.12-100 56 .16 69 .18 15.31 18.89 1 6 . 8 17 .7 FM.12-50 56.07 5 9 . 2 0 15.29 15.79 16 .7 1 7 . 1 SEM. 11-100 53.72 6 6 . 9 5 14.65 18 .18 16 .5 17 .5 SBM.11-50 50.67 56 .86 13.82 15.35 1 6 . 5 1 7 . 0 SBM. 12-100 51.68 64 .99 14.09 17 .00 1 6 . 8 17 .7 SBM. 12-50 52.49 57 .47 14.31 14.94 16 .7 1 7 . 3 Pennask FM.11-100 4 1 . 3 0 43 .60 10.59 11.25 1 6 . 3 1 6 . 4 FM.11-50 37 .88 38 .12 9 .72 9 . 1 1 1 6 . 0 1 5 . 9 FM. 12-100 39 .77 42 .17 10.20 10.46 1 6 . 4 1 6 . 4 FM. 12-50 40 .07 4 0 . 7 1 10.28 10 .36 1 6 . 4 1 6 , 2 SEM. 11-100 42 .28 43 .02 10.84 11.45 1 6 . 8 1 6 . 6 SBM.11-50 37.37 37 .60 9 .59 9 . 8 1 16 .2 1 6 . 1 SEM. 12-100 36 .49 39 .18 , 9 .36 10.07 1 6 . 0 1 6 . 0 SBM. 12-50 41.82 4 2 . 5 1 10.73 10.77 1 6 . 6 1 6 . 5 Premier FM.11-100 43 .48 4 4 . 9 0 11 .80 11 .75 16 .7 1 6 . 8 FM.11-50 41 .60 41 .45 11.29 10.52 1 6 . 6 1 6 . 4 FM.12-100 38 .41 42 .64 10.43 11.08 1 6 . 0 16 .2 FM. 12-50 36.47 37 .14 9 .90 9 .47 1 5 . 8 1 5 . 8 SBM. 11-100 39 .11 42 .12 10.62 11 .13 16 .2 16 .3 SBM.11-50 38.79 39 .69 10.53 10 .25 1 6 . 1 1 6 . 0 SBM. 12-103 42 .28 46 .39 ' 11 .48 12.22 16 .5 16 .8 SBM.12-50 41.27 42 .65 11.20 10.93 1 6 . 4 1 6 . 5 -171-Table VIIIA. Analysis of variance table for r e l a t i v e growth as l i v e tissue for groups of age 0 and age 1 rainbow trout fed one of four diets to satiation for 21 days. Age 0, Relative Growth Source of Variation d.f. Mean Square F-ratio Probability Strain 2 12.884 456.43 0.0000 Feeding level 1 3.4512 122.26 0.0000 Protein source 1 0.1867 6.62 0.0301 Protein concentration 1 0.0329 1.17 0.3082 St x F l 2 0.6679 23.66 0.0002 St x Pr 2 0.0665 2.36 0.1503 St x Co 2 0.0681 2.41 0.1448 Fl x Pr 1 0.0047 0.17 0.6918 F l x Co 1 0.0001 0.01 0.9425 Pr x Co 1 0.0006 0.02 0.8882 Residual 9 0.0282 Total 23 3 Age 1, Relative Growth Source of Variation d.f. Mean Square F-ratio Probability Strain 2 0.7036 98.14 0.0000 Feeding level 1 0.6673 93.07 0.0000 Protein source 1 0.0352 4.92 0.0537 Protein concentration 1 0.0387 5.40 0.0452 St x F l 2 0.0660 9.21 0.0066 St x Pr 2 0.0206 2.88 0.1078 St x Co 2 0.0109 1.52 0.2701 F l x Pr 1 0.0000 0.00 0.9925 F l x Co 1 0.0515 7.19 0.0252 Pr x Co 1 0.0021 0.30 0.5991 Residual 9 0.0072 Total 23 Newman-Keuls multiple range test was performed on means using a significance probability level of 0.05. Percent of liv e body weight per day. -172-Table IXA. Analysis of variance table for r e l a t i v e growth as dry tissue for groups of age 0 and age 1 rainbow trout fed one of four diets at satiation for 21 days. Age 0, Relative Growth Source of Variation d.f. Mean Square F-ratio Probability Strain 2 15.406 325.38 0.0000 Feeding level 