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The nutrition of the female pastel mink (Mustela vison) Farrell, David James 1966

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THE NUTRITION OF THE FEMALE PASTEL MINK (Mustela vlson) by DAVID JAMES FARRELL Diploma i n A g r i c u l t u r e , The Royal A g r i c u l t u r a l College, Cirencester, England, 1954 B.S.A., Univ e r s i t y of B r i t i s h Columbia, 1964 A Thesis Submitted i n P a r t i a l Fulfilment of the Requirements for the Degree of MASTER OF SCIENCE IN AGRICULTURE i n the D i v i s i o n of Animal Science We accept t h i s thesis as conforming to the standard required from candidates for the Degree of Master of Science i n Ag r i c u l t u r e THE UNIVERSITY OF BRITISH COLUMBIA July, 1966 In presenting t h i s thesis i n p a r t i a l f u l f i l m e n t of the requirements for an advanced degree at the University of B r i t i s h Columbia, I agree that the Library s h a l l make i t f r e e l y available for reference and study. I further agree that permission., for extensive copying of t h i s thesis for scholarly purposes may be granted by the Head of my Department or by his representatives. I t i s understood that copying or publication of t h i s thesis f o r f i n a n c i a l gain s h a l l not be allowed without my written permission. Department of ^UtA^a£ </c • The University of B r i t i s h Columbia Vancouver 8 , Canada ABSTRACT A study, comprised of f i v e p a r t s , has been p a r r i e d out on seven a d u l t , female, p a s t e l mink. Metabolic responses to ambient temperature have shown that these mink cannot t o l e r a t e temperatures much above 29°C, but are not unduly d i s t u r b e d by low temperatures around 0°C Under s l e e p i n g c o n d i t i o n s , and w i t h i n t h e i r thermal n e u t r a l zone (25_2 C) , the three animals measured d i d not demonstrate an abnormally high metabolic r a t e . Under c o n d i t i o n s pf prolonged f a s t , these mink appeared to maintain normal a c t i v i t y , although they l o s t much bodyweight. The apparently h i g h , d a i l y , u r i n a r y , n i t r o g e n e x c r e t i o n , when r e l a t e d to heat p r o d u c t i o n , gave a value of 2.5 mg of u r i n a r y n i t r o g e n per C a l o r i e (A.D.E.). The e f f e c t of a d d i t i o n s of f i b r e to a b a s a l r a t i o n has shown an in v e r s e r e l a t i o n s h i p between t h i s component and the time of passage of the feed. The apparent d i g e s t i b i l i t y of the ash component i n the r a t i o n was markedly decreased w i t h i n c r e a s i n g increments of d i e t a r y f i b r e , but that of the f a t was only very s l i g h t l y reduced. Under these experimental c o n d i t i o n s , n i t r o g e n r e t e n t i o n appears to be always p o s i t i v e , p o s s i b l y r e f l e c t i n g a constant demand f o r f u r growth, and a constant l o s s of n i t r o g e n i n the form of ammonia. Maintenance energy (A.D.E.) requirements of these mink have been q u a n t i t a t e d . The e f f e c t s of a decrease i n cage c a p a c i t y and the additions of f i b r e to the r a t i o n appear to decrease the animal's energy requirements. The C a l o r i c intake of a one kg mink i s almost i d e n t i c a l to that suggested by the N.R.C. Water intake, when rel a t e d to energy (A.D.E.), i s appreciably l e s s than the 1 gm / C a l o r i e of heat produced generally accepted for mammals. However, i t i s i n close agree-ment with figures obtained for the cat and for the mouse. The addit i o n of a non-nutritive bulk to the r a t i o n s i g n i f i c a n t l y increases the water intake when rel a t e d to the A.D.E. of the r a t i o n . i v TABLE OF CONTENTS Page ABSTRACT v i i TABLE OF CONTENTS •.. i v LIST OF TABLES v i i LIST OF FIGURES v i i i ACKNOWLEDGEMENTS . x INTRODUCTION • , . 1 PART I - THE METABOLIC RATE OF THE MINK 3 Introduction . . . . . . . . 3 Experimental 3 Animals 4 Apparatus 4 Acclimation 4 Metabolic determinations 4 Results and Discussion ; . . 5 A. Metabolic Rate i n Relation to Ambient Temperature . . . . . . . . . . . 5 B. Basal Metabolism 9 Bibliography 14 PART II - STUDIES ON THE MINK DURING STARVATipN 16 Introduction • 16 Experimental 16 Animals , • 16 Housing . . . . . 16 Data C o l l e c t i o n . . . . . 17 Chemical Analysis . . . . . . . . 17 Results , 18 Discussion 23 Bibliography . . . . . 28 V TABLE OF CONTENTS (cont'd) Page PART III - THE EFFECT OF THE ADDITION OF FIBRE TO THE RATION 30 Introduction 30 Experimental . . . ." . 31 General 31 Animals 31 A n a l y t i c a l Methods 34 Time of Passage Studies 34 Results and Discussion . . . . . 35 1. Time of Passage 35 2. Apparent D i g e s t i b i l i t y . 35 3. Nitrogen Retained 38 Bibliography 42 PART IV - ENERGY REQUIREMENTS FOR MAINTENANCE 44 Introduction 44 Experimental 46 Animals and Treatment 46 Rations . . . . 46 Housing 46 Special Equipment 46 Data C o l l e c t i o n 47 Results 48 Discussion 55 Bibliography 60 PART V - WATER REQUIREMENTS FOR MAINTENANCE . . . . . . . 63 Introduction . . . . . 63 Experimental 64 Special Equipment 64 Feed Moisture 64 Metabolic Water 64 Results 65 v i TABLE OF CONTENTS (cont'd) Page D i s c u s s i o n . 65 B i b l i o g r a p h y , . . 71 APPENDICES I An I n d i r e c t Animal Calorimeter 73 I I Mink Cereal Grain P e l l e t s 78 I I I I n d i v i d u a l Weight Records (grams) of Con t r o l s . . 79 IV I n d i v i d u a l Weekly Weight Records (grams) 80 V I n d i v i d u a l D a i l y Feed Intake Records (grams) . . 81 VI D a i l y Feed (dry) Intake and Mean Body Weight of Mink During D i g e s t i b i l i t y T r i a l s i n Metabolism Cages 85 VI I Mean Net D a i l y Water Intake f o r Each Mink (grams) 86 V I I I I n d i v i d u a l Weekly Weigh-back of Feed (grams) , . 87 IX Mean D a i l y Urine Volume Voided by Mink Housed i n Metabolism Cages and Measured During S t a r v a t i o n and D i g e s t i b i l i t y T r i a l s . , . . 88 v i i LIST OF TABLES TABLE Page PART I: THE METABOLIC RATE OF THE MINK I The r e s p i r a t i o n rate of mink no. P7 recorded during metabolism t r i a l s at various ambient temperatures . . . 8 II Measurements of the basal metabolic rate of three mink 10 II I Heat production of f a s t i n g adult mink 12 PART I I : STUDIES ON THE MINK DURING STARVATION I The mean d a i l y f a e c a l excretion, and i t s composition from mink fasted 19 II D a i l y loss i n body weight of three fasted mink during January 20 II I The d a i l y nitrogen excretion of fasted mink during September and January 22 IV The r e l a t i o n s h i p between the heat production qf an untrained fasted mink i n the respirometer and the animal's calculated basal metabolism rate . 25 PART I I I : . THE ...EFFECT OF. THE -ADDITION OF FIBRE TO THE RATION I The composition of the basal r a t i o n on an "as mixed" basis 32 II Composition and mean r e s u l t s of analyses of the diet s used . 33 III Time (minutes) required for a marked feed to appear i n the faeces of female p a s t e l mink on d i e t s containing various f i b r e l e v e l s 35 IV The apparent nitrogen retained by female p a s t e l mink during metabolism studies , . 39 v i i i LIST OF FIGURES FIGURE Page PART I: THE METABOLIC RATE OF THE MINK 1 The r e l a t i o n s h i p between rate of oxygen consumption and ambient temperature for mink no. P7 6 2 The r e l a t i o n s h i p between rate of oxygen consumption and ambient temperature for mink no. P5 7 PART I I I : THE EFFECT OF THE ADDITION OF FIBRE TO THE RATION 1 The apparent d i g e s t i b i l i t y of the f a t , p r o t e i n , ash and complete rations as affected by f i b r e l e v e l i n the r a t i o n 36 PART IV: ENERGY REQUIREMENTS FOR MAINTENANCE 1 The r e l a t i o n s h i p between the apparent d i g e s t i b l e energy intake and the body weight of a l l mink on a l l four rations and housed i n ranch-type cages . . . . . . . . 4 9 2 The r e l a t i o n s h i p between the apparent d i g e s t i b l e energy intake and the body weight of those mink which showed no weight change and were housed i n ranch-type cages and maintained on the basal r a t i o n 50 3 The r e l a t i o n s h i p between the apparent d i g e s t i b l e energy intake and the body weight of mink receiving the basal r a t i o n and housed i n metabolism cages 51 4 A diagrammatic representation of the apparent d i g e s t i b l e energy intake of each i n d i v i d u a l mink on the four rations and of t h e i r weight changes while on the rations 54 PART V: WATER REQUIREMENTS FOR MAINTENANCE 1 The r e l a t i o n s h i p between t o t a l water and apparent d i g e s t i b l e energy intake of mink rec e i v i n g the basal r a t i o n and housed i n ranch-style cages 66 i x LIST OF FIGURES (cont'd) FIGURE Page 2 The r e l a t i o n s h i p between water intake and body weight of mink re c e i v i n g the basal r a t i o n and housed i n ranch-style cages 67 3 The r e l a t i o n s h i p between water intake and body weight of mink re c e i v i n g the basal r a t i o n , housed i n ranch-style cages, and demonstrating weight s t a s i s 68 APPENDIX 1 A diagrammatic representation of the respirometer . . 74 X ACKNOWLEDGEMENTS I wish to thank Dr. B.A. Eagles, Dean of the F a c u l t y of A g r i c u l t u r e and Chairman of the D i v i s i o n of Animal Science, f o r h i s permission to undertake t h i s p r o j e c t and f o r the use of the req u i r e d f a c i l i t i e s . A l s o my thanks are extended to those at the U n i v e r s i t y of V i c t o r i a who permitted the completion of t h i s study at that i n s t i t u t i o n . To Dr. A.J. Wood, Dean of A r t s and Science a t the U n i v e r s i t y of V i c t o r i a (formerly P r o f e s s o r of Animal Science at the U n i v e r s i t y of B r i t i s h Columbia) I wish to express my s i n c e r e thanks f o r h i s i n t e r e s t , encouragement and guidance throughout the course of t h i s study. F i n a l l y , the author i s s i n c e r e l y g r a t e f u l to h i s w i f e , P e a r l , whose s a c r i f i c e s and encouragement have made these years of graduate study p o s s i b l e . INTRODUCTION INTRODUCTION ".... the p r a c t i c a l problems of meeting the n u t r i t i o n a l needs of stock are major i n l i v e s t o c k husbandry. At the outset i t i s important to r e a l i z e the c e n t r a l and overriding importance of energy i n any consideration of n u t r i t i o n . " K.L. Blaxter The general lack of precise information on basic n u t r i t i o n a l requirements of the mink i s becoming more apparent with the increasing demands of the industry to reduce feed costs. To date,, the majority of mink research has centred around the replacement of one r a t i o n ingredient with another and the recording of the r e s u l t s obtained i n terms of p e l t q u a l i t y and growth rate performance. The f a i l u r e to provide the mink industry with a dry synthetic d i e t on which an animal can grow, reproduce and l a c t a t e , i s evidence enough that t h i s r a p i d l y growing industry i s i n need of a more fundamental approach to i t s research problems. Because much of the f i n a n c i a l support for mink research has been provided by the feed Industry and the mink industry, i t follows that the r e s u l t s must be of such a nature that t h e i r a p plications to p r a c t i s e be both obvious and immediate. Some current problems facing the mink industry concern-pelt q u a l i t y , kidney damage, the sudden deaths of apparently healthy animals, and the f a i l u r e of females to l a c t a t e , to mention but four. . It may be of some importance to re-examine the nutrient requirements of t h i s species, bearing i n mind the e f f e c t s of 2 other r a t i o n components on the absorption of these n u t r i e n t s , the implications of high energy r a t i o n s , and the e f f e c t s of storage on the a v a i l a b i l i t y and destruction of these nutrients present i n animal proteins. It i s the object of t h i s thesis to study i n t e n s i v e l y a few mink under c l e a r l y defined conditions, uncomplicated by appreciable growth or reproductive stresses. The f i n a l r e s u l t s may not be s t a r t l i n g but they may be siuch that others can study c e r t a i n i n t e r e s t i n g aspects i n more depth. Some of t h i s subject matter under consideration may not be applicable to the operation of an a g r i c u l t u r a l enterprise. But such apparently impractical investigations are extremely important because they "have d i g n i f i e d the c a l l i n g of a g r i c u l t u r e and have given the farmer an i n t e l l e c t u a l background and basis for his thinking that cannot be e a s i l y measured." F.B. Mumford. THE NUTRITION OF THE FEMALE PASTEL MINK (Mustela vison) PART I: THE METABOLIC RATE OF THE MINK 3 INTRODUCTION Basal metabolism values serve as a u s e f u l baseline i n estab-l i s h i n g the energy requirements of a species for maintenance and for production (2, 5, 7, 8). The main object of t h i s study has been to measure the basal metabolic rate of the mink. R e l a t i v e l y l i t t l e information i s a v a i l a b l e on the heat production of fur bearing animals (11, 12). Russian workers have reported values for the heat production of adult s i l v e r foxes (13) and of mink (10). EXPERIMENTAL The energy metabolism of an animal may be reduced to a minimum l e v e l by removing those influences that tend to increase i t s heat production; i n p a r t i c u l a r , the influence of feed, a c t i v i t y and the stimulus of heat or cold. For the purposes of t h i s study, the following conditions were established for the metabolic rate measurements: 1. The basal metabolic rate measurements commenced not less than f i v e and one h a l f hours a f t e r feeding. Time of passage studies had shown that the mink becomes post-absorptive about f i v e hours a f t e r the ingestion of i t s l a s t feed. 2. The animal was i n a state of complete r e s t . Observations had shown that a state of complete r e s t i n the mink can only be assured i n the n a t u r a l l y sleeping, state; hence a l l measurements have been made with animals asleep. 