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The Effects of Dietary Protein Levels, Ahemeral Light and Dark Cycles, and Intermittent Photoperiods on the Performance of Chicken Broiler Parent Genotypes1
The Effects of Dietary Protein Levels, Ahemeral Light and Dark Cycles, and Intermittent Photoperiods on the Performance of Chicken Broiler Parent Genotypes1 F. G. PROUDFOOT Research Station, Agriculture Canada, Kentville, Nova Scotia, Canada B4N 1J5 (Received for publication, July 9, 1979)
1980 Poultry Science 59:1258-1267 INTRODUCTION There are a n u m b e r of reports in t h e literature involving t h e evaluation of diets with different protein levels fed to laying birds (Gleaves et al, 1 9 7 7 ; Patel and McGinnis, 1 9 7 7 ; Ivy and Gleaves, 1976). However, all of this research involved table egg p r o d u c t i o n stock and, t h u s , t h e results may n o t be applicable to meat parent g e n o t y p e s used for t h e p r o d u c t i o n of hatching eggs. F u r t h e r m o r e , these egg p r o d u c t i o n stocks were fed ad libitum during t h e laying period whereas the a m o u n t of feed offered m e a t parent stocks is restricted, being based o n gains in b o d y weights and egg p r o d u c tion. It has been reported t h a t ahemeral light-dark cycles can be used t o alter t h e p e r f o r m a n c e of t h e domestic fowl (Cooper and Barnett, 1 9 7 6 ; Foster, 1 9 6 8 , 1 9 6 9 ; and Morris, 1 9 7 3 ) . As much of t h e early e x p e r i m e n t a t i o n was conducted with commercial egg p r o d u c t i o n stocks, it was desirable to evaluate t h e effects of these
1
Contribution No. 1670.
ahemeral light-dark cycles on m e a t parent g e n o t y p e s . Foster ( 1 9 6 8 ) reported that egg p r o d u c t i o n was increased by t h e lengthening of the day cycle and Morris (1973) indicated t h a t initial egg size was increased and shell strength improved. Morris ( 1 9 7 3 ) also reported t h a t egg p r o d u c t i o n was decreased by increasing the length of t h e light-dark cycle. It would be of considerable advantage if early egg size and shell strength, particularly during the later stages of egg p r o d u c t i o n , could be improved for t h e p r o d u c t i o n of hatching eggs and the subseq u e n t p r o d u c t i o n of broiler chickens. T w o e x p e r i m e n t s were c o n d u c t e d . T h e objective of t h e first e x p e r i m e n t was to study t h e effects of feeding breeder diets with t w o calculated protein levels (13.6 and 15.4%) and to s t u d y the effects of c o n t i n u o u s and intermittent p h o t o p e r i o d s involving b o t h conventional and 27-hr ahemeral light-dark cycles. The objective of t h e second experiment was to extend t h e study of 24-hr cycled i n t e r m i t t e n t p h o t o p e r i o d s and c o m p a r e t h e m with 27-hr ahemeral light-dark cycles initiated at different ages and reverted back to 24-hr cycles at t h e same t i m e .
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ABSTRACT Two experiments were undertaken to estimate the effect of: 1) two dietary protein levels (13.6 and 15.4%) in breeder diets fed to commercial meat parent genotypes; and 2) 6 photoperiods involving both 24-hr and 27-hr (ahemeral) day cycles with single stage and intermittent lighting for birds housed in floor pens. It was concluded that the 13.6% protein breeder diet, which provided from 14.8 to 20.9 g of protein per bird per day and from 301 to 425 kcal of ME per bird per day, was adequate to support optimum performance. The ahemeral light treatment 14L:13D used from 168 to 448 days had a depressing effect on egg production and feed efficiency compared with the conventional 24-hr day cycle with 14L:10D light treatment. The 14L:13D treatment, however, did result in increased egg size and improved shell strength. The intermittent light treatments, whether ahemeral or 24-hr cycle, resulted in improved egg weight and shell strength. The ahemeral intermittent treatment (10L:12D:2L:3D) had the effect of depressing fertility and hatchability, whereas the 24-hr intermittent photoperiod (10L:9D:2L:3D) resulted in fertility and hatchability equal to or better than other treatment. It was concluded that the 24-hr intermittent light treatment (10L:9D:2L:3D) supported performance which was equal to or better than other light treatments including the 27-hr ahemeral day cycles. Furthermore, ahemeral day cycles resulted in large numbers of eggs laid on the floor (Ca. 50%). First and second order interactions appeared to be of minor importance.