1 4.5240 95.55 0.0000 Protein source 1 0.2795 5.90 0.0380 Protein concentration 1 0.0304 0.64 0.4437 St x F l 2 0.8532 18.02 0.0007 St x Pr 2 0.2452 5.18 0.0319 St x Co 2 0.0837 1.77 0.2252 F l x Pr 1 0.0711 1.50 0.2516 F l x Co 1 0.0517 1.09 0.3233 Pr x Co 1 0.0032 0.07 0.8015 Residual 9 0.0473 Total 23 Age 1, Relative Growth Source of Variation d.f. Mean Square F-ratio Probability Strain 2 0.8375 60.38 0.0000 Feeding level 1 1.1585 83.52 0.0000 Protein source 1 0.1026 7.39 0.0236 Protein concentration 1 0.0050 0.36 0.5624 St x F l 2 0.0626 4.51 0.0439 St x Pr 2 0.0014 0.10 0.9077 St x Co 2 0.0238 1.72 0.2334 Fl x Pr 1 0.0057 0.37 0.5602 F l x Co 1 0.0078 0.56 0.4721 Pr x Co 1 0.0453 3.27 0.1041 Residual 9 0.0139 Total 23 Newraan-Keuls multiple range test was performed on the means using a significance probability level of 0.05. Percent of dry body weight per day. -173-Table XA. Analysis of variance table for condition f a c t o r and c o e f f i -c i e n t of v a r i a t i o n f o r c o n d i t i o n f a c t o r of groups of age 0 and age 1 rainbow trout receiving one of eight dietary treatments f o r 21 days. Age 0, Condition Factor Source of V a r i a t i o n d.f. Mean Square F - r a t i o P r o b a b i l i t y Time 1 0.0184 13.88 0.0011 S t r a i n 2 0.2612 196.94 0.0000 Feeding l e v e l 1 0.0120 9.07 0.0062 Diet 3 0.0032 2.43 0.0909 T i x St 2 0.0002 0.17 0.8437 T i x F l 1 0.0012 0.90 0.3514 T i x Dt 3 0.0003 0.21 0.8874 St x F l - 2 0.0053 4.01 0.0321 St x Dt 6 0.0036 2.72 0.0381 F l x Dt 3 0.0034 • 2.58 0.0778 Residual 23 0.0013 To t a l 47 Age 1, C o e f f i c i e n t of V a r i a t i o n , Condition Factor Source of V a r i a t i o n d.f. Mean Square F - r a t i o P r o b a b i l i t y Time 1 1.3534 0.52 0.4780 S t r a i n 2 16.887 6.49 0.0058 Feeding l e v e l 1 0.7351 0.28 0.6001 Diet 3 8.7680 3.37 0.0358 T i x St 2 12.558 4.83 0.0178 T i x F l 1 5.4540 2.10 0.1611 T i x Dt 3 3.0467 1.17 0.3422 St x F l 2 2.5319 0.97 0.3928 St x Dt 6 7.0097 2.70 0.0394 F l x Dt 3 1.8965 0.73 0.5451 Residual 23 2.6008 To t a l 47 1 Four d i e t s (2 protein sources x 2 f e e d i n g l e v e l s ( s a t i a t i o n and 50 using the Newman-Keuls range test protein concentrations) fed at two % s a t i a t i o n ) . Means were compared (p<0.05). Refer to t a b l e s XX f o r a d e f i n i t i o n of c o n d i t i o n f a c t o r . Tab le X I A . Mean c o n v e r s i o n o f f e e d , p r o t e i n and energy i n groups o f ra inbow t r o u t g i v e n one o f f o u r d i e t s ( T a b l e I I ) a t s a t i a t i o n (100) o r 50 % o f s a t i a t i o n ( 5 0 ) f o r 21 days a t age 0 . D i e t a r y Mean Feed P r o t e i n P r o d u c t i v e Net Net Treatment I n i t i a l BW Convers ion E f f i c i e n c y P r o t e i n P r o t e i n Energy Convers ion and S t r a i n gm. E f f i c i e n c y R a t i o Va lue E f f i c i e n c y Convers ion Energy Sun V a l l e y FM.1-100 0 .58 0 .682 3.182 0 .347 0 .701 0 .195 0 .301 FM.1-50 0 .54 0 .767 3.575 0 .390 1.111 0 . 