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The influence of slat material, slat coverage and breeder age on broiler breeder reproduction and progeny… Decolongon, Joji 1990

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THE INFLUENCE OF SLAT MATERIAL, SLAT COVERAGE AND BREEDER AGE ON BROILER BREEDER REPRODUCTION AND PROGENY GROWTH by J O J I DECOLONGON B . S c . ( A g r . ) The U n i v e r s i t y o f B r i t i s h C o l u m b i a , 1986 A THESIS SUBMITTED.IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE i n , THE FACULTY OF GRADUATE STUDIES (DEPARTMENT OF ANIMAL SCIENCE) We a c c e p t t h i s t h e s i s as conforming t o the r e q u i r e d s t a n d a r d THE UNIVERSITY OF BRITISH COLUMBIA JULY 1990 (c) J O J I DECOLONGON, 1990 In presenting t h i s thesis i n p a r t i a l f u l f i l 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 fr e e l y available for reference and study. I further agree that permission for extensive copying of thi s thesis for scholarly purposes may be granted by the Head of my Department or by his or her representatives. It i s understood that copying or publication of t h i s thesis for f i n a n c i a l gain s h a l l not be allowed without my written permission. DEPARTMENT OF ANIMAL SCIENCE The University of B r i t i s h Columbia 2075 Wesbrook Place Vancouver, Canada V6T 1W5 Date: 31 JULY 1990 ABSTRACT This study was conducted to examine the potential of p l a s t i c s l a t s as f l o o r i n g material for maintenance of b r o i l e r breeders. Although p l a s t i c s l a t s are more expensive than wood s l a t s , p l a s t i c s l a t s are more durable and easier to clean. Wood and p l a s t i c s l a t s were tested as f u l l and p a r t i a l f l o o r i n g to determine the ideal proportion of slat s for b r o i l e r breeder f l o o r s . Space allotment was 2040 cm^/bird on a l l f l o o r treatments. . Arbor Acres b r o i l e r breeders, one of the more common strains in B r i t i s h Columbia, were raised to 58 weeks of age to monitor the influence of s l a t material and s l a t coverage on egg production and progeny growth over one production cycle. Since the pens were not set up to determine the number of eggs lo s t through s l a t s , "egg production" values were actually egg recovery values. Over-all egg recovery was s i g n i f i c a n t l y higher on p a r t i a l wood (PWS) and p a r t i a l p l a s t i c s l a t s (PPS) than on either of the f u l l s l a t treatments. Breeders on f u l l wood slat s (FWS) had higher ove r - a l l egg production than those on f u l l p l a s t i c s l a t s (FPS) . Differences were s i g n i f i c a n t for three biweekly periods, but s l a t s did not influence the o v e r - a l l incidence of f l o o r eggs and cracked f l o o r eggs. The incidence of ii ABSTRACT cracked nest eggs was s i g n i f i c a n t l y higher in FWS and FPS than i n PWS and PPS pens during four lay periods and over-a l l . The proportion of non-cracked nest eggs, which was taken as an approximation of the proportion of settable eggs, was higher for p a r t i a l s l a t pens than f u l l s l a t pens, and FWS pens had a higher proportion of non-cracked nest eggs than FPS pens. To monitor f e r t i l i t y and hatchability, eggs were incubated at 37, 42, 46, 50 and 56 weeks of breeder age. F e r t i l i t y , h a t c h a b i l i t y of t o t a l eggs set and hatch a b i l i t y of f e r t i l e eggs was not affected by type of s l a t s . Progeny from the hatch at 37, 46 and 56 week of breeder age were grown in Petersime battery cages to three weeks of age. The progeny of breeders on FPS had lower f i r s t week weight gain than the other progeny groups due to moisture loss when 7 FPS progeny were l o s t during the second growth t r i a l . Weekly and o v e r - a l l feed conversion of progeny was not affected by types of s l a t s used by parents. The 56th week progeny were grown in Petersime battery cages to market age (six weeks). PWS and FPS progeny had higher t h i r d week weight gain than PPS progeny. During the sixth week, FWS and PWS progeny had higher weight gain than FPS and PPS progeny. The sixth week feed.conversion of FPS in ABSTRACT progeny was higher than that of the other three progeny groups. No other differences were seen. As long as sl a t s were used as p a r t i a l f l o o r i n g , there were no differences i n egg production on wood or p l a s t i c s l a t s . The proportion of "settable" eggs, f e r t i l i t y , and hat c h a b i l i t y of eggs of p l a s t i c s l a t breeders were comparable with that of wood s l a t breeders regardless of s l a t coverage. There were s i g n i f i c a n t differences in the 3-week growth of 37th, 46th and 56th week progeny and the 6-week growth of 56th week progeny on the d i f f e r e n t s l a t types, but the differences were not due to s l a t treatments. There was no interaction between breeder age and s l a t material, therefore the influence of s l a t material on egg production and progeny growth did not vary with breeder age. Although egg recovery and the number of settable eggs were lower for FPS breeders, breeders on p l a s t i c s l a t s performed as well as those on wood sl a t s i n the present study. IV TABLE OF CONTENTS Page ABSTRACT i i TABLE OF CONTENTS V LIST OF TABLES v i i LIST OF FIGURES v i i i LIST OF APPENDIX TABLES i x ACKNOWLEDGEMENTS X 1. INTRODUCTION 1 2. LITERATURE REVIEW . . . 2 2.1. STUDIES ON SLATS 2 2.1.1. S l a t s and Egg Production 2 2.1.2. S l a t s and the Incidence of Cracked Eggs 6 2.1.3. S l a t s and F e r t i l i t y .6 2.1.4. S l a t s and H a t c h a b i l i t y 7 2.1.5. S l a t s and Labor Requirements 10 2.1.6. Conclusions .11 2.2. STUDIES ON BREEDER AGE 11 2.2.1. Breeder Age and Egg Production 11 2.2.2. Breeder Age and F e r t i l i t y 13 2.2.3. Breeder Age and H a t c h a b i l i t y ..16 2.2.4. Breeder Age and Embryo M o r t a l i t y 19 2.2.5. Breeder Age and Progeny Growth 21 2.2.6. Conclusions 24 3. OBJECTIVES 2 5 4. MATERIALS AND METHODS 2 6 4.1. BROODING PROCEDURES 2 6 4.2. LIGHTING 27 4.3. HOUSING DURING LAY 27 4.4. FEEDING PROGRAM 3 2 4.5. EGG COLLECTION 32 4.6. FERTILITY AND HATCHABILITY TESTS 3 2 4.7. GROWTH TRIALS 33 4.8. STATISTICAL ANALYSIS ...35 5. RESULTS 41 5.1. THE INFLUENCE OF SLAT MATERIAL AND SLAT COVERAGE . 41 5.1.1. Egg Recovery 41 5.1.2. Incidence of Fl o o r Eggs 42 v TABLE OF' CONTENTS 5.1.3. Incidence of Cracked F l o o r Eggs 42 5.1.4. Incidence of Cracked Nest Eggs ..42 5.1.5. Percent " S e t t a b l e " Eggs.. 43 5.1.6. F e r t i l i t y , H a t c h a b i l i t y of T o t a l Eggs Set (TES) and H a t c h a b i l i t y of F e r t i l e Eggs (FES) 49 5.1.7. Temporal D i s t r i b u t i o n of Embryo M o r t a l i t y ... 49 5.1.8. Growth, from Hatch t o Three Weeks of Age, of 37th, 46th and 56th Week Progeny 52 5.1.9. Growth, from Hatch t o S i x Weeks of Age, of 56th Week Progeny . .55 5.2. THE INFLUENCE OF BREEDER AGE 58 5.2.1. F e r t i l i t y , H a t c h a b i l i t y of T o t a l Eggs Set (TES) and H a t c h a b i l i t y of F e r t i l e Eggs (FES) 58 5.2.2. Temporal D i s t r i b u t i o n of Embryo M o r t a l i t y ... 60 5.2.3. Growth, from Hatch t o Three Weeks of Age, of 37th, 46th and 56th Week Progeny 62 5.3. THE INFLUENCE OF SEX OF PROGENY ON.GROWTH 68 5.3.1. Growth, from Hatch to S i x Weeks of Age, of 56th Week Progeny 68 6. DISCUSSION 71 6.1. THE INFLUENCE OF SLAT MATERIAL AND SLAT COVERAGE . 71 6.1.1. Egg Recovery 71 6.1.2. The Incidence of F l o o r Eggs 77 6.1.3. The Incidence of Cracked F l o o r Eggs ... 78 6.1.4. The Incidence of Cracked Nest Eggs 78 6.1.5. Percent " S e t t a b l e " Eggs 79 6.1.6. F e r t i l i t y 80 6.1.7. H a t c h a b i l i t y of T o t a l Eggs Set (TES) and F e r t i l e Eggs (FES) 81 6.1.8. Temporal D i s t r i b u t i o n of Embryo M o r t a l i t y ... 82 6.1.9. The Growth, from Hatch t o Three Weeks of Age, of 37th, 46th and 56th Week Progeny 83 6.1.10. Growth, from Hatch t o S i x Weeks of Age, of 56th Week Progeny 84 6.1.11. Conclusions 84 6.2. THE INFLUENCE OF BREEDER AGE 8 6 6.2.1. F e r t i l i t y . 86 6.2.2. H a t c h a b i l i t y of T o t a l Eggs Set (TES) and F e r t i l e Eggs (FES) 88 6.2.3. Temporal D i s t r i b u t i o n of Embryo M o r t a l i t y ... 89. 6.2.4. Growth, from Hatch t o Three Weeks of Age, of 37th, 46th and 56th Week Progeny .. 93 6.2.5. Conclusions 96 6.3. THE INFLUENCE OF SEX OF PROGENY 97 6.3.1. Conclusions 98 7. BIBLIOGRAPHY 99 APPENDIX 104 V i LIST OF TABLES Page T a b l e 1. The I n f l u e n c e o f S l a t s on Egg Rec o v e r y 44 T a b l e 2. The I n f l u e n c e o f S l a t s on t h e I n c i d e n c e o f F l o o r Eggs . 4 5 T a b l e 3. The I n f l u e n c e o f S l a t s on t h e I n c i d e n c e o f Cracked F l o o r Eggs 46 T a b l e 4. The I n f l u e n c e o f S l a t s on t h e I n c i d e n c e o f Cracked Nest Eggs 47 T a b l e 5. The I n f l u e n c e o f S l a t s on t h e S e t t a b i l i t y o f Eggs 4 8 T a b l e 6. The I n f l u e n c e o f S l a t s on P e r c e n t F e r t i l i t y and H a t c h a b i l i t y . 50 T a b l e 7. The I n f l u e n c e o f S l a t s on t h e Temporal D i s t r i b u t i o n o f Embryo M o r t a l i t y . . . . 51 T a b l e 8. The I n f l u e n c e o f B r e e d e r S l a t s on Body Weight, Body Weight G a i n , Feed I n t a k e and Feed C o n v e r s i o n , from Hatch t o Three Weeks o f Age, o f 37 t h , 46th and 56th Week Progeny 53 T a b l e 9. The I n f l u e n c e o f S l a t s on Body Weight, Body Weight G a i n , Feed I n t a k e and Feed C o n v e r s i o n , from Hatch t o S i x Weeks o f Age, o f 56th Week Progeny 56 T a b l e 10. P e r c e n t F e r t i l i t y and H a t c h a b i l i t y o f Eggs a t D i f f e r e n t B r e e d e r Ages 59 T a b l e 11. The I n f l u e n c e o f B r e e d e r Age on t h e D i s t r i b u t i o n o f Embryo M o r t a l i t y 61 T a b l e 12. The I n f l u e n c e o f B r e e d e r Age on Body Weight, Body Weight G a i n , Feed I n t a k e And Feed C o n v e r s i o n , from Hatch t o Three Weeks o f Age, o f 37 t h , 46 t h and 5 6 t h Week Progeny . . 64 T a b l e 13. The I n f l u e n c e o f B r e e d e r Age on Body Weight, Body Weight G a i n , Feed I n t a k e And Feed C o n v e r s i o n , from Hatch t o Three Weeks o f Age, o f 37 t h , 46 t h and 56th Week Progeny, w i t h A d j u s t e d H a t c h i n g Weight . . . . . 66 T a b l e 14. Body Weight, Body Weight G a i n , Feed I n t a k e and Feed C o n v e r s i o n , from H a t c h t o S i x Weeks o f Age, of Male and Female Progeny o f 56-Week O l d Br e e d e r s 69 v i i LIST OF FIGURES Page Figur e 1. Dimensions of Pens 3 0 Figure 2. Dimensions of Wood and P l a s t i c S l a t s 31 Fig u r e 3. Weekly Egg Production of Study F l o c k and T y p i c a l Arbor Acres F l o c k 75 v i i i LIST OF APPENDIX TABLES Page Appendix Table 1. Weekly Egg Recovery on D i f f e r e n t S l a t Types 105 Appendix Table 2. Weekly Egg Recovery on Wood vs. P l a s t i c S l a t s 106 Appendix Table 3. Weekly Egg Recovery on F u l l vs. P a r t i a l S l a t s 107 Appendix Table 4. The Influence of Breeder Age on Hatching Egg Weight 108 Appendix Table 5. Composition of Chick S t a r t e r D i e t s ... 109 Appendix Table 6. Composition of Developer Di e t s 110 Appendix Table 7. Composition of Breeder Di e t s I l l i x ACKNOWLEDGEMENT S This thesis would not have been without the patient guidance of my thesis advisor, Dr. Robert Fitzsimmons. I thank the members of my advisory committee, Dr. R. B l a i r , Dr. K. M. Cheng and Dr. J. Hunt for th e i r advice and suggestions on the experiments and the thesis. Dr. Mark Newcombe's assistance with s t a t i s t i c s i s greatly appreciated. The help of the following farm s t a f f was invaluable in the maintenance of the b r o i l e r breeder and progeny fl o c k s : Ray Soong, Robert Chan, Alan Enns and Chris Shingera. Ell e n Teng offered r e l i a b l e and e f f i c i e n t help in the weighing of b r o i l e r prog.eny. I am grateful for having been made recipient of the B r i t i s h Columbia Egg Marketing Board Award in 1988 and 1989. Special thanks are due to my husband, Andy Hickman, for his loving support and intere s t i n my pursuits. I express my gratitude to my parents for t h e i r tolerance of my ideas. This project received f i n a n c i a l support from the B r i t i s h Columbia B r o i l e r Breeder Hatching Egg Producers Association. 1. INTRODUCTION Housing has become an important aspect of present-day-poultry production systems. In non-tropical latitudes, the t o t a l confinement of poultry has made possible the year-round production of eggs and meat despite seasonal va r i a t i o n in daylength and environmental temperatures. Poultry can now be grown and eggs produced at a l l seasons by c o n t r o l l i n g l i g h t , temperature and v e n t i l a t i o n in "windowless" houses (Wilson, 1974). Prior to the development of environment-controlled housing, poultry house construction in the United States and Canada varied from one region to another i n order to make the best of l o c a l c l i m a t i c conditions. Extremes in weather conditions resulted in poor production (Wilson, 1974) . The advent of large commercial flocks in t o t a l l y -enclosed houses necessitated changes i n f l o o r management. In North America, p a r t i a l s l a t f l o o r i n g and wire cages became popular solutions to the problem of wet l i t t e r (Wilson, 1974). Wet l i t t e r has been known to r e s u l t in d i r t y and contaminated eggs, increased ammonia ( N H 3 ) production, respiratory d i s t r e s s and other disease conditions, a l l leading to poor egg production and poor weight gain among birds (Wilson and Vohra, 1980; Wilson, 1974) . 1 2. LITERATURE REVIEW 2.1. STUDIES ON SLATS 2 . 1 . 1 . S l a t s and Egg Production B r o i l e r breeders have generally been maintained on l i t t e r f l o o r s at 3600 cm 2/bird. Layers, however, have been kept not only on l i t t e r but also on s l a t f l o o r s in combination with l i t t e r or wire f l o o r s (Wilson, 1974; Cooper and Barnett, 1972). Consequently, e a r l i e r studies on s l a t s were conducted using commercial layers (Magruder and Nelson, 1965; Osborn et a l . , 1959; Yao, 1959). F e r t i l i t y and h a t c h a b i l i t y were not reported. Nevertheless, egg production data from these studies were useful, leading the way for studies on alternative f l o o r types for b r o i l e r breeders (Andrews et a l . , 1988; Parkhurst, 1974; Cooper and Barnett, 1972; Nordskog and Schierman, 1965). Osborn et a l . (1959) and Yao (1959) reported that the disincentives to using f u l l s l a t f l o o r s were as follows: lower egg production per b i r d , more non-layers, higher mortality, and more birds laying fewer than 50 eggs during t h e i r respective 6- and 5-month experiments. The advantages to using f u l l s l a t f l o o r s were as follows: 2.5 times as many eggs produced per square foot on s l a t f l o o r as on l i t t e r (3 f t 2 / b i r d , or 2787 cm 2/bird on l i t t e r vs. 1 f t 2 / b i r d , or 929 2 LITERATURE REVIEW cm^/bird on slats) and a lower mature body weight. Yao (1959) found s t a t i s t i c a l l y s i g n i f i c a n t differences between the two f l o o r systems in terms of egg production per bird, egg production per square foot and mature body weight. Because of the difference i n mature body weight, Yao (1959) inferr e d that less feed was consumed for each dozen of eggs produced on s l a t s than on l i t t e r . A longer, 3-year study by Magruder and Nelson (1965) found that mortality was higher, and egg production was lower on f u l l s l a t f l o o r s . This was in agreement with Osborn et a l . (1959) and Yao (1959) . Although nothing was said about mature body weight, Magruder and Nelson (1965) reported that less feed, although not s i g n i f i c a n t l y , was required to produce a dozen eggs on f u l l l i t t e r than on f u l l s l a t s . This l a s t finding did not support the inference put forward by Yao (1959). Space allotment per b i r d was 675 crn^ on s l a t s , vs. 1800 cm^ on l i t t e r . Studies conducted to investigate the influence of cage density on layer performance would l a t e r explain why egg production and body weight gain was not as good on s l a t s compared to l i t t e r . It has been found that egg production (Madrid et a l . , 1981/ Carew et a l . , 1980; Sefton, 1976; Mather and Greaves, 1970) and body weight gain (Madrid et a l . , 1981; Carew et a l . , 1980) decreased as the area per b i r d decreased and the number of birds per cage increased 3 LITERATURE REVIEW w i t h i n a c e r t a i n range. Madrid et a l . (1981) suggested that a high p r o p o r t i o n of the energy consumed by crowded l a y e r s was spent f o r maintenance r a t h e r than f o r production ( i . e . , egg production, body weight g a i n ) ; thus, the lower egg production on s l a t s when more b i r d s were placed on f u l l s l a t s than on f u l l l i t t e r . The compromise that r e s u l t e d was the combination of s l a t and l i t t e r f l o o r s , or what i s known today as p a r t i a l s l a t f l o o r . Producers found t h a t optimal b i r d d e n s i t y was lower on p a r t i a l s l a t s than on f u l l s l a t s and yet higher than on l i t t e r . There was so much i n t e r e s t i n s l a t s t h a t only combination f l o o r s and f u l l s l a t f l o o r s were compared at f i r s t (Parkhurst, 1974; Cooper and Barnett, 1972). ; Cooper and Barnett (1972), i n comparing the p a r t i a l s l a t f l o o r (60% s l a t , 40% l i t t e r ) with f u l l s l a t f l o o r found that hen-day egg production was s i g n i f i c a n t l y higher on the p a r t i a l s l a t f l o o r s (59.7% vs. 53.2%). Each b i r d had 1672 cm 2 of f l o o r space on both f l o o r types. Parkhurst (1974) found t h a t hen-day egg production was higher, but not s i g n i f i c a n t l y , on 50% s l a t - 5 0 % l i t t e r than on f u l l s l a t f l o o r . Average egg production was 56.3%, 57.0%, 55.5% and 53.2% vs. 51.9%, 55.2%, 55.0% and 54.4%, on f u l l vs. p a r t i a l s l a t r e s p e c t i v e l y , f o r 4 d i f f e r e n t s t r a i n s . Space allotment was 2000 cm 2/bird on a l l f l o o r types. 