4 3. The animal was w i t h i n i t s thermoneutral zone. Animals Two female p a s t e l ranch mink s e l e c t e d from a group of s i x animals (3) were used to determine both the zone of thermoneutrality and the b a s a l metabolic r a t e . A t h i r d mink from the same group was se l e c t e d f o r the determination of b a s a l metabolism only. Apparatus The apparatus used f o r metabolic r a t e measurements was an i n d i r e c t , closed c i r c u i t respirometer„ A d e s c r i p t i o n of the apparatus and i t s operation appears i n Appendix I . A c c l i m a t i o n Because the mink becomes hyperactive f o r prolonged periods when placed i n a confined space and i n u n f a m i l i a r surroundings, i t was f i r s t necessary to t r a i n the animals f o r periods up to four weeks to accept the environment of the respirometer (Appendix I) p r i o r to any metabolic t r i a l s . M etabolic determinations A l l t r i a l s were c a r r i e d out between 1400 and 1700 hours„ Extensive observations showed t h i s to be the pe r i o d of minimal a c t i v i t y 0 At the outset i t was necessary to a s c e r t a i n the thermal n e u t r a l zone of t h i s s p e c i e s . During these determinations, the mink had continuous access to t h e i r normal feed. The animals were asleep during the 5 period of measurement. The mink might therefore be considered to be i n the r e s t i n g state (2) rather than i n the basal state. RESULTS AND DISCUSSION A. Metabolic Rate i n Relation to Ambient Temperature The response of the mink, i n terms of oxygen consumption, to changes i n ambient temperature i s i l l u s t r a t e d i n Figure 1 and Figure 2. The equations for the near l i n e a r portions of these l i n e s were calculated using the method of l e a s t squares. Over t h i s temperature range, the oxygen consumption changed 1.00 cc/gm/24hr/°C for mink No. P7, and for mink No. P5 the corresponding value was 0.92. At 0°C the oxygen consumption was 40.4cc02/gm/24hr f o r mink No. P7, and 41.4cc02/gm/24hr for mink No. P5. A test of s i g n i f i c a n c e shows that the slopes of the two response l i n e s are not s i g n i f i c a n t l y d i f f e r e n t (F=.05). I t seems safe to conclude that basal metabolic rate can be determined within the thermal neutral zone shown i n Figure 1 and Figure 2. With the a v a i l a b l e instrumental procedures i t i s not possible to measure, metabolic rate with s u f f i c i e n t p r e c i s i o n to delineate a c r i t i c a l thermal neutral point. For example, i n the case of P7, oxygen uptake i s r e l a t i v e l y constant between 17 and 27°C. The record of the re s p i r a t o r y rate for one of the mink (Table I) agrees with t h i s observation. 6 \ FIGURE 1 : THE RELATIONSHIP BETWEEN RATE OF OXYGEN CONSUMPTION AND AMBIENT TEMPERATURE FOR MINK NO. P7 40 FIGURE 2 : THE RELATIONSHIP BETWEEN RATE OF OXYGEN CONSUMPTION AND AMBIENT TEMPERATURE FOR MINK NO. P5 TABLE I; THE RESPIRATION RATE OF MINK NO. P7 RECORDED DURING METABOLISM TRIALS AT VARIOUS AMBIENT TEMPERATURES Temperature Respiration Rate TC) (Respirations/Min) 16.2 21 18.5 21 22.6 21 24.2 19 26.1 20 29.0 21 Subsequent measurements of Basal Metabolic rate were carried out at a temperature of 25±2°C. Extrapolation of the linea r portion of the temperature response l i n e does not intercept the abscissa precisely at predicted normal body temperature. This departure i s not unexpected since the determinations were carried out over an extended period of time; hence, some fluctuation: i n the body weight of the mink was unavoidable, and as stated the animals were i n the resting rather than i n the basal state. A close observation of both animals during thermal adjustment t r i a l s showed that the mink has excellent powers of thermoregulation. At very low temperatures the mink takes the shape of a b a l l and with increasing ambient temperatures slowly unfolds. Mink No. P5 appeared more reluctant to regulate by changing body shape than did mink No. P7, Measurements could not be carried out on either animal at temperatures 9 above 29°C. Both animals became r e s t l e s s and the required sleeping condition could not be attained f or a s u f f i c i e n t length of time. I t would appear, therefore, that under p r a c t i c a l ranch conditions an ambient temperature approaching 29°C should be avoided when conditions of high humidity e x i s t . On the other hand, a temperature of about 2°C did not unduly disturb either animal. B. Basal Metabolism Basal heat production per unit of body weight i n mature animals of d i f f e r e n t species decreases r a p i d l y with increasing body weight, but remains r e l a t i v e l y constant when expressed per unit of surface area. The l a t t e r parameter i s d i f f i c u l t to measure with any degree of p r e c i s i o n and for t h i s reason i s not a good reference base (2). On the basis of interspecies comparisons, Brody (2) and Kleiber (5) have formulated equations r e l a t i n g body weight to basal heat production,, At the present time, there are i n s u f f i c i e n t data to suggest that i n t r a and i n t e r s p e c i f i c r e l a t i o n s of body s i z e and metabolic rate are the same. Lee (6) reported that a l i n e a r equation represented metabolism data on rabbits as well as a power function. Haywood (4) found that the basal metabolic rate of the genus Peromyscus does not d i f f e r from Brody's interspecies approximation. (2) However, within races of the genus, the weight exponents ranged between 0.54 and 0.94. Some of t h i s v a r i a t i o n was a t t r i b u t e d to differences i n t i s s u e metabolism a r i s i n g from differences between i n d i v i d u a l s 10 TABLE I I : MEASUREMENTS OF THE BASAL METABOLIC RATE OF THREE MINK Body No, of Weight Cal/Kg BW1*0 Cal/Kg BW'73 Cal/Kg BW'75 T r i a l s Kg Cal/24hr /24hr /24hr /24hr Mink No. P7 3 . 0.655 52.4 80.0 71.5 72.0 1 0.640 53.4 83.4 74.5 74.7 3 0.633 60.9 91.8 82.4 83.1 Mean 0.653 55.6 85.1 76.1 76.6 Mink No. P5 3 0.656 57.4 87.5 78.2 78.8 2 0.648 56.3 86.9 77.4 78„3 2 0.670 49.2 73.4 64.7 66.5 3 0.692 58.5 84.5 76.6 77.3 Mean 0.667 55.4 83.1 74.3 75.2 Mink No. P3 2 0.795 66.3 83.3 77.4 78.7 4 0.790 61.2 77.5 72.7 73.0 6 0.785 68.5 87.3 79.1 82.1 3 0.781 68.3 87_A 79J5 82.3 Mean 0.788 66.1 83.9 77.2 79.0 Mean of a l l Measurements 84.0 75.9 76.9 i n the composition of the p h y s i o l o g i c a l l y active body mass. Haywood's hypothesis i s not i n agreement with work c i t e d by Blaxter (1). For comparative purposes, the data presented i n Table II has been calculated by r a i s i n g body weight to three d i f f e r e n t power functions. Each basal metabolic rate used i n the preparation of the table i s the mean of a number of determinations, each of which was of not less than ten minutes duration when the mink was observed to be i n the state defined as basal at the outset. These r e s u l t s suggest that the basal metabolic rate of the sleeping, conditioned mink i s not abnormally high. The values obtained are s l i g h t l y higher than would be predicted by the regression equations proposed by Kleiber (5) and Brody (2). O l d f i e l d (9) obtained average figures ranging from 111.0 to 250 Cal/kg 1 , 0/24hr for three mink. He noted that a c e r t a i n amount of d i f f i c u l t y was encountered i n maintaining a quiescent state i n the animals a f t e r a 24 hour f a s t . The present findings are considerably lower than those reported by Perel'dik and Titova (6). These r e s u l t s are presented i n summary form i n Table I I I . 12 TABLE I I I ; HEAT PRODUCTION OF FASTING ADULT MINK (Perle'dik & Tltova, 1950) Season January, February March, A p r i l May, July August, October November, December Mean for Year Daily Heat Production, K Cal Per Kg Body Weight Per Sq. M.. of Surface Area 140 149 170 151 129 150 1748 1840 2001 1778 1627 1815 Unfortunately, access to t h e i r o r i g i n a l paper was not possi b l e . The apparent seasonal fl u c t u a t i o n s i n the heat production appear to follow c l o s e l y the seasonal p r o d u c t i v i t y of the mink, as we l l as changes i n p h y s i o l o g i c a l l y active body mass. For these reasons, the data may not represent true basal values. Scholander (11), i n h i s study on A r c t i c mammals, found that one of the few mammals which had a deviation of greater than 20% i n basal metabolic rate from Brody's interspecies equations was the A r c t i c Weasel (Mustela r i x o s a ) . However, s i m i l a r data on two weasels from Wisconsin showed only a s l i g h t elevation above the standard curve. The basal metabolic rate of one of Scholander's weasels compared with the other was greatly elevated, and the body weight of these A r c t i c weasels indicated that they were probably immature. The B.M.R„/24hr for one weasel was 31 Cal at 70 gm, the other 29 Cal at 38 gm„ When the data,are transformed to body weight 13 the heat production becomes 228 Cal/Kg/24hr and 333 Cal/Kg/24hr re s p e c t i v e l y . Because of the numbers of mink involved i n these basal metabolic rate determinations and because of t h e i r narrow weight range, i t has not been possible to formulate an equation r e l a t i n g basal heat production to body weight i n the mink as was done i n the cases of the i n t e r s p e c i f i c comparisons mentioned previously. 14 BIBLIOGRAPHY 1. Blaxter, L.K. 1962. The energy metabolism of ruminants. Hutchinson and Co., London. 2. Brody, S. 1945. Bioenergetics and growth. Reinhold Pub. Corp., New York. 3. F a r r e l l , D.J. 1966. Part IV. Energy requirements for maintenance. (Included i n t h i s thesis) 4. Haywood, J.S. 1965. Metabolic rate and i t s temperature - adaptive s i g n i f i c a n c e i n s i x geographic races of Peromyscus. Can. J . Zoo. 43, 309-323. 5. K l e i b e r , M. 1961. The F i r e of L i f e . Wiley and Sons. New York. 6. Lee, R.C. 1939. Size and basal metabolism of the adult r a b b i t . J . N u t r i t i o n , 18, 489-500. 7. M i t c h e l l , H.H. L.E. Card, and T.S. Hamilton. 1931. A t e c h n i c a l study of the growth of White leghorn chickens. I l l i n o i s Agr. Expt. Sta. B u l l . No. 376, 83-139. 8. Morrison, F.B. 1959. Feeds and feeding. 22nd. ed., Morrison Publishing Co., C l i n t o n , Iowa. 9. O l d f i e l d , J.E. 1949. A study of nitrogen metabolism with s p e c i a l reference to mink. Unpublished Master's Thesis, Dept. of Animal S c i . , University of B r i t i s h Columbia. 10. Perel'dik, M.N. and M.I. Titova. 1950. (Experimental determination of feeding standards for adult breeding mink.) Karakul. Zver., _3_, No. 2, 29. (Quoted by Aitken, F.C. 1963 i n Feeding of fur-bearing animals. Technical Communication No. 23, Commonwealth Bureau of Animal N u t r i t i o n , Aberdeen.) 11. Scholander, P.F. 1950 a. R.-Hock, V. Walters, and L. I r v i n g . Adaptation to cold i n a r c t i c and t r o p i c a l mammals and birds i n r e l a t i o n to body temperature, i n s u l a t i o n and basal metabolic rate. B i o l . B u l l . £9, 237-258. 15 12. Scholander, P.F. 1950 b. V. Walters, R. Hock and L. I r v i n g . Body i n s u l a t i o n of some a r c t i c and t r o p i c a l mammals and b i r d s . B i o l . B u l l . 99, 237-258. 13. Titova, M.I. 1950. (Influence of length of daylight on basal metabolic rate i n s i l v e r foxes.) Karakul. Zver., _3, No. 3, 55. (Quoted by Aitken, F.C. 1963 i n Feeding of fur-bearing animals. Technical Communication No. 23, Commonwealth Bureau of Animal N u t r i t i o n , Aberdeen.) THE NUTRITION OF THE FEMALE PASTEL MINK (Mustela vison) PART I I : STUDIES ON THE MINK DURING STARVATION INTRODUCTION It i s common ranch p r a c t i s e , i n preparation for breeding, to r e s t r i c t the feed intake of the mink i n order to induce a loss i n body weight. This leads to the consumption of the d a i l y feed o f f e r i n g i n a few hours. Because the mink has an exceptionally rapid feed t r a n s i t time (10, 18, 20, 26) i t w i l l r a p i d l y evacuate i t s digestive t r a c t and i n so doing enters a state of endogenous catabolism. I t i s of i n t e r e s t , therefore, to study the metabolism of t h i s species under such conditions, p a r t i c u l a r l y i t s endogenous excretions. Much data has been published on the e f f e c t s of starvation on man (3, 4), on the dog (13), on the r a t (2), and on other domestic species (13) but much of i t may not be relevant to the small carnivore. EXPERIMENTAL Animals Five adult female pastel mink, selected from a group of seven animals (10), were used i n two series of t r i a l s c a r r i e d out for a period of f i v e days i n September, and for three days i n the following January. P r i o r to t h i s experiment, the animals were fed a basal r a t i o n (10). Water was provided ad l i b i t u m i n conventional water cups. Housing The metabolism room was adequately l i g h t e d and v e n t i l a t e d , and subject to the p r e v a i l i n g outside environmental temperatures. 