2 3 0 0 .437 FM.2-100 0 .58 1.079 3.320 0 .384 0.687 0 .302 0 .431 FM.2-50 0 .63 1.100 3.385 0 .383 0 .970 0 .293 0 .539 SBM.1-100 0.57 0 .753 3.442 0 .385 0 .735 0 .216 0 .323 SBM. 1-50 0.55 0 .817 3.736 0 .409 1.121 0 . 2 3 1 0 .438 SBM. 2-100 0 .56 1.040 3.357 0 .408 0 .728 0 . 3 1 0 0 .444 SBM.2-50 0 .58 1.049 3.386 0 .382 1.003 0 . 2 9 0 0 .546 Pennask FM. 1-100 1.78 0 .134 0.626 0 .020 0 .647 0 .009 0.127 FM.1-50 1.80 - 0 . 2 2 4 - 1 . 0 4 6 - 0 . 1 1 8 1.106 - 0 . 0 7 9 0 .507 FM.2-100 1.73 0 .205 0 .631 - 0 . 0 4 7 0 .373 - 0 . 0 0 4 0 .286 FM.2-50 1.74 0 .388 1.193 - 0 . 0 9 0 0 .714 - 0 . 0 4 8 0 .506 SBM.1-100 1.78 0 .363 1.662 0 .163 0 .569 0 .116 0 .316 SBM.1-50 1.68 0 .361 1.649 0 .050 0.837 0 .066 0 .448 SBM.2-100 1.81 0 .413 1.333 0 .177 0 .482 0 . 1 2 0 0.447 SBM.2-50 1.81 0 .472 1.525 0.077 0 .680 0 .113 0 .523 Premier FM. 1-100 2 .69 0 .716 3.340 0 .292 0 .726 0 .207 0.473 FM.1-50 2.72 0 .505 2.354 0 .281 1.031 0 .226 0 .687 FM.2-100 2 .70 0 .629 1.936 " 0 .252 0 .632 0 . 2 3 0 0.567 FM.2-50 2 .63 0 .515 1.585 0 .215 0 .917 0 .194 0 .821 SBM.1-100 2.67 0 .586 2.678 0.332 0 .706 0 .213 0.447 SBM.1-50 2.66 0 .448 2.049 0 .255 0 .975 , 0 . 1 8 0 0 .631 SBM.2-100 2.76 0 .632 2.041 0 .286 0 .572 0 .258 0 .505 SBM.2-50 2.63 0 .575 1.857 0 .259 0 .795 0 .225 0 .691 T a b l e X I B . Mean c o n v e r s i o n o f f e e d , p r o t e i n and energy i n groups o f ra inbow t r o u t f e d one o f f o u r d i e t s ( T a b l e I I ) a t s a t i a t i o n (100) o r 50 % o f s a t i a t i o n (50 ) f o r 21 days a t age 1 . D i e t a r y Mean Feed P r o t e i n P r o d u c t i v e Net Ne-Trea tment I n i t i a l BW Convers ion E f f i c i e n c y P r o t e i n P r o t e i n Energy Convers i t and S t r a i n gnu E f f i c i e n c y R a t i o Va lue E f f i c i e n c y Convers ion Energy Sun V a l l e y FM. 11-100 55 .89 0 .496 2.453 0 .206 0 .366 0.229 0 .350 FM. 11-50 45 .36 0 .528 2 .611 0 .252 0 . 5 1 1 0 .211 0 .402 FM. 12-100 56 .16 0 .674 2.239 0 .185 0 .287 0.262 0 .375 FM. 12-50 56 .07 0 .328 1.090 0 .021 0 . 2 1 1 0.105 0 .313 SBM.11-100 53 .72 0 .610 2.998 0 .282 0 .412 0.257 0 .357 SBM.11-50 50 .67 0 .564 2.773 0.197 0 .428 0.216 0 . 3 9 1 SBM. 12-100 51 .68 0 .746 2.363 0 .273 0 .369 0 .228 0 .339 SBM.12-50 52 .49 0 .573 1.815 0.252 0 . 