4 LITERATURE REVIEW Later, Andrews et a l . (1988) compared egg production on f u l l l i t t e r , 2/3 slat-1/3 l i t t e r combination (wood or plastic-covered wire) and f u l l s l a t f l o o r s of p l a s t i c -covered wire, at 2730 cm2/, 1740 cm2/ and 1660 cm 2/bird, respectively. They found s i g n i f i c a n t l y higher hen-day egg production (59.8%) and s i g n i f i c a n t l y less feed consumed per dozen eggs produced among b r o i l e r breeders on f u l l l i t t e r f l o o r than on other f l o o r types; the l a t t e r finding i s i n agreement with that of Magruder and Nelson (1965) . There were no s i g n i f i c a n t differences i n egg production or feed consumption per dozen eggs between the other three f l o o r types despite differences in b i r d density between f u l l and p a r t i a l s l a t treatments. Hen-day egg production on the other f l o o r types were as follows: 51.7% on p a r t i a l wood s l a t s , 50.5% on fl o o r s of p a r t i a l plastic-covered s l a t s and 50.3% on fl o o r s of f u l l plastic-covered wire. An e a r l i e r study, conducted by Johnston and Zindel (1963) found that percent hen-day egg production was 61.0% in cages, 60.5% on l i t t e r f l o o r and 56.0% on sl a t t e d f l o o r . Floor space per b i r d was 405 cm2 in cages and 2088 cm2 on l i t t e r and slat t e d f l o o r . No s i g n i f i c a n t differences in egg production were found between the l a t t e r two f l o o r types. As a proportion of the t o t a l number of eggs l a i d , f l o o r eggs accounted for 7.3% and 6.3%, respectively, from the birds on l i t t e r and slat t e d f l o o r . Without any c l a r i f i c a t i o n in the 5 LITERATURE REVIEW said study about the f l o o r types, "sl a t t e d f l o o r " was taken to mean f u l l y s l a t t e d f l o o r in the context of the present study. 2.1.2. Slats and the Incidence of Cracked Eggs The study by Cooper and Barnett (1972) found that cracked eggs comprised 2.3% and 2.9% of t o t a l eggs produced on f u l l s l a t and p a r t i a l s l a t f l o o r s , respectively. Without stating the values, Magruder and Nelson (1965) found that the percentage of broken she l l s was the same for f u l l wood and f u l l l i t t e r f l o o r s . No d i s t i n c t i o n was . made between cracked nest eggs and cracked f l o o r eggs. 2.1.3. Slats and F e r t i l i t y Cooper and Barnett (1972) found that cumulative f e r t i l i t y was higher on the combination f l o o r s than on the f u l l s l a t f l o o r s . During nine 28-day periods, Parkhurst (1974) found that f e r t i l i t y i n Pilch-DeKalb breeders tended to be higher on the p a r t i a l s l a t f l o o r s than on f u l l s l a t f l o o r s during the f i r s t 28-day and the l a s t four 28-day period. Neither Cooper and Barnett (1972) nor Parkhurst (1974) found these differences to be s i g n i f i c a n t . Nordskog and Schierman (1965) examined cumulative f e r t i l i t y of White Leghorns on f u l l l i t t e r , 50% slat-50% l i t t e r , and f u l l s l a t f l o o r s . Floor space per bird was 2945 6 LITERATURE REVIEW cm2 for a l l f l o o r types. They found that i n one of the two t r i a l s , f e r t i l i t y was best on l i t t e r and poorest on slat s during the f i r s t ten days of mating. After 18 days the difference i n percent f e r t i l i t y between the highest and the lowest test group was only 2%. They suggested that s l a t s caused a lag. in normal mating a c t i v i t y in some males which may extend for a week to 10 days. Through seven 28-day periods, Andrews et a l . (1988) found s i g n i f i c a n t differences i n f e r t i l i t y only during the second 28-day period, and only between p a r t i a l wood (97.2%) and p a r t i a l plastic-covered wire (92.2%) s l a t s . F u l l l i t t e r (94.7%) and f u l l plastic-covered wire s l a t s (95.6%) were intermediate. Cumulative f e r t i l i t y was highest for f u l l plastic-covered wire s l a t s (95.2%) and lowest for p a r t i a l p l a s t i c s l a t s (93.5%). There was no drop i n f e r t i l i t y among birds on sl a t s ( f u l l or p a r t i a l , both wood and p l a s t i c -covered wire) during the second half of production as seen by Parkhurst (1974). In the study by Andrews et a l . (1988), birds on slat s did not s p e c i f i c a l l y exhibit a lag in f e r t i l i t y at the st a r t of production. Instead, p a r t i a l wood sla t s gave improved ov e r - a l l f e r t i l i t y . 2.1.4. S l a t s and H a t c h a b i l i t y In t h i s section, a l l hat c h a b i l i t y data w i l l be ha t c h a b i l i t y of a l l eggs set except where stated otherwise. 7 LITERATURE REVIEW Parkhurst (1974) and Cooper and Barnett (1972) did not fi n d any s i g n i f i c a n t differences in cumulative h a t c h a b i l i t y between f u l l and p a r t i a l s l a t f l o o r s . Andrews et a l . (1988) found s i g n i f i c a n t differences in the h a t c h a b i l i t y of t o t a l eggs set at the end of the second and t h i r d 28-day periods after 24 weeks of age, but not in the o v e r - a l l h a t c h a b i l i t y . At the end of the second period, h a t c h a b i l i t y in f u l l l i t t e r (92.2%), p a r t i a l wood (93.1%) and f u l l plastic-covered wire s l a t (92.8%) pens was s i g n i f i c a n t l y higher than that i n p a r t i a l plastic-covered wire pens (86.8%). At the end of t h i r d period, h a t c h a b i l i t y was s i g n i f i c a n t l y higher in p a r t i a l plastic-covered wire (92.8%) and p a r t i a l wood (92.8%) s l a t pens than in f u l l plastic-covered wire s l a t (88.7%) pens. Andrews et a l . (1988) also reported s i g n i f i c a n t differences in the ha t c h a b i l i t y of f e r t i l e eggs at the end of the second, t h i r d and seventh 28-day periods, although none was found in o v e r - a l l h a t c h a b i l i t y of f e r t i l e eggs. At the end of the second and seventh 28-day periods, h a t c h a b i l i t y was s i g n i f i c a n t l y higher in f u l l l i t t e r (97.4% and 97.2%, respectively) than in p a r t i a l plastic-covered wire s l a t (94.1% and 94.2%, respectively) pens, and intermediate in p a r t i a l wood (97.0% and 96.3%, respectively) and f u l l plastic-covered wire s l a t (97.1% and 95.3%, respectively) pens. At the end of the t h i r d 28-day period, 8 LITERATURE REVIEW hat c h a b i l i t y was s i g n i f i c a n t l y higher i n p a r t i a l wood (96.2%) than i n f u l l plastic-covered wire'slat (92.4%) pens, and intermediate in f u l l l i t t e r (92.6%) and p a r t i a l p l a s t i c -covered wire s l a t (95.2%) pens. Andrews et a l . (1988) suggested that the s i g n i f i c a n t differences in ha t c h a b i l i t y at the end of certain periods while none was found in ov e r - a l l h a t c h a b i l i t y was due to the immaturity of some of the males or the v a r i a t i o n in the handling of eggs p r i o r to incubation. Bac t e r i a l contamination•of hatching eggs i s an inherent r i s k in keeping breeders on l i t t e r . In a study by Quarles et a l . (1968), average counts of bacteria on egg surface were higher in l i t t e r than i n wire f l o o r houses. A i r in l i t t e r f l o o r houses averaged 5 to 10 times as many bacteria per cubic meter as i n a i r of wire f l o o r houses. Hatchability was s i g n i f i c a n t l y higher for eggs from wire f l o o r houses. A l a t e r study by Quarles et a l . (1970) using a similar comparison, confirmed the previous r e s u l t s . Furthermore, the number of bacteria i n the a i r was s i g n i f i c a n t l y correlated with the number of bacteria on the egg surface, but neither a i r nor egg surface b a c t e r i a l count was correlated with h a t c h a b i l i t y . Examination of unhatched eggs showed that 94% of pipped eggs and late dead embryos and 100% of c u l l chicks from l i t t e r f l o o r tested po s i t i v e for 9 LITERATURE REVIEW coliform bacteria compared with 33% and 20%, respectively, of those from wire f l o o r (Quarles et a l , 1970). When Carter et a l . (1973) compared p a r t i a l s l a t and wire f l o o r s , they found that bacteria counts on the egg s h e l l surface was s i g n i f i c a n t l y higher in p a r t i a l s l a t houses. Counts of bacteria i n the a i r were not taken, and h a t c h a b i l i t y was not compared between the two f l o o r types. Instead, Carter et a l . (1973) c h i l l - s t r e s s e d chicks and i s o l a t e d more types of enteric bacteria from chicks of breeders on p a r t i a l s l a t than from counterparts on t o t a l wire f l o o r . No further study was done to test the ef f e c t of the presence of enteric bacteria on the growth of b r o i l e r chicks. 2.1.5. Slats and Labor Requirements Because more birds were housed on s l a t f l o o r s than on l i t t e r f l o o r s , producers were able to handle more birds with less work, and thus u t i l i z e chore time more e f f i c i e n t l y (Wallace's Farmer, 1962; Marley, 1959; Wallace's Farmer, 1958). Barn clean-out was required less frequently with s l a t f l o o r s ; producers cleaned out once a year or a f t e r shipping a flock (Wallace's Farmer, 1962; Marley, 1959; Wallace's Farmer, 1958) . This " a l l - i n - a l l - o u t " practice of housing flocks has been recognized as an e f f e c t i v e method of 10 LITERATURE REVIEW c o n t r o l l i n g the spread of d i s e a s e between the p r e v i o u s and the subsequent f l o c k . Magruder and Ne l son (1965) found a r e d u c t i o n i n l a b o r requ irement from 3 5 . 3 to 1 9 . 7 m i n u t e s / b i r d / y e a r by u s i n g f u l l s l a t f l o o r s i n s t e a d of f u l l l i t t e r f l o o r s . As f o r e c a s t by F r a n c e (1959) , f u l l s l a t f l o o r s reduced l a b o r r e q u i r e m e n t s by about h a l f . 2 . 1 . 6 . Conclusions These s t u d i e s show t h a t by p l a c i n g more b i r d s per u n i t f l o o r space , s l a t s min imize l a b o r but lower egg p r o d u c t i o n per hen . Egg q u a l i t y , f e r t i l i t y and h a t c h a b i l i t y are not s i g n i f i c a n t l y a f f e c t e d by the use of s l a t s . F u l l l i t t e r gave the b e s t egg p r o d u c t i o n , however the l a b o r and f l o o r space requ irements of t o d a y ' s l a r g e f l o c k s f a v o r the use of s l a t s . P a r t i a l s l a t s may be the i d e a l midd le g r o u n d . 2 . 2 . STUDIES ON BREEDER AGE 2 . 2 . 1 . Breeder Age and Egg Production A t the s t a r t of egg p r o d u c t i o n , l a y e r s and b r e e d e r s q u i c k l y i n c r e a s e egg numbers, r e a c h i n g a peak a t about 3 0 - 3 2 weeks of age (Nordskog, 1 9 8 0 ) . Mather and L a u g h l i n (1979) have found ev idence t h a t i n caged b r o i l e r b r e e d e r s , the average l e n g t h of the c l u t c h 11 LITERATURE REVIEW decreases from 4.15 eggs at peak, production to 1.10 eggs 48 weeks l a t e r . Therefore, the decline i n egg production among older breeders i s p a r t l y due to the increase in the number of non-productive days between clutches. Mather and Laughlin (1979) also suggested that the eggs may spend a longer time in the oviduct of older birds,, but have not found any evidence to support t h e i r claim. As production progresses, larger eggs represent a progressively larger proportion of the t o t a l eggs l a i d . When McNaughton et a l . (1978) grouped chicken eggs into 2-gram weight classes, the r e s u l t i n g frequency d i s t r i b u t i o n showed that the f i r s t 50.3% of the eggs from the 29-week old breeders was spread from the <47-gram to the 55-56 gram cla s s . At 58 weeks of age, the f i r s t 52.2% of the eggs from the same breeders was spread from the 51-52-gram to the 65-66-gram c l a s s . Four-week production data from 3 d i f f e r e n t Ross I b r o i l e r breeder flocks indicated that the average egg weight consistently increased from 55 grams at 28 weeks of age to 75-76 grams at 60-62 weeks of age (Kirk et a l . , 1980). In a study involving 3 commercial breeder flocks of the same s t r a i n , Mather and Laughlin (1979) found that the mean egg weight consistently increased in a l l of the f l o c k s . In the f i r s t flock, mean egg weight increased from 54.5 grams at 28 weeks of age to 66.3 grams at 53 weeks of age. In the 12 LITERATURE REVIEW second flock, the mean egg weight increased from 57.4 grams at 30 weeks to 67.2 grams at 55 weeks; and, in the t h i r d flock, from 60.4 grams at 32 weeks to 69.3 grams at 57 weeks. 2.2.2. Breeder Age and F e r t i l i t y Studies involving chicken indicate that f e r t i l i t y , l i k e egg production, increases at the beginning of the production cycle, peaks and then slowly declines. Kirk et a l . (1980) noted that Ross I b r o i l e r breeding stock had a peak f e r t i l i t y of nearly 100% at about 34 weeks of age; at 60 weeks of age, f e r t i l i t y declined to about 89%. The f e r t i l i t y of 12 d i f f e r e n t flocks of New Hampshire breeders, with an average age of 160 days (22.8 weeks) at the s t a r t of production, was monitored by Tomhave (1958) for 365 days (52.1 weeks) of production. The study period was divided into 50-day production periods. A peak f e r t i l i t y of 90.0% was attained during days 51-100 of production (30.1-37.1 weeks of age). This production period includes the 34th week of age, the age at which peak f e r t i l i t y was detected by Kirk et a l . (1980) in Ross I b r o i l e r breeders. The proportion of f e r t i l e eggs declined considerably from 87.1% during days 201-250 to 81.4% during days 251-300. Parkhurst (1974) observed an increase in f e r t i l i t y among b r o i l e r breeders on a i l f u l l and p a r t i a l wood sl a t s 13 LITERATURE REVIEW during the f i r s t three 28-day periods af t e r 23 weeks of age, with f e r t i l i t y peaking during the t h i r d test period. Thereafter, f e r t i l i t y decreased. The t h i r d 28-day period includes week 34 of breeder age, the time during which Kirk et a l . (1980) observed a peak of nearly 100% f e r t i l i t y in Ross I breeders. Additionally, the t h i r d 28-day period i s included within days 51-100, the period of peak f e r t i l i t y in the study by Tomhave (1958) . Andrews et a l . (1988) found s i g n i f i c a n t differences in f e r t i l i t y between p a r t i a l wood s l a t and f u l l and p a r t i a l f l o o r i n g of plastic-covered wire, found s i g n i f i c a n t differences in f e r t i l i t y between p a r t i a l wood (97.2%) and p a r t i a l plastic-covered wire s l a t s (92.2%) during the t h i r d 28-day period after 24 weeks of age. F e r t i l i t y on f u l l l i t t e r (94.7%) and f u l l plastic-covered wire (95.6%) s l a t s was intermediate; no s i g n i f i c a n t differences were found in o v e r - a l l f e r t i l i t y . Regardless of f l o o r type, Nordskog and Schierman (1965) detected an increase i n f e r t i l i t y during the f i r s t 10 days of putting male and female White Leghorns on p a r t i a l s l a t and f u l l l i t t e r f l o o r s , with birds on the p a r t i a l s l a t f l o o r s showing a slower increase. The report did not elaborate on f e r t i l i t y trends af t e r the f i r s t 10 days of production. 14 LITERATURE REVIEW R e i n h a r t and H u r n i k (1984) found t h a t f e r t i l i t y of eggs l a i d a t 3 3 - 3 5 weeks of b r e e d e r age was s i g n i f i c a n t l y h i g h e r (p<0 .001) compared w i t h those l a i d by the same breeders a t 5 0 - 5 2 weeks of age ( 9 6 . 3 % v s . 9 1 . 9 % ) . Without r e p o r t i n g egg p r o d u c t i o n , Q u a r l e s et a l . (1970) s t a t e d t h a t i n S i n g l e Comb White Leghorns , p r o d u c t i o n ( i . e . , age of breeder) was c o r r e l a t e d w i t h f e r t i l i t y ; f e r t i l i t y i n c r e a s e d w i t h p r o d u c t i o n d u r i n g s i x t e e n 1 4 - d a y t e s t p e r i o d s a f t e r 20 weeks of b r e e d e r age . There was no d i s t i n c t peak, but f e r t i l i t y d e c l i n e d d u r i n g the l a s t q u a r t e r of the e x p e r i m e n t a l p e r i o d . T i n d e l l and M o r r i s (1964) noted t h a t the f e r t i l i t y of c h i c k e n eggs c o l l e c t e d from d i f f e r e n t h a t c h e r i e s p r o g r e s s i v e l y i n c r e a s e d as average egg weight i n c r e a s e d from 4 2 . 5 to 6 1 . 5 grams. Assuming t h a t the l a r g e r eggs were l a i d by o l d e r b r e e d e r s , T i n d e l l and M o r r i s (1964) s t a t e d t h a t the females l a y i n g the s m a l l eggs were j u s t coming i n t o p r o d u c t i o n and were not b e i n g covered by the males as e f f i c i e n t l y as t h e i r c o u n t e r p a r t s l a y i n g l a r g e r eggs, hence the lower f e r t i l i t y i n s m a l l eggs . A v e r y e a r l y s t u d y , conducted by H a l b e r s l e b e n and Mussehl ( 1 9 2 2 ) , showed t h a t "extremely s m a l l and extremely l a r g e " c h i c k e n eggs ( 4 6 - 4 9 and 5 9 - 6 5 grams, r e s p e c t i v e l y ) had the lowest f e r t i l i t y ( 8 0 - 8 1 % ) , w h i l e eggs weighing 5 0 - 5 8 grams had the b e s t f e r t i l i t y (87%) . The a u t h o r s d i d not 15 LITERATURE REVIEW mention the breed studied, or whether the d i f f e r e n t sizes of eggs came from hens of d i f f e r e n t ages. Proudfoot and Hulan (1981) did not see differences in f e r t i l i t y between chicken eggs weighing 46-50 grams and 53-57 grams. These investigators concluded that f e r t i l i t y i s not influenced by egg size. In l i g h t of the study by Halbersleben and Mussehl (1922), Proudfoot and Hulan (1981) should have observed higher f e r t i l i t y in eggs weighing 46-50 grams than in those weighing 53-57 grams. Neither report mentions the breed of chicken used for the study. Proudfoot and Hulan (1981) obtained a l l egg sizes from breeders of the same age, but Halbersleben and Mussehl (1922) made no statement in this respect. . Therefore the discrepancy could not be attributed to differences i n the breed used or to the fact that egg sizes represented d i f f e r e n t breeder ages in one study and not i n the other. 