17 The mink were housed i n mesh wire, galvanized, rectangular cages measuring 43 cm. i n height, 30 cm. i n width, and 36 cm. i n length. The cages sat above aluminum funnels. A piece of fine-mesh wire screen was placed i n the funnel o u t l e t . A glass cylinder containing 1 ml. of sulphuric a c i d , placed beneath the funnel, trapped the voided urine. Data C o l l e c t i o n The mink were considered to be i n the postabsorptive state f i v e and one h a l f hours following the removal of feed. Animals were weighed at t h i s time and again at the end of the experimental period. During the l a t e r t r i a l s , the animals were weighed d a i l y . The volume of the urine was recorded following decantation of the urine from the c y l i n d e r s , which were then washed several times with d i s t i l l e d water, the washings being added to the c o l l e c t e d urine. Chemical Analysis The metabolic faeces were c a r e f u l l y scraped o f f the funnel and placed i n a previously extracted, tared, f a t - e x t r a c t i o n thdanble. The material was dried at 100°C to a constant weight, then extracted for 16 hours with petroleum ether (30-60°C b o i l i n g range). The extracted residue was ground to a powder with a mortar and p e s t l e . Representative duplicate samples were analyzed f o r nitrogen, using a micro-kjeldahl procedure. Mercuric oxide was used as a c a t a l y s t . Ash was determined by heating duplicate samples at 600°C for twelve hours. 18 Following the removal of a l l fae c a l matter, the aluminum funnels were rinsed several times with hot d i s t i l l e d water, these washings being added to the voided urine. Every precaution was taken to avoid contamination of the faeces with urine. The t o t a l urine c o l l e c t i o n was f i l t e r e d under vacuum through a No. 1 Whatman f i l t e r -paper. The t o t a l volume of the f i l t r a t e was recorded and duplicate aliquots were assayed for nitrogen using a micro-kjeldahl procedure. RESULTS The mean d a i l y quantity and composition of the endogenous faeces, together with the mean d a i l y weight loss of each animal, i s presented i n Table I. The low ether extract and the high protein content may be worthy of note i n that they d i f f e r appreciably from that reported for the young c a l f (6) and for man (8). R e f l e c t i n g these differences i n composition, the calculated energy content of the faeces i s approximately 4.9 Calories per gm and i s lower than values c i t e d by McKenzie (15) for other species. The d a i l y mean weight los s was 41.0 gm for the mink i n the September t r i a l and 44.1 gm for those i n the January t r i a l . The former figure includes the exceptionally high weight loss of mink No. P6 which averaged 48.8 gm. This animal became i l l during the l a t t e r part of the f a s t i n g period and for th i s reason the data from t h i s animal are not included i n the c a l c u l a t i o n s . A post-mortem examination revealed that i t was s u f f e r i n g from acute TABLE I: THE MEAN DAILY FAECAL EXCRETION, AND ITS COMPOSITION FROM MINK FASTED Day No No. of Animals Mean Body Weight Dry Matter Proximate analysis T r i a l Gm Gm/lOOgm Body weight Ether Extract % Protein (Nx6.25) % Ash % 1 3 688 1.263-' 0.184 6.8 60.9 September 2 3 657 1.189 0.181 5.4 55.5 September 3 3 616 0.663 0.108 5.2 60.0 September 4 2 598 0.602 0.100 8.6 54.6 September 5 2 546 0.758 0.139 14.0 44.9 September 1 3 696 1.767 0.394 10.5 54.4 11.0 January 2 3 656 0.849 0.129 6.6 55.7 11.9 January 3 3 614 0.891 0.145 5.4 56.6 10.7 January 20 TABLE I I ; DAILY LOSS IN BODY WEIGHT OF THREE FASTED MINK DURING JANUARY Mink N o o PI P2 P5 Day 1 2 3 1 2 3 1 2 3 Mean Body Weight (gm) 756 718 672 666 623 583 668 628 586 Daily Weight Loss (gm) 52 38 46 45 43 40 49 44 43 Weight loss as a % of the mean Daily Weight 6.8 5.3 6.8 6.9 6.8 6.8 7.3 7.1 7.3 21 n e p h r i t i s . The d a i l y weight l o s s , when expressed as a percent of the mean d a i l y body weight f o r the January group (Table II) i s remarkably constant and i s much greater than figures reported f o r man, 0.6% (4) and for the dog, 0.83% (13) during the f i r s t t h i r t y days of f a s t i n g . I t i s , however, i n good agreement with values obtained on f a s t i n g wild rats (2), but i s greater than measurements on f a s t i n g laboratory rats (2). The t o t a l body weight losses during starvation of these two groups of rats was 35.1% and 39.0%, r e s p e c t i v e l y , of the s t a r t i n g weight. These figures are i n good agreement with a mean body weight loss of 34.6% recorded f o r two mink that died of starv a t i o n during a vitamin B^ deficiency experiment at t h i s laboratory (unpublished). For the dog, a loss of 62.7% has been reported (13). The animal survived the f a s t i n g t r i a l . The present r e s u l t s would suggest that the mink has a r e l a t i v e l y high maintenance energy require-ment per unit of body weight as has been demonstrated i n other studies (11). Table I I I r e l a t e s the d a i l y nitrogen loss i n the faeces and i n the urine to body weight during the two t r i a l s . The mean nitrogen to urine volume r a t i o for a l l animals was 27 mg/cc. The same f i g u r e has been obtained when the mink were on feed. This r a t i o f o r a f a s t i n g man (4) has been calculated to be 8.3 mg/cc. TABLE I I I : THE DAILY NITROGEN EXCRETION OF FASTED MINK DURING SEPTEMBER AND JANUARY Body Weight Nitrogen Body Weight Nitrogen Body Weight Nitrogen Day (gm) Faecal Urinary T o t a l (gm) Faeca] Urinary Total (gm) Faeca] Urinary T o t a l T r i a l Mink No, P4 P5 P6 1 766 49 216 335 684 111 341 452 613 52 334 386 September 2 730 134 212 346 646 98 594 57 222 279 September 3 694 62 309 371 607 51 432 483 546 63 564 587 September 4 658 66 215 281 568 44 488 532 (481 15 891 1006) September 5 622 214 530 53 451 504 (432 125 1199 1324) September Mink No, PI P2 P5 1 756 129 428 557 666 228 395 623 668 105 544 649 January 2 718 103 387 490 623 87 427 514 628 41 517 558 January 3 672 105 513 618 586 100 420 520 586 44 462 506 January r o 23 DISCUSSION The marked tendency of the urinary nitrogen to f a l l o f f r a p i d l y i n i t i a l l y , and then to increase on the t h i r d day i s probably i n d i c a t i v e of the diminishing glycogen reserves (12). I t also suggests the i n a b i l i t y of the adipose tissue to maintain the animal for a long duration without an apparent increase i n protein catabolism. Fat reserves, although v i t a l as sources of energy, are not always i n d i c a t i v e of s u r v i v a l time, and death often comes when apparently adequate f a t stores s t i l l e x i s t (14). Despite the s i m i l a r i t y i n the s t a r t i n g weights of the two groups of mink, the consistently higher nitrogen excretion of the January group together with the increased body weight loss suggests the degradation of large amounts of protein t i s s u e . By c a l c u l a t i o n , the composition of the weight loss i s 31.5% protein for the January group and 27.3% for the September group. These figures are higher than those reported for f a s t i n g man (3, 4) and the f a s t i n g laboratory rat (2) but are i n agree-ment with those measured on f a s t i n g wild rats (2). The r e l a t i o n s h i p between the minimal endogenous urinary nitrogen and the basal metabolic rate i n a wide range of mature animals i s , with few exceptions, a f a i r l y constant 2 mg of nitrogen per Calorie (22). The t o t a l endogenous nitrogen i s about twenty-five per cent higher than t h i s figure (22). I t i s very apparent that under these experimental conditions, t h i s r e l a t i o n s h i p does not apply to those mink 24 which excreted i n excess of 5 mg of urinary nitrogen per Calorie of calculated basal heat produced (9). One reason f o r t h i s high f i g u r e i s that nitrogen excretion during a period of star v a t i o n i s not the i r r e d u c i b l e minimum. I t i s well recognized that under conditions of fas t the presence of carbohydrate has a sparing" action on protein catabolism (8). This implies that nitrogen i s not only required f o r replacing endogenous protein losses of the animal, but i s also intimately associated with the mobili z a t i o n of f a t . Under conditions of sta r v a t i o n , an increase i n water intake can cause a pronounced increase i n urea nitrogen due to a stimulation of protein catabolism (13). Despite these f a c t o r s , i t does appear that even under conditions of sta r v a t i o n , the urinary nitrogen excretion of the mink i s e x t r a o r d i n a r i l y high when compared with other species under s i m i l a r conditions. Nevertheless, the data are i n good agreement with measurements made by O l d f i e l d (19), who was working with mink. M i t c h e l l (17) states that the minimal nitrogen excretion and basal metabolism represent the i d l i n g speed of the organism. There i s , however, some evidence that i n a growing animal t h i s r e l a t i o n s h i p also remains f a i r l y constant. Blaxter (5), working with young calves, found that the more intense basal metabolism of these animals i s associated with a more intense endogenous nitrogen metabolism, and that the r e l a t i o n s h i p between urinary nitrogen and basal heat produced was 1.9 Mg/Cal. Terroine and Sorg-Matter (23) studied the r a t i o s of endogenous nitrogen to basal heat production i n several d i f f e r e n t species exposed to d i f f e r e n t environmental temperatures. / 25 I t was found that at the lower temperatures the e l i m i n a t i o n of endogenous n i t r o g e n increased as w e l l as d i d the b a s a l metabolism and somewhat i n the same p r o p o r t i o n , so that the r a t i o of these two e n t i t i e s was not g r e a t l y d i s t u r b e d . I t i may be p o s t u l a t e d , t h e r e f o r e , that under non-productive c o n d i t i o n s , as heat production increases so too does endogenous n i t r o g e n l o s s , and i n such a manner that the r e l a t i o n s h i p between these two e n t i t i e s i s not appr e c i a b l y a l t e r e d . Frequent observations of these animals during the f a s t i n g t r i a l s revealed beyond question that the animals could not be con-sidered to be i n the b a s a l s t a t e of energy metabolism. U n l i k e many other s p e c i e s , a c t i v i t y d i d not appear to d i m i n i s h w i t h f a s t i n g over the p e r i o d of these t r i a l s . Furthermore, that the normal a c t i v i t y increment of the mink i s e x c e p t i o n a l l y high has been confirmed through feed i n t a k e t r i a l s (11) and through measurements (Table I¥) c a r r i e d out on f a s t e d mink i n the respirometer (Appendix I ) . TABLE IV: THE RELATIONSHIP BETWEEN THE HEAT PRODUCTION OF AN UNTRAINED FASTED MINK IN THE RESPIROMETER AND THE ANIMAL'S CALCULATED BASAL METABOLISM RATE Measured Heat R a t i o of Mink B.W. Ambient C a l c u l a t e d B.M.R. Per i o d Production H.P./B.M.R. No. (gms) Temp. °C (84W 1* 0) C a l . (hours) (Cal/24hrs) P5 688 17.0 57.7 2.32 186.8 3.20 P6 714 21.0 59.7 1.22 187.1 3.13 P2 760 16.3 63.8 1.16 259.2 4,06 P2 755 16.2 63.4 1,20 228,6 3.60 P4 889 16.1 74.8 3.46 215.0 2.87 26 When one considers the small dimensions of the cage i n the respirometer, and that these animals were not noticeably a c t i v e for the e n t i r e period of heat production measurements, the figures are e x t r a o r d i n a r i l y high. In order to obtain some estimate of energy u t i l i z a t i o n , the regression equation (y=0.226X+1A„0) r e l a t i n g apparent d i g e s t i b l e energy intake i n Calories to body weight, derived from other work with these mink (11) , was used to c a l c u l a t e heat production and i s i n good agreement with the energy obtained by r e l a t i n g the C a l o r i c equivalent to weight loss as suggested by Wishnofsky (25)„ Using t h i s calculated heat production f i g u r e , the mean r a t i o of urinary nitrogen excretion i n mg to Cal (A.D.E.) for a l l mink becomes 2.5. I t would appear, therefore, that although the nitrogen requirement of a mink i s high, i t i s not so when related to t h i s animal's maintenance heat production. It i s worthy of note that f a s t i n g studies on wild and on laboratory rats (2) revealed that the wild rats had a considerably higher heat production than t h e i r counterparts, as w e l l as a higher endogenous urinary nitrogen l o s s . The adult cat not only has an apparently high dietary protein requirement (16) i n keeping with a high energy intake, but t h i s species excretes about 0.4 gm of endogenous urinary nitrogen/kg body weight on a nitrogen-free d i e t (16) and i s reported to require 0.36 gm nitrogen/kg body weight for nitrogen balance (1). Since the C a l o r i c intake of an adult cat has been found to be about 80-90 Calories/kg/day (16), the r a t i o of endogenous urinary nitrogen per Calorie i s therefore about 4.0. 27 M i t c h e l l (17) and many others have suggested that t h i s nitrogen:energy r e l a t i o n s h i p i s a good estimate of the minimum protein requirements of a mature animal. This statement must be accepted with a good deal of reservation when one considers the marked decrease i n the urea f r a c t i o n of the urine from animals under conditions of fa s t (6), and from animals receiving a low nitrogen d i e t (12). The urea nitrogen l e v e l can decrease to as low as 70% of the t o t a l nitrogen i n the f a s t i n g man (4) and 81.5% i n the f a s t i n g dog (13) . Even lower figures have been reported by Blaxter (6) for ruminants. This d i s t r i b u t i o n of nitrogen would not only overestimate the animal's minimal protein requirements but, under conditions of f a s t , could overestimate the protein tissue catabolized i f the t o t a l nitrogen f i g u r e i s used to determine t h i s p r o t e i n . From these r e s u l t s , one may conclude that although the adult mink has a high dietary protein requirement when expressed as a percentage of the r a t i o n , i t i s not unduly so i f i t i s expressed on a per Calorie basis because of t h i s animal's high maintenance energy demands. 28 BIBLIOGRAPHY 1. A l l i s o n , J.B., S.A. M i l l e r , J.R. McCoy and M.K. Brush. 