4 4 0 0.153 0 .368 Pennask FM.11-100 4 1 . 3 0 0 .405 2.006 0 .379 0 . 4 4 1 0 .180 0 .301 FM. 11-50 37 .88 0 .096 0 .474 - 0 . 0 6 8 0 .073 - 0 . 2 6 6 - 0 . 0 2 2 FM.12-100 39 .77 0 .603 2.002 0 .275 0 .335 0 .043 0 .205 FM. 12-50 40 .07 0 .351 1.167 0 .338 0 .468 0.009 0 .363 SBM.11-100 4 2 . 2 8 0 .180 0 .886 0 .483 0 . 5 7 0 0 .318 0 .490 SBM. 11-50 37 .37 0 .117 0 .579 0 .272 0 . 4 5 0 0.076 0 .398 SEM.12-100 36 .49 0 .719 2.276 0 .415 0 .475 0.242 0 .405 SBM. 12-50 41 .82 0 .357 1.131 0 .385 0 .504 0 .159 0 .502 Premier FM. 11-100 4 3 . 4 3 0 .298 1.475 0 .091 0 . 5 0 1 0.073 0 .294 FM.11-50 4 1 . 6 0 - 0 . 0 6 6 - 0 . 3 2 6 - 0 . 3 7 1 0 .445 - 0 . 2 4 5 0 .193 FM.12-100 3 8 . 4 1 0.747 2.482 0 .033 0 .299 0.158 0 .329 FM. 12-50 36 .47 0.247 0 .821 - 0 . 2 7 3 0 .148 - 0 . 2 0 5 0 .127 SBM.11-100 3 9 . 1 1 0 .475 2.335 0 .175 0 .465 0 .120 0 .278 SBM.11-50 38 .79 0 .275 1.351 - 0 . 1 2 0 0 .422 - 0 . 0 0 1 0 .294 SBM.12-100 4 2 . 2 8 0 .569 1.801 0.142 0 .316 0 .180 0 .322 SBM.12-50 41 .27 0.413 1.307 - 0 . 2 0 2 0 .156 - 0 . 1 1 1 0 .183 -176-Table XIIA. A n a l y s i s of v a r i a n c e t a b l e f o r feed c o n v e r s i o n e f f i c i e n c y f o r groups of age 0 and age 1 rainbow t r o u t fed one of fo u r d i e t s at s a t i a t i o n or 50 % of s a t i a t i o n for 21 days. Age 0, Feed Conversion E f f i c e i n c y . 2 Source of V a r i a t i o n d.f. Mean Square F - r a t i o P r o b a b i l i t y S t r a i n 2 0.8373 72.56 0.0000 Feeding l e v e l 1 0.0088 0.76 0.4058 Protein source 1 0.0428 3.70 0.0864 Protein concentration 1 0.1997 17.30 0.0024 St x F l 2 0.0154 1.33 0.3111 St x Pr 2 0.0561 4.86 0.0370 St x Co 2 0.0428 3.71 0.0670 F l x Pr 1 0.0045 0.39 0.5474 F l x Co 1 0.0182 1.58 0.2407 Pr x Co 1 0.0097 0.84 0.3826 Residual 9 0.0115 Tota l 23 Age 1, Feed Conversion E f f i c i e n c y . Source of V a r i a t i o n d.f. Mean Square F - r a t i o P r o b a b i l i t y S t r a i n 2 0.1071 9.38 0.0063 Feeding l e v e l 1 0.3065 26.84 0.0006 Protein source 1 0.0351 3.08 0.1134 Protein concentration 1 0.2246 19.68 0.0016 St x F l 2 0.0166 1.45 0.2844 St x Pr 2 0.0141 1.24 0.3354 St x Co 2 0.0449 3.93 0.0593 F l x Pr 1 0.0211 1.85 0.2069 F l x Co 1 0.0275 2.41 0.1553 Pr x Co 1 0.00004 0.00 0.9852 Residual 9 0.0114 To t a l 23 1 Means for s i g n i f i c a n t main e f f e c t s and i n t e r a c t i o n s were compared by the Newman-Keuls mu l t i p l e range te s t at a p r o b a b i l i t y "".evel of 0.05. 