2.2.3. Breeder Age and Hatchability The influence of breeder age on hat c h a b i l i t y seems to be a function of egg weight. Egg sizes in the extreme have been shown to have lower h a t c h a b i l i t y than those i n the intermediate. Since chicken eggs have been found to consistently increase in size as the flock ages (Kirk et a l . , 1980; Mather and Laughlin, 1979)> extremely small eggs near the beginning of lay and extremely large eggs near the 16 LITERATURE REVIEW end of l a y would have lower h a t c h a b i l i t y than eggs l a i d during the middle of the l a y i n g c y c l e . Except when sta t e d otherwise, a l l h a t c h a b i l i t y data presented w i l l be h a t c h a b i l i t y of t o t a l eggs s e t . In the study by K i r k et a l . (1980) the maximum h a t c h a b i l i t y of Ross I b r o i l e r breeder eggs was 91%, and occurred at 44 weeks of age; average egg weight at t h i s time was 65 grams. At 60 weeks of age, h a t c h a b i l i t y had d e c l i n e d to 82%, and average egg weight was 75 grams. The lower h a t c h a b i l i t y before and a f t e r the peak - was thought to be due, i n p a r t , to an e f f e c t of egg weight. I t appeared t h a t an optimal egg weight was i n v o l v e d , and that the smaller eggs from a young f l o c k and the l a r g e r eggs from an older f l o c k were not as hatchable as those weighing c l o s e to the optimal weight. No mention was made of egg weight i n a study by Tomhave (1958), but i t was found t h a t the age of breeders had l i t t l e i n f l u e n c e on the h a t c h a b i l i t y during the f i r s t f i v e 50-day t e s t periods (250 days). H a t c h a b i l i t y slowly increased from the s t a r t of production u n t i l i t peaked at 79.7% during days 151-200 of production, and then decreased from 77.4% during days 201-250 to 69.3% during days 251-300. The peak p e r i o d covers weeks 44-51 of age, and confirms the r e s u l t s from the study by K i r k et a l . (1980) where peak h a t c h a b i l i t y of a l l eggs set was seen at 44 weeks of age. The h a t c h a b i l i t y of 17 LITERATURE REVIEW f e r t i l e eggs remained consistently between 88.1 and 90.3% from days 1-250, and stayed within 85% from day 251 to the end of the study period (day 365). McNaughton et a l . (1978) found s i g n i f i c a n t differences in h a t c h a b i l i t y between eggs from parents of d i f f e r e n t ages only when egg sizes were d i f f e r e n t . Eggs from 29-week old breeders were assigned to either the 47-52 or 57-62-gram groups, and those from 58-week old breeders to either the 57-62 or 67-74-gram groups. The ha t c h a b i l i t y of the three weight groups were s i g n i f i c a n t l y d i f f e r e n t from each other. The l i g h t e s t group had the highest h a t c h a b i l i t y (86%), the 57-62-gram group was intermediate (80.3 at 29 weeks of age and 81.4% at 58 weeks of age) and the 67-74-gram group the lowest (75.4%). Without stating that eggs of d i f f e r e n t size groups came from parents of d i f f e r e n t ages, Halbersleben and Mussehl (1922) reported that "extremely large (59-65 grams) and extremely small (46-49 grams) eggs" did not hatch as well as those weighing 50-58 grams. Average h a t c h a b i l i t i e s were 29%, 33% and 41.6%, respectively. Proudfoot and Hulan (1981) concluded that within the intermediate size ranges, h a t c h a b i l i t y was unaffected by size d i f f e r e n t i a l s . Their study indicated that h a t c h a b i l i t y of eggs weighing 46-50 grams (56.5%) was not s i g n i f i c a n t l y 18 LITERATURE REVIEW di f f e r e n t from that of eggs weighing 53-57 grams (.58.6%). No explanation was given for the low o v e r - a l l h a t c h a b i l i t y . 2.2.4. B r e e d e r Age and Embryo M o r t a l i t y Although the pattern of embryo mortality during incubation in chicken and turkey eggs has been well documented (Byerly et a l . , 1933; Byerly, 1930; Payne, 1919), very l i t t l e work has been done to investigate the changes that occur i n the pattern with the change in breeder age. The two c r i t i c a l periods found by Payne (1919) during the incubation of chicken eggs occurred on days 4-6 and on days 18-20 ' of incubation, and were consistent for both natural and a r t i f i c i a l incubation. Insko and Martin (1935) found two peaks of chicken embryo mortality; one on day 2 and the other on day 19 of incubation, with the early peak being two days e a r l i e r than, and the late peak coinciding with Payne's (1919). The two c r i t i c a l periods detected by Insko and Martin (1935) i n the development of turkey embryos were days 4 and 25 of incubation. They stated that the second mortality peak occurred at the same r e l a t i v e time as in chicken eggs. However, the f i r s t peak did not, and Insko and Martin (1935) attributed t h i s difference to the greater length of time required to heat turkey eggs to incubation temperature. 19 LITERATURE REVIEW R e i n h a r t and H u r n i k (1984) d i v i d e d the i n c u b a t i o n p e r i o d of c h i c k e n eggs i n t o days 1 - 8 , days 9 - 1 8 and days 1 9 -21 t o c o r r e s p o n d w i t h the m o r t a l i t y p e r i o d s i n t h e e a r l i e r s t u d i e s (Insko and M a r t i n , 1 9 3 5 ; Payne, 1 9 1 9 ). M o r t a l i t y d u r i n g days 1-8 and days 9 - 1 8 was h i g h e r , but not s i g n i f i c a n t l y , i n eggs from 50 -52-week o l d b r e e d e r s than i n eggs from 33 -35-week o l d b r e e d e r s . M o r t a l i t y d u r i n g days 1 9 - 2 1 was s i g n i f i c a n t l y h i g h e r i n eggs from the o l d e r b r e e d e r s . F or b o t h b r e e d e r ages, t h e eggs were a s s i g n e d t o f o u r w e i g h t groups: s m a l l , medium, l a r g e and e x t r a l a r g e w i t h average weight of 5 9 . 3 , 6 3 . 0 , 6 5 . 6 and 6 9 . 6 grams r e s p e c t i v e l y . The r e p o r t d i d not s t a t e t h e p r o p o r t i o n of eggs from each of t h e two b r e e d e r age groups i n each egg w e i g h t group. T h e r e f o r e , i t i s unknown whether l a r g e r eggs predominated when b r e e d e r s were 5 0 - 5 2 weeks o l d , as i s u s u a l l y seen f o r c h i c k e n s . Embryo m o r t a l i t y d u r i n g days 1-8 was h i g h e r , but not s i g n i f i c a n t l y , i n t h e s m a l l and e x t r a l a r g e eggs than i n t h e medium and l a r g e eggs. M o r t a l i t y d u r i n g days 9 - 1 8 was s i m i l a r f o r a l l w e i g h t group. D u r i n g days 1 9 - 2 1 , the m o r t a l i t y i n e x t r a l a r g e eggs was s i g n i f i c a n t l y h i g h e r t h a n i n t h e o t h e r t h r e e groups. There was no s i g n i f i c a n t i n t e r a c t i o n between b r e e d e r age and egg w e i g h t . 20 LITERATURE REVIEW 2.2.5. Breeder Age and Progeny Growth A consistent r e l a t i o n s h i p has been found between the weight of the unincubated egg and the weight of the chick at hatch. In a summary of studies in six domestic b i r d species, Shanawany (1987) concluded that hatching weight depended upon a li n e a r function of egg weight at setting. It was estimated that hatching weight increases by 0.59 gram for every gram increase in egg weight. Shanawany (1987) reported that on average,, hatching weight of chicken, turkey, duck, goose, pheasant and quail represent 68.0%, 63.0%, 57.8%, 58.9%, 62.0% and 66.9%, respectively, of the unincubated egg weight. The percentage was s i g n i f i c a n t l y d i f f e r e n t between the species except between the duck and the goose. Since Kirk et a l . (1980) and McNaughton et a l . (1978) reported that larger eggs predominate in older chicken breeders, chicks from these breeders would be heavier than those from younger breeders. Numerous studies have been conducted to investigate the influence of egg weight on chick growth (Proudfoot and Hulan, 1981/ Deaton et a l . , 1979/ Gardiner, 1973/ T i n d e l l and Morris, 1964/ Goodwin, 1961/ Kosin et a l . , 1952/ Skoglund et a l . , 1952/ Wiley, 1950/ Upp, 1928/ Halbersleben and Mussehl, 1922) but few have addressed the influence of 21 LITERATURE REVIEW egg weight on chick growth as related to breeder age (Pone et a l . , 1985; McNaughton et a l . , 1978). In two experiments, McNaughton et a l . (1978) investigated the influence of breeder age on the body weight of chicks using eggs of comparable weight. From 29-week old breeders, eggs weighing 47-54 and 57-62 grams were obtained, and from 58-week old breeders, 57-62 and 67-74 grams. Br o i l e r s from the heavier eggs were consistently heavier at 1 day and 2, 4 and 6 weeks of age. S t a t i s t i c a l comparisons were made between the body weights at market age only, with the two sexes separate. In the f i r s t experiment, birds were marketed at 8 weeks of age, and at seven weeks and four days of age in the second t r i a l . Both experiments showed that there were no s i g n i f i c a n t differences in the body weight of female chicks from 29- and 58-week old breeders when the egg weights were uniform. On the other hand, the female progeny of 29-week old breeders obtained from eggs weighing 47-54 grams were s i g n i f i c a n t l y l i g h t e r than those from 57-62 grams and the progeny of 58-week old breeders. During the f i r s t experiment, male b r o i l e r s hatched from eggs weighing 67-74 grams were s i g n i f i c a n t l y heavier than those from eggs weighing 47-54 grams. No differences in male body weight were detected during the second experiment. McNaughton et a l . (1978) concluded that the age of parents influenced the 22 LITERATURE REVIEW market body weights of t h e i r progeny through differences in egg weights. • Without choosing a p a r t i c u l a r egg weight group at 27, 42 and 52 of breeder age, Pone et a l . (1985) compared the growth of male chicks from 27-, 42- and 52-week old Cobb breeders. The b r o i l e r s were raised separately according to parental age and intermingled, both on l i t t e r and p l a s t i c -covered perforated metal f l o o r s . At one day of age,. body weights for the respective parental age groups were 36.1, 41.2 and 42.7 grams. The 31-day body weights were 948, 998 and 1030 grams, respectively. At both times, the body weight of the .three progeny groups were s i g n i f i c a n t l y d i f f e r e n t from each other. At 44, 47 and 52 days of age, the body weights of progeny from 42- and 52-week old breeders were s t a t i s t i c a l l y equal and were s i g n i f i c a n t l y higher than that of progeny of 27-week old breeders. Grouping the male b r o i l e r s according to the type of fl o o r i n g , Pone et a l . (1978) found that those raised on sla t s were consistently heavier than those raised on l i t t e r . When male b r o i l e r s from a l l parental age groups were grown intermingled on each of the two f l o o r types, differences were s i g n i f i c a n t only at 52 days of age. On the other hand, when the parental age groups were raised separately, differences were s i g n i f i c a n t at 44 and 47 days of age. It 23 LITERATURE REVIEW was c o n c l u d e d t h a t the type of r e a r i n g ( separate v s . c o m p e t i t i v e ) d i d not a l t e r the i n f l u e n c e of p a r e n t a l age on c h i c k w e i g h t . Wi thout showing feed consumption v a l u e s , Pone et a l . (1985) s t a t e d t h a t b r o i l e r s from the youngest p a r e n t s consumed l e s s feed a t each of the we ighing days ment ioned . In agreement w i t h McNaughton et a l . ( 1 9 7 8 ) , Pone et a l . (1985) c o n c l u d e d t h a t the e f f e c t of b r e e d e r age on the growth of progeny i s not m a n i f e s t e d when egg weights are e q u a l i z e d . 2.2.6. C o n c l u s i o n s H a t c h a b i l i t y and f e r t i l i t y i n c r e a s e s h o r t l y a f t e r the b e g i n n i n g of egg p r o d u c t i o n , peak and then d e c l i n e . Progeny growth however, i n c r e a s e s c o n s t a n t l y w i t h egg w e i g h t . I n f o r m a t i o n on the i n f l u e n c e of breeder age on embryo m o r t a l i t y i s i n s u f f i c i e n t f o r any c o n c l u s i o n to be made. 24 3. OBJECTIVES P r e s e n t - d a y i n t e n s i v e p o u l t r y p r o d u c t i o n systems r e q u i r e the use of s l a t s as a manure management p r a c t i c e . Wood s l a t s have been w i d e l y used, however t h e r e has been some i n t e r e s t i n p l a s t i c s l a t s . Some of the app a r e n t b e n e f i t s of p l a s t i c s l a t s a r e c l e a n e r f l o o r i n g and g r e a t e r d u r a b i l i t y . T h i s s t u d y was conducted t o i n v e s t i g a t e t h e i n f l u e n c e of wood and p l a s t i c s l a t s , e i t h e r i n c o m b i n a t i o n w i t h l i t t e r o r as f u l l f l o o r i n g , on the i m p o r t a n t economic performance parameters of A r b o r A c r e s b r o i l e r b r e e d e r s and growth of the progeny over one p r o d u c t i o n c y c l e . The f o l l o w i n g hypotheses were t e s t e d : 1) P l a s t i c s l a t s r e s u l t i n h i g h e r egg p r o d u c t i o n , f e r t i l i t y and h a t c h a b i l i t y . 2) The progeny of p l a s t i c s l a t b r e e d e r s grow more e f f i c i e n t l y t han wood s l a t progeny. 4 . MATERIALS AND METHODS 4.1. BROODING PROCEDURES 7 Arbor Acres b r o i l e r breeders housed at the Animal Science Poultry Unit breeder barn were used for th i s study. The Arbor Acres Male and Female Management Guide (1985) was adhered to in r a i s i n g the b r o i l e r breeders to 24 weeks of age. Brooder heat lamps were used to supply additional heat during brooding. A temperature of 32°C at f l o o r level was maintained for the f i r s t 3 days. Temperature was dropped every 3 days u n t i l 21-22°C was attained. The l a s t heat lamps were removed at 26 days of age. Room temperature was maintained near 15°C thereafter. From one day to 4 weeks of age, males and females were brooded together on wood shavings at 159 birds for each of eight 3 m x 3.6 m pens. At 4 weeks of age, 60 cm-high s l a t s were i n s t a l l e d on 60% of the f l o o r area of a l l the pens. At 11 weeks of breeder age, f u l l s l a t arrangements were i n s t a l l e d in half of the 24 pens, and birds in each of the 8 brooding pens were divided into three groups and assigned to respective pens. At 13 weeks of age, the chicks were diagnosed to have staphylococcus i n f e c t i o n , and were given t e t r a c y c l i n e for a week, followed by p e n i c i l l i n at 17, 19 and 30 weeks of age. 26 MATERIALS AND METHODS The chicks were vaccinated against Marek's disease at one day of age, and against Newcastle/Bronchitis at 2, 10 and 16 weeks of age. 4.2. LIGHTING Lighting in each pen was provided by a 100-watt incandescent bulb from the time the heat lamps were removed through to the end of the 17th week. In each hallway, one 22-watt c i r c l e fluorescent lamp was provided for each of two adjacent pens. The b r o i l e r breeders were provided with 10 hours of l i g h t from one day of age to the end of the 17th week. At the start of the 18th week, photoperiod was increased by one hour every week, u n t i l 14 hours was attained. Photoperiod was maintained at 14 hours u n t i l the end of the study. 4.3. HOUSING DURING LAY Shortly p r i o r to the onset of lay (week 22) the number of birds per pen was equalized into 47 females and 6 males. Dead and c u l l e d females were replaced u n t i l 28 weeks of age. Each pen was 3 m x 3.6 m, and f l o o r space allotment was 2040 cm 2/bird. The pens were situated in two rooms which were separated by the feedroom. The f i r s t room contained pens 1 to 8, and the second contained pens 9 to 24. The pens formed two lines down the middle of each room. MATERIALS AND METHODS The i n f l u e n c e of s l a t m a t e r i a l (wood vs. p l a s t i c ) and s l a t coverage ( f u l l vs. p a r t i a l ) were examined on parameters which w i l l be mentioned subsequently. Breeders were fed two types of d i e t , formulas f o r which are l i s t e d i n Appendix Tables 5 , 6 and 7 . Since there was no s i g n i f i c a n t d i e t e f f e c t , r e p l i c a t e s have been combined f o r the a n a l y s i s of t h i s t h e s i s . Another v a r i a b l e name, s l a t type, was created to d i s t i n g u i s h each of the four kinds of f l o o r i n g systems r e s u l t i n g from the s l a t m a t e r i a l and s l a t coverage treatments. Six pens were assigned randomly to each of the 4 s l a t type treatments. The s l a t type names were as f o l l o w s : 1) F u l l wood s l a t s (FWS) 2) P a r t i a l wood s l a t s (PWS) 3) F u l l p l a s t i c s l a t s (FPS) 4) P a r t i a l p l a s t i c s l a t s (PPS) Each of the 8 v a r i a b l e combinations was represented by one pen i n the room c o n t a i n i n g pens 1 to 8, and by two pens i n the other room. The rooms were assigned to treatments at r e g u l a r i n t e r v a l . Figure 1 i l l u s t r a t e s the pen set-up. In pens with p a r t i a l s l a t s (PWS and PPS), 60% of the f l o o r area was covered w i t h s l a t s r a i s e d 60 cm above the concrete f l o o r , and the r e s t of the f l o o r area was covered w i t h 5 cm-deep wood shavings. A s l a t t e d step-up, 30 cm wide and 30 cm 2 8 MATERIALS AND METHODS above the concrete f l o o r , was placed along the slatted area on recommendation of the b r o i l e r breeder company. In f u l l s l a t pens (FWS and FPS), 60% of the f l o o r area was covered with s l a t s raised 60 cm above the f l o o r , and the rest with sl a t s raised 30 cm above the f l o o r . Each pen had four 20-k.g tube feeders with pans at 41.9 cm diameter and one hanging round automatic waterer at 34.3 cm diameter. A 12-hole metal nest, with wooden perches, was situated on each of two sides of every pen at the uniform height of 60 cm above the f l o o r . In p a r t i a l s l a t pens, one end of the nests was set on the sla t s and the other over extended over the l i t t e r area. In f u l l s l a t pens, one end of the nests was set over the 60-cm high s l a t s and the other extended over the 30-cm high s l a t s . Figure 2 i s an i l l u s t r a t i o n of the dimensions of wood and p l a s t i c s l a t s . The p l a s t i c s l a t s were 1.2 cm wide, and had 1.8 cm x 9.3 cm openings which were separated by 0.8 cm-s t r i p along the short axis. The wood sl a t s were 3.5 cm wide and 2 cm apart. Waste was allowed to accumulate under the s l a t area throughout the study, but the wood shavings in p a r t i a l s l a t pens was p e r i o d i c a l l y changed. MATERIALS AND METHODS F i g u r e 1. D i m e n s i o n s of P e n s * 60 c m - h i g h slats \ \ 30 cm-high slats \ \ 3.0 rrr 3.6 m F U L L SLAT P E N S 60 cm-high slats \ step-up \ litter 3.0 m 3.6 m PARTIAL SLAT P E N S •Not drawn to scale. N ests. 30 MATERIALS AND M E T H O D S F i g u r e 2. D i m e n s i o n s of S l a t s * 9.3 cm 0.8 cm P L A S T I C S L A T S • N o t d r a w n to s c a l e . 