1956. Studies on the n u t r i t i o n of the cat. The North Am. Vet. 37, 38. 2. Benedict, F.G. and E.L. Fox. 1934. Protein and energy metabolism of wild and Albino rats during a prolonged f a s t i n g . Am. J . Ph y s i o l . 108, 285. 3. Benedict, F.G. 1915. A study of prolonged f a s t i n g . Carnegie Inst. Wash. Publ. No. 203. 4. Benedict, F.G. 1907. The influence of inaBJitLon on metabolism. Carnegie Inst. Wash. Publ. No. 77. 5. Blaxter, K.L. and W.A. Wood. 1951. The n u t r i t i o n of the young Ayrshire c a l f . 1. The endogenous nitrogen and basal energy metabolism of the c a l f . B r i t . J . N u t r i t i o n , 5_, 11-25. 6. Blaxter, K.L. and W.A. Wood. 1951. The n u t r i t i o n of the young Ayrshire c a l f . 3. The metabolism of the c a l f during st a r v a t i o n and subsequent realimentation. B r i t . J . N u t r i t i o n , 5., 29-55. 7. Dickinson, CD. and P.P. Scott. 1956. N u t r i t i o n of the cat. 2. Protein requirements for growth of weanling k i t t e n s and young cats maintained on a mixed d i e t . B r i t . J . N u t r i t i o n , 10, 311-316. 8. Everett, M.R. 1942. Medical biochemistry 2nd ed. Hamish Hamilton Medical Books, London. 9. F a r r e l l , D.J. 1966 a. Part I. The metabolic rate of the mink. (Included i n th i s thesis.) 10. F a r r e l l , D.J. 1966 b. Part I I I . The e f f e c t s of the addi t i o n of f i b r e to the r a t i o n . (Included i n t h i s thesis.) 11. F a r r e l l , D.J. 1966 c. Part IV. Energy requirements f o r maintenance. (Included i n t h i s thesis.) 12. Fisher R.B. 1954. Protein metabolism. Meuthen, London. 13. Howe, P.E., H.A. M a t t i l l and P.B. Hawk. 1912. Fasting studies. VI. D i s t r i b u t i o n of nitrogen during a fa s t of one hundred and seventeen days. J . B i o l . Chem. 11, 103-127. 29 14. Lusk, G. 1928. The elements of the science of n u t r i t i o n . Saunders, P h i l a d e l p h i a . 15. McKenzie, R.M. 1964. The response of the laboratory r a t to changes i n the c a l o r i c density and p r o t e i n : c a l o r i e rates of i t s r a t i o n . Unpublished Master's t h e s i s , Dept. of Animal S c i . , University of B r i t i s h Columbia. 16. M i l l e r , S.A. and J.B. A l l i s o n . 1958. The dietary nitrogen requirements of the cat. J . N u t r i t i o n , 64_, 493-501. 17. M i t c h e l l , H.H. 1962. Comparative n u t r i t i o n of man and domestic animals. Vol. 1. Academic Press, New York. 18. Neseni, R. and B. Piatkowski. 1959. (Transit time of feed i n mink) Arch. TierernMhr. .8, 296. (Quoted i n Nutr. Abstr. and Revs. 1959. 29^ , 507) 19. O l d f i e l d , J.E. 1949. A study of nitrogen metabolism with s p e c i a l reference to mink. Unpublished Master's t h e s i s , Dept. of Animal S c i . , University of B r i t i s h Columbia. 20. Sibbald, I.R., D.G. S i n c l a i r , E.V. Evans and D.L.T. Smith. 1962. The rate of passage of feed through the d i g e s t i v e t r a c t of the mink. Can. J . Biochem. and P h y s i o l . 40-, 1391-1394. 21. Smuts, D.B. 1935. The r e l a t i o n between the basal metabolism and the endogenous nitrogen metabolism, with p a r t i c u l a r reference to the estimation of the maintenance requirement of protein. J . N u t r i t i o n , 9^, 403-433. 22. Terroine, E.F. and H. Sorg-Matter. 1927. L o i quantitative de l a despense azot£e minime des homeothermes:Validite i n t e r s p e c i f i q u e . Arch, intern, p h y s i o l . 29^ 121-132. 23. Terroine, E.F. and H. Sorg-Matter. 1928. Influence de l a temperature exte"neure sur l a defense azot£e endogene des homeothermes. Arch, intern, p h y s i o l . ^0, 115-125. 24. Waterhouse, H.N. and D.S. Camer. 1962. Growth rate, food and c a l o r i e consumption of laboratory cats. Proc. Animal Care Panel, 12, 267-274. 25. Wishnofsky, M. 1958. C a l o r i c equivalent of gained or l o s t weight. Amer. J . Anim. N u t r i t i o n , 6_, 542-546. 26. Wood, A.J. 1956. The black fox magazine and modern mink breeder. 39_, (1), 12. THE NUTRITION OF THE FEMALE PASTEL MINK (Mustela vison) PART I I I : THE EFFECT OF THE ADDITION OF FIBRE TO THE RATION 30 INTRODUCTION It i s well known that the time of feed passage of the mink i s exceptionally rapid (17, 23). The e f f e c t s of d i f f e r e n t markers has been studied by Wood (25). Data from t h i s laboratory (unpublished) on the time of feed passage of the laboratory rat would i n d i c a t e that the l e v e l of dietary .fibre w i l l a f f e c t the t r a n s i t time through the digestive system. I t has been suggested that the f i b r e i n a r a t i o n may increase p e r i s t a l s i s and may draw moisture into the i n t e s t i n a l t r a c t (13). Both these factors w i l l tend to increase the rate of passage of the feed. McKenzie (12) has studied the e f f e c t of f i b r e l e v e l i n the d i e t of the laboratory rat and i t s e f f e c t on the d i g e s t i b i l i t y of the r a t i o n and of i t s major components. Much information i s a v a i l a b l e on the d i g e s t i b i l i t y of various feed ingredients by the mink (1, 10, 11, 16, 19). The object of t h i s experiment i s to study the e f f e c t of f i b r e l e v e l i n a mink r a t i o n on the time of passage of the feed through the d i g e s t i v e t r a c t and on the apparent d i g e s t i b i l i t y of the r a t i o n and of i t s components. Nitrogen balance studies were c a r r i e d out concurrently with these d i g e s t i b i l i t y t r i a l s , i n order to ascertain any change i n nitrogen retention with season or with d i f f e r e n t dietary f i b r e l e v e l s . EXPERIMENTAL General Nitrogen balance studies and d i g e s t i b i l i t y studies were ca r r i e d out i n metabolism cages (4), f i t t e d with modified mink feeders (22). P r i o r to the s t a r t of a t r i a l , the mink were fasted for f i v e and one-half hours. They were then weighed and fed, ad l i b i t u m , a basal r a t i o n (Table I ) , or the basal r a t i o n plus a measured quantity of non-nutritive bulk. Proximate analysis and composition of these rations are shown i n Table I I . The d i g e s t i b i l i t y studies continued for a period of f i f t y -three and one-half hours. At the end of f o r t y eight hours, feed was removed and f i v e and one-half hours l a t e r the mink were weighed and returned to t h e i r ranch-type pens. During the "test period", ( i ) the animals were fed three times a day, ( i i ) a l l waste feed was gathered and weighed d a i l y , and ( i i i ) the t o t a l faeces excreted were c o l l e c t e d d a i l y . Animals Four adult female p a s t e l mink were used to determine the apparent d i g e s t i b i l i t y of the r a t i o n and of i t s major components. The time of passage studies were determined on s i x animals as were the nitrogen retention studies. TABLE I: THE COMPOSITION OF THE BASAL RATION ON AN "AS MIXED" BASIS Ingredient Per Cent of the Ration Cereal Mix 1 30.5 Horse Meat 19.3 Pork L i v e r 2.9 F i s h 2 26.1 Corn O i l 8.7 Water 12.5 The r a t i o n was mixed i n a s i n g l e batch and then frozen i n 800 gm l o t s i n p l a s t i c bags, and was stored at -20°C. 1. See Appendix II 2. Equal quantities of grey cod (Gadus macrocephlus) and dover sole (Microstomus p a c i f i c u s ) 33 TABLE I I : COMPOSITION AND MEAN RESULTS OF ANALYSES OF THE DIETS USED Ration % Ba s a l 1 B a s a l 2 Basal +7 Basal +14 Basal +20 Basal 100 100 93 86 80 A l p h a c e l 3 - - 7 14 20 MC% 65 65 65 65 65 Analysis % on dry weight basis No. of Samples 6 8 6 6 4 Li p i d s 30.8 29.0 27.4 26.3 22.6 Ash 7.. 1 8.8 6.5 6.1 5.7 Protein 30.8 32.4 29.1 25.3 24.8 Gross energy Cal/gm 5.81 5.81 5.58 5.51 5.28 A.D.E. Cal/gm 4.47 4.47 3.97 3.72 3.37 A.D.N.,mg A.D.E.,Cal 78.4 78.4 82.9 74.0 78.0 . 1. B l i g h and Dyer - chloroform extracted samples - Analysis on whole samples. 2. Petroleum ether extracted samples. Analysis on extracted samples. 3. N u t r i t i o n a l Biochemical Corp., Cleveland, Ohio. A n a l y t i c a l Methods (a) Dry matter was determined by drying representative samples at 100°C to a constant weight. (b) Crude protein (Nx6.25) and urinary nitrogen was determined by a micro-kjeldahl procedure. (c) Non-volatile ash was determined by heating samples at 600°C for twelve hours. (d) Total l i p i d s were extracted using the B l i g h and Dyer modified method (3). The basal r a t i o n was also extracted with petroleum ether (30-60°C b o i l i n g range). Analysis for ash and nitrogen were then c a r r i e d out on the extracted residue. For comparative purposes, these two sets of proximate analysis are shown i n Table I I . (e) Gross energy values were obtained by combustion i n a Parr adiabatic oxygen bomb. (f) Dry matter d i g e s t i b i l i t y was measured through t o t a l c o l l e c t i o n of the feed and faeces. Time of Passage Studies Time of passage studies on mink housed i n ranch-style cages commenced at 8:30 a.m. At t h i s time, feed containers were washed and replenished with a f e r r i c oxide-marked feed. The mink could be observed through a window i n an adjoining room with a minimum of disturbance to the animals. 35 RESULTS AND DISCUSSION 1. Time of Passage The e f f e c t of r a t i o n f i b r e l e v e l on the times of passage has been summarized i n Table I I I . TABLE I I I : TIME (MINUTES) REQUIRED FOR A MARKED  FEED TO APPEAR IN THE FAECES OF FEMALE  PASTEL MINK ON DIETS CONTAINING VARIOUS FIBRE LEVELS Ration Basal Basal +7 Basal +14 Basal +20 Mean time of passage (mins.) 137 Standard deviation 31.6 No. of Determinations 10 119 21.8 109 28.5 102 29.7 10 There appears to be an inverse r e l a t i o n s h i p between the time of passage of the feed through the digestive t r a c t and the f i b r e l e v e l i n the r a t i o n . The i n d i v i d u a l times of passage ranged from 73 minutes on the highest fibre r a t i o n to 200 minutes on the basal feed. 2. Apparent D i g e s t i b i l i t y The apparent d i g e s t i b i l i t y of the r a t i o n and of i t s major components are presented i n Figure 1. A l l determinations were c a r r i e d FIGURE 1: THE APPARENT DIGESTIBILITY OF THE FAT, PROTEIN, ASH AND COMPLETE RATIONS, AS AFFECTED BY FIBRE LEVEL IN THE RATION ADDED FIBRE TO THE RATION, % 37 out on the same three mink, except for those on the highest f i b r e r a t i o n , when two mink were used. The r e s u l t s c l e a r l y show that the apparent d i g e s t i b i l i t y of the ash component of the r a t i o n i s greatly decreased by increased f i b r e l e v e l i n the r a t i o n and decreases more or less i n a l i n e a r fashion. The apparent d i g e s t i b i l i t y of the f a t i s only s l i g h t l y reduced at the 20% f i b r e l e v e l while the protein f r a c t i o n s t a r t s to decrease at l e v e l s of dietary f i b r e i n excess of 7%. Since an inverse r e l a t i o n s h i p e x i s t s between the rate of passage of the feed through the d i g e s t i v e t r a c t and the r a t i o n f i b r e l e v e l , there would be a decrease i n the time during which the dige s t i v e enzymes are i n contact with t h e i r substrates. The i n c l u s i o n of a non-nutritive bulk i n the r a t i o n would presumably s h i e l d the r a t i o n components from the enzymes. McKenzie (12) has shown that with the laboratory r a t , a decrease i n the apparent d i g e s t i b i l i t y of both protein and f a t did not occur at r a t i o n f i b r e l e v e l s below 24%. McKenzie (12) suggests that t h i s decrease i n apparent d i g e s t i b i l i t y may be due i n part to an increase i n endogenous f a e c a l f a t and f a e c a l p rotein as measured by Meyer (14). The a b i l i t y of the mink to e f f i c i e n t l y digest f a t suggests that t h i s animal i s provided with an abundance of l i p a s e . I t has been recognized for some time that the adult mink can e f f e c t i v e l y handle high l e v e l s of dietary f a t (24). The adult cat can equally w e l l acept high f a t di e t s (19). Since the 38 fa t content of mink milk on a dry weight basis i s about 35% (7), i t i s reasonable to expect that the mink k i t can also r e a d i l y digest f a t . Of some p r a c t i c a l s i g n i f i c a n c e i s the marked depression of the apparent d i g e s t i b i l i t y of the ash component even at low f i b r e l e v e l s . This low d i g e s t i b i l i t y of ash could conceivably lead to a mineral deficiency during periods of s t r e s s . A consideration of the mineral requirements of t h i s species must therefore recognize the l e v e l of dietary f i b r e i n order to ensure an adequate absorption of these elements. 