2 Mean BW gain (g) / g dry feed consumed. -177-Table XIIIA. A n a l y s i s of v a r i a n c e t a b l e f o r P r o t e i n E f f i c i e n c y R a t i o f o r groups of age 0 and age 1 rainbow t r o u t f e d one of f o u r d i e t s at s a t i a -t i o n or 50 % of s a t i a t i o n for 21 days.l Age 0, Protein E f f i c i e n c y Ratio.2 Source of V a r i a t i o n d.f. Mean Square F - r a t i o P r o b a b i l i t y S t r a i n 2 12.269 49.06 0.0000 Feeding l e v e l 1 0.2204 0.88 0.3724 Protein source 1 0.8948 3.58 0.0911 Protein concentration 1 0.1201 0.48 " 0.5058 St x F l 2 0.2710 1.08 0.0378 St x Pr 2 1.0066 4.02 0.0564 St x Co 2 0.7185 2.87 0.1084 F l x Pr 1 0.1173 • 0.47 0.5107 F l x Co 1 0.3567 1.43 0.2629 Pr x Co 1 0.1256 0.50 0.4965 Residual 9 0.2501 T o t a l 23 Age 1, Protein E f f i c i e n c y Ratio. Source of V a r i a t i o n d.f. Mean Square F - r a t i o P r o b a b i l i t y S t r a i n 2 2.3343 10.42 0.0045 Feeding l e v e l 1 4.6139 20.60 0.0014 Protein source 1 0.4059 1.81 0.2112 Protein concentration 1 0.0322 0.14 0.7134 St x F l 2 0.3243 1.45 0.2850 St x Pr 2 0.3289 1.47 0.2806 St x Co 2 1.2640 5.64 0.0258 F l x Pr 1 0.4048 1.81 0.2117 F l x Co 1 0.0542 0.24 0.6344 Pr x Co 1 0.0745 0.33 0.5783 Residual 9 0.2240 To t a l 23 1 Means for s i g n i f i c a n t main e f f e c t s and i n t e r a c t i o n s were compared by the Newman-Keuls mult i p l e range test at a p r o b a b i l i t y l e v e l of 0.05. 2 Mean BW gain (g) / g protein consumed. -178-Table XIVA. A n a l y s i s of v a r i a n c e t a b l e f o r P r o d u c t i v e P r o t e i n Value of groups of age 0 and age 1 rainbow t r o u t f e d one of f o u r d i e t s at s a t i a -t i o n or 50 % of s a t i a t i o n f o r 21 days.l Age 0, Productive Protein Value.2 Source of V a r i a t i o n d.f. Mean Square F - r a t i o P r o b a b i l i t y S t r a i n 2 0.2666 470.34 0.0000 Feeding l e v e l 1 0.0104 18.45 0.0020 Protein source 1 0.0315 55.51 0.0000 Protein concentration 1 0.0005 0.97 0.3499 St x F l 2 0.0060 10.66 0.0042 St x Pr 2 0.0159 28.14 0.0001 St x Co 2 0.0012 2.04 0.1865 F l x Pr 1 0.0008 1.38 0.2703 F l x Co 1 0.0001 0.14 0.7209 Pr x Co 1 0.0003 0.81 0.3914 Residual 9 0.0006 T o t a l 23 Age 1, Productive Protein Value. Source of V a r i a t i o n d.f. Mean Square F - r a t i o P r o b a b i l i t y S t r a i n 2 0.2912 26.47 0.0002 Feeding l e v e l 1 0.2216 20.14 0.0015 Protein source 1 0.0859 7.81- 0.0209 Protein concentration 1 0.0006 0.05 0.8264 St x F l 2 0.0494 4.50 0.0443 St x Pr 2 0.0027 0.24 0.7899 St x Co 2 0.0099 0.90 0.4390 F l x Pr 1 0.0046 0.42 0.5319 F l x Co 1 0.0151 1.37 0.2714 Pr x Co 1 0.0011 0.10 0.7569 Residual 9 0.0110 To t a l 23 1 Means for s i g n i f i c a n t main e f f e c t s and i n t e r a c t i o n s were compared by the Newman-Keuls mult i p l e range test c t a p r o b a b i l i t y l e v e l of 0.05. 