31 MATERIALS AND METHODS 4.4. FEEDING PROGRAM Breeders were fed st a r t e r diets ad l i b from day one to the end of 3 weeks. From 4 to 20 weeks, breeders were fed developer diets on a limited feed program skipping the Wednesday and Sunday of each week. From 21 weeks of age to the end of the study, breeder diets were fed everyday as recommended by the Arbor Acres B r o i l e r Breeder Male and Female Feeding and Management Guide (1985) . Diet formulas are l i s t e d i n Appendix Tables 5, 6 and 7. 4.5. EGG COLLECTION Starting at 24 weeks of age, eggs were coll e c t e d from the nests and the s l a t and s l a t - l i t t e r f l o o r in each pen 3 times a day. Eggs that f e l l through the s l a t s were not counted. Eggs on the f l o o r were counted separately from eggs i n the nest. The numbers of cracked eggs on the f l o o r and in the nest were also recorded. Eggs were shipped to a commercial hatchery once a week for hatching. The breeders were shipped after 58 weeks of age. 4.6. FERTILITY AND HATCHABILITY TESTS Settable eggs were incubated to hatch at the UBC Animal Science Poultry Unit approximately every f i v e (5) weeks st a r t i n g at 37 weeks of age for f e r t i l i t y and hat c h a b i l i t y . As in commercial hatcheries, d i r t y , cracked and thin-shelled 32 MATERIALS AND METHODS eggs were discarded. Sample size was 75-100 eggs per pen. Eggs were l e f t overnight at room temperature p r i o r to incubation. A r e l a t i v e humidity of 60-70% during the f i r s t 18 days and 80% during the l a s t 3 days of incubation was aimed at, but the Robbins incubators fluctuated greatly in r e l a t i v e humidity for short periods of time. Incubator temperature was more consistent and thermometer readings of 99.2°F +_ 0.90 (37.3°C +.0.50) were attained. The eggs that were set were candled between the 7th and 10th days of incubation to remove i n f e r t i l e eggs and early dead embryos. Viable embryos as determined during the candling were transferred to a Robbins hatcher at day 18 for hatching. Those unhatched aft e r 21 days of incubation were opened to determine the f i n a l stage of development and to record abnormalities. The time of death of the embryo was c l a s s i f i e d into 4 stages: early (days 0-7), middle (days 8-14), late (days 15-21) and pipped for embryos that break the egg s h e l l but do not hatch. 4.7. GROWTH TRIALS Chicks were selected from the hatch of the 37th- and 46th-week c o l l e c t i o n s and grown out to three weeks. Chick from the 56th week c o l l e c t i o n were grown out to market age (six weeks). Except for discarding the deformed and 33 MATERIALS AND METHODS crippled chicks, no c u l l i n g was practiced. Two r e p l i c a t e groups of ten chicks were randomly assigned to battery brooders to represent each of the parental pens. Body weight and feed intake were measured at the end of each week. Battery cages (Petersime Chick Batteries) used to house chicks from the f i r s t to the t h i r d week were 98 cm(L) x 69 cm(W) x 24 cm(H). The 48 battery cages were on 4 t r o l l e y s of 12 cages each; in each t r o l l e y the 12 cages were stacked 6 high, side by side. Each battery cage was equipped with 63 cm-long feed troughs and 67 cm-long water troughs. Heating c o i l s in each cage provided additional heat during the f i r s t two weeks, when battery cage temperature was maintained near 27°C. Thereafter, the temperature was maintained near 20°C. The 56th week progeny were taken only from eggs which weighed 66-78 grams before incubation. This procedure, done only for t h i s growth t r i a l , was aimed at minimizing var i a t i o n due to differences in egg weight and i n i t i a l chick weight. The chicks were sexed aft e r hatching, so that each parental pen was represented by one group of 10 male chicks and one group of 10 female chicks. After body weight and feed intake were measured on the t h i r d week, each r e p l i c a t e of 10 birds was reduced to 7 birds for optimum space allotment i n grower cages; c r i p p l e and weak birds were 34 MATERIALS AND METHODS discarded, and in pens without c r i p p l e or weak birds, excess chicks were randomly picked out. Body weight and feed intake were measured on the 5th and 6th weeks. During the t h i r d to the sixth week of the l a s t grow-out t r i a l , chicks were housed in 66 cm(L) x 66 cm(W) x 36 cm (H) cages. Each of the 4 t r o l l e y s of 12 cages had 3 groups of 4 cages high. The feed and water troughs were 60 cm long. The b r o i l e r chicks were given non-medicated commercial feed. During the f i r s t three weeks, b r o i l e r starter with 23% protein was used. During the fourth and f i f t h weeks of the l a s t t r i a l , b r o i l e r grower with 20% protein was given to the chicks, and b r o i l e r f i n i s h e r with 18% protein on the sixth week. Feed and water were provided ad l i b to the b r o i l e r s throughout the experiment. A 100-watt incandescent bulb, hung about 1 meter above each t r o l l e y , provided l i g h t 24 hours a day throughout the study. 4.8. STATISTICAL ANALYSIS Analysis of variance (ANOVA), s p e c i f i c a l l y the General Linear Models procedure of SAS (1985) , was applied to a l l of the egg production and progeny growth parameters. Analysis showed that except in interactions with the other main eff e c t s , breeder- diet did not s i g n i f i c a n t l y influence any of the parameters measured. Therefore, means of breeder diet 35 MATERIALS AND METHODS groups were combined and the degrees of freedom were added to the e r r o r term i n subsequent analyses. Parameters measured included percent biweekly and over-a l l egg production, percent f l o o r eggs, cracked nest eggs, cracked f l o o r eggs and " s e t t a b l e " eggs. Percentage values were transformed using a r c s i n e transformation f o r s t a t i s t i c a l a n a l y s i s ( L i , 1964) . The s t a t i s t i c a l model used was: Y i j k l = P + R i + M j + c k + < M C > j k + E i j k l ' and i = l,2,...,6; j = l , 2 ; k=l,2; 1 = 1,2, . . .,24; where Y i j k l = one of the dependent v a r i a b l e s (% biweekly egg production, ,% f l o o r eggs, % cracked nest eggs,. % cracked f l o o r eggs or % " s e t t a b l e " eggs) . Y i j k l ^ s t h e e < 3 g production status of the Y^-h p e n D f ^ he i t n r e p l i c a t e with the j ^ s l a t m a t e r i a l and the k ^ s l a t coverage; yx = the t h e o r e t i c a l population mean, R^ = e f f e c t of the i * - * 1 r e p l i c a t i o n , Mj = e f f e c t of whether s l a t m a t e r i a l was wood or p l a s t i c , = e f f e c t of whether s l a t coverage was f u l l or p a r t i a l ; ( M C ) = e f f e c t of two-way i n t e r a c t i o n i n v o l v i n g main e f f e c t s ; E ^ j ^ ^ = random e r r o r . The i n f l u e n c e of breeder age, s l a t m a t e r i a l and s l a t coverage on percent f e r t i l i t y , percent h a t c h a b i l i t y , and percent incidence of embryo m o r t a l i t y were a l s o analyzed using ANOVA with repeated measures. Arcsine transformation 36 MATERIALS AND METHODS (Li , 1964) was applied to percentage values before s t a t i s t i c a l analysis. The s t a t i s t i c a l model used was: Y i j k l n = >» + R i + M j + c k + < M C>jk + E 1 i j k + A l + ( A M) j l + (AC) k l + ( A M C ) j k l + E 2 i j k l n , and i = l,2, . .,6; j = l , 2 ; k=1,2; 1 = 1,2, . . , 5; n=l,2,..,120; where Y i j k l n = i s o n e °f the dependent variables (% f e r t i l i t y , % ha t c h a b i l i t y , % incidence of embryo mortality). Y i j k l n -*-s t h e reproductive status of the females in the. n t h pen of i t h r e p l i c a t i o n with the j t h s l a t material and the k1-^ s l a t coverage, during the l t n breeder age; u = t h e o r e t i c a l population mean, Rj_ = e f f e c t of the i 1 - * 1 ^replication, Mj = e f f e c t of whether s l a t material was wood or p l a s t i c , C k = ef f e c t of whether s l a t coverage was f u l l or p a r t i a l , (MC) j k = e f f e c t of two-way i n t e r a c t i o n between the main e f f e c t s , E l j _ k i = error term for te s t i n g the main ef f e c t s , A]_ = the e f f e c t of a s p e c i f i c breeder age, (AM) (AC) k]_ = ef f e c t s of. two-way interactions involving breeder age, (AMC) j k]_ = e f f e c t of three-way i n t e r a c t i o n between the main e f f e c t s and breeder age, E2^j k]_ n = error term for test i n g the sub-plot e f f e c t s . The influence of breeder age, s l a t material and s l a t coverage on •the three-week growth of 37th, 46th and 56th week progeny were analyzed using the following s t a t i s t i c a l model: Y i j k l m n = ? + R i + R P i j + M k + c l + < M C>kl + E l i j k l 37 MATERIALS AND METHODS + Am + ( A M>km + ( A C ) l m + (AMC) k I l t l + E 2 i j k l m n , a n d ' i = l , 2 , . . , 6 ; j = l , 2 ; k = l , 2 ; 1=1,2; rrt=l,2,3; n=l,..,144; where ^ i j k i r a n = ^ s one of t h e growth parameters of progeny (body w e i g h t , w e i g h t g a i n , f e e d i n t a k e , f e e d c o n v e r s i o n ) . Y i j k l m n ^ s the growth s t a t u s of t h e progeny i n the j t h cage from t h e i t h p a r e n t a l pen w i t h t h e k t h s l a t m a t e r i a l and t h e I1-*1 s l a t c o v e r a g e d u r i n g t h e m t h b r e e d e r age; J J = t h e o r e t i c a l p o p u l a t i o n mean,. Rj_ = e f f e c t of the i * - * 1 • p a r e n t a l pen, R ^ i j •= e f f e c t of the j t h progeny cage from the p a r e n t a l pen, M k = e f f e c t of whether s l a t m a t e r i a l of the p a r e n t a l pen was wood o r p l a s t i c , C]_ = e f f e c t of whether s l a t c o v erage of th e • p a r e n t a l p e a was f u l l or p a r t i a l , (MC) k ] _ = e f f e c t of two-way i n t e r a c t i o n between t h e main e f f e c t s , E l i j k . i = e r r o r term f o r t e s t i n g t h e main e f f e c t s , A m = e f f e c t of a s p e c i f i c b r e e d e r age, (AM) k m and (AC.) ^ m = e f f e c t of two-way i n t e r a c t i o n s i n v o l v i n g ' b r e e d e r age; (AMC) k ] _ m = e f f e c t of three-way i n t e r a c t i o n between the main e f f e c t s and b r e e d e r age E 2 j _ j k ] _ m n = e r r o r - t e r m f o r t e s t i n g t h e s u b - p l o t e f f e c t s . H a t c h i n g w e i g h t of progeny was a d j u s t e d i n a c o v a r i a n c e a n a l y s i s t o e l i m i n a t e t h e e f f e c t o f b r e e d e r age on t h e growth of progeny ( H i c k s , 1982). The f o l l o w i n g s t a t i s t i c a l model was used: Y i j k l m n = P + R i + R P i j + M k + c l + < M C > k l + E 1 i j k l + A m •+ ( A M ) k m + ( A C ) l m + ( A M C ) k l m . + E 2 i j k l m n 3 8 MATERIALS AND METHODS + H B W T i j k l n u v and i=l,2,..,6; j=l,2; k=l,2; 1=1,2; m=l,2,3; n=l,..,144; where Y j _ j k ] _ m n = ^ s o n e °f t n e growth parameters of progeny (body weight, weight gain, feed intake, feed conversion). Yijk.imn ^ s the growth status of the progeny in the j t l r i cage from the p t' 1 parental pen with the k ^ s l a t material and the 1 t h s l a t coverage during the m t h breeder age; JJ = the o r e t i c a l population mean, Rj_ = e f f e c t of the i t h parental pen, RPj_j = e f f e c t of the j t h progeny cage from the i t h parental pen, Mk = ef f e c t of whether s l a t material of the parental pen was wood or p l a s t i c , C]_ = e f f e c t of whether s l a t coverage of the parental pen was f u l l or p a r t i a l , (MC) k]_ = effect of two-way interaction between the main eff e c t s ; E l i j k i = error term for testing the main eff e c t s , A m = e f f e c t of a s p e c i f i c breeder age, (AM) k m and (AC) l m, = ef f e c t of two-way interactions involving breeder age; (AMC) k ] _ m = eff e c t of three-way in t e r a c t i o n between the main ef f e c t s and breeder age, E2^j k]_ mn = error term for testing the sub-plot effects, HBWTj_j^i^n = the covariate, hatching weight of progeny. In the analysis of the six-week growth of 56th week progeny, the independent variables involved were s l a t material, s l a t coverage and sex of progeny. The following s t a t i s t i c a l model was used: Y i j k l n = P + R i + M j + C k + s l + <MC)jk + (MS)ji 39 MATERIALS AND METHODS - ( C S ) k l + (MCS) j k l + E i j k l n , and i=l,2.,,6; j=l,2; k=l,2; 1=1,2; n=1,2,...,48; where Y i j k l n = ^ s o n e °^ the growth parameters of progeny (body weight, weight gain, feed intake, feed conversion). Y i j k i n i s the growth status of progeny of the 1 t h sex in the i 1 - ^ r e p l i c a t i o n , produced by breeders on the jth S ] _ a t material and the k t h s l a t coverage; p = th e o r e t i c a l population mean, Mj = e f f e c t of whether s l a t material of the parental pen was wood or p l a s t i c , C k = ef f e c t of whether s l a t coverage of the parental pen was f u l l or p a r t i a l s l a t , S]_ = ef f e c t of whether sex of progeny was male or female; (MC) j k , (MS) j]_, (CS) k]_ = effects of two-way interactions between the main ef f e c t s ; (MCS)j k l = the ef f e c t of three-way interaction between the main effects; Ej_j k]_ n = random error. The p d i f f procedure of the SAS General Linear Models (1985) was used to evaluate treatment differences among the means i n a l l ' of the above analyses. 40 5. RESULTS The influence of s l a t material and s l a t coverage on egg production, f e r t i l i t y , h a t c h a bility, d i s t r i b u t i o n of embryo mortality and growth of 37th, 46th and 56th week progeny w i l l be presented. The influence of breeder age on f e r t i l i t y , h atchability, d i s t r i b u t i o n of embryo mortality and growth of 37th, 46th and 56th week progeny, as well as the influence of sex of progeny on the growth of 56th week progeny w i l l likewise be presented. Due to wide variations in weekly data, egg production, the incidence of f l o o r eggs, cracked nest and cracked f l o o r eggs were analyzed on a biweekly basis (lay periods). 5.1. THE INFLUENCE OF SLAT MATERIAL AND SLAT COVERAGE 5 .1 .1 . Egg Recovery The s l a t material x s l a t coverage int e r a c t i o n was s i g n i f i c a n t for ov e r - a l l egg recovery (Table 1). P a r t i a l wood (PWS) and p a r t i a l p l a s t i c (PPS) s l a t pens had"higher o v e r - a l l egg recovery rate than either f u l l wood (FWS) or f u l l p l a s t i c 1 (FPS) s l a t pens, and FWS pens had higher egg recovery rate than FPS pens. During lay periods 5, 6, 7, 10, 12, 13 and 14, PWS and PPS pens hadhigher egg recovery than either FWS or FPS. Except during lay periods 12, 15 and 16, egg recovery was higher in FWS pens than in FPS 41 RESULTS pens. The r e p l i c a t i o n e f f e c t was s i g n i f i c a n t during lay periods 2, 5 and 6. 5.1.2. Incidence of Floor Eggs Although the incidence of f l o o r eggs during lay periods 4, 9 and 15 was influenced by s l a t s , the o v e r - a l l incidence of f l o o r eggs was not (Table 2). During lay periods 4 and 9, the incidence of f l o o r eggs was higher in PWS and FPS pens than i n FWS pens. During lay period 15, PWS, FPS and PPS pens had a higher proportion of f l o o r eggs than FWS pens. 5.1.3. Incidence of Cracked Floor Eggs During lay periods 10 and 11, the incidence of cracked f l o o r eggs was higher in FPS pens than in PWS and PPS pens. During lay period 14, FPS pens had a higher incidence of cracked f l o o r eggs than PWS, FPS and PPS pens (Table 3). 5.1.4. Incidence of Cracked Nest Eggs The incidence of cracked nest eggs was higher in FWS and FPS pens than in PWS and PPS pens during lay periods 4, 8, 9 and 11 (Table 4). Differences were seen only during two other lay periods; during lay period 12, the incidence of cracked nest eggs was higher i n FWS and FPS pens than in PWS pens; and, during lay period 16, FPS pens had a higher incidence of cracked nest eggs than FWS, PWS and PPS pens. 42 RESULTS The o v e r - a l l incidence of cracked nest eggs was higher i n FWS and FPS pens than i n PWS and PPS pens, and t h i s was r e f l e c t e d i n the higher o v e r - a l l incidence of cracked nest eggs i n f u l l than p a r t i a l s l a t pens. 5.1 .5 . Percent " S e t t a b l e " Eggs When the number of non-cracked nest eggs was used as an estimate of percent " s e t t a b l e " eggs, i t was found t h a t the s l a t m a t e r i a l x s l a t coverage i n t e r a c t i o n was s i g n i f i c a n t (Table 5 ) . PWS and PPS pens had a higher p r o p o r t i o n of-" s e t t a b l e " eggs than e i t h e r FWS or FPS pens. A d d i t i o n a l l y , the p r o p o r t i o n was higher i n FWS pens than i n FPS pens . 43 RESULTS Table 1. The Influence of Slats on Egg Recovery 1 Standard Breeder Slat Type 2 Error Lay Age of the Period (Weeks) FWS PWS FPS PPS Mean 1 24-25 9 .2 a 10 .0 a 6.1b 9.9a 1 .00 2* 26-27 42 .2 a 45 .7 a 33. 5 b 44.9 a 1 .15 3 28-29 66 .6 a 70 .4 a 55. 3 b 67. 3 a 2 .05 4 30-31 69 • 3 b 75 .4 a 60.8 C 71.6 a' b i .67 5* 32-33 72 .0 b 78 .8 a 62.3° 77.5 a l .33 6* 34-35 70 .9 b 76 .9 a 61.4 C 76.8 a l .21 7 36-37 66 .6 b 72 .5 a 59.5 C 73. 6 a l .50 8 38-39 65 .4 b 69 > 9a,b 59.0 C 70. 9 a l .64 9 40-41 63 . l b 68 .0 a 5 6 . l c 66.8 a' b l .38 10 42-43 59 .8 b 67 .3 a 53.5 C 65.4 a l .58 11 44-45 58 .7 a 63 .7 a 52. 2 a •64. 4 a 2 . 17 12 46-47 55 .3 b 60 .8 a 50.2 b 62. 5 a 1 .76 13 48-49 52 57 .4 a 47 .7 b 60. 6 a 1 .59 14 50-51 50 .4 b 54 .6 a 46.0 C 57 .5 a 1 .38 15 52-53 47 . l a 53 .9 a 44.7 a 53. 2 a •1 .84 16 54-55 47 . l b 51 .6 a' b 43.7 b 54. 0 a 1 .65 Mean 56 .0 b 61 . l a 49. 