3. Nitrogen Retained The measurements r e l a t i n g to the nitrogen balance studies c a r r i e d out on each mink are presented i n Table IV. The nitrogen retained has been expressed i n mg. N /100 gm of body weight and as a percentage of the absorbed feed nitrogen. This l a t t e r f i g u r e , often used as a measure of nitrogen retention, has l i t t l e value when each mink receives d i f f e r e n t quantities of pr o t e i n . The retained nitrogen may remain r e l a t i v e l y constant but i t w i l l appear to increase with decreasing nitrogen intake when expressed as a percentage of the absorbed nitrogen. The nitrogen retained appears to be greatest i n September and tends to decrease thereafter. This trend may r e f l e c t the pr o t e i n increment associated with fur growth. I t i s , however, d i f f i c u l t to TABLE IV: THE APPARENT NITROGEN RETAINED BY FEMALE PASTEL MINK DURING METABOLISM STUDIES Mean Absorbed Nitrogen Nitrogen Nitrogen Body Weight Feed Urinary Retained Nitrogen Retained Retained Mink Weight Change Nitrogen Nitrogen for period Retained /day Mg/day No Month Ration gm gm gm gm gm % r r i c r /100 gm B.W. P4 Sept Basal 804 -5 2.632 2.060 0.572 21.7 257 32.0 P5 Sept Basal 722 +23 2.323 2.180 0.143 6.2 64 8.8 P6 Sept Basal 650 +2 3.865 2.642 .1.223 31,6 548 84.3 PI Jan Basal 821 -9 .2.674 2.640 0.034 1.3 15 1.8 P2 Jan Basal 724 -28 2.643 2.394 0.249 9.4 117 16.3 P5 Jan Basal 730 -16 2.332 2.116 0.216 9.3 97 29.5 PI Jan Basal +7 717 -2 3.427 3.105 0.322 9.4 144 20.1 P2 Jan Basal +7 703 -6 3.422 3.052 0.370 10.8 166 23.6 P5 Jan Basal +7 701 +4 3.538 3.262 0.276 7.8 124 17.7 PI Dec Basal +14 852 +15 2.988 2.786 0.202 6.8 91 10.6 P2 Dec Basal +14 722 -13 2.746 2.529 0.217 7.9 97 13.5 P5 Dec Basal +14 690 +1 3.004 2.918 0.086 2.9 38 5,6: P4 Nov Basal +20 666 +9 2.715 2.336 0.379 14.0 170 25.5 P5 Nov Basal +20 660 +9 2.783 2.460 0.323 11.6 145 21.8 40 account for the high nitrogen retention figures obtained for mink during January, e s p e c i a l l y when the animals were lo s i n g weight. Any c o r r e c t i o n f o r endogenous nitrogen losses would merely increase the retained f i g u r e . These data are i n close agreement with studies c a r r i e d out by S i n c l a i r & Evans (21). Recalculation of t h e i r data from four of t h e i r groups of animals, each containing eight.mink, gave values of nitrogen retained (mg per 100 gm of body weight) of 5.6, 22.4, 29.6 and 14.8. The low figure i s a good example of protein being u t i l i z e d to meet energy purposes f i r s t , and the animals:'' protein requirements second, when other nutrients i n the r a t i o n are i n s u f f i c i e n t to meet the animals' energy requirements.(2). Roberts and Kirk (13), working with adult female mink, have reported even greater quantities of nitrogen retained, but o f f e r no explanation for the magnitude of these f i g u r e s . The continual replacement of dermal and hair losses may account for part of the nitrogen retained. O l d f i e l d (18) measured these losses and found them to be n e g l i g i b l e . A continual high rate of fur growth i s not l i k e l y on the basis of the work done by Leoschke and Elvehjerh (9). M i t c h e l l (15) has calculated that the d a i l y growth of h a i r i n the r a t w i l l account for 42 mg N/day on the assumption that the r a t cycles i t s h a i r every 35 days. This increment of nitrogen for h a i r growth would be i n the same range as that measured for the mink per 100 gm of body weight. A f i n a l p o s s i b i l i t y i s a loss of nitrogen i n the form of ammonia, through pathways other than those measured i n t h i s study. Because ammonia has a high d i f f u s i o n rate through tissues (6), and because high l e v e l s of meat protein can elevate blood ammonia l e v e l s (7), losses of; nitrogen through the lungs and i n the faeces may be substantialo The ammonia i n the l a t t e r component could only be measured i f the faeces were c o l l e c t e d i n acid or almost immediately following defecation. The c o n s i s t e n t l y small p o s i t i v e nitrogen balance suggests that the mink has a constant demand for protein which i s u t i l i z e d f o r productive purposes, the most obvious of which i s fur growth, and i s l o s i n g nitrogen as ammonia through various channels. 42 BIBLIOGRAPHY l o Bernard, R., S.E. Smith and L.A. Maynard. 1942. Digestion of cereals by minks and foxes with s p e c i a l reference to starch and crude f i b r e . C o r n e l l Vet. 32_, 29-36. 2. Blaxter, K.L. and W.A. Wood. 1952. N u t r i t i o n of the young Ayrshire c a l f . 4. Some factors a f f e c t i n g the b i o l o g i c a l value of protein determined by nitrogen-balance methods. B r i t . J . N u t r i t i o n , _5, 55-67. 3. B l i g h , E.G. and W.J. Dyer. 1959. A rapid method of t o t a l l i p i d extraction and p u r i f i c a t i o n . Can. J . Biochem and Phy s i o l . 37, 911. 4. F a r r e l l , D.J. 1966. Part I I . Studies on the f a s t i n g mink. (Included i n t h i s thesis) 5. F a r r e l l , D.J. 1966. Part IV. Energy requirements f o r maintenance. (Included i n t h i s thesis) 6. Groves, T.D.D. 1966. Personal communication. 7. Harper, H.A. 1963. Review of p h y s i o l o g i c a l chemistry. 9th ed. Lange Medical Publi c a t i o n s , Los A l t o s . 8. Jorgensen, G. 1960. (Composition and n u t r i t i v e value of mink milk.) Dansk Pelsdr-avi:, 23, 119-137. (Quoted i n Nutr. Abstr. & Revs. 1960, 30, 1219.) 9. Leoschke, W.L. and C.A. Elvehjem.. 1959. The importance of arginnine and methionine for growth and fur development of mink fed p u r i f i e d d i e t s . J . N u t r i t i o n , 69_, 147-150. 10. Leoschke, W.L. 1959. The d i g e s t i b i l i t y of animal fats and proteins by mink. Am. J . Vet. Res. 20, 1086-1089. 11. L o o s l i , J.K. and L.A. Maynard. 1939. Proc. Am. Soc. of Animal Prod., Dec. 400. 12. McKenzie, R.M. 1964. The response of the laboratory rat to changes i n the c a l o r i c density and p r o t e i n : c a l o r i e r a t i o of i t s r a t i o n . Unpublished Master's t h e s i s , Dept. of Animal S c i . , University of B r i t i s h Columbia. 43 13. Maynard, A.B. and J.K. L o o s l i . 1962. Animal N u t r i t i o n 5th ed. McGraw-Hill Book Company, Inc., Toronto. 14. Meyer, J.H. 1956. Influence of dietary f i b r e on metabolic and endogenous nitrogen excretion. J . N u t r i t i o n , 58, 407-414. 15. M i t c h e l l , H.H. 1962. Comparative n u t r i t i o n of man and domestic animals. Vol. 1. Academic Press, New York. 16. Nordfelt, S., G. Melin and B. Thelander. 1955. (Digestion experiments with mink.) Kgl. Lantlouks hogsk. Statens Husdjursforsok Sagtyck No. 114, 14. (Quoted i n Nutr. Abstr. and Revs. 1956, 26^ 830.) 17. Neseni, R. and B. Piatkowski. 1958. (Transit time of feed i n the mink.) Arch. Turernahning J3, 296-308. Quoted i n Nutr. Abstr. and Revs. 1959, 29, 507. 18. O l d f i e l d , J.E. 1949. A study of nitrogen metabolism with s p e c i a l reference to mink. Unpublished Master's t h e s i s , Dept. of Animal S c i . , University of B r i t i s h Columbia. 19. Roberts, W.K. and R.J. K i r k . 1965. D i g e s t i b i l i t y and nitrogen u t i l i z a t i o n of raw f i s h and dry meals by mink. Fur of Canada. 30, (3), 3. 20. Scott, P.P. 1960. I I . The Cat. Vet. Record. 72^ , 6-9. 21. S i n c l a i r , D.G., E.V. Evans and I.R. Sibbald. 1962 a. The influence of apparent d i g e s t i b l e energy and apparent d i g e s t i b l e nitrogen i n the d i e t on weight gain, feed consumption and nitrogen retention of growing mink. Can. J . Biochem. and P h y s i o l . 40, 1375-1589. 22. S i n c l a i r , D.G. and E.V. Evans. 1962 b. A metabolism cage designed for use with mink. Can. J . Biochem. and P h y s i o l . 40, 1395-1399. 23. Sibbald, I.R., D.G. S i n c l a i r , E.V. Evans and D.L.T. Smith. 1962. The rate of passage of feed through the dig e s t i v e t r a c t of the mink. Can. J . Biochem. and P h y s i o l . 40, 1391-1394. 24. T r a v i s , H.F. and P.J. Schaible. 1961. E f f e c t of dietary f a t l e v e l s upon reproductive performance of mink. Quart. B u l l . Michigan Ag r i c . Expt. Stat. 43, 518. 25. Wood, A.J. 1956. The black fox magazine and modern mink breeder. 39, (1), 12. THE NUTRITION OF THE FEMALE PASTEL MINK (Mustela vison) PART IV: ENERGY REQUIREMENTS FOR MAINTENANCE 44 INTRODUCTION The accurate measurement of the energy intake of an animal under defined conditions i s of prime importance since i t i s t h i s component of the r a t i o n which p r i m a r i l y governs feed intake. This fa c t has been proven experimentally with rats (18, 31), chickens (9, 29), swine (24), dogs (26), lambs (4), calves (15), c a t t l e (3) and mink k i t s (33). Some data are av a i l a b l e on the energy requirements for maintenance of adult mink (10, 25, 27). These workers do not generally specify the sex, s t r a i n , season or conditions under which the measurements were made. Because of the feeding habits of the mink, i t i s extremely d i f f i c u l t to measure with any degree of p r e c i s i o n t h i s animal^s d a i l y feed intake. The d i f f i c u l t y of maintaining weight s t a s i s during the feeding t r i a l can often lead to erroneous con-clusions since the energy increment associated with weight change i s both v a r i a b l e and d i f f i c u l t to measure. Further, the energy associated with weight gain i s i n excess of that released to the system through weight loss of body t i s s u e . Kielowiowski (12) has estimated the metabolizable energy of 1 gm of protein gain to be 7-8 C a l o r i e s , and for f a t th i s f i g u r e i s 15 Calories for the lamb and 11.7 f o r the baby pi g . Since the oxidation of f a t and protein y i e l d only 9.3 and 5.6 Calories/gm r e s p e c t i v e l y , i t i s clear one cannot v a l i d l y associate the same energy value to one gram of weight change, even though the 45 composition of the gain and loss may be i d e n t i c a l . Wishnofsky (35), working with humans, has estimated the c a l o r i c equivalent of 1 gm of body weight gain or loss to be 4.5 C a l o r i e s . Under f a s t i n g con-d i t i o n s , t h i s figure f a l l s to 3.2 Cal/gm of body weight l o s t . The mink, with such a rapid time of passage (32, 37), under conditions of infrequent feeding, could be almost constantly degrading and synthesizing body tis s u e depending on the presence or absence of feed. In order to obtain a true p i c t u r e of t h i s animal's energy requirements, the presence of feed at a l l times i s necessary. The enormous weight f l u c t u a t i o n that can occur among adult mink and between sexes was apparent from work done by McMillan (17) i n the course of a study on fungal t o x i c o s i s . During a period of twenty-eight days i n January, 12 adult mink were placed on high energy rations (6000 gross Cal/kg). The mean body weight gain recorded for male mink for that period was 398 gm. One gained 740 gm. The females, on the other hand, gained 90 gm. During experimentation, often no d i s t i n c t i o n between sexes i s made. The object of t h i s experiment i s the accurate measurement of the feed intake of one s t r a i n of mink under defined conditions, and of the e f f e c t of feeding rations with varying l e v e l s of a v a i l a b l e energy. 46 EXPERIMENTAL Animals and Treatment Five mink were selected from a group of seven adult female pastels of s i m i l a r age, s t r a i n and n u t r i t i o n a l h i s t o r y . Because of i n f e r t i l e males, these mink did not produce k i t s the season preceding the experimental period. With the exception of three two-weekly periods when the mink received 'bulked' r a t i o n s , or when undergoing metabolism t r i a l s , the animals were maintained on the basal r a t i o n . Rations D e t a i l s of the composition and of the analysis of the experimental rations are outlined i n Part I II of t h i s thesis {8). Housing The mink were housed i n rectangular wire mesh ranch-type cages, 40 cm high, 45 cm wide and 60 cm long, arranged i n banks of three and divided by means of a double wire mesh p a r t i t i o n . These cages were suspended from the wa l l of a room which was adequately l i g h t e d and v e n t i l a t e d but exposed to the p r e v a i l i n g outside environ-mental temperatures. Special Equipment The animals were fed i n mink feeders (34). These were s l i g h t l y modified i n order to permit b o l t i n g d i r e c t l y to the cage. A small 47 tray was suspended below the wire mesh cyl i n d e r to c o l l e c t feed s p i l l a g e . Data C o l l e c t i o n (a) Feeding: The mink were fed t h r i c e d a i l y a measured quantity of feed of known moisture content. Any weigh-back from the previous feed was recorded. (b) Daily Routine: At 0800 hours - P r i o r to feeding the animals, the feed cups were washed and dr i e d . - A l l waste feed was c o l l e c t e d from the feeders and from the aluminum trays. - Faeces and urine were removed from the aluminum trays, which were replaced with clean ones. - Water bo t t l e s were checked and replenished i f necessary. (c) Feed weigh-back: Waste feed c o l l e c t e d from the trays was dri e d to a constant weight. To t h i s was added any feed adhering to the feeders or cage f l o o r which was removed by means of a s t e e l wire brush, and was c o l l e c t e d on wax paper. (d) Weighing: For the purposes of t h i s study, one week constitutes the i n t e r v a l from 0800 hours Tuesday to 0800 hours the following Tuesday. On 48 t h i s day the feed was removed at 0800 hours, the mink were then weighed at 1030 hours on a beam balance to an attempted accuracy of ± 1 gm. Control animals, maintained on a nearby mink ranch, were weighed approximately each month (Appendix I I I ) . RESULTS Because of the lower standard error, i t was found that the data i s best represented by an arithmetic rather than a logarithmic regression equation. The r e l a t i o n s h i p between apparent d i g e s t i b l e energy (A.D.E.) intake and the mean body weight of a l l mink housed i n ranch-type cages duringLthe period September 1 and January 21, has been summarized i n Figure 1. Symbols have been selected i n order to d i s t i n g u i s h between those animals which showed no weight change (± 10 gm) from those which gained or l o s t weight (>± 10 gm) during a seven day period. The mean A.D.E. intake (Cals) of those mink that demonstrated weight s t a s i s (± 10 gms) on the basal r a t i o n for a period of seven days between September 1 and November 29 has been plotted against body weight and i s presented i n Figure 2. Because of the highly s i g n i f i c a n t c o r r e l a t i o n (r=0.805) of the data and because the mink showed no weight change, t h i s equation w i l l represent the standard curve for these] mink maintained under the stated conditions. I t i s recognized that the maintenance energy includes an increment FIGURE 1: THE RELATIONSHIP BETWEEN THE APPARENT DIGESTIBLE ENERGY INTAKE AND THE BODY