2 [(Mean carcas protein f i n a l , g) - (Mean carcass protein i n i t i a l , g)]/ g protein consumed. -179-Table XVA. Analysis of variance table f o r Energy Conversion of groups of age 0 and age 1 rainbow t r o u t f e d one of four d i e t s a t s r . t i a t i o n or 50 % of s a t i a t i o n f o r 21 days.l Age 0, Energy Conversion. Source of V a r i a t i o n d.f. Mean Square F - r a t i o P r o b a b i l i t y S t r a i n 2 0.1111 228.82 0.0000 Feeding'level 1 0.0026 5.41 0.0451 Protein source 1 0.0142 29.17 0.0004 Protein concentration 1 0.0093 19.20 0.0018 St x F l 2 0.0014 2.84 0.1107 St x Pr 2 0.0110 22.68 0.0003 St x Co 2 0.0026 5.29 0.0303 F l x Pr 1 0.0000 0.00 0.9641 F l x Co 1 0.0001 0.19 0.6735 Pr x Co 1 0.0003 1.14 0.3144 Residual 9 0.0005 To t a l 23 Age 1, Energy Conversion. Source of V a r i a t i o n d.f. Mean Square F - r a t i o P r o b a b i l i t y S t r a i n 2 0.0896 12.48 0.0025 Feeding l e v e l 1 0.1996 27.82 0.0005 Protein source 1 0.0686 9.56 0.0129 Protein concentration 1 0.0001 0.02 0.8975 St x F l 2 0.0206 2.87 0.1083 St x Pr 2 0.0192 2.67 0.1230 St x Co 2 0.0033 0.46 0.6451 F l x Pr 1 0.0097 1.35 0.2744 F l x Co 1 0.0014 0.19 0.6697 Pr x Co 1 0.0044 0.61 0.4537 Residual 9 0.0072 a T o t a l 23 1 Means for s i g n i f i c a n t main e f f e c t s and i n t e r a c t i o n s were compared by the Newman-Keuls mult i p l e range t e s t at e. p r o b a b i l i t y l e v e l of 0.05. 2 Mean carcasss gross energy gain, K c a l ^ - T l / Kcal consumed. -180-Table XVIA. A n a l y s i s of v a r i a n c e t a b l e f o r Net P r o t e i n E f f i c i e n c y of groups of age 0 and age 1 rainbow t r o u t f e d one of f o u r d i e t s at s a t i a -t i o n or 50 % of s a t i a t i o n f o r 21 days.l Age 0, Net Protein E f f i c i e n c y 2 Source of V a r i a t i o n d.f. Mean Square F - r a t i o P r o b a b i l i t y S t r a i n 2 0.0860 28.20 0.0001 Feeding l e v e l 1 0.5726 187.82 0.0000 Protein source 1 0.0069 2.26 0.1667 Protein concentration 1 0.1214 39.83 0.0001 St x F l 2 0.0025 0.81 0.4729 St x Pr 2 0.0063 2.06 0.1834 St x Co 2 0.0128 4.20 0.0514 F l x Pr 1 0.0088 2.88 0.1240 F l x Co 1 0.0099 3.24 0.1053 Pr x Co 1 0.0051 1.68 0.2267 Residual 9 0.0030 T o t a l 23 Age 1, Net Protein E f f i c i e n c y Source of V a r i a t i o n d.f. Mean Square F - r a t i o P r o b a b i l i t y S t r a i n 2 0.0099 0.78 0.4865 Feeding l e v e l 1 0.0140 1.10 0.3214 Protein source 1 0.0354 2.78 0.1296 Protein concentration 1 0.0482 3.79 0.0834 St x F l 2 0.0117 0.92 0.4343 St x Pr 2 0.0161 1.27 0.3275 St x Co 2 0.0424 3.33 0.0825 F l x Pr 1 0.0011 0.09 0.7707 F l x Co 1 0.0031 0.24 0.6344 Pr x Co 1 0.0004 0.03 0.8577 Residual 9 0.0127 T o t a l 23 1 Means f o r s i g n i f i c a n t main e f f e c t s and i n t e r a c t i o n s were compared by the Mewman-Keuls mu l t i p l e range t e s t at a pvobability l e v e l of 0.05. 