5 C 61. l a 1 .20 Meanx 58 .4a(Wood) 55.2 b(Plastic) 0 .84 Meanx 52 .7 D (Full) 60. 9 a ( P a r t i a l ) 0 .84 Percent hen-day egg recovery. FWS = f u l l wood sl a t s ; PWS = p a r t i a l wood s l a t s ; FPS = f u l l p l a s t i c s l a t s ; PPS = p a r t i a l p l a s t i c s l a t s . Values followed by d i f f e r e n t l e t t e r s within a l i n e are s i g n i f i c a n t l y d i f f e r e n t (P<0.05). Slat material x s l a t coverage interaction i s s i g n i f i c a n t (P<0.05). Sign i f i c a n t r e p l i c a t i o n e f f e c t (P<0.05). 44 RESULTS Table 2. The Influence of S l a t s on the Inci d e n c e 1 of Fl o o r Eggs Standard Breeder S l a t Type 2 E r r o r Lay Age ' of the Period (Weeks) FWS PWS FPS PPS Mean 1 24-25 10. 8 a 13.2 a 8.0a 6.6a 3.11 2 26-27 6.0a 9.6a 6.9a 6.8a 1.43 3 28-29 4 .3 a 7.3 a 5.5 a 5.8 a 1.02 4 30-31 2.4 b 5.9 a 4.9a 4.7 a' b 0.92 5 32-33 3.4a 6.8a 7.5a 4.6a 1.05 6 34-35 3.2 a 6.5a 7 ,3 a 4.8a 1.05 7 36-37 2.2 a 5.4a 6.4a 5.0 a 0.95 8 38-39 2.6 a 5.0 a 5.8a 4 .7 a 0.90 9 40-41 2.8 b 5.3 a 6.4a 4.7 a' b 0.86 10 42-43 2.0 a 4.9a 5.1 a 4.7 a 0.93 11 44-45 2.0 a 4.6a 4 .0 a 4 .5 a 1.07 12 46-47 2.1 a 2 .9 a 3.6a 3.8a 0.75 13 48-49 2.2 a 4 . l a 4.3a 4 . l a 0.99 14 50-51 1.9a 3.2a 2.4a 3.2a 0.62 15 52-53 1 .3 b 3.0 a 4 .2 a 4 . l a 0.67 16 54-55 2.4 a 4. l a 3.7 a 4.8a 1.00 Mean 3.2 a 5.7 a 5.4a 4 .8 a 0.77 Mean 4 .4 a (Wood) 5.1 a (Plastic) 0.54 Mean 4 .3 a(Full) 5.2 a(Partial) 0.54 F l o o r eggs as a percentage of t o t a l egg production f o r a given l a y p e r i o d . FWS = f u l l wood s l a t s ; PWS = p a r t i a l wood s l a t s ; FPS = f u l l p l a s t i c s l a t s ; PPS = p a r t i a l p l a s t i c s l a t s . Values f o l l o w e d by d i f f e r e n t l e t t e r s w i t h i n a l i n e are s i g n i f i c a n t l y d i f f e r e n t (P<0.05). 45 RESULTS Table 3. The Influence of Slats on the Incidence 1 of Cracked Floor Eggs Standard Breeder Slat Type 2 Error Lay Age of the Period (Weeks) FWS PWS FPS PPS Mean3 1 24-25 16.7 a 16.7 a 13.9 a 1.6a 6.90 2 26-27 17.8 a 18. l a 20.5 a 24.3 a 4..52 3 28-29 13.3 a 1 5 . l a 22. l a . 1 7 . l a 3.99 4 30-31 22.6 a 9.6a 18.9 a 14.2 a 5.31 5 32-33 20 . l a 14.0 a 27. 5 a 14 .4 a 5.35 6 34-35 15.5 a 9.8a 20. 3 a 13.2 a 3.61 7 36-37 30.5 a 16.4 a 18.0 a 13. 0 a 5.13 8 38-39 24 .4 a 18.8 a 23. 2 a 5.3 a 6.73 9 40-41 15.8 a 12. l a 2 7 . l a 11.3 a 4.55 10 42-43 16.8 a' b 7.8 b 2 7 . l a 10.2 b 3.26 11 44-45 16.2 a' b 1.3b 20.2 a 3.8b 4.84 12 46-47 19.3 a 21. 3 a 24.4 a 5.6 a 6.90 13 48-49 13.2 a 1 5 . l a 17.9 a 1 6 . l a 5.87 14 50-51 14 .8 b 12. 6 b 40.5 a 12. 4 b 6.85 15 52-53 35.2 a 13. 8 a 3 7 . l a 13.9 a 9.90 16 54-55 2 6 . l a 8.5a 21. 0 a 10.7 a 7.85 Mean 19.9 a 13.2 a 23. 7 a 11.7 a 2.76 Mean 16.6a(Wood) 17.7 a(Plastic) 2.01 Mean 21.8 a(Full) 12. 4 a ( P a r t i a l ) 2.18 Cracked eggs on the f l o o r as a percentage of the number of f l o o r eggs for a given lay period. FWS = f u l l wood s l a t s ; PWS = p a r t i a l wood s l a t s ; FPS = f u l l p l a s t i c s l a t s ; PPS = p a r t i a l p l a s t i c s l a t s . Values followed by d i f f e r e n t l e t t e r s within a l i n e are s i g n i f i c a n t l y d i f f e r e n t (P<0.05). 46 RESULTS Table 4. The Influence of Slats on the Incidence 1 of Cracked Nest Eggs Standard Breeder Slat Type 2 Error Lay Age ; ; 0 f the Period (Weeks) FWS PWS FPS PPS Mean 1 24-25 0 .8 a 0 .2 a 0 .9 a 0.3a 0 .50 2 26-27 . I .4 a 0.9a 1 .4 a 1.0a 0 .20 3 28-29 1 . l a 0.6a 1 . l a 0.2a 0 .23 . 4 30-31 1 .5 a 0.7b 1 .5 a 0.7b 0 .22 5 32-33 1 .8 a 0.6a 2 • 0 a 0.9a 0 .26 6 34-35 1 . l a 0.9a 1 .6 a 0.8a 0 .30 7 36-37 1 .5 a 0.5a 1 .8 a 0 .7 a 0 .36 8 38-39 1 .6 a 0.5b 2 -2 a 0.8b 0 .23 9 40-41 2 . l a 0.7b 1 .9 a 0.8b 0 .19 10. 42-43 2 .2 a 0.6a 1 .5 a 1. 0 a 0 .26 11 . 44-45 1 .8 a 0.8b 2 .3 a 1.0b 0 .22 12* 46-47 1 .5 a 0.8b 2 .2 a 1.0 a' b 0 .29 13 48-49 2 . l a 1. l a 1 .9 a 1 .0 a 0 .32 14 50-51 1 .9 a 1.6a 2 .5 a 1.5a 0 . 45 15 52-53 3 .3 a 2.0 a 2 .8 a 2.3 a 0 .56 16 54-55 1 .9 b 1.5b 3 .2 a 2.0 b 0 .34 Mean 1 .7 a 0.9b 1 .9 a 1 .0 b 0 .13 Mean 1 .3a(Wood) 1 •5S (Plastic) 0 .09 Mean 1 . 8 a (Full) 1 .0 b (Partial) 0 .09 Cracked eggs in the nest as a proportion of t o t a l number of eggs in the nest. FWS = f u l l wood s l a t s ; PWS = p a r t i a l wood s l a t s ; FPS = f u l l p l a s t i c s l a t s ; PPS = p a r t i a l p l a s t i c s l a t s . Values followed by d i f f e r e n t l e t t e r s within a l i n e are s i g n i f i c a n t l y d i f f e r e n t (P<0.05). S i g n i f i c a n t r e p l i c a t i o n e f f e c t (P<0.05). 4 7 RESULTS Table 5. The Influence of Slats on the S e t t a b i l i t y of Eggs Variable Percent Settable Eggs-Slat Type 3 FWS PWS FPS PPS SEM4 53. 4 b 57 .2 a 45.9 C 57.5 a 1.16 (5300) 2 (5786) (4622) (5779) (150.7) Slat M a t e r i a l x Wood P l a s t i c SEM4 55 51 0 3 a ,7b .82 (5543) (5200) (106.5) Slat Coverage x F u l l P a r t i a l SEM4 49 57 0 7 b 3 a ,82 (4961) (5782) (106.5) The number of non-cracked nest eggs as a proportion of the t o t a l number of eggs in the nest and on the f l o o r . Values in parentheses are the cumulative number of non-cracked nest eggs from 24 to 56 weeks of breeder age. FWS = f u l l wood s l a t s ; PWS = p a r t i a l wood s l a t s ; FPS = f u l l p l a s t i c s l a t s ; PPS = p a r t i a l p l a s t i c s l a t s . Standard error of the mean. Values followed by d i f f e r e n t l e t t e r s within a column and within a variable are s i g n i f i c a n t l y d i f f e r e n t (P<0.05). Slat material x s l a t coverage interaction i s s i g n i f i c a n t (P<0.05). 48 ' RESULTS 5.1.6. F e r t i l i t y , Hatchability of Total Eggs Set (TES) and Hatchability of F e r t i l e Eggs (FES) T a b l e 6 shows t h a t s l a t s d i d not i n f l u e n c e f e r t i l i t y , h a t c h a b i l i t y of t o t a l eggs se t (TES) and h a t c h a b i l i t y of f e r t i l e eggs ( F E S ) . 5.1.7. Temporal D i s t r i b u t i o n of Embryo Mortality Except f o r the i n c i d e n c e of e a r l y dead embryos, s l a t m a t e r i a l and s l a t coverage d i d not i n f l u e n c e the temporal d i s t r i b u t i o n of embryo m o r t a l i t y (Table 7 ) . Eggs from wood s l a t b r e e d e r s , as opposed to eggs from p l a s t i c s l a t b r e e d e r s , had a h i g h e r i n c i d e n c e of e a r l y dead (ED) embryos. 49 RESULTS Table 6. The Influence of Slats on Percent F e r t i l i t y and Hatchability Variable F e r t i l i t y Hatchability of Total Eggs Set (TES) Hatchability of F e r t i l e Eggs (FES) Slat Type FWS PWS FPS PPS SEM1 90.8 a 94.4 a 93.9 a 91.0 a 0.91 67.6 a 71.8 a 67. 8 a 69.9 a 1.35 73.9 a 75. 8 a 7 2 . l a 76.3 a 1.25 Slat Material Wood P l a s t i c SEM1 92. 6 a 92.5 a 0.74 69.7 a 68 .9 a 1 .04 74.8 a 74.2 a 0.92 Slat Coverage F u l l P a r t i a l SEM1 92.3 a 92 .7 a 0.74 67 .7 a 70.9 a 1.04 73.0 a 76. 0 a 0.92 1 2 a, b Standard error of the mean. FWS = f u l l wood s l a t s ; PWS = p a r t i a l wood sl a t s ; FPS = f u l l p l a s t i c s l a t s ; PPS = p a r t i a l plastic- s l a t s . Means followed by d i f f e r e n t l e t t e r s within a column and within a variable are s i g n i f i c a n t l y d i f f e r e n t (P<0.05). 50 RESULTS Table 7.' The Influence of Slats on the Temporal D i s t r i b u t i o n of Embryo Morta l i t y Embryo M o r t a l i t y 1 ' Variable ED MD LD PA PD Slat Type FWS 6. , 9 a 0. 6 a 6 . 7 a 7 . 8 a 1. ,2 a PWS 6. , l a 0. 8 a 6 . 9 a 7 . 5 a •1. , 3 a FPS 5. . 2 a 0. 8 a 8.4a 10 .3 a 1. ,4a PPS 5. . 2 a 0. 3 a 6 . 7 a 7 . 6 a 1. . 2 a SEM4 0, .50 o. 18 0.62 0.79 0, .21 .at Material Wood 6 . 5 a 0 . 7 a 6 .8 a 7 . 6 a 1 . 3 a P l a s t i c 5. . 2 b 0 . 6 a 7 . 6 a 9 . 0 a ' 1 . 3 a SEM4 0. .35 0 .13 0.44 0.56 0 .15 Slat Coverage F u l l 6.0a 0.7a 7.6 a 9.0a 1.3a P a r t i a l - 5.7 a 0.6a 6.8a 7. 6 a 1. 3 a SEM4 • 0.35 0.13 0.44 0.56 0.15 Values represent percent mortality of t o t a l eggs set. ED = early dead; MD = mid-dead; LD = late dead; PA = pipped a l i v e ; PD = pipped dead. FWS = f u l l wood s l a t s ; PWS = p a r t i a l wood s l a t s ; FPS = f u l l p l a s t i c s l a t s ; PPS = p a r t i a l p l a s t i c s l a t s . Standard error of the mean. Means followed by d i f f e r e n t l e t t e r s within a column and within a variable are s i g n i f i c a n t l y d i f f e r e n t (P<0.05). 1 2 3 4 a, b 51 RESULTS 5.1.8.' Growth, from Hatch to Three Weeks of Age, of 37th, 46th and 56th Week Progeny The weekly body weight of 37th, 46th and 56th week progeny was not affected by the s l a t material and s l a t coverage in the parental pens (Table 8 ) . The f i r s t week weight gain (BWT'GN-1) of FWS, PWS and PPS progeny was higher than that of FPS progeny. The weight gain of progeny during the rest of the three-week study was not affected by s l a t s . PWS progeny had higher feed intake during the f i r s t week (FI-1), as well as higher t o t a l feed intake (C-FI) than the other three progeny groups. During the second week, FWS and PWS progeny had higher feed intake than FPS and PPS progeny. There was a s i g n i f i c a n t parental pen r e p l i c a t i o n e f f e c t in the second week and ov e r - a l l feed intake and feed conversion. Despite differences in weight gain and feed intake, no s i g n i f i c a n t differences were found in the weekly and over-a l l feed conversion of the d i f f e r e n t progeny groups. 52 Table 8. The Influence of Breeder S l a t s on Body Weight, Body Weight Gain, Feed Intake and Feed Conversion, from Hatch t o Three Weeks of Age, of 37th, 46th and 56th Week Progeny FWS S l a t T y p e 1 , 2 PWS FPS PPS Standard E r r o r of the Mean Body weight(g) H-BWT BWT-1 BWT-2 BWT-3 3. 47 , 154 . 370, 674 , Body weight g a i n ( g ) 4 : BWTGN-1 BWTGN-2 BWTGN-3 C-BWTGN 106 . 6' 216.7J 303 . 7' 627 . 0' Feed i n t a k e ( g ) 5 : r x-x FI-2' C-FI' 125 . 2A 299 . 9C 483 . 5£ 908 . 6* 47 . 2C 156.5' 376. 5* 688 . 8^  109.3' 220 . 0'c 312.3 e 641. 6' 129.8* 307.6 a 497 . 8 a 935.2 a 47.2 C 148 . 6' 363 .7' 662 . 0' 101.4" 2 1 5 . l a 298.3 a 614.8 a 123 . 0* 296.61 484 . 0' 903 . 6* 47 . 2 a 153.9 a 365.8 a 668.5 a 106.7 a 211.9 a 302.7 a 621.3 a 12 6 . 8r 297.2° 481.2 a 905.2~ 0.20 1.40 3 .31 7 . 67 1, 2 , 6, 7 1, 2 , 34 54 54 63 44 86 17 63 Feed conversion : FC-1 1.17 a 1.19 a FC-2* 1.38 a 1.40 a FC-3 1.59 a 1.59 a C-FC* 1.45 a 1.46 a 1.21' 1. 38' 1. 62' 1.47' 1. 19' 1.40' 1. 59 J 1.46' 0.013 0.012 0.033 0 . 014 1 2 3 4 5 6 Each r e p l i c a t e was a cage of ten b i r d s . FWS = f u l l wood s l a t s ; PWS' = p a r t i a l wood s l a t s ; FPS = f u l l p l a s t i c s l a t s ; PPS = p a r t i a l p l a s t i c s l a t s . H-BWT, BWT-1, BWT-2 and BWT-3 are body weight at hatch and at the end of Weeks 1, 2 and 3, r e s p e c t i v e l y . (BWTGN-1) = (BWT-1)-(H-BWT); BWTGN-2 = (BWT-2)-(BWT-1); (BWTGN-3) = (BWT-3)-(BWT-2); C-BWTGN = (BWT-3)-(H-BWT). FI - 1 , FI-2, FI-3 are feed intake during Weeks 1, 2 and 3, r e s p e c t i v e l y ; (C-FI) = (FI-1)+(FI-2)+(FI-3). (FC-1) = (FI-1)/(BWTGN-1); (FC-2) = (FI-2)/(BWTGN-2); 53 (FC-3) = (FI-3)/(BWTGN-3); (C-FC) = (C-FI)/(C-BWTGN). Values followed by d i f f e r e n t l e t t e r s w i t h i n a l i n e are s i g n i f i c a n t l y d i f f e r e n t (P<0.05). S i g n i f i c a n t r e p l i c a t i o n e f f e c t (P<0.05). 54 RESULTS 5.1.9. Growth, from Hatch to Six Weeks of Age, of 56th Week Progeny Parental s l a t material and s l a t coverage did not influence the body weight and feed intake of 56th week progeny at any time during the 6-week growth t r i a l (Table 9) . The t h i r d week body weight gain (BWTGN-3) of PWS and FPS progeny was higher than that of PPS progeny. During the sixth week, FWS and PWS progeny had higher weight gain than FPS and PPS progeny. FPS progeny had higher sixth week feed conversion (FC-6) than the other three progeny groups. No other differences in feed conversion were seen. 55 RESULTS Table 9. The Influence of Slats on Body Weight, Body Weight Gain, Feed Intake and Feed Conversion, from Hatch to Six Weeks of Age, of 56th Week Progeny Standard Slat Type 1' 2' 3 Error , of the FWS PWS FPS PPS Mean Body weight(g) H-BWT 50. 2 a 50 .6 a 50 .0 a 49 .8 a 0 .44 BWT-1 152. 0 a 157 .9 a 153 .4 a 154 .0 a 2 .56 BWT-2 371 . 0 a 373 .4 a 364 .5 a 373 .2 a 4 .24 BWT-3 699. 5 a 709 .9 a 699 .3 a 689 .8 a 7 .14 BWT-5 .1488 . 8 a 1524 .4 a 1496 .4 a 1498 .2 a 17 .76 BWT-6 1881 . 8 a 1908 .7 a 1838 .4 a 1874 .4 a 27 .54 Body weight gain(g) 5. BWTGN-1 101'. 8 a 107 .3 a 103 .4 a 104 .2 a 2 .57 BWTGN-2 219. 0 a 215 .5 a 211 . l a 219 .3 a 3 .47 BWTGN-3 328 . 5a,b 1 336 .5 a 334 .9 a 316 .6 b 5 .40 BWTGN-5 789 . 3 a 814 .5 a 797 . l a 808 .4 a 14 .90 BWTGN-6 393. 0 a 384 .4 a 342 .0 b 37 6 .2 b 14 .53 C-BWTGN 1831 . 6 a 1858 .2 a 1788 .5 a 1824 •7 a • 27 .54 Feed i n t a k e ( g ) b : FI-1 114 . 7 a 126 .4 a 115 .2 a 115 • 5 a 3 .26 FI-2 292. 2 a 298 .7 a 292 .3 a 291 .4 a 3 .30 FI-3 490 . 5 a 510 .3 a 493 .0 a 481 -8 a 7 .74 FI-5 1697 . 3 a 1720 .4 a 1651 .2 a 1714 .7 a 28 .92 FI-6 1101. 8 a 1045 .8 a 1058 .6 a 1031 • 8 a 29 .49 C-FI 3696 . 5 a 3701 .6 a 3610 .3 a 3635 .2 a 59 .13 Feed conver sion"^ : FC-1 1 . 13 a 1 . 18 a 1 . l l a 1 . l l a 0 .043 FC-2 1 . 33 a 1 .39a 1 .38a 1 .33 a 0 .019 FC-3 1 . 49 a 1 .52a 1 . 47 a •1 .52a 0 .019 FC-5 2 . 15 a 2 . l l a 2 . 07 a 2 . 12 a 0 .030 FC-6 2. 80 b 2 .72b 3 . 10 a 2 .74b 0 .136 C-FC 2. 02 a 1 .99 a 2 .02a 1 . 99 a 0 .020 The range of weight of hatching eggs was 66-78 grams. Each parental s l a t type was represented by 6 cages of 10 male and six cages of 10 female chicks from hatch to three weeks of age. From the fourth to the sixth week, the number of birds per cage was reduced to 7. FWS = f u l l wood s l a t s ; PWS = p a r t i a l wood s l a t s ; FPS = f u l l p l a s t i c s l a t s ; PPS = p a r t i a l p l a s t i c s l a t s . H-BWT, BWT-1, BWT-2, BWT-3, BWT-5 and BWT-6 are body weight at hatch and at the end of Weeks 1, 2, 3, 5 and 6, respectively. (BWTGN-1) = (BWT-1)-(H-BWT); (BWTGN-2) = (BWT-2)-56 RESULTS (BWT-1); (BWTGN-3) = (BWT-3)-(BWT-2); (BWTGN-5) = (BWT-5)-(BWT-3); (BWTGN-6) = (BWT-6)- (BWT-5); (C-BWTGN) = (BWT-6)-(H-BWT). FI-1, FI-2, FI-3, FI-5 and FI-6 are feed.intake during Weeks 1, 2, 3, 4 and 5, and 6, respectively; (C-FI) = (FI-1) + (FI-2) + (FI-3) + (FI-5) + (FI-6) . (FC-1) = (FI-1)/(BWTGN-1); (FC-2) = (FI-2)/(BWTGN-2); (FC-3) = (FI-3)/(BWTGN-3); (FC-5) = (FI-5) /(BWTGN-5) ; (CFC-6) = (FI-6)/(BWTGN-6); (C-FC) = (C-FI)/(C-BWTGN). Values followed by d i f f e r e n t l e t t e r s within a li n e are s i g n i f i c a n t l y d i f f e r e n t (P<0.05) . 57 RESULTS 5.2. THE INFLUENCE OF BREEDER AGE 5.2.1. F e r t i l i t y , Hatchability of Total Eggs Set (TES) and Hatchability of F e r t i l e Eggs (FES) Table 10 shows that f e r t i l i t y was high (94.8-96.7%) when breeders were 37, 42 and 46 weeks of age. A s i g n i f i c a n t decrease i n f e r t i l i t y was seen at 50 weeks of breeder age. A further, decrease in f e r t i l i t y occurred when breeders were 56 weeks old. The h a t c h a b i l i t y of t o t a l eggs set (TES) was influenced by the breeder age x s l a t material and the breeder age x s l a t material x s l a t coverage interactions (Table 10). The ha t c h a b i l i t y of f e r t i l e eggs (FES) was highest at 37 weeks of breeder age. FES decreased at 42 weeks, and did not decrease again u n t i l 56 weeks of breeder age. 58 RESULTS Table 10. Percent F e r t i l i t y and Hatchability of Eggs at Different Breeder Ages 1 Breeder Age (Weeks) F e r t i l i t y Hatchability of Total Eggs Set(TES) x'y Hatchability of F e r t i l e Eggs(FES) 37 96.7 a . 86.6 a 89.7 a 42 94.8 a 70. 5 b 74. l b 46 95.4 a 70.8 b 74 ,3 b 50 89.4 b 65. 2 C 73. 0 b 56 86. 3 C 53.3 d 61.5 C SEM2 1.17 1.50 1.39 1 Mean egg weight was 68.1, 68.6, 70.6 and 71.8 g at 42, 46, 50 and 56 weeks of breeder age, respectively; egg weight at 37 weeks of age was unknown. 2 Standard error of the mean. a,b,c,d values followed by d i f f e r e n t l e t t e r s within a column are s i g n i f i c a n t l y d i f f e r e n t (P<0.05). x Breeder age x s l a t material interaction i s s i g n i f i c a n t (P<0.05). y Breeder age x s l a t material x s l a t coverage interaction i s s i g n i f i c a n t (P<0.05). 59 RESULTS 5.2.2. Temporal D i s t r i b u t i o n of Embryo M o r t a l i t y The incidence of early dead (ED) and late dead (LD) embryos both increased s i g n i f i c a n t l y at 42 weeks from the time when breeders were 37 weeks old (Table 11). At 56 weeks of breeder age, ED and LD embryos increased further over the 50th week incidence. The incidence of pipped a l i v e (PA) and pipped dead (PD) embryos increased at 42 weeks of breeder age, and did not increase further. The incidence of MD embryos was not influenced by breeder age. 60 RESULTS Table 11. The Influence of Breeder Age on the D i s t r i b u t i o n of Embryo Mortality Breeder Age Embryo M o r t a l i t y 1 ,2,3 (Weeks) ED MD LD PA PD 37 2.9 C 0.4a 2.4 C 3.9 b 0.4b 42 4.9b l . l a 6.2b 10. 3 a 1.7a 46 6.4b 0.5a 7.9 b 8.5a 1.2a 50 6.2b 0.5a 7.8 b 8.1a 1.6a 56 8.9a 0.5a 11 .5 a 10.6 a • 1.6a SEM4 0.56 0.21 0.69 0.88 0.23 Mean egg weight was 68.1, 68.6, 70.6 and 71.8 g at 42, 46, 50 and 56 weeks of breeder age, respectively; egg weight was not taken at 37 weeks of age. Values represent percent mortality of t o t a l eggs ED = Early dead; MD = Mid-dead; LD = Late dead; PA = Pipped a l i v e ; PD = Pipped dead. Standard error of the mean. Values followed by d i f f e r e n t l e t t e r s within a column are s i g n i f i c a n t l y d i f f e r e n t (P<0.05). 61 RESULTS 5.2 .3 . Growth, from Hatch to Three Weeks of Age, of 37th, 46th and 56th Week Progeny The 56th week progeny had the highest hatching body weight (H-BWT), followed by the 46th week progeny; the 37th week progeny had the lowest hatching weight (Table 12) . No other s i g n i f i c a n t differences in the body weight and weight gain of progeny were found except where the BWTGN-1 was higher for the 37th week progeny. The 37th week progeny had higher f i r s t week (FI-1), second (FI-2) week and ov e r - a l l feed intake (C-FI) than the other two progeny groups. Additionally, the f i r s t week feed intake (FI-1) of the 46th week progeny was higher than that of 56th week progeny. The o v e r - a l l (C-FI) feed intake of the 56th week progeny was higher than that of 46th week progeny. The 37th week progeny had higher weekly and ove r - a l l feed conversion than the other two progeny groups. The 46th week progeny had higher f i r s t week feed conversion (FC-1) than the 56th week progeny. The second week feed conversion (FC-2) of the 56th week progeny was higher than that of 46th week progeny. There were no differences in the t h i r d week (FC-3) and o v e r - a l l (C-FC) feed conversion of the 46th and 56th progeny. Table 13 shows that the adjustment of hatching weight (H-BWT) to 47.2 grams resulted in the elimination of 62 RESULTS d i f f e r e n c e s i n second (FC-2) and t h i r d week feed conversion (FC-3) seen i n Table 12, as w e l l as the d i f f e r e n c e s i n the o v e r - a l l feed intake (C-FI). 