WEIGHT OF ALL MINK ON ALL FOUR RATIONS AND HOUSED IN RANCH-TYPE CAGES. (Symbols have been used between those animals those which gained or i n order to d i f f e r e n t i a t e which l o s t weight from maintained body weight.) FIGURE 2: THE RELATIONSHIP BETWEEN THE APPARENT DIGESTIBLE ENERGY INTAKE AND THE BODY WEIGHT OF THOSE MINK WHICH SHOWED NO WEIGHT CHANGE AND WERE HOUSED IN RANCH-TYPE CAGES AND MAINTAINED ON THE BASAL RATION IOOU ! i TOO 8 0 0 5 0 0 BODY WEIGHT, grams FIGURE 3: THE RELATIONSHIP BETWEEN THE APPARENT DIGESTIBLE ENERGY INTAKE AND THE BODY WEIGHT OF MINK RECEIVING THE BASAL RATION AND HOUSED IN METABOLISM CAGES (Data from other sources have been included f o r comparative purposes.) BODY WEIGHT, grams 52 associated with fur growth and temperature f l u c t u a t i o n s . At no time did the temperature f a l l below 7°C. The mean d a i l y temperature for the e n t i r e period was 10.7°C. In view of the above r e s u l t s , the question a r i s e s as to whether r e s t r i c t i o n of the cage capacity w i l l influence feed intake. For t h i s reason, the A.D.E. (Cal) intake by animals maintained for short periods of time i n the smaller metabolism cages on the basal r a t i o n has been plotted against mean body weight (Figure 3). A te s t of s i g n i f i c a n c e ('t'=6.672 for 24df) shows that these animals consumed s i g n i f i c a n t l y less feed than when housed i n ranch-type cages. For comparative purposes, plotted on t h i s same graph i s the data of Hodson and Smith (10) on which the 1953 N.R.C. (23) maintenance requirements for energy for thei mink are based. Measurements obtained by S i n c l a i r , et a l (33) have been pl o t t e d on the same graph. These data have been selected because they were obtained from mink housed i n small metabolism cages. In order to test the hypothesis that a mink eats to meet an energy requirement, a comparison of the mean c a l o r i c intake of those mink which were maintained on the basal r a t i o n without weight change with the energy intake of those mink re c e i v i n g the basal r a t i o n plus added f i b r e , showed no s i g n i f i c a n t d i f f e r e n c e ('t'=0.851 for 41df) between energy intake and body weight. However, when a comparison was made between the same group on the basal r a t i o n and those mink on the rations with added f i b r e also showing no weight change, there was a s i g n i f i c a n t l y ('t'=3.892 for 26df) lower energy intake by the l a t t e r group. The data has been i l l u s t r a t e d g r a p h i c a l l y i n Figure 4. FIGURE 4: A DIAGRAMMATIC REPRESENTATION OF THE APPARENT DIGESTIBLE ENERGY INTAKE OF EACH INDIVIDUAL MINK ON THE FOUR RATIONS AND OF THEIR WEIGHT CHANGES WHILE ON THE RATIONS Each bar represents the mean d a i l y A.D.E. intake expressed i n Cal/100 gm body weight for a one week period. The heavily shaded areas represent weight gain, i f placed at the top of a bar, and weight loss i f placed at the bottom of a bar. One centimetre i s equal to t h i r t y grams of weight change. The bar representing the basal r a t i o n (unshaded) i s the mean figu r e of a l l measurements during which the animal demonstrated weight s t a s i s . DISCUSSION The main purpose of t h i s study has been to e s t a b l i s h a r e l a t i o n s h i p between body weight and the energy u t i l i z e d by t h i s s t r a i n of mink for maintenance purposes. In t h i s experiment, i t has been con s i s t e n t l y found that energy expenditure for maintenance purposes tends to vary d i r e c t l y with body weight and not with body weight raised to some f r a c t i o n a l power, as has been found by several workers (1, 5,13) for i n t e r s p e c i f i c comparisons of basal metabolism. Without much experimental evidence, these findings are often extended i n order to estimate i n t r a s p e c i f i c energy requirements for maintenance (22). Because the present measurements r e l a t i n g energy intake to body weight cover animals displaying only a narrow weight range, a curve j o i n i n g the two weight extremities would appear to be almost l i n e a r i f i t were placed on the e n t i r e i n t e r s p e c i f i c scale as calculated from Brody's equation (5). The present data, even i f i t were expressed as body weight to a power function of 0.73, would s t i l l f a l l within the standard error l i m i t s of Brody's data. Some i n t r a -s p e c i f i c data on basal or r e s t i n g metabolism of horses (5) and rabbits (14) show that heat production does not i n fa c t vary with body weight raised to some f r a c t i o n a l power but with body weight r a i s e d to unity. This phenomenon i s less s u r p r i s i n g with the mink since the increment of energy associated with a c t i v i t y i s i n excess of 200% above the basal energy expenditure. There i s some evidence that the energy expenditure associated with muscular a c t i v i t y may vary d i r e c t l y 56 with body weight (21, 5). On would, therefore, expect the t o t a l maintenance energy requirement of the mink to vary with body weight raised to a f r a c t i o n a l power closer to one than to 0.7, because a c t i v i t y i s such an unusually large portion of the t o t a l maintenance energy of t h i s species. Of p a r t i c u l a r i n t e r e s t are the measurements associated with mink housed i n metabolism cages. The highly s i g n i f i c a n t decrease associated with confinement i s expected and i s also of approximately the same magnitude as that found i n the cat (20). The data of Hodson and Smith (10) on mink, unspecified as to sex, s t r a i n or time of year, were selected from d i f f e r e n t feeding t r i a l s , a l l of which were c a r r i e d out i n metabolism cages. The animals were c a r e f u l l y selected because they demonstrated a f a i r l y constant body weight throughout the t r i a l . However, two of the s i x selected mink gained i n excess of 50 gm. Despite the scatter and apparent lack of c o r r e l a t i o n of the date, the requirement of a 1 kg mink i s i n precise agreement with that predicted by the present equation calculated from the data on measurements made on mink i n metabolism cages (Figure 3). For present purposes, there i s l i t t l e advantage to correcting the apparent d i g e s t i b l e energy for endogenous faeces and for urinary nitrogen losses. The energy associated with metabolic faeces (7) and that associated with the urine, corrected for endogenous nitrogen, i s t h e o r e t i c a l l y s e l f - c a n c e l l i n g . The conclusion i s that the apparent d i g e s t i b l e energy of the basal r a t i o n i s approximately equal to i t s metabolizable energy. 57 When the basal r a t i o n plus 20% or 14% added f i b r e was fed to these mink, they generally l o s t weight f o r the f i r s t week, but on the second week they e i t h e r maintained or even gained body weight, despite a s i g n i f i c a n t l y lower apparent d i g e s t i b l e energy intake than when receiving the basal r a t i o n . There are several possible explanations for these observations: (a) The i n i t i a l weight loss may be associated with a lack of a c c e p t a b i l i t y of the r a t i o n supplemented with high f i b r e . This i s not l i k e l y since the mink did not go o f f feed but i n fac t increased feed consumption on a unit weight b a s i s . (b) The mink may have become quiescent during the second week and thereby conserved energy. This was not apparent through observations. (c) The d i s t e n t i o n of the gut may have occurred gradually and therefore increased the mink's capacity to handle larger quantities of the feed concurrent with a gradual increase i n feed time of passage, thereby permitting a larger intake of feed per unit time. (d) The mink may have been able to u t i l i z e the heat increment of feeding, c a l l e d the s p e c i f i c dynamic a f f e c t , or S.D.A. (5, 13), which would be dissipated as waste heat within the animal's comfort zone but u t i l i z e d with decreasing ambient temperatures. Since the mean d a i l y temperature during the period when the animals received the basal r a t i o n and the basal r a t i o n plus the 20% added f i b r e was 10.7°C i n both cases, t h i s could not have been a factor„ But i t 58 may have been a factor when the mink received the other two rations when the temperature was as low as 2.7°C„ (e) These observations on the e f f e c t s of added dietary f i b r e on the apparent economy of energy are i n agreement with B i e l y and Marsh (2) and with McKenzie (18) , who a t t r i b u t e s these discrepancies to the use of apparent d i g e s t i b l e energy, which does not take into account the increase i n metabolic faeces associated with increasing feed intake (30) , and increasing l e v e l s of dietary f i b r e (19). This would tend to underestimate the true energy intake of a mink and i s one probable explanation for the apparent conservation of energy. (f) A more l i k e l y explanation of the apparent decrease i n energy requirements with increasing r a t i o n f i b r e by the mink may be the increase i n net energy, which could r e s u l t from a lower S.D.A. because of lower nutrient concentrations, p a r t i c u l a r l y p r o t e i n , at any one time r e l a t i v e to the high concentration of nutrients i n the basal r a t i o n . I t i s therefore postulated that concurrent with decreasing r a t i o n q u a l i t y , there i s a greater increase i n the net energy than would be predicted on the basis of the apparent d i g e s t i b l e energy of each r a t i o n , i n keeping with the law of diminishing returns as outlined i n d e t a i l by Brody (5). These measurements r e l a t i n g apparent d i g e s t i b l e energy intake of the mink on the basal r a t i o n without any weight change are d i f f i c u l t to compare with other data (6, 10, 16, 25, 27) because of the lack of defined conditions. Over the weight range considered, 59 they do agree well with an equation formulated by Wood and F a r r e l l (36) r e l a t i n g the apparent d i g e s t i b l e i energy of adult female mink against body weight. This data has been c o l l e c t e d from many sources. Because of the good agreement between the present measure-ments and those c a r r i e d out by Jorgensen (11) during a fourteen day period at the end <5f October, i t i s anticipated that the standard curve representing the data i n Figure 2 may be u t i l i z e d as a basis on which to predict the energy requirements of female mink maintained under p r a c t i c a l ranch conditions during the autumn. 60 BIBLIOGRAPHY 1. Benedict, F.G. 1938. V i t a l energetics. A study i n comparative basal metabolism. Carnegie Inst. Wash. Publ. No. 503. 2. B i e l y , J . and B. March. 1961. Some hi g h l i g h t s of n u t r i t i o n research i n the poultry science department of the University of B r i t i s h Columbia. Feedstuffs. 33, (23), 26. 3. Blaxter, K.L., F.W. Wainman, and J.L. Davidson. 1966. The voluntary intake of food by sheep and c a t t l e i n r e l a t i o n to t h e i r energy requirements for maintenance. Animal Prod. .8_, 75-83. 4. Brent, B.E., D. Richardson, W.S. Tien and C.S. Menzies. 1961. D i g e s t i b i l i t y studies on l e v e l s of concentrates i n complete p e l l e t e d rations for fattening lambs. J . Animal S c i . 20_, 526-528„ 5. Brody, S. 1945, Bionergetics and growth. Reinhold Publo Corp., New York. 6. Ebner, K.E. 1955. Studies i n mink n u t r i t i o n with s p e c i a l reference to supplementary protein sources. Unpublished Master's t h e s i s , Dept. of Animal S c i . , University of B r i t i s h Columbia. 7. F a r r e l l , D.j.~. 1966 a. Part I I . Studies on the mink during s t a r v a t i o n I (Included i n t h i s t h e s i s ) . 8. F a r r e l l , D.J. 1966 b. Part I I I . The e f f e c t s of the addition of f i b r e to the r a t i o n . (Included i n t h i s t h e s i s ) . 9. H i l l , F.W. and L.M. Dansky. 1954. Studies of the energy requirements of chickens. Poultry S c i . 33, 112-119. 10. Hodson, A.Z. and S.E. Smith. 1945. Estimated maintenance energy requirement of foxes and mink. Amer. Fur Breeder, 18_, 44. 11. Jorgensen, G. 1961. (Feeding standards of young mink of d i f f e r e n t s t a r t i n g weights). Dansk P e l s d r a v l , 24, 185-189. 12. Kielanowski, J . 1965. Estimates of energy cost of protein deposition i n growing animals. Energy metabolism edited by K.L.Blaxter„ European assn. for animal prod, Publ. No. 11, Academic Press, New York. 61„ 13o K l e i b e r , M. 1961„ The f i r e of l i f e . Wiley and Sons, Inc. New York. 14o Lee, R.C. 1939. Si z e and b a s a l metabolism i n the r a b b i t , J . N u t r i t i o n , 18, 489-500, 15, Leche, T,F, 1964, The i n f l u e n c e of the plane of n u t r i t i o n on the e a r l y growth of the H o l s t e i n c a l f . Unpublished Master's t h e s i s , Dept. of Animal S c i . , U n i v e r s i t y of B r i t i s h Columbia. 16. Maloney, J,V, 1949. A n u t r i t i o n experiment to determine the maintenance requirements of mink. Unpublished Batchelor's t h e s i s , Dept. of Animal S c i . , U n i v e r s i t y of B r i t i s h Columbia, 17, M c M i l l a n , K„R. 1965, Fungal t o x i c o s i s i n the mink (Mustela vison) Unpublished Master's t h e s i s , Dept. of Animal S c i . , U n i v e r s i t y of B r i t i s h Columbia, 18. McKenzie, R„M. 1964, The response of the l a b o r a t o r y r a t to changes i n the c a l o r i c d e n s i t y and p r o t e i n : c a l o r i e r a t i o of i t s r a t i o n . Unpublished Master's t h e s i s , Dept. of Animal S c i . , U n i v e r s i t y of B r i t i s h Columbia, Meyer, J.H, 1956, Influence of d i e t a r y f i b r e on metabolic and endogenous n i t r o g e n e x c r e t i o n . J , N u t r i t i o n , 58, 493-500. M i l l e r , S,A„ and J.B. A l l i s o n . 