PROTEIN, PHOTOPERIOD, AND EGG PRODUCTION
197 3). At 154 days of age each male p o p u l a t i o n was reduced at r a n d o m to a m a x i m u m of 5 males with up to 5 males in reserve. During t h e brooding and rearing period (1 t o 168 days) t h e p h o t o p e r i o d was decreased in weekly d e c r e m e n t s of 15 min from a 17-hr day until a 14-hr day was attained at 168 days of age, at which t i m e adult light t r e a t m e n t s were initiated. Six different adult p h o t o p e r i o d s were compared (Table 2). T r e a t m e n t s 1, 3, and 6 were all on 24-hr cycles with t r e a t m e n t s 1 and 6 differing only in t h a t birds u n d e r t r e a t m e n t 6 were exposed to a c o n t i n u o u s dim light ( < . l lx) and t r e a t m e n t 1 had a t o t a l black-out w h e n the main lights were off. Experiment 2. One h u n d r e d and fifty dozen hatching eggs were o b t a i n e d from each of four commercial breeders to supply four well-known female line genotypes. Male chicks of one g e n o t y p e were obtained t o mate at m a t u r i t y with the four female lines. Fifty-five female chicks from each of t h e four female-line genotypes and 14 male line chicks were r a n d o m l y assigned to one pen in each light controlled zone, so t h a t there were 12 pens of each female-line g e n o t y p e in t h e test building. All stock were given t h e same dietary regimen, using the low protein (13.6%) breeder diet (Table 1). Skip-a-day feeding was started at 4 2
TABLE 1. Composition of the starter, grower, and breeder diets Breeder diets Ingredients
Starter
Grower (%)
Ground corn Ground wheat Ground oats Ground barley Fishmeal (63%) Soybean meal (49%) Dehydrated alfalfa (16%) Ground limestone Dicalcium phosphate Salt (NaCl) Micro-nutrients 3 Calculated analyses: Crude protein ME kcal/kg
20 28 15 15 3 15 1.5 .75 .75 .5 .5 18.4 2885
20 30 20 20 5..5 1..5 .75 1..25 .5 .5
13. 3
Low protein
High protein
15 30 20 20 3 3 2 5 1
15 30 20 16 5 5 2 5 1
•
13.i 2760
15.4 2754
Amount for 1 kg of starter and grower diets contained 5,000 IU vitamin A; 1,000 ICU vitamin D, ; 1 rag vitamin K; 4 mg riboflavin; 20 mg niacin ; 5 mg d-calcium pantothenate; 1 rag folic acid; 5 Mg vitamin B, 2; 50 mg manganese; 40 mg zinc; 5 mg copper; 1 mg iodine. The supplement for the breeder diets was similar but contained 400 mg choline.
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MATERIALS AND METHODS A windowless brooding and rearing house containing 4 8 pens was used for b o t h experim e n t s . T h e t w o e x p e r i m e n t s were c o n d u c t e d concurrently. A service r o o m was located m i d w a y in t h e building and a central alleyway 1.83 m wide e x t e n d e d t h e length of the building with equal n u m b e r s of pens on each side of t h e alleyway. Each block of 4 pens constituted a light controlled zone. T h e general lay-out of the laying house was the