63 RESULTS Table 12. The Influence of Breeder Age on Body Weight, Body Weight Gain, Feed Intake And Feed Conversion, from Hatch to Three Weeks of Age, of 37th, 46th and 56th Week Progeny 1 Standard Breeder Age (Weeks)2 Error of the 37, 46 56 Mean Body weight(g) J: H-BWT 43 .7 C 47 .8 b 50 .3 a 0.20 BWT-1 154 .0 a 151 .2 a 154 .6 a 1.20 BWT-2 367 .5 a 371 .0 a 369 .4 a 2.77 BWT-3 663 .2 a 666 .5 a 691 .3 a 6.44 Body weight gain(g) 4 . .3 a BWTGN-1 110 103 .4 b 104 .3 b 1.21 BWTGN-2 213 .5 a 219 .8 a 214 .8 a 2.19 BWTGN-3 295 .7 a 295 .5 a 321 .9 a 5.48 C-BWTGN 619 .5 a 618 .7 a 641 .0 a 6.42 Feed intake (g) ->: FI-1 141 .3 a 121 .5 b 115 .8 C 1.28 FI-2* 316 .4 a 291 .0 b 293 .7 b 2.47 FI-3 508 . l a 457 .8 a 493 •9i 4.42 C-FI* 963 .6 a 869 .9 C 903 .4 b 6.19 Feed conversion": FC-1 1 .27a 1 .18 b 1 . l l c 0.012 •k FC-2 1 .49 a 1 .32° 1 .37 b 0.011 FC-3 1 ,75 a 1 .55 b 1 .54b 0.028 C-FC* 1 .56a 1 .41 b 1 .41 b 0.012 1 Mean egg weight was 68.6 g and 71.8 g 46 and 56 week; of breeder age, respectively; egg weight was not taken at 37 weeks of age. Each parental s l a t type was represented by 12 cages of 10 chicks. For the 56th week growth t r i a l , each parental s l a t type was represented by 6 cages of 10 male and 6 cages of 10 female chicks. H-BWT, BWT-1, BWT-2 and BWT-3 are body weight at hatch, and at the end of Weeks 1, 2 and 3 , r e s p e c t i v e l y (BWTGN-1) = (BWT-1)-(H-BWT); (BWTGN-2) = (BWT-2)-(BWT-1); (BWTGN-3) = (BWT-3)-(BWT-2); (C-BWTGN) = (BWT-3)-(H-BWT). FI-1, FI-2, FI - 3 are feed intake during Weeks 1, 2 and 3 , respectively; (C-FI) = (FI-1)+(FI-2)+(FI - 3 ) . (FC-1) = (FI-1)/(BWTGN-1); (FC-2) = (FI-2)/(BWTGN-2); (FC-3) = (FI-3)/(BWTGN-3); (C-FC) = (C-FI)/(C-BWTGN). Values followed by d i f f e r e n t l e t t e r s within a l i n e 64 RESULTS are s i g n i f i c a n t l y d i f f e r e n t (P<0.05). Sig n i f i c a n t r e p l i c a t i o n e f f e c t (P<0.05). RESULTS Table 13. The Influence of Breeder Age on Body Weight, Body Weight Gain, Feed Intake And Feed Conversion, from Hatch to Three Weeks of Age, of 37th, 46th and 56th Week Progeny, with Adjusted Hatching Weight 1 Breeder Age (Weeks) 2 Standard Error 37 46 56 Mean Body weight(g) 3: H-BWT 47. 2 47 .2 47. 2 BWT-1 158. l a 150.6a 151. l a 2.46 BWT-2 376. 0 a 369.7 a 361. 9 a 5.86 BWT-3 686. 9 a 663.0 a 670. 8 a 13.51 Body weight gain(g) 4 . 8 a BWTGN-1 110. 103.4b 103. 8 b 2.46 BWTGN-2 217. 9 a 219.l a 210. 8 a 4.53 BWTGN-3 310. 9 a 293. 3 a 308. 8 a 11.63 C-BWTGN 639. 6 a 615.8a 623. 5 a 13.51 Feed intake(g)^: l c FI-1 146. 0 a 120.9 b 112. 2.52 FI-2* 327 . 0 a 289.5 b 284 . 7 b 5.03 FI-3 515. 0 a 456.9 b 488. 2 a 9.10 C-FI* 987. 0 a 867.0 b 884. 6 b 12 .75 Feed conversion": FC-1 1. 30 a 1.18b 1. 09 c 0.024 FC-2* 1. 50 a 1.32b 1 . 36 b 0.010 FC-3 1. 69 a 1.59a 1. 59 a 0.058 C-FC* 1. 55 a 1.41b 1. 42 b .0 .012 Mean egg weight was 68.6 g and 71.8 g 46 and 56 weeks of breeder age, respectively; egg weight was not taken at 37 weeks of age. Each parental s l a t type was represented by 12 cages of 10 chicks. For the 56th week growth t r i a l , each parental s l a t type was represented by 6 cages of 10 male and 6 cages of 10 female chicks. H-BWT, BWT-1, BWT-2 and BWT-3 are. body weight at hatch, and at the end of Weeks 1, 2 and 3, r e s p e c t i v e l y (BWTGN-1) = (BWT-1)-(H-BWT); (BWTGN-2) = (BWT-2)-(BWT-1); (BWTGN-3) = (BWT-3)-(BWT-2); (C-BWTGN) = (BWT-3)-(H-BWT). FI-1, FI-2, FI-3 are feed intake during Weeks 1, 2 and 3, respectively; (C-FI) = (FI-1)+(FI-2)+(FI-3). (FC-1) = (FI-1)/(BWTGN-1); (FC-2) = (FI-2) /(BWTGN-2); (FC-3) = (FI-3) /(BWTGN-3); (C-FC) = (C-FI)/(C-BWTGN) . 5 6 66 RESULTS a,b,c values followed by d i f f e r e n t l e t t e r s within a l i n e are s i g n i f i c a n t l y d i f f e r e n t (P<0.05).. 67 RESULTS 5 . 3 . THE INFLUENCE OF SEX OF PROGENY ON GROWTH 5.3.1. Growth, from Hatch to Six Weeks of Age, of 56th Week Progeny From t h r e e to s i x weeks of age, male progeny had h i g h e r weekly body weight , body weight g a i n and feed i n t a k e T a b l e 14) . A d d i t i o n a l l y , male progeny had h i g h e r o v e r - a l l weight g a i n and feed i n t a k e than female progeny . The second week body weight (BWT-2) and weight g a i n (BWTGN-2) were i n f l u e n c e d by an i n t e r a c t i o n between sex of progeny , s l a t m a t e r i a l and s l a t coverage . Female progeny had h i g h e r t h i r d week feed c o n v e r s i o n than male progeny . No o t h e r d i f f e r e n c e s i n the feed c o n v e r s i o n of male and female progeny were d e t e c t e d d u r i n g the s ix-week growth t r i a l . 68 RESULTS Table 14. Body Weight, Body Weight Gain, Feed Intake and Feed Conversion, from Hatch to Six Weeks of Age, of Male and Female Progeny of 56-Week Old Breeders 1 Standard Sex of Progeny 2 Error of the Male Female Mean Body weight(g)^: -H-BWT 50.3 a 50 . 0 a 0.31 BWT-1 • 155.3 a 153.6a 1.81 BWT-2^ 378.5 a 362.6 b 3.00 BWT-3 731.6 a 667.6 b 5.05 BWT-5 1569..43 1434.5b 12.56 BWT-6 1970 .2 a 1781 .4 b 19.47 Body weight gain(g) 4: 103.3 a BWTGN-1 105.0 a 1.82 BWTGN-2^ 223.2a 209.0 b 2.45 BWTGN-3 353. l a .305.0b 3.82 BWTGN-5 837 .8 a 766. 9 b 10.53 . BWTGN-6 400.8a 347.0 b 10 .27 C-BWTGN 1919. 9 a • 1731 .4 b .19.47 Feed intake(g)^: FI-1 116.8a 119.0a 2.30 FI-2 298.4 a 288 .9 a 2 .33 FI-3 507 . 4 a 480 .3 b 5.48 FI-5 1763.8a 1627.9b 20.45 FI-6 1111 . l a 1008.0b 20 .85 CF-I 3797.5a 3524 . l b . 41.81 Feed conversion": FC-1 l . l l a . 1.15a 0.031 FC-2' 1.34a 1.38a 0.013 FC-3 1.44b 1.57a 0.013 FC-5 2.11 a 2.12a 0.020 FC-6 2.77 a 2.90a 0.096 C-FC 1.98a 2.04a 0.014 The range of weight of hatching eggs was 66-78 grams. Each parental s l a t type was represented by 6 cages of 10 male and six cages of 10 female chicks from hatch to three weeks of age. From the fourth to the.sixth week, the number of birds per cage was reduced to 7. H-BWT, BWT-1, BWT-2, BWT-3, BWT-5 and BWT-6 are body weight at hatch and at the end of Weeks 1, 2, 3, 5 and 6, respectively. (BWTGN-1) = (BWT-1)-(H-BWT); (BWTGN-2) = (BWT-2)-(BWT-1); (BWTGN-3) = (BWT-3)-(BWT-2); (BWTGN-5) = 1 2 3 4 69 RESULTS (BWT-5)-(BWT-3); (BWTGN-6) = (BWT-6)- (BWT-5); (C-BWTGN) = (BWT-6)-(H-BWT). 5 FI-1, FI-2, FI-3, FI-5 and FI-6 are feed intake during Weeks 1, 2, 3, 4 and 5, and 6, respectively; (C-FI) = (FI-1) + (FI-2) + (FI-3) + (FI-5) + (FI-6) . 6 (FC-1) .= (FI-1) / (BWTGN-1) ; (FC-2) = (FI-2)/(BWTGN-2); (FC-3) = (FI-3) /(BWTGN-3); (FC-5) = (FI-5) /(BWTGN-5) ; (FC-6) = (FI-6)/(BWTGN-6); (C-FC) = (C-FI)/(C-BWTGN) a , b Values followed by d i f f e r e n t l e t t e r s within a l i n e are s i g n i f i c a n t l y . d i f f e r e n t (P<0.05). y Sex of progeny x s l a t material x s l a t coverage inte r a c t i o n i s s i g n i f i c a n t (P<0.05). 70 6. DISCUSSION 6.1. THE INFLUENCE OF SLAT MATERIAL AND SLAT COVERAGE 6.1.1. Egg R e c o v e r y In the present study, egg recovery was taken as an approximation of egg production. The hypothesis that p l a s t i c s l a t s r e s u l t in higher egg production i s supported by the higher egg recovery i n PPS vs. FWS (Table 1). However, as long as the proportion of s l a t coverage was consistent for wood and p l a s t i c s l a t s , wood sl a t s had as equal (PWS vs. PPS), or better (FWS vs. FPS), egg recovery as p l a s t i c s l a t s . The r e p l i c a t i o n e f f e c t during three lay periods indicates that environmental conditions in the barn was not homogeneous. The r e p l i c a t i o n e f f e c t during lay period 2 was due to the higher value in two r e p l i c a t e s . During lay period 5, the value i n one r e p l i c a t e was higher, and in another r e p l i c a t e lower, than others; during lay period 6, the value for one r e p l i c a t e was lower. There i s no apparent explanation for the influence of pen location on egg recovery. Parkhurst (1974), who found that, egg production was higher, although not s i g n i f i c a n t l y , on p a r t i a l than f u l l s l a t s , believed that low egg production in f u l l s l a t pens 71 DISCUSSION was due to lower recovery of eggs in the l a t t e r pens. For t h i s hypothesis to explain the difference in ov e r - a l l egg production in f u l l and p a r t i a l s l a t pens, two assumptions have to be made: f i r s t l y , the number of eggs l a i d (before breakage and other losses) was equal i n f u l l and p a r t i a l s l a t pens, and secondly, an equal proportion of f l o o r eggs were l a i d on sl a t s as on l i t t e r i n p a r t i a l s l a t pens. The difference in egg production would then be attributed to the higher number of eggs remaining on the f l o o r in p a r t i a l s l a t pens. The pens were not set up to count the eggs that broke and went through the s l a t s , therefore i t i s not possible to determine the extent to which the egg production values obtained i n the present study underestimated the actual number of eggs l a i d . In t h i s respect, the "egg production" values reported in Table 1 are actually^egg recovery values. Although differences were s i g n i f i c a n t only during three lay periods, data in Table 3 suggest that f l o o r eggs on f u l l s l a t s were more l i k e l y to crack than f l o o r eggs on p a r t i a l s l a t s . If the proportion of cracked f l o o r eggs i s i n d i c a t i v e of the proportion of eggs that broke and went through the s l a t s , then Parkhurst's (1974) hypothesis could explain the lowered egg recovery i n f u l l s l a t pens compared to p a r t i a l s l a t pens (Table 1). Andrews et a l . (1988), on the other hand, did not f i n d any s i g n i f i c a n t differences i n "egg production" between 72 DISCUSSION f u l l - s l a t (plastic-covered wire) and either of two p a r t i a l s l a t f l o o r s (plastic-covered wire and wood). Floor space per b i r d was s l i g h t l y higher on p a r t i a l s l a t f l o o r s than on f u l l s l a t f l o o r s in the study by Andrews et a l . (1988) . Floor space.per b i r d was uniform for p a r t i a l and f u l l s l a t pens in the present study, and was s l i g h t l y higher than that for either p a r t i a l or f u l l s l a t pens by Andrews et a l . (1988). However, the difference in f l o o r space allotment would not f u l l y account for the disagreement i n the r e s u l t s . Cooper and Barnett (1972), with equal f l o o r space per b i r d on f u l l and p a r t i a l s l a t s , found that "egg production" on the p a r t i a l • s l a t s was s i g n i f i c a n t l y higher than on f u l l s l a t s . Floor space per b i r d was also equal for f u l l and p a r t i a l s l a t pens in the study by Parkhurst (1974), but space allotment was s l i g h t l y higher than i n the study by Cooper and Barnett (1972) and nearly equal to that in the present study. Parkhurst (1974) found that "egg production" was equal for f u l l and p a r t i a l s l a t pens. Only Andrews et a l . (1988) compared wood sl a t s with another f l o o r i n g material. These workers, however, did not f i n d s i g n i f i c a n t differences in the over-all "egg production" of b r o i l e r breeders i n p a r t i a l l y floored pens of plastic-covered wire and wood s l a t s . In the present study, s l a t material influenced o v e r - a l l egg recovery from breeders in f u l l s l a t pens but not breeders in p a r t i a l s l a t pens. 73 DISCUSSION The differences in o v e r - a l l egg recovery between wood and p l a s t i c s l a t breeders appear to be a function of s l a t coverage. The higher o v e r - a l l egg recovery from p a r t i a l s l a t (PWS and PPS) breeders could be attributed, in part, to the higher egg numbers compared to f u l l s l a t (FWS and FPS) breeders during lay periods 5, 6, 7, 10, 12, 13 and 14. Simi l a r l y , the higher o v e r - a l l egg "recovery" from FWS breeders compared to FPS breeders r e f l e c t s the higher biweekly egg numbers among the former breeders throughout the study'except for lay periods 11, 12, 13, 15 and 16. Compared to t y p i c a l Arbor Acres b r o i l e r breeder flocks, the experimental flock had lower o v e r - a l l "egg production". Figure 3 shows that peak production occurred at 32-33 weeks of age for both the study flock and t y p i c a l Arbor Acres flock, a f t e r which time the difference i n "egg production" between the two flocks s l i g h t l y increased i n favor of the l a t t e r . Despite depressed egg recovery, the general shape of the production curve of the study flock c l o s e l y resembled that of the t y p i c a l Arbor Acres flock with a difference in o v e r - a l l production levels of 15% and 7% for f u l l and p a r t i a l s l a t s , respectively. 74 % H e n d a y p r o d u c t i o n Figure 3. Weekly Egg Production of Study Flock and Typical Arbor Acres Flock 100 24 28 32 36 40 44 Age of Breeders (Weeks) Typical Flock Study Flock (Partial Slats) •%r Study Flock (Full Slats) • Adapted Irom Arbor Acres Broiler Breeder Male and Female Feeding and Management Guide (1985). DISCUSSION The b r o i l e r breeders had staphylococcus i n f e c t i o n at 13 weeks of age. The breeders had swollen hocks, and some were observed to be s i t t i n g for longer periods of time than usual. With mobility r e s t r i c t e d , breeders were probably not consuming enough nutrients necessary for growth, s p e c i f i c a l l y the development of the reproductive organs, a process which commences at about 12 weeks of age. Improper development of reproductive organs r e s u l t s in lower egg production. At 43 and 58 weeks of age, mean body weight of female breeders was nearly 6% and 9%, respectively, higher than the upper l i m i t of the target weight suggested by the Arbor Acres Feeding and Management Guide (1985). It i s a well-known fac t that obesity in chickens r e s u l t s i n lower egg production (The Technical Centre for A g r i c u l t u r a l and Rural Cooperation, 1987; Nordskog, 1980). No single s l a t material nor s l a t coverage group appeared to have higher mean body weight than others during either weighing, therefore the impact of obesity on egg production would have been similar for a l l s l a t treatments. The present study and Cooper and Barnett (1972) have shown that "egg production" was higher on p a r t i a l than f u l l s l a t f l o o r s . If "egg production" data supplied by Arbor Acres was obtained from flocks housed exclusively or mainly on p a r t i a l s l a t s , then'a reduction in "egg production" could 76 DISCUSSION be expected where f u l l s l a t s are used, as was seen i n the present study. 6.1.2. The Incidence of F l b o r Eggs Dorminey (1974) and Hurnik et a l . (1973) observed that the incidence of f l o o r eggs was u s u a l l y highest at the beginning of l a y , and then d e c l i n e d as production progressed. The same p a t t e r n was evident i n the present study (Table 2). When Dorminey (1974) examined the i n f l u e n c e of a r t i f i c i a l l i g h t i n g and nest l o c a t i o n on the incidence of f l o o r eggs i n p a r t i a l wood s l a t pens, one of the treatments was s i m i l a r to PWS pens i n the present study. Dwarf White Leghorn hens were provided w i t h nests on the . w a l l f a c i n g 100-W incandescent bulbs o f f - c e n t e r . The incidence of f l o o r eggs was 3.3%, 2.8% and 0.9% during 25-29, 37-41 and 49-53 weeks of age. The values s t a t e d are lower than that f o r PWS treatment at corresponding ages i n the present study (Table 2). The discrepancy may be due to d i f f e r e n c e s i n the l o s s of f l o o r eggs through s l a t s . Since the p r o p o r t i o n of eggs l o s t through s l a t s i n the present study i s unknown, i t i s d i f f i c u l t to determine the extent to whichathe reported values of incidence of f l o o r eggs (Table 2) underestimate the a c t u a l values, and the impact of such egg l o s s on egg recovery r a t e s . 77 DISCUSSION 6.1.3. The I n c i d e n c e o f C r a c k e d F l o o r Eggs No d i f f e r e n t i a t i o n was made as to whether a f l o o r egg was l a i d on l i t t e r or on s l a t s i n the p a r t i a l s l a t pens. I w i l l assume f o r t h i s d i s c u s s i o n t h a t p r o p o r t i o n a l l y as many f l o o r eggs were l a i d on the s l a t s as on l i t t e r i n p a r t i a l s l a t pens. P h y s i c a l l y , s l a t s are harder m a t e r i a l than l i t t e r , t h e r e f o r e i n the absence of l i t t e r i n f u l l s l a t pens, s i g n i f i c a n t l y more eggs would be cracked i n f u l l than i n p a r t i a l s l a t pens. The data i n Table 3 a l s o suggests that where only s l a t s are present as f l o o r i n g (as i n f u l l s l a t pens), p l a s t i c material- r e s u l t s i n a higher incidence of cracked f l o o r eggs. On the other hand, the incidence of cracked f l o o r eggs may be an i n d i c a t i o n of the p r o b a b i l i t y of egg l o s s . Pens with a higher incidence of cracked f l o o r eggs may have a higher l o s s of f l o o r eggs. Therefore, the incidence of cracked f l o o r eggs would not be a true r e f l e c t i o n of the i n f l u e n c e of s l a t s on the i n t e g r i t y of egg s h e l l s . 