2 [(Carcass protein, g) fed + (Carcass protein loss, g)starved]/ o protein consumed. -181-Table XVIIA. Analysis of variance table f o r Net Conversion of Energy of groups of age 0 and age 1 rainbow t r o u t f e d one of f o u r d i e t s at s a t i a -t i o n or 50 % of s a t i a t i o n f o r 21 days.l Age 0, Net Conversion of Energy2 Source of V a r i a t i o n d.f. Mean Square F - r a t i o P r o b a b i l i t y S t r a i n 2 0.1084 78.77 0.0000 Feeding l e v e l 1 0.2065 149.99 0.0000 Protein source 1 0.0001 0.05 0.8224 Protein concentration 1 0.0461 33.50 0.0003 St x F l 2 0.0076 5.56 0.0268 St x Pr 2 0.0070 5.09 0.0334 St x Co 2 0.0015 1.06 0.3858 F l x Pr 1 0.0066 4.80 0.0563 F l x Co 1 0.0004 0.28 0.6102 Pr x Co 1 0.0014 1.02 0.3378 Residual 9 0.0014 To t a l 23 Age 1, Net Conversion of Energy Source of V a r i a t i o n d.f. Mean Square F - r a t i o P r o b a b i l i t y S t r a i n 2 0.0253 2.79 0.1143 Feeding l e v e l 1 0.0118 1.30 0.2833 Protein source 1 0.0501 5.51 0.0434 Protein concentration 1 0.0005 0.05 0.8272 St x F l 2 0.0072 0.79 0.4322 St x Pr 2 0.0322 3.54 0.0732 St x Co 2 0.0070 0.77 0.4918 F l x Pr 1 0.0075 0.82 0.3888 F l x Co 1 0.0036 0.40 0.5434 Pr x Co 1 0.0033 0.37 0.5596 Residual 9 0.0091 To t a l 23 1 >.eans f o r s i g n i f i c a n t main e f f e c t s and i n t e r a c t i o n s were compared by the Newman-Keuls mu l t i p l e range t e s t at a p r o b a b i l i t y l e v e l of 0.05. 2 [(Carcass energy gain, K c a l ) f e d + (Carcass energy l o s s , ; K c a l ) s t a r v e d ] / Kcal gross energy consumed. -182-Table XIVA. Measurements of dissolved oxygen made during analysis of ammonia excretion by s t r a i n s of age 1 rainbow trout. -Ul Concentration (mg.l S t r a i n Time of day 11.00 11.30 12.30 13.30 14.30 15.30 Day 1 * * * Sun Valley 6.4 7.0 6.0 Pennask 6.7 8.2 7.6 Premier 7.4 7.8 6.2 C o n t r o l 2 9.2 8.2 8.2 Day 2 Sun Valley 6.8 6.2 6.7 6.2 6.6 6.2 Pennask 8.2 8.0 7.3 8.0 8.2 7.1 Premier 6.6 6.1 6.4 6.0 6.7 5.8 Control 8.2 8.2 8.2 8.2 8.2 8.1 During t r i a l run of experiment using SBM.11 (Table IIa,b). A s t e r i s k i n d i a t e s end of one hour p e r i o d w i t h no water f l o w ( i . e . s t a n d i n g water). Similar to experimental tanks, but without f i s h . 

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