1958, The d i e t a r y n i t r o g e n requirements of the c a t . J . N u t r i t i o n , 64^ 493-500. M i t c h e l l , H.H. 1962. Comparative n u t r i t i o n of man and domestic animals. V o l , I , Academic P r e s s , New York, Mo r r i s o n , F,B. 1959. Feeds and feeding. 22nd, ed,, Morrison P u b l i s h i n g Co., C l i n t o n , Iowa, N a t i o n a l research c o u n c i l , committee on animal n u t r i t i o n , U.S.A. 1953, N u t r i e n t requirements f o r domestic animals. 7, N u t r i e n t requirements f o r foxes and minks, Nat, Acad. Science:- Nat, Res. C o u n c i l , Washington, Publ. No, 296. Noland, P.R. and K,W. Sc o t t . I960, E f f e c t of v a r y i n g p r o t e i n and energy in t a k e s on growth and carcass q u a l i t y of swine, J , Animal S c i , 19 67-74. 25. N o r d f e l d t , S, 1947. (Studies of the feed consumption of mink) Lantbrukshogsk„ Husdjursforsoksanst, Sartryck Forhandsmedd No062„ (as quoted i n Nutr. A b s t r . Rev. 1948, 18, 453). 26. Outko, J.A., R,E. Wuthier, and P . H . P h i l l i p s , 1957, The e f f e c t s of increased d i e t a r y f a t upon the p r o t e i n requirement of the growing dog. J . N u t r i t i o n , 62_, 163-169. 19. 20. 21. 22. 23. 24. 62 27. Palmer, L.S. 1927 - 28, D i e t i c s and i t s r e l a t i o n to fur production. Amer.-Fox and Fur Farmer, 7_, 22; 3_, 18. 28. Perel'dik, M.N. and M.I. Titova. 1950. (Experimental determination of feeding standards f or adult breeding mink) Karakul. Zver. 3, No. 2, 29. (As quoted by Aitken, F.C. 1953. Feeding of fur-bearing animals, Technical Communication No. 23 Aberdeen: Commonwealth Bureau of Animal N u t r i t i o n . 29. Peterson, D.W., C.R. Gran, and N.F. Peek. 1954. Growth and food consumption i n r e l a t i o n to dietary l e v e l s of pro t e i n and fibrous bulk. J . N u t r i t i o n , 52, 241-257. 30. Schneider, B.H. 1935. The r e l a t i o n s h i p of metabolic nitrogen. Nitrogen i n the faeces of the r a t , swine and man. Biochem. J , 28, ,360. 31. Sibbald, I.R., R.T. Berg, and J.P. Bowland. 1956. D i g e s t i b l e energy i n r e l a t i o n to food intake and nitrogen retention i n the weanling r a t . J . N u t r i t i o n , 59, 385-392. 32. Sibbald, I.R., D.G. S i n c l a i r , E.V.Evans, and D.L.T.Smith. 1962. The rate of passage of feed through the dige s t i v e t r a c t of the mink. Can. J . Biochem. and Ph y s i o l . 40, 1391-1394. 33. S i n c l a i r , D.G., E.V.Evans, and I.R.Sibbald. 1962. The influence apparent d i g e s t i b l e .energy and apparent d i g e s t i b l e nitrogen i n the di e t on weight gain, feed consumption,.and nitrogen retention of growing mink. Can. J . Biochem. and Ph y s i o l . 40_, 1375-1389. 34. S i n c l a i r , D.G, and E.V.Evans. 1962. A metabolism cage designed f o r use with mink. Can. J . Biochem and P h y s i o l . 40_, 13.95-1399. 35. Wishnofsky, M. 1958. C a l o r i c equivalents of gained or l o s t weight. Am. J . C l i n . N u t r i t i o n , 6_s 542-546. 36. Wood, A.J. and D.J. F a r r e l l , 1965. Some observations, on mink n u t r i t i o n . West. Fur Farmer, j4, ( 8 ) , 12, 37. Wood, A.J. 1956. The black fox magazine and modern>mink breeder. 39, ( 1 ) , 12. THE NUTRITION OF THE FEMALE PASTEL MINK (Mustela vlson) PART V: WATER REQUIREMENTS FOR MAINTENANCE 63 INTRODUCTION Even under c o n t r o l l e d conditions, the task of measuring the water requirements of a species over a r e l a t i v e l y long period of time presents many problems. One of these Is the measurement of the water associated with a change i n body composition, which may or may not occur with a change i n body weight. Presenting s i m i l a r d i f f i c u l t i e s i s the measurement of the metabolic water or water of oxidation of the feed. Several equations have been formulated (12,16,18) which attempt to correct for the above and other variables by u t i l i z i n g several paramaters which would be extremely d i f f i c u l t to con t r o l and measure i n the mink for a lengthy period under maintenance conditions. Of p r a c t i c a l s i g n i f i c a n c e i s the measurement of the t o t a l water intake by a species under non-stress conditions and the r e l a t i o n of t h i s data to some parameter which w i l l permit a comparison with the water intake of other species. Richter (19) and Adolph (1) have expressed water requirements per Calorie of heat produced, thereby implying that the dominant r o l e of water i n the animal i s c l o s e l y r e l a t e d to the heat produced by the system. Many factors can change the water requirements of a species, such as temperature (2,5), s a l t s i n the feed (10), as well as p h y s i o l o g i c a l adaptation (20), to name but a few. The object of t h i s experiment i s the accurate measurement of water consumption by the mink under non-stress conditions, since no such datum i s av a i l a b l e f o r t h i s species. 64 EXPERIMENTAL Because water intake was measured concurrent with feed intake studies, d e t a i l s of animals, housing, n u t r i t i o n and management are i d e n t i c a l to those outlined i n that study (8). Special Equipment For each mink, water was provided ad l i b i t u m from an inverted four-ounce b o t t l e closed by a one-hole No. 8 rubber stopper through which was inserted a st r a i g h t length of Pyrex glass tubing. By means of a strong rubber band, the b o t t l e was fastened onto a s t r i p of metal bolted at eit h e r end to wa l l brackets. The water b o t t l e tube was inserted through the wire mesh of the cage roof. The b o t t l e was therefore independent of any vib r a t i o n s i n the cage. Any drips from the b o t t l e were c o l l e c t e d i r i mineral o i l placed i n a metal container d i r e c t l y below the glass tubing o u t l e t . This container sat on the aluminum tray beneath the cage. Feed Moisture T r i p l i c a t e feed samples were dried at 100° C to a constant weight i n order to determine t h e i r moisture content. Because of the s p e c i a l mink feeders (21) and because the mink were fed t h r i c e d a i l y , evaporative losses of moisture from the feed were considered to be n e g l i g i b l e . A c o r r e c t i o n was made for the moisture associated with the small quantities of waste feed c o l l e c t e d d a i l y . Metabolic Water A correction has been' made for the metabolic water associated with the feed, by u t i l i z i n g the c o e f f i c i e n t s obtained from the oxidation equations of t y p i c a l proteins, fats and carbohydrates. 65 RESULTS The r e l a t i o n s h i p between total"*" water intake and apparent d i g e s t i b l e energy (A 0D 0E.) i n Calories for those mink re c e i v i n g the basal 2 r a t i o n and housed i n ranch-type cages i s presented i n F i g . 1. The water intake, when rela t e d to bodyweight ( F i g . 2) shows a poor c o r r e l a t i o n (r=0.278). But when only those animals are included that showed no weight fl u c t u a t i o n s (- 10 gm) are included, a high c o r r e l a t i o n (r=0.901) e x i s t s between these two v a r i a b l e s . When f i b r e was added to the basal r a t i o n , there was a s i g n i f i c a n t increase (t=.01) i n the t o t a l water intake when expressed on a per c a l o r i e b a s i s , but was about the same when expressed on a dry matter intake basis (2.80 gm water/gm dry matter). When the mink were on the highest f i b r e r a t i o n , they consumed more water (t=.01) than when they received the other two rations with less added f i b r e . DISCUSSION The consistent r e l a t i o n s h i p between the energy (A.D„E„) of the feed and water intake suggests that on the basal r a t i o n the mink consumed 0.68 gm of t o t a l water per Calo r i e (A„D.E„) of basal r a t i o n and somewhat more (0„77 gm/Calorie) when f i b r e was added to the basal r a t i o n . I t i s , however, possible that these two figures may agree i f the water intake were expressed on a net energy bas i s . The r e l a t i o n s h i p i s i n good agreement with the figure of 0.78 calculated from water intake and feed intake data for the cat (7) and the figure of 0.61 for the mouse (17). Adolph (1) has concluded that under non-stress lo Total water intake=the summation of feed water, metabolic water and b o t t l e water, 2„ Water intake=the summation of feed water and b o t t l e water only. FIGURE 1: THE RELATIONSHIP BETWEEN TOTAL WATER AND APPARENT DIGESTIBLE ENERGY INTAKE OF MINK RECEIVING THE BASAL RATION AND HOUSED IN RANCH-STYLE CAGES 150 O O 100 50 o o o y = 0.442x + 40.8 S = 5.7 R r = 0.622 for 43df 170 190 210 230 250 APPARENT DIGESTIBLE ENERGY, Calories FIGURE 2: THE RELATIONSHIP BETWEEN WATER INTAKE AND BODYWEIGHT OF MINK RECEIVING THE BASAL RATION AND HOUSED IN RANCH-STYLE CAGES 150 BODYWEIGHT, grams FIGURE 3: THE RELATIONSHIP BETWEEN WATER INTAKE AND BODYWEIGHT OF MINK RECEIVING THE BASAL RATION, HOUSED IN RANCH-STYLE CAGES, AND DEMONSTRATING WEIGHT STASIS WATER INTAKE, grams o o o <J1 o o o > > o H CO 00 o o 0 > <J5 O rt CO II II II O o • • * o o t - 1 H i or + vO OJ CX • r h On > 69 conditions the voluntary consumption for a l l mammals i s 1 gm of water per C a l o r i e . M i t c h e l l (15) has recalculated data on water intake of steers and has obtained a mean figure of 1.21 gm of water per C a l o r i e , i n close agreement with that of 1.01 gm/gross Calo r i e reported by Macdonald and B e l l (14) for l a c t a t i n g cows and a s i m i l a r figure has been measured for the monkey (23). Benedict's (4) f i g u r e for a f a s t i n g man i s 0.81 gm/ C a l o r i e of heat produced. It i s worthy of note that the mean t o t a l water intake of eleven female mink rec e i v i n g high energy synthetic r a t i o n s , fed dry, was 0.52 gm per calculated C a l o r i e (A.D.E.) (unpublished). The f i b r e l e v e l s , calculated from the composition of the r a t i o n ingredients were less than 0.4% and the ash contents did not exceed 6% on a dry weight ba s i s . Richter (19) has r e l a t e d water intake to body surface area, t h i s varied between 1050 gm and 1238 gm per sq. meter for dogs, r a t s , cats, monkeys and humans. Surface area i s d i f f i c u l t to measure with any degree of p r e c i s i o n . This i s p a r t i c u l a r l y true i n the case of the l i v e mink, and for t h i s reason, i t has not been used as a basis on which to express water intake. The high c o r r e l a t i o n between dry matter consumed and water intake (Fig, 3) during weight s t a s i s i s i n contrast to the low c o r r e l a t i o n obtained during weight f l u c t u a t i o n s . i T h i s suggests that only during weight s t a s i s i s feed intake a good base against which to r e l a t e water intake. Nevertheless, i t i s the one which i s most generally used for domestic animals, L e i t c h and Thomson (13) have reported r a t i o s of 2:1 for sheep and 3:1 for horses and pigs. Holine (11) has reported that bacon pigs showed l i t t l e e f f e c t when li m i t e d to 1:5 lbs of water per l b . of feed. Provision of an unrestricted supply of water i n addition to the allowance of 1% lb added to each lb of meal, resulted i n a marked improvement i n the d a i l y feed consumption and i n the rate of weight gain (3). The figure of 2.8:1 for the cat (7) i s i d e n t i c a l to that measured for the mink, but much higher than for the mouse (3), when a figure of only 1.3:1 has been obtained. The mere fact that the average water intake per gram of dry feed ingested was the same on the basal and on the added f i b r e rations suggests that with decreasing r a t i o n d i g e s t i b i l i t y the water content of the faeces decreased since the f a e c a l output increases with increasing dietary f i b r e l e v e l s . This, then, tends to oppose a theory which attempts to explain the inverse r e l a t i o n s h i p between the time of passage of the feed and r a t i o n f i b r e l e v e l (9), unless water i s withdrawn from the faeces i n the large i n t e s t i n e . From the water measurements c a r r i e d out on these mink, i t may be concluded that the water intake of a 900 gm mink demonstrating weight s t a s i s i s 110.2 gm per day, using the equation from F i g . 3. Based on the calculated A.D.E. intake for the same mink (8) and using the equation r e l a t i n g water to energy (A.D.E.) i n F i g . 1, the water intake would be 117.4 gm per day. 71 BIBLIOGRAPHY 1. Adolph, E.F. 1933, The metabolism and d i s t r i b u t i o n of water i n body and t i s s u e s . P h y s i o l , Revs. 13_, 336-371. 2. Bailey, C,B. 1964, E f f e c t of environmental temperature on feed, digestion, water metabolism, body temperature and c e r t a i n blood c h a r a c t e r i s t i c s of sheep. Can, J . Animal S c i . 44, 68-75. 3. Barber, R.S., R. Braude, and K.G.Mitchell, 1963. Further studies on the water requirements of the growing p i g . Animal Prod. 5_, 277-282, 4. Benedict, F.G. 1915, A studyof prolonged f a s t i n g . Carnegie Inst. Wash. Publ. No. 203. 5. Benedict, F.G. 1923. Under n u t r i t i o n i n steers. Carnegie Inst. Wash. Publ. No. 203. 6. Bing, F.G. 1923. and L.B. Mendel. 1931. The r e l a t i o n s h i p between food and water intake i n mice. Am. J . P h y s i o l . 98, 169-179. 7. Carver, D.S. and H.N. Waterhouse. 1962. The v a r i a t i o n i n the water consumption of cats. Proc. Animal Care Panel 12_, 267-270. 8. F a r r e l l , D. J . 1966. Part IV. Energy requirements for maintenance. (Included i n t h i s t h e s i s ) . 9. F a r r e l l , D.J. 1966. Part I I I . The e f f e c t s of the add i t i o n of f i b r e to the r a t i o n . (Included i n t h i s t h e s i s ) . 10. Gamble, J.L., M.C. Putnam, and C.F. McKhaun. 