6.1.4. The I n c i d e n c e of C r a c k e d N e s t Eggs In f u l l s l a t pens, about 15 cm of one end of the nest perches overhung the 60 cm-high s l a t s and the r e s t overhung the 30 cm-high s l a t s . In p a r t i a l s l a t pens about 15 cm of one end of the nest perches a l s o overhung the 60 cm-high 78 DISCUSSION sla t s however, the rest of the perches was 60 cm above the l i t t e r f l o o r . The greater distance between the f l o o r and the perches in p a r t i a l s l a t pens may have resulted in lower breeder t r a f f i c into and out of the nests. Consequently, nest eggs in p a r t i a l s l a t pens would not be subject to as much hen t r a f f i c as those in f u l l s l a t pens. The lower incidence of cracked nest eggs in p a r t i a l s l a t pens may be a r e f l e c t i o n of lower breeder t r a f f i c into and out of the nests.. The absence of l i t t e r on the f l o o r may be another reason for the higher breeder t r a f f i c in and out of nests in f u l l s l a t pens. Since l i t t e r was present only i n the nests in the f u l l s l a t pens, breeders were using the nests not only for egg-laying but also dusting. On the other hand, breeders i n p a r t i a l s l a t pens had access to l i t t e r on the l i t t e r f l o o r , and were not causing any nest t r a f f i c other than for egg laying. However, the behaviour was not monitored i n the present study. The lower value in one r e p l i c a t e during lay period 12 resulted i n the s i g n i f i c a n t r e p l i c a t i o n e f f e c t . This e f f e c t may be random. 6.1.5. Percent "Settable" Eggs Since the number of eggs discarded p r i o r to shipping to the commercial hatchery was not monitored, the number of 79 DISCUSSION non-cracked nest eggs was taken as an approximation of percent " s e t t a b l e " eggs (Table 5). As with o v e r - a l l egg recovery (Table 1), p a r t i a l s l a t pens (PWS and PPS) had a higher proportion of " s e t t a b l e " eggs than . e i t h e r of the f u l l s l a t pens (FWS and ' FPS), and the s a i d p r o p o r t i o n was higher f o r FWS than FPS pens. S l a t m a t e r i a l and s l a t coverage not only i n f l u e n c e egg recovery, but a l s o , to a larg e extent, the s u i t a b i l i t y of eggs f o r in c u b a t i o n . The p r o p o r t i o n of s e t t a b l e eggs underlines the importance of f l o o r i n g systems and management on the p r o f i t a b i l i t y of any operation. 6.1.6. F e r t i l i t y The lack of s i g n i f i c a n t d i f f e r e n c e s i n o v e r - a l l f e r t i l i t y due to s l a t m a t e r i a l and s l a t coverage (Table 6) does not support the hypothesis t h a t p l a s t i c s l a t s r e s u l t i n higher f e r t i l i t y . L ikewise, no d i f f e r e n c e s were found i n o v e r - a l l f e r t i l i t y due to f l o o r type i n previous s t u d i e s (Andrews et a l . , 1988; Parkhurst, 1974; Cooper and Barnett, 1972; Nordskog and Schierman, 1965). In the present study, f e r t i l i t y l e v e l s among breeders on s l a t m a t e r i a l and s l a t coverage groups were w i t h i n 1% of each other. 80 DISCUSSION 6.1.7. Hatchability of Total Eggs Set (TES) and F e r t i l e Eggs (FES) The lack of s i g n i f i c a n t differences i n the hatc h a b i l i t y of t o t a l eggs set and f e r t i l e eggs due to s l a t material and s l a t coverage (Table 6) does not support the hypothesis that p l a s t i c s l a t s r e s u l t in higher ha t c h a b i l i t y . Only Andrews et a l . (1988) has compared wood sl a t s and plastic-covered wire for ha t c h a b i l i t y . They compared ha t c h a b i l i t y of eggs from pens with entire f l o o r s of plastic-covered wire (FPS), f l o o r s with 2/3 plastic-covered wire (PPS) and f l o o r s with 2/3 wood (PWS) s l a t s . Andrews et a l . (1988) found that the o v e r - a l l h a t c h a b i l i t y of t o t a l eggs set and f e r t i l e eggs was s t a t i s t i c a l l y equal for a l l three f l o o r types tested. The same was found for the corresponding s l a t types in the present study (Table 6). Andrews et a l . (1988) found s i g n i f i c a n t differences in ha t c h a b i l i t y of t o t a l eggs set and f e r t i l e eggs near the beginning and end of the study. It was suggested that male immaturity and egg handling procedures were possible causes for the' v a r i a t i o n of h a t c h a b i l i t y on s l a t types, implying that s l a t types did not d i r e c t l y influence h a t c h a b i l i t y . Since no s i g n i f i c a n t interaction was found between s l a t type and breeder age i n the present study, the lack of s i g n i f i c a n t differences in h a t c h a b i l i t y on d i f f e r e n t s l a t types was consistent throughout the study. Therefore, the 81 DISCUSSION res u l t s of the current study are consistent with those of Andrews et a l . (1988). Quarles et a l . (1968, 1970) inferred that l i t t e r in poultry houses may be a source of contamination and could possibly lower h a t c h a b i l i t y . Results of t h e i r studies did not support t h e i r inference. Likewise, Table 6 implies that the presence of l i t t e r in p a r t i a l s l a t pens did not lower h a t c h a b i l i t y . Parkhurst (1974) and Cooper and Barnett (1972) reported no s i g n i f i c a n t differences i n the over-all h a t c h a b i l i t y of eggs taken from f u l l and p a r t i a l s l a t pens. 6.1.8. Temporal D i s t r i b u t i o n of Embryo Mortality No previous studies have investigated the influence of s l a t s for breeders on embryo mortality. In the present study, s i g n i f i c a n t differences were seen in the incidence of early dead embryos on wood vs. p l a s t i c s l a t s (Table 7). The higher incidence of ED embryos in wood s l a t pens (Table 7) i s d i f f i c u l t to explain. Location in the incubator has been found to influence the development of embryos (Reinhart and Hurnik, 1984). Since s l a t treatments were not blocked for incubator location, the influence of s l a t material on ED mortality could not be i s o l a t e d from the influence of variations within the incubator. 82 DISCUSSION 6.1.9. The Growth, from Hatch to Three Weeks of Age, of 37th, 46th and 56th Week Progeny Seven FPS progeny were l o s t 4 days after hatch during the second growth t r i a l . Water loss between death of the chicks and weighing lowered the f i r s t week weight gain (BWTGN-1) of the progeny group (Table 8 ) . Despite differences i n weight gain and feed intake, no one progeny group had improved weekly or ov e r - a l l feed conversion due to parental s l a t material or s l a t coverage. The r e s u l t s of t h i s study do not support the hypothesis that the progeny of p l a s t i c s l a t breeders grow more e f f i c i e n t l y than those of wood s l a t breeders. The s i g n i f i c a n t parental pen r e p l i c a t i o n effect i n the second week feed intake resulted from the high feed intake of progeny of breeders in one r e p l i c a t e and low feed intake of progeny of breeders i n two r e p l i c a t e s . The r e p l i c a t i o n e f f e c t i n the ov e r - a l l feed intake i s due to the low feed intake of progeny of breeders in one r e p l i c a t e . The r e p l i c a t i o n effects mentioned resulted in corresponding r e p l i c a t i o n effects in feed conversion. There i s no •apparent re l a t i o n s h i p between the location of parental pens and feed intake of progeny, therefore the r e p l i c a t i o n effects may be random. 83 DISCUSSION 6.1.10. Growth, from Hatch to Six Weeks of Age, of 56th Week Progeny Although differences were s i g n i f i c a n t for the t h i r d (BWTGN-3) and sixth (BWTGN-6) week weight gain, only the sixth week feed conversion (FC-6) was affected by parental s l a t material and s l a t coverage (Table 9). Variations in egg weight could not have caused the differences seen in Table 9 since hatching egg weight was r e s t r i c t e d to 66-78 grams, and the mean hatching body weight was equal for a l l s l a t type groups. This s l a t type ef f e c t may be random. 6.1.11. Conclusions Over-all egg recovery was higher from b r o i l e r breeders on p a r t i a l s l a t s , regardless of s l a t material, than from breeders on f u l l s l a t s (Table 1). The ov e r - a l l egg recovery from breeders on f u l l s l a t s was affected by s l a t material: breeders on f u l l wood slat s (FWS) had s i g n i f i c a n t l y higher egg numbers than those o n ' f u l l p l a s t i c s l a t s (FPS). The biweekly egg recovery generally r e f l e c t e d over-all. egg recovery. There i s no apparent explanation for the s i g n i f i c a n t r e p l i c a t i o n e f f e c t on egg recovery during three lay periods. PWS and FPS pens had higher incidence of f l o o r eggs during two lay periods; during one lay period, PWS, FPS and PPS pens had higher incidence of f l o o r eggs (Table 2 ) . 84 DISCUSSION However, the o v e r - a l l incidence of f l o o r eggs was not i n f l u e n c e d by s l a t s . Low egg production on f u l l s l a t s (Table 1) was f u r t h e r lowered by higher o v e r - a l l incidence of cracked nest eggs (Table 4). The s i g n i f i c a n t r e p l i c a t i o n e f f e c t on the incidence of cracked nest eggs during one l a y per i o d was thought to be random. The p r o p o r t i o n of " s e t t a b l e " eggs, based on the pr o p o r t i o n of non-cracked nest eggs, was higher f o r PWS and PPS eggs than f o r FWS or FPS eggs, and was higher f o r FWS than FPS eggs (Table 5). S l a t m a t e r i a l and s l a t coverage d i d not s i g n i f i c a n t l y i n f l u e n c e f e r t i l i t y and TES or FES h a t c h a b i l i t y (Table 6). Only the incidence of ED embryos was i n f l u e n c e d by s l a t s (Table 7). The incidence of ED embryos was higher on wood than on p l a s t i c s l a t s . When the i n f l u e n c e of p a r e n t a l s l a t s on the growth of 37th, 46th and 56th week progeny was examined, i t was found t h a t FPS progeny had lower f i r s t week weight gain (BWTGN-1) than the other progeny groups (Table 8). This was l i k e l y due to moisture l o s s when 7 FPS progeny were l o s t during the second growth t r i a l . D i f f e r e n c e s were seen i n feed intake of the progeny, however the weekly and o v e r - a l l feed conversion was not i n f l u e n c e d by p a r e n t a l s l a t treatment. The s i g n i f i c a n t p a r e n t a l pen r e p l i c a t i o n e f f e c t on the 85 DISCUSSION second week and ov e r - a l l feed intake and feed conversion were thought to be random. Only the t h i r d week (BWTGN-3) and sixth week (BWTGN-6) weight gain and sixth week (FC-6) feed conversion of 56th week progeny were influenced by slats (Table 9). PWS and FPS progeny had higher t h i r d week weight gain (BWTGN-3) than PPS progeny. During the sixth week, FWS and PWS progeny had higher weight gain than FPS and PPS progeny. The sixth week feed conversion (FC-6) of FWS, PWS and PPS progeny was better than that of FPS progeny. 6.2. THE INFLUENCE OF BREEDER AGE. 6.2.1. F e r t i l i t y Previous studies indicate that f e r t i l i t y , l i k e egg production, i s highest during the f i r s t six months of production. When the f i r s t f e r t i l i t y t r i a l was performed at 37 weeks of age, f e r t i l i t y was at a respectable 96.7% (Table 10), which i s t y p i c a l of a well-managed fl o c k . Peak f e r t i l i t y at about 37 weeks of age i s t y p i c a l of b r o i l e r breeder f l o c k s . Andrews et a l . (1988), Kirk et a l . (1980), Parkhurst (1974) and Tomhave (1958) detected peak f e r t i l i t y at about the same age. Reinhart and Hurnik (1984) found that the f e r t i l i t y of eggs l a i d by breeders was s i g n i f i c a n t l y higher (P<0.001) at 86 DISCUSSION 33-35 weeks of age than at 50-52 weeks of age. In the present study, f e r t i l i t y at 50 weeks of age was also s i g n i f i c a n t l y lower than at 37 weeks of age. Previous studies have shown that average egg weight increases as production progresses (Kirk et a l . , 1980; Mather and Laughlin, 1979; McNaughton et a l . , 1978). Furthermore, others have shown that eggs which were produced early and late during the production year, as well as, in the extreme weight classes did not hatch as well (Tindell and Morris, 1964; Halbersleben and Mussehl, 1922). The correlation between egg weight and f e r t i l i t y l evels i s i n d i c a t i v e of behavioral and physiological changes i n domestic fowls during the reproduction cycle. Low f e r t i l i t y in the early part of the reproductive cycle may be due to irr e g u l a r male mating a c t i v i t y (Tindell and Morris, 1964) , or poor semen quality (Moreng and Avens, 1985). The decline in f e r t i l i t y late in the reproductive cycle, as was seen in the present study (Table 10), may be attributed to the decrease in the number of males producing semen and decline in i n d i v i d u a l semen production, as well as the advancing age of the hen (Moreng and Avens, 1985). In the present study, no d i s t i n c t i o n was made between the influence of advancing male or female age. Foot and leg problems have been found to occur more frequently among layers on sloping wire f l o o r when compared 87 DISCUSSION wit h deep l i t t e r f l o o r s (Simonsen et a l . , 1980). Foot and leg problems could i n h i b i t mating. There appeared to be minimal foot and l e g problems during the l a y i n g p e r i o d i n t h i s study. 6.2.2. H a t c h a b i l i t y of T o t a l Eggs Set (TES) and F e r t i l e Eggs (FES) H a t c h a b i l i t y u s u a l l y reaches a peak at about the same time as seen f o r egg production and f e r t i l i t y , and then slowly d e c l i n e s . The l e v e l of t o t a l h a t c h a b i l i t y (TES) i n t h i s study was w i t h i n normal range of the t y p i c a l f l o c k at peak (Table 10) . However, the drop at 42 weeks and l a t e r was s i g n i f i c a n t and more dramatic than expected. The breeder age x s l a t m a t e r i a l x s l a t coverage I n t e r a c t i o n i n t o t a l h a t c h a b i l i t y (TES) i s d i f f i c u l t to e x p l a i n . The breeder age x s l a t m a t e r i a l i n t e r a c t i o n i s due to a dramatic decrease i n t o t a l h a t c h a b i l i t y (TES) of eggs of p l a s t i c s l a t breeders at 42 weeks of breeder age. The drop i n TES h a t c h a b i l i t y at 50 and 56 weeks of breeder age co i n c i d e d with a decrease i n f e r t i l i t y at the same age (Table 10) . The d e c l i n e i n the h a t c h a b i l i t y of f e r t i l e eggs (FES) at 42 weeks of age apparently r e s u l t e d from an increase i n the incidence of e a r l y dead, l a t e dead embryos, pipped a l i v e 88 DISCUSSION and p i p p e d dead embryos (Table 11) . There was a f u r t h e r s i g n i f i c a n t i n c r e a s e i n t h e i n c i d e n c e of e a r l y dead and l a t e dead embryos a t 56 weeks of b r e e d e r age, c o i n c i d i n g w i t h a d e c r e a s e i n FES h a t c h a b i l i t y . The n e x t s e c t i o n w i l l d i s c u s s the f a c t o r s t h a t were thou g h t t o i n c r e a s e embryo m o r t a l i t y and, t h e r e f o r e lower h a t c h a b i l i t y . 6.2.3. Temporal D i s t r i b u t i o n o f Embryo M o r t a l i t y As t h e b r e e d e r s aged and egg p r o d u c t i o n dropped, more egg c o l l e c t i o n s were r e q u i r e d f o r subsequent h a t c h e s . Thus, eggs were s t o r e d f o r l o n g e r p e r i o d s . D u r i n g t h e f i r s t t h r e e h a t c h t r i a l s , eggs were c o l l e c t e d f o r t h r e e c o n s e c u t i v e days and i n c u b a t e d one day a f t e r t h e l a s t c o l l e c t i o n day. For the f o u r t h t r i a l , eggs were c o l l e c t e d f o r t h r e e c o n s e c u t i v e days and i n c u b a t e d f o u r days a f t e r t h e l a s t day of i n c u b a t i o n . D u r i n g t h e f i f t h t r i a l , eggs were c o l l e c t e d f o r f i v e c o n s e c u t i v e days and a s i x t h day f o u r days l a t e r , and i n c u b a t e d t h e day a f t e r t h e s i x t h c o l l e c t i o n day. I n t h e f i r s t t h r e e t r i a l s , eggs c o l l e c t e d d u r i n g t h e f i r s t day were i n s t o r a g e f o r t h r e e days; i n t h e f o u r t h t r i a l , f i v e days; and i n t h e l a s t t r i a l , n i n e days. S t o r a g e of eggs has been shown t o reduce h a t c h a b i l i t y by i n c r e a s i n g the number of embryonic deaths a t a l l s t a g e s i n i n c u b a t i o n and by i n c r e a s i n g t o t a l i n c u b a t i o n p e r i o d 89 DISCUSSION (Mather and Laughlin, 1976). It has also been shown that the length of egg storage i s d i r e c t l y proportional to the retardation of growth and number of malformed embryos regardless of breeder age (Mather and Laughlin, 1979). The increasing length of egg storage as the study progressed could be p a r t l y responsible for the decline in hatchability as the breeders aged. Generally, ED and LD embryos have higher frequency than MD embryos. In young breeder flocks, the incidence of ED, MD and LD i s about 3.0%, 0.5% and 2.0%, respectively. In older flocks, the corresponding values are 5.0-7.0%, 1.0-1.5% and 3.0-4.0% (Roberson and McDaniel, 1989). Sudden onset of cold weather may be p a r t i a l l y responsible for the sudden increase in embryonic mortality during the second hatch t r i a l (Table 11). It i s a well-known fact that extreme c h i l l i n g of f e r t i l e eggs during storage causes embryonic mortality throughout incubation. In t h i s p a r t i c u l a r case, the influence of ambient temperature on embryo mortality would be d i f f i c u l t to distinguish from that of breeder age. Kirk et a l . (1980) and Reinhart and Hurnik (1984) have concluded that larger eggs hatch better at low humidity settings. Most of the eggs l a i d by older breeders would therefore hatch better under humidity settings lower than the optimum for eggs l a i d by younger breeders. The low DISCUSSION surface-to-volume r a t i o in large size eggs necessitates a low humidity setting to allow adequate gas exchange and water loss across the egg s h e l l needed for embryonic development. In the present study, RH was generally set at about 70% during days 1-18 and about 80% during days 19-21, but humidity readings fluctuated for short periods of time. The humidity setting was d i f f i c u l t to regulate, much less re-set to compensate for the increase i n egg s i z e . High humidity i s known to increase embryonic mortality throughout incubation (Rosenberg, 1989), as well as lower hat c h a b i l i t y . The higher incidence of ED embryos from eggs of 50-week old breeders compared to eggs of 37-week old breeders (Table 11) could be due to increased storage periods. Reinhart and Hurnik (1984) reported s i g n i f i c a n t l y higher (P<0.001) late embryo (LD) mortality during days 19-21 in eggs from 50-52 week old breeders compared with those from 33-35 week old breeders. Malformations and malpositions were found to be the most common form of mortality. In addition, they observed that the incidence of late dead embryos was s i g n i f i c a n t l y higher i n extra large eggs (69.6 grams) than i n smaller sized eggs (59.3-65.6 grams). It was suggested that the predominance of larger eggs was responsible for the s i g n i f i c a n t increase in the incidence of late dead embryos when breeders were 50-52 91 DISCUSSION weeks of age. The s i g n i f i c a n t increase in egg size with breeder age in the present study (Appendix Table 4) may explain the s i g n i f i c a n t increase in the incidence of LD embryos at 50 weeks of breeder age (Table 11). In the determination of LD embryos, no d i s t i n c t i o n was made between malformations and malpositions. Malpositions can be caused by several factors, some of which are f a i l u r e to turn eggs, n u t r i t i o n a l d e f i c i e n c i e s , excessively old hens, genetic problems or stale sperm (Rosenberg, 1989) . The increasing length of egg storage as the breeders aged may yet be another factor. None of the f i r s t two factors mentioned could have possibly influenced the present study. The other factors, or a combination thereof, could have resulted i n the increased incidence of LD embryos (Table 23). According to Rosenberg (1989) , malformations are usually not related to incubation, but r e s u l t from genetics, mating, n u t r i t i o n and setting eggs upside down. The influence of factors mentioned on the incidence of malformations in the present study was not determined. Reinhart and Hurnik (1984) reported that the proportion of late-removal chicks was s i g n i f i c a n t l y higher when breeders were 50-52 weeks than at 33-35 weeks of age. They suggested that larger eggs require longer incubation time than smaller eggs. Thus, as breeders age and produce larger 92 DISCUSSION eggs, a greater proportion of the eggs would require longer incubation. The late-removal chicks that Reinhart and Hurnik (1984) referred to correspond to PA embryos in the present study. Most of these embryos would have hatched l a t e r i f allowed more time in the incubator. In agreement with the above findings, the incidence of PA embryos was s i g n i f i c a n t l y higher at 50 weeks than at 37 weeks of breeder age. The increase i n the incidence of pipped dead embryos at 42 weeks of breeder age may be due to the onset of cold weather during egg c o l l e c t i o n , as well as the fluctuation i n r e l a t i v e humidity. To at t a i n optimum hatchability, adjustments should be made for the increase in the incubation time for eggs of older breeders. Several hatch p u l l s can be done so early-hatching chicks do not stay too long in the incubator and get dehydrated. 6.2.4. Growth, from Hatch t o Three Weeks of Age, o f 37th, 46th and 56th Week Progeny The s i g n i f i c a n t increase i n the hatching weight of 46th and 56th week progeny from that of the 37th week progeny (Table 12) was most l i k e l y due to the increase in hatching egg weights (Appendix Table 4). 93 DISCUSSION Pone et a l . (1985) reported that hatches at 27, 42 and 52 weeks of breeder age resulted in s i g n i f i c a n t increases i n the hatching weight of progeny at 42 and 52 weeks of breeder age. The present study indicates that the s i g n i f i c a n t differences in body weight had disappeared by as early as one week of age (Table 12). Numerous studies have shown that the age to which the body weight advantage could extend i s variable and could be influenced by: (a) the breed involved (Kosin et a l . , 1952; Wiley, 1950), (b) the sex of the chicks (Gardiner, 1973; M e r r i t t and Gowe, 1965; T i n d e l l and Morris, 1964; Kosin et a l . , 1952), (c) whether the chicks were raised separately according to egg weight (Gardiner, 1973; T i n d e l l and Morris, 1964) and (d) the type of f l o o r i n g (Pone et a l . , 1985) . A high correlation has been reported between hatching or day-old weight and body weight during the e a r l i e r weeks of growth (Gardiner, 1973; Kosin et a l . , 1952; Wiley, 1950; Upp, 1928). Therefore, one would expect the 37th week progeny to have been the l i g h t e s t at one week of age. Instead, there were no s i g n i f i c a n t differences in the f i r s t week body weight (BWT-1) of the progeny groups because the 37th week progeny had higher f i r s t week weight gain (BWTGN-1) . 94 DISCUSSION When the hatching weights were standardized to remove the i n f l u e n c e of egg s i z e and hatching weight of c h i c k s on growth, d i f f e r e n c e s i n f i r s t week weight gain were not e l i m i n a t e d , while some d i f f e r e n c e s i n the second week feed conversion (FC-2) and a l l d i f f e r e n c e s i n the t h i r d week (FC-3) feed conversion were e l i m i n a t e d . This may be an i n d i c a t i o n t h a t , independent of egg weight, the progeny of younger breeders u t i l i z e feed more e f f i c i e n t l y than the progeny of older breeders, and t h i s e f f e c t disappears as progeny age. I t has been reported that the t r a n s f e r of l i p i d s from yolk to ch i c k l i v e r during embryogenesis . and s h o r t l y a f t e r hatch i s not as e f f i c i e n t i n the progeny of younger breeders (Noble and T u l l e t t , 1989). While the progeny of older breeders can adequately u t i l i z e fat' both from d i e t and remnant y o l k , the progeny of younger breeders have to r e l y l a r g e l y on d i e t a r y f a t f o r energy. This e f f e c t i s demonstrated by higher feed conversion of the 37th week progeny w i t h adjusted hatching weight (Table 13). The p o s s i b l e i n e f f i c i e n t u t i l i z a t i o n of yolk may have r a i s e d the feed conversion of the 37th week progeny u n t i l the second week of growth, r e s u l t i n g i n higher o v e r - a l l feed conversion f o r t h i s progeny group. 95 DISCUSSION The significance of the r e p l i c a t i o n effect in the second week and o v e r - a l l feed intake and feed conversion was discussed in Section 6.1.9. 6.2.5. C o n c l u s i o n s F e r t i l i t y declined s i g n i f i c a n t l y at 50 and 56 weeks of breeder age (Table 10). The h a t c h a b i l i t y of t o t a l eggs set decreased at 42, 50 and 56 weeks of breeder age, with a dramatic decrease i n the h a t c h a b i l i t y of eggs of 42-week old - p l a s t i c s l a t breeders. The h a t c h a b i l i t y of f e r t i l e eggs decreased s i g n i f i c a n t l y at 42 and 56 weeks of breeder age. The influence of advancing female breeder age was not distinguished from that of advancing male breeder age. The incidence of ED and LD embryos increased s i g n i f i c a n t l y at 42 and 56 weeks, and that of PA and PD embryos at 42 weeks of breeder age (Table 11). The increase in ED, LD, PA and PD mortality at 42 weeks of breeder age was thought to be due to the onset, of cold weather during egg c o l l e c t i o n for the said hatch t r i a l . Increases in embryo mortality were also attributed to the increasing length of egg storage and d i f f i c u l t y in regulating humidity. As breeders aged, the hatching weight (H-BWT) of progeny increased s i g n i f i c a n t l y (Table 12). The 37th week progeny gained more than the other progeny groups during the f i r s t week of growth, and had the least favorable feed 96 DISCUSSION conversion throughout the three-week growth period. The standardization of hatching body weight eliminated some differences in the second week and over-all feed conversion, but not i n the f i r s t week weight gain (Table 13). With adjusted hatching weight, differences in feed conversion disappeared by the t h i r d week of growth. Differences during the f i r s t two weeks of growth resulted in differences in o v e r - a l l feed conversion (Table 13). • The f i r s t week feed conversion of 37th progeny was highest, followed by that of 46th week progeny, while that of 56th week progeny was lowest. The second week and ov e r - a l l feed conversion of ,37th week progeny was higher than that of the other two progeny groups. 6.3. THE INFLUENCE OF SEX OF PROGENY In mammals, as well as in birds, males exhibit a greater increase in early growth than females, and thi s i s due, i n part, to higher secretion levels of androgens (Mendel, 1980). Since the hatching weights of male and female progeny of 56-week old breeders were p r a c t i c a l l y equal, the differences in body weight and weight gain from two to 6 weeks of age (Table 14) could be attributed to di f f e r e n t hormone leve l s , and not to any advantage in hatching egg weight. Table 14 shows that although male progeny consumed DISCUSSION s i g n i f i c a n t l y more f e e d from week 3 t o 6 and o v e r - a l l , male progeny u t i l i z e d f e e d more e f f i c i e n t l y o n l y d u r i n g the t h i r d week of growth. R e s u l t s from a study by G a r d i n e r (1973) i n d i c a t e t h a t when male and female b r o i l e r s were d e r i v e d from eggs of t h e same w e i g h t , the males had c o n s i s t e n t l y h i g h e r weekly body w e i g h t s from one week t o e i g h t weeks of age. The o v e r - a l l f e e d c o n v e r s i o n f o r the e n t i r e eight-week s t u d y p e r i o d was s l i g h t l y h i g h e r f o r males than f o r f e m a l e s , b u t the o p p o s i t e was seen i n Table 14. There seems t o be no e x p l a n a t i o n f o r t h e s i g n i f i c a n t sex of progeny x s l a t m a t e r i a l x s l a t coverage i n t e r a c t i o n i n t he second week body w e i g h t (BWT-1) and weight g a i n (BWTGN-1). 6.3.1. Conclusions From t h e t h i r d t o t h e s i x t h week of growth, t h e male 56th week progeny had h i g h e r body w e i g h t and w e i g h t g a i n (Table 14). Male progeny a l s o had h i g h e r o v e r - a l l w e i g h t g a i n (C-BWTGN). Male progeny however, had b e t t e r (lower) f e e d c o n v e r s i o n than female progeny o n l y d u r i n g the t h i r d week of growth. 98 7. BIBLIOGRAPHY Andrews, L.D., L. Stamps, Z. Johnson and A.R. Arbabi, 1988. 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The i n t e r a c t i o n o f cage s i z e , cage l e v e l , s o c i a l d e n s i t y , f e a r f u l n e s s , and p r o d u c t i o n of S i n g l e Comb White Leghorns. P o u l t r y S c i . 55:1922-1926. Shanawany, M.M., 1987. H a t c h i n g w e i g h t i n r e l a t i o n t o egg w e i g h t i n d o m e s t i c b i r d s . World's P o u l t . S c i . J . 43 (2) :105-115. Simonsen, H.B., K. V e s t e r g a a r d and P. W i l l e b e r g , 1980. The e f f e c t of f l o o r t y p e and d e n s i t y on egg l a y e r s . P o u l t r y S c i . 59:2202-2206. 102 BIBLIOGRAPHY Skoglund, W.C, K.C Seegar and A.T. Ringrose, 1952. Growth of b r o i l e r chicks hatched from various sized eggs when reared in competition with each other. Poultry S c i . 31:796-799. The Technical Centre for A g r i c u l t u r a l and Rural Cooperation, 1987. Manual of Poultry Production in the Tropics. English ed. R.R. Say, translator. CAB International, Oxon, UK. T i n d e l l , D. and D.R. Morris, 1964. The effects of egg weight on subsequent b r o i l e r performance. Poultry S c i . 43:534-538. Tomhave, A.E., 1958. F e r t i l i t y and h a t c h a b i l i t y of eggs produced by New Hampshire breeders during t h e i r f i r s t 365 days of production. Poultry S c i . 37:27-29. Upp, C , 1928. Egg weight, day old chick weight and rate of growth in single comb Rhode Island Red chicks. Poultry S c i . 7:151-155. Wallace's F., 1962. Slat f l o o r s for poultry? 87:49. Wallace's F., 1958. Slatted f l o o r s for poultry houses. 83:44-45. Wiley, W.H., 1950. The influence of egg weight on the pre-hatching and post-hatching growth rate in the fowl. I I : Egg weight - chick weight r a t i o s . Poultry S c i . 29:595-604. Wilson, W.O., 1974. Housing. Pages 218-247 i n : American Poultry History, 1823-1973. 1st ed. O.A. Hanke, J.L. Skinner and J.H. Florea, ed. American Printing and Publishing, Inc., Madison, WI. Wilson, W.O. and P. Vorha, 1980. Poultry management. Pages 641-657 i n : Animal Agriculture: The Biology, Husbandry and Use of Domestic Animals. 2nd ed. H.H. Cole and W.N. Garrett, ed. W.H. Freeman and Company, San Francisco, CA. Yao, T.S., 1959. The influence of s l a t t e d f l o o r and l i t t e r f l o o r on the genetic v a r i a t i o n i n chickens. Poultry S c i . 38:1472-1473. 103 104 APPENDIX Appendix Table 1. Weekly Egg Recovery on Different Slat Types 1 Breeder Age (Weeks) Slat Type 2 Standard Error of the Mean FWS PWS FPS PPS 24 4 . 4 4 . ,2 2. .9 3. .8 0. .87 25 14. .0 15. .9 9. .3 16. .0 1. .36 26 31, .5 33, .8 23. .5 35. .3 1. .50 27 52. .9 57 . 6 43. .4 54. .4 1. .56 28 64. . 4 67. .0 53, .0 63. .8 2. .42 29 68, .8 73. .9 57. .6 70. .8 1. .98 30 68. .6 73. .7 59. . D 71. ,7 1. .78 31 70; .0 77, .0 62. .1 71. .4 1. .83 32 72. .8 79. .9 61. .2 76. .3 1, .46 33 71.. .2 77. .7 63. .3 78. .6 1, .32 34 71 , . 1 77 . 7 61. .6 77 . 0 1, .34 35 70. .8 76. .2 61. .2 76. .6 1, .43 36 68. .5 ' 72. . 1 59. .6 74. .3 1, .64 37 64 . 7 72. .9 59, .4 73. .0 1, .72 38 65, . 1 70. .5 59, .3 70, .4 1, .43 39 65. .7 69, . 4 58 , .8 71. .4 2, .09 40 63, .0 68. .2 58, .2 67. .8 . 1, .77 41 63, .2 67, .8- 54 , .0 65. .8 1. .38 42 60 , .0 66. . 1 54 , .0 62. .7 1, .70 43 59, .6 68, .5 52, .9 68. .0 1, .83 44 58 , .4 64. .4 54 , .2 64 . 2 1, .99 45 59, . 1 63, .0 50, .1 64. .6 2, .80 46 56, .0 62, .1 50, .8 62. .9 1, .71 47 54, .6 59, .5 49, .7 62 , .2 2, .05 4 8 52, .7 57, .9 47, .6 60. .5 1. .72 49 51, .8 56, .9 47, .8 60, .7 1, .80 50 51, .0 55, .5 47 , .2 58, .7 •1. .61 51 49, .7 53, .7 44 . 8 56. .3 1, .37 52 46, .0 52, .9 44, .2 53, .3 1, .82 53 48, .1 54, .8 45, .1 53. .1 2, .01 54 47, . 1 50, .9 44, .0 54. .3 1. .80 55 47 , .0 52, .4 43, .4 53. .8 1, .77 1 2 Percent hen-day egg recovery. FWS = f u l l wood slats;.PWS = p a r t i a l wood sla t s ; FPS = f u l l p l a s t i c s l a t s ; PPS = p a r t i a l p l a s t i c s l a t s . 105 APPENDIX Appendix Table 2. Weekly Egg Recovery on Wood vs. P l a s t i c S l a t s 1 Breeder Slat Material Standard Age Error (Weeks) Wood Pl a s t i c of the Mean 24 4.2 3.3 0.61 25 15.0 12.7 0.96 26 32 .7 29.4 1. 06 27 55.3 48.9 1.11 28 65.7 . 58.4 1.71 29 71.3 64 .2 1 . 40 • 30 71.2 65.6 1.26 31 73.5 66.8 1 .29 32 76.4 68.7 1 .03 33 74.5 71.0 0 .94 34 74 . 4 69.3 0.95 35 73.5 68 .9 1 .01. 36 70.3 66.9 1 .16 37 68 .8 66.2 1 .22 38 67 .8 64 . 8 1.01 39 67 .6 65 .1 1.48 40 .65.6 63.0 1 .25 41 65 .5 59.9 . 0.98 42 63 .1 58.3 1.20 43 64 . 1 60.5 1 .30 44 61 .4 59 .2 1 . 41 45 61 .0 57.4 1.98' 46 59.0 56.8 1.21 47 57 .0 56.0 1.45. 48 55 .3 54 .0 1.21 4 9 54 . 4 54 .3 1 .27 50 53.3 53 .0 1 .14 51 • 51.7 50 .5 0 .97 52 49.5 48.8 1.29 53 51.5 49.1 1 .42 54 49.0 49.2 1 .27 55 49 . 7 48.6 • 1 .25 Percent hen-day egg recovery. 106 APPENDIX Appendix Table 3. Weekly Egg Recovery on F u l l vs. P a r t i a l Slats Breeder Slat Coverage Standard Age Error (Weeks) F u l l P a r t i a l of the Mean 24 3.6 4.0 0.61 25 11.7 16.0 0.96 26 27 .5 34 .6 1.06 27 48.2 56.0 1.11 28 58.7 65.4 1.71 29 63 .2 72.3 1.40 30 64 .1 72.7 1.26 31 66.0 74 .2 1.29 32 67 .0 78.1 1.03 33 67.3 78 .2 0.93 34 66.3 77 .3 0.95 35 66.0 76.4 1.01 36 64 . 0 73.2 1.16 37 62 .0 73.0 1 .22 38 62.2 70 . 4 1.01 39 • 62.2 70.4 1 .48 40 60 .6 68 .0 1.25 41 58 .6 66.8 0.98 42 57 .0 64 . 4 1 .20 43 56 .3 68 .3 1.30 44 56.3 64 .3 1.41 45 54 .6 63.8 1 . 98 46 53.4 62.5 1 .21 47 " 52 .2 60 . 9 1 . 45 43 50 .2 59.2 1.21 49 49.8 58 . 8 1 .27 50 49.1 57 . 1 1.14 51 47 .3 55.0 0.97 52 45.1 53.1 1 .29 53 46.6 54 .0 1 . 42 54 45.6 52.6 1 .27 55 45.2 53.1 1 .25 Percent hen-day egg recovery. 107 APPENDIX Appendix Table 4. The Influence of Breeder Age on Hatching Egg Weight Hatching Egg Variable Weight (g) Breeder Age (Weeks) 42 67.9 d 46 68.7 C 50 '• 70.6 D 56 71.8 a SEM1 . 0.21 Slat Material (M) Wood 69.8 a P l a s t i c 69.6 a SEM1 0.15 Slat Coverage (M) F u l l 69.8 a P a r t i a l 69.7 a SEM1 0.15 Slat Type (M x C ) 2 FWS 70.0 a PWS 69.8 a FPS ' 69.6 a PPS 69.7 a SEM1 0.21 1 Standard error of the mean. 2 FWS = f u l l wood s l a t s ; PWS = p a r t i a l wood s l a t s ; FPS = f u l l p l a s t i c s l a t s ; PPS = p a r t i a l p l a s t i c s l a t s . a,b,c,d Means followed by d i f f e r e n t l e t t e r s within one variable are s i g n i f i c a n t l y d i f f e r e n t (P<0.05). 108 APPENDIX Appendix Table 5. Composition of Chick. Starter Diets Energy Source Ingredient(g/kg) Fat Starch Corn 539.20 339.32 Soybean meal 279.00 287.10 Wheat 132.61 235.02 Corn starch 100.00 Calcium phosphate 17.01 17.37 Limestone 8.51 8.09 Iodized s a l t 5.00 5.00 Vitamin/mineral premix 2.50 2.50 DL Methionine 0.42 0.40 Alphacel 15.75 5.20 1000.00 1000.00 Calculated analysis: Protein (%) 19.00 19.00 ME (kcal/kg) 2800 2800 109 APPENDIX Appendix Table 6. Composition of Developer Diets Energy Source Ingredient (g/kg) Fat Starch Corn 423.71 415.87 Wheat middlings 156.86 201.60 Barley' 200.00 79.44 Soybean meal 148.65 166.29 Wheat 23.84 Corn starch 100.00 Animal tallow 10.00 Calcium phosphate 18.27 17.62 Limestone 7.82 8.32 Iodized s a l t 5.00 5.00 Vitamin/mineral premix 5.00 5.00 DL Methionine 0.85 0.86 1000.00 1000.00 Calculated analysis: Protein (%) 15.00 15.00 ME (kcal/kg) 2700 2700 110 APPENDIX Appendix Table 7. Composition of Breeder Diets Energy Source Ingredient (g/kg) Fat Starch Corn 685. ,28 570. 69 Soybean meal 200. ,14 ' 213. ,13 Corn starch 100. ,00 Animal tallow 10. .33 5. .68 Herring meal 7. .50 14. ,08 Limestone 65. .07 64, .81 Calcium phosphate 20, .27 20. .09 Iodized s a l t 5, .00 5, .00 Vitamin/mineral premix 5. .00 5. .00 DL Methionine 0 .92 1, .14 L Lysine 0 .49 0. .38 1000 .00 1000 .00 Calculated analysis: Protein (%) 15.50 15.50 ME (kcal/kg) 2850 2850 111 

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