1929. The optimal water requirements i n renal function. I. Measurements of water drinking by rats according to increments of urea and of several s a l t s i n the food. Am. J . P h y s i o l . 88_, 571-580. 11. Holine, D.W. and K.L. Robinson. 1965. A study of water allowance for bacon pigs. Animal Prod, 7_, 377-384, 12. Lavietes, P.H. 1935. The metabolic measurement of water exchange. J . C l i n . Invest. 14, 57-69. 13. L e i t c h , I. and J.S. Thomson. 1944. The water economy of farm animals. N u t r i t i o n Abstr. Revs. 14, 197-223. 72 14. MacDonald, M.A. and J.M. B e l l . 1958. E f f e c t s of low f l u c t u a t i n g temperatures on farm animals: I I . Influence of ambient a i r temperature on water intake of l a c t a t i n g H o l s t e i n - F r i e s i a n cows. Can. J . Anim. S c i . 38_, 23-32. 15. M i t c h e l l , H.H. 1962. Comparative n u t r i t i o n of man and domestic animals. Vol. I. Academic Press, New York. 16. Newburgh, L. H„, M.W. Johnston, and Falcon-Leeves. 1930. Measurements of t o t a l water exchange. J . C l i n . Invest. 8^, 161-166. 17. Nishimura, T. 1966. Personal communication. 18. Peters, J.P., D.M. Kydel, and P.H. Lavietes. A note on the c a l c u l a t i o n of water exchange. J . C l i n . Invest. 12_, 689-693. 19. Richter, C 0P. 1938. Factors determining voluntary water ingestion i n normals and i n i n d i v i d u a l s with maximum diabetes i n s i p i d u s . Am. J . Ph y s i o l . 122, 668-675. 20. Schmidt-Nielsen, K. and B. Schmidt-Nielsen. 1952. Water metabolism i n desert mammals. P h y s i o l . Revs. 32_, 135-166. 21. S i n c l a i r , D.G. and E.V. Evans. 1962. A metabolism cage designed for use with mink. Can. J . Biochem. and Ph y s i o l . 40_, 1395-1399. 22. Wayner, M.J. 1964. T h i r s t . The Macmillan Pub. Co., New York. 23. Wood, A.J. and M.A. Kennard. 1956. The feeding, housing and management of a small monkey colony. Can, J . Comp. Med. 20, 294-301. APPENDICES 73 APPENDIX I  AN INDIRECT ANIMAL CALORIMETER FOR MINK INTRODUCTION An e f f e c t i v e calorimeter for the study of mink metabolism must provide an animal chamber of s u f f i c i e n t s i z e to permit the mink to l i v e within the chamber for prolonged periods. Experience has shown that a long period of t r a i n i n g i n the calorimeter i s e s s e n t i a l i f the mink i s to be persuaded to remain i n a state of complete r e s t for periods of s u f f i c i e n t duration to allow the accurate measurements of metabolic rate. PRINCIPLE The calorimeter developed to meet t h i s requirement i s of the closed c i r c u i t volumetric type. The carbon dioxide produced by the animal i s absorbed by an agitated sodium hydroxide s o l u t i o n . Oxygen consumed by the animal i s replaced through a metering device with the ai d of a pressure-sensing manostat. DESCRIPTION OF THE CALORIMETER A schematic representation of the basic design features of the calorimeter i s shown i n Figure 1. The pertinent regulatory devices are enumerated i n the figure according to the following sequence: 1. A c y l i n d e r of oxygen (A), (99.6% minimal oxygen content) with the usual pressure regulators. FIGURE I: A DIAGRAMMATIC REPRESENTATION OF THE RESPIROMETER 2. A solenoid valve (N) to co n t r o l oxygen flow from the open pressure regulator to the animal chamber, 2 3. A proportional flow c o n t r o l l e r (L)to a c t i v a t e the power c i r c u i t to the solenoid valve. 3 4. A pre-calibrated wet test gas meter (K) to measure the volume of oxygen consumed. 5. A water manometer (H) to sense changes i n pressure i n the animal chamber. Clipped to the manometer i s a sensing probe to transmit pressure changes from the manometer to the proportional c o n t r o l l e r . 4 6. An anaerobic incubator (E) to serve as a temperature regulated animal chamber (30 cm x 30 cm x48 cm ). 7. A thermally regulated water bath"* (g) to provide a r e s e r v o i r of ethylene glycol, of known temperature for c i r c u l a t i o n through the heat exchange c o i l - f a n system (G) mounted i n the back wall of the animal chamber. 8. Two thermistors within the animal chamber to determine the i n t e r i o r 6 temperature by means of an external tele-thermometer (M). 1. Control Co. of Canada, Co o k v i l l e , Ontario. 2. Matheson of Canada, Ltd., Whitby, Ontario. 3. P r e c i s i o n S c i e n t i f i c Co., Chicago, I l l i n o i s . 4. National Appliance Co., Portland 23, Oregon. 5. E. H. Sargent & Co., Chicago, I l l i n o i s . 6. Yellowstone Instrument Co., Yellowstone, Ohio. 9„ A polyethylene c e n t r i f u g a l pump (D) for c i r c u l a t i o n of thecarbon dioxide absorbing potassium hydroxide s o l u t i o n contained i n a shallow pyrex dish (4.4 cm x 22 cm x. 27 cm) r e s t i n g below the animal cage within the chamber. 10. A rectangular cage (18 cm x 25 cm x 30 cm) of 2.5 cm square mesh galvanized 12 gauge i s mounted on a metal droppings pan (F) provided with a removable tray. OPERATION OF THE CALORIMETER The animal under study i s admitted to the wire cage and then placed i n the respirometer chamber. The chamber door i s l e f t ajar and the c i r c u l a t i n g fan of the heating/cooling unit i s allowed to run con t i n u a l l y . The animal i s fed and watered within the chamber for a prolonged period (2-3 weeks) to permit i t to adjust to the experimental conditions. The singular lack of metabolic rate measurements on t h i s semi-domesticated animal i s i n d i c a t i v e of the great d i f f i c u l t y i n obtaining a quiescent state for a period of time s u f f i c i e n t to obtain meaningful data. To measure the oxygen consumption of the animal, a ten percent s o l u t i o n of potassium hydroxide i s introduced into the pyrex dish and i s maintained i n an agitated condition by the polyethylene c i r c u l a t i n g pump. Temperature con t r o l i s maintained by c i r c u l a t i n g 1. Cole-Parmer Instrument & Equipment Co., Chicago 10, I l l i n o i s 77 ethylene g l y c o l from the thermally regulated r e s e r v o i r through the heat exchange c o i l . The animal i s observed u n t i l i t i s asleep. At t h i s time, the door of the chamber i s closed, pressure within the chamber i s adjusted to the ambient barometric pressure, and the manostat-sensing probe-pressure co n t r o l l e d system i s activated to maintain a constant pressure within the system through the measured addit i o n of oxygen from the oxygen c y l i n d e r . The carbon dioxide i s absorbed c o n t i n a l l y i n the agitated KOH s o l u t i o n . The animal i s observed through the window i n the chamber door. The oxygen consumption i s measured over the period during which the animal i s asleep. A f t e r conversion to standard conditions, the oxygen consumption values are converted to c a l o r i c equivalents on the assumption that the R.Q. i s 0.8 and the thermal equivalent per l i t r e of oxygen i s 4.80 C a l o r i e s . APPENDIX II Mink Cereal Grain P e l l e t s Ingredients • Tomato Pomace Ground Wheat Wheat Bran Wheat Germ Meal Oat Groats Fis h Meal (70%) Soya Meal (50%) Linseed O i l Meal A l f a l f a Leaf Meal Skim Milk Powder Brewer's Yeast Steamed Bone Meal Iodized Salt Molasses - Cane S t a b i l i z e d Fat Dry Vitamin A - 1,000,000 I.U. Dry Vitamin D - 150,000 I.U. Amounts (lbs) 100 590 100 65 150 200 200 100 100 100 20 20 5 100 150 2,000 APPENDIX III Individual Weight Records (grams) of Controls* Animal Adult Female : Barren i Pastels Adult F e r t i l e Female Pastels Female Standard Darks API AP2 AP3 AP4 AP5 AP6 AB7 AB8 AB3 Week 0 668 573 765 915 605 830 3 704 574 784 729 634 609 919 702 799 7 775 587 763 787 705 690 1047 785 1065 11 818 610 747 837 737 810 1081 760 1105 *Mink maintained on ranch operated by: A. Peace, 4175 Douglas St., V i c t o r i a , B.C. APPENDIX IV Individual Weekly Weight Records (grams) Animal PI P2 P3 P4 P5 P6 Week 0 823 792 822 866 661 700 1 864 747 785 819 719 631 2 851 756 765 827 681 606 3 862 727 795 4 890 750 828 699 558 5 858 751 830 740 667 6 858 746 833 745 691 7 822 746 832 744 698 8 835 748 849 741 726 9 804 685 841 702 690 10 805 706 849 668 698 11 852 746 907 642 654 12 860 743 922 655 716 13 878 736 913 700 14 870 732 914 702 15 860 749 876 706 * 787 683 810 634 16 838 718 874 650 706 17 835 726 926 697 735 18 837 747 920 649 737 * Commencement of second period. APPENDIX V Individual D a i l y Feed Intake Records (grams) 81 Mink No. Day PI P2 P3 P4 P5 1 55.2 56.4 50.3 61.1 2 65.1 50.9 46.4 60.3 3 51.3 49.3 37.6 42.6 56.9 4 41.9 33.7 65.6 38.1 5 51.7 40.5 46.1 32.7 44.3 6 47.2 49.6 48.8 46.8 7 44.1 34.4 42.8 43.6 25.9 8 53.5 44.7 37.6 9 31.3 50.4 49.2 10 35.4 40.9 42.8 11 34.4 32.1 36.2 12 47.0 37.2 36.2 13 .45.2 42.1 35.4 14 45.6 41.9 37.7 15 41.8 43.4 46.3 45.5 53.2 16 62.6 42.5 56.2 45.3 62.2 17 49.3 49.5 57.3 30.9 45.3 18 56.7 41.5 54.2 32.6 47.4 19 53.4 44.2 46.5 26.9 41.1 20 45.5 J6 . > 21 45.1 23.2 28.7 22 42.5 36.3 46.6 23 50.8 33.1 43.3 24 49.8 40.6 46.7 25 40.0 40.4 47.4 26 48.4 34.9 50.9 27 56.4 54.9 28 57.2 52.3: 60.3 29 47.4 41.1 44.8 30 44.4 34.7 44.7 48.7 48.4 31 45.9 37.3 47.8 50.0 50.7 32 45.7 38.2 41.0 45.9 55.2 33 44.4 37.4 45.0 58.2 51.4 34 44.8 38.8 47.0 51.4 55.4 35 46.2 39.2 46.2 44.9 55.1 Ration Basal APPENDIX V (cont'd) 82 Mink No, Day PI P2 P3 P4 P5 36 58.7 48.5 41.9 51.1 48.4 37 47.1 38.5 42.0 41.3 35.8 38 45.7 34.8 46.3 41.8 39.2 39 48.5 39.6 47.7 42.6 44.1 40 46.8 39.4 47.8 38.7 45.1 41 50.3 40.8 47.9 42.5 38.9 42 51.1 41.5 48.6 37.1 41.2 43 49.2 44.0 47.6 42.7 43.4 44 50.0 43.3 50.7 33.6 43.2 45 46.6 39.9 47.3 46.4 41.5 46 46.6 38.4 48.9 43.3 39.8 47 48.2 38.4 47.6 44.6 41.3 48 47.7 40.5 42.1 40.4 41.9 49 43.4 39.2 42.7 39.3 41.8 50 51.9 42.9 46.4 43.2 42.4 51 50.4 44.3 46.1 34.1 41.6 52 53.5 44.2 48.0 42.3 41.9 53 54.4 39.3 46.6 45.2 44.1 54 53.7 43.9 46.5 48.6 43.0 55 49.6 39.9 47.8 40.3 44.0 56 52.7 hi. .o 47.9 . 36.9 45.9 57 39.7 48.6 46.4 41.9 48.2 58 53.0 55.2 52.1 23.6 42.0 59 46.7 57.4 54.8 49.2 46.4 60 49.4 51.9 54.1 39.7 47.4 61 51.7 65.1 56.7 44.6 51.9 62 46.5 60.3 56.5 47.8 52.6 63 46.5 57.0 59.3 52.2 52.5 64 60.7 45.2 55.7 36.1 48.2 65 58.1 49.1 58.5 40.2 55.3 66 60.8 54.9 63.0 33.4 49.4 67 61.7 56.4 54.4 40.6 58.7 68 62.4 54.0 67.2 45.7 57.1 69 57.0 54.0 56.3 35.9 54.5 70 55.6 55.7 54.9 43.5 49.1 Ration Basal Basal+20 APPENDIX V (cont'd) 83 Mink No. Day PI P2 P3 P4 P5 71 51.1 47.1 50.0 72 59.8 50.5 56.8 73 47.7 56.8 65.5 74 63.6 61.2 58.5 75 55.8 47.0 54.2 76 54.5 53.4 51.7 46. a 57.9 77 56.5 47.8 59.3 49.6 55.1 78 58.0 47.5 51.1 48.9 56.3 79 55.4 47.9 54.3 38.6 50.9 80 57.6 54.9 58.4 43.5 52.4 81 48.8 53.3 55.2 48.6 52.3 82 48.5 45.7 35.1 33.4 52.0 83 48.9 36.6 43.6 38.6 34.9 84 54.0 44.3 47.2 33.6 41.4 85 46.6 41.6 37.0 39.5 86 51.0 43.6 47.3 42.9 87 53.2 45.6 52.6 46.7 88 54.9 48.9 50.6 49.7 89 43.3 42.9 48.7 45.2 90 47.8 41.1 53.0 43.6 91 56.4 45.3 i- ~ •'< J-> . X 73.6 92 48.5 48.3 49.9 49.5 93 54.1 50.4 54.6 53.7 94 53.0 48.9 51.1 50.1 95 52.3 57.7 52.4 55.3 96 52.5 45.8 44.5 49.6 97 55.4 44.4 41.3 51.2 98 49.2 47.7 57.7 52.9 99 52.0 44.5 53.6 54.5 100 51.7 48.7 46.9 49.9 101 50.5 47.4 50.9 49.7 102 55.2 53.2 56.7 56.4 103 59.1 55.7 56.6 58.7 104 58.4 56.3 48.8 46.0 105 53.6 46.9 51.5 49.8 Ration Basal Basal+14 APPENDIX V (cont'd) 84 Mink No. Day PI P2 P3 P4 P5 Ration 106 50.4 49.4 55.4 58.8 A 107 62.9 53.1 54.1 58.0 108 58.3 53.1 59.9 60.0 109 60.0 47.3 64.9 53.5 110 63.7 54.7 64.6 54.3 Basal+7 111 68.9 46.8 65.1 55.4 112 55.6 51.8 64.8 57.6 113 43.0 47.5 69.1 44.9 49.9 114 55.4 50.9 65.3 44.7 57.7 115 24.1 33.6 51.2 47.2 31.9 116 46.9 53.1 60.3 51.6 58.4 117 51.8 49.1 61.9 44.8 54.1 118 48.5 45.9 53.2 45.9 53.0 119 37.9 33.4 69.9 50.6 40.3 X 120 44.6 42.9 49.2 40.7 51.6 121 51.0 47.2 54.7 44.5 49.9 122 54.9 46.9 50.3 43.5 49.5 123 46.2 46.0 44.8 47.7 42.8 Basal 124 51.6 47.5 44.7 47.8 54.1 125 46.1 38.4 31.5 43.0 36.5 126 49.5 43.2 48.6 44.6 44.1 V APPENDIX VI Dail y Feed (Dry) Intake And Mean Body Weight Of Mink  During D i g e s t i b i l i t y T r i a l s i n Metabolism Cages Mink No. P4 P5 P6 Feed Intake (grams) 39.2 36.7 47.4 PI P2 P5 39.1 35.7 33.9 PI P2 P5 35.0 38.2 33.0 PI P2 P3 66.6 47.7 55.1 P4 P5 49.0 56.1 Mean Body Weight (grains)  Ration 804 721 650 Basal Basal Basal 813 711 722 Basal Basal Basal 822 703 701 Basal+7 Basal+7 Basal+7 844 729 689 Basal+14 Basal+14 Basal+14 660 694 Basal+20 Basal+20 APPENDIX VII Mean Net Dail y Water Intake for Each Week (grams) 11 Mink No. Week PI P2 P3 P4 P5 1 122.2 78.9 88.4 100.1 103.8 2 95.0 84.8 93.0 3 125.4 91.5 112.5 4 144.0 101.0 109.4 5 103.0 87.5 95.6 113.6 108.5 6 106.3 95.4 105.6 106.8 78.3 7 111.6 94.8 102.5 116.8 83.2 8 120.1 107.9 108.9 105.4 86.6 9 103.7 131.8 111.7 97.2 85.6 10 133.5 124.8 119.9 95.4 98.7 11 126.6 125.4 119.9 12 120.3 116.1 113.3 101.2 111.9 13 126.2 89.0 110.3 99.3 14 112.9 113.0 110.0 111.3 15 116.1 113.7 116.6 118.9 16 137.2 117.7 146.1 133.8 17 103.4 111.7 152.3 123.4 119.1 18 120.3 115.9 122.0 129.5 116.3 87 APPENDIX ¥111  Individual Weekly Weigh-back Of Feed (grams) Animal PI P2 P3 P4 P5 Week 1 15.3 15.0 51.0 15.5 2 10.1 12.7 43.9 3 6.2 4.0 8.8 13.9 5.0 4 2.2 2.3 16.5 5 6.4 2.3 15.4 16.0 8.8 6 11.8 3.5 16.5 8.1 17.3 7 7.4 4.5 9.6 8.1 13.3 8 9.6 5.4 7.0 15.4 9.4 9 17.7 55.0 50.1 30.4 28.8 10 19.9 23.5 26.6 23.0 26.6 11 12.9 8.3 15.0 4.6 4.6 12 10.8 8.0 12.2 11.4 7.9 13 9.4 9.0 11.5 10.3 14 8.1 11.8 19.9 21.9 15 9.0 15.5 17.3 19.1 16 13.7 7.4 14.1 7.5 17 4.6 20.5 10.4 31.7 6.8 18 15.9 6.4 7.3 15.0 13.0 88 APPENDIX IX Mean D a l l y Urine Volume Voided By Mink  Housed In Metabolism Cages And Measured  During S t a r v a t i o n And D i g e s t i b i l i t y T r i a l s S t a r v a t i o n D i g e s t i b i l i t y V o l . Urine V o l . Urine Mink No. Day ml/day Mink No. ml/day PI 1 22.0 PI 42.0 2 12.5 PI 49.0 3 12.0 - P2 51.5 P2 1 14.0 P2 84.0 2 14.5 3 19.0 P3 29.5 P3 1 24.0 P4 32.0 2 14.0 P4 29.5 3 13.0 P4 1 9.0 P5 40.5 2 15.0 P5 50.5 3 10.0 P5 29.0 4 21.5 P5 57.5 5 23.0 P5 53.0 P5 1 10.0 2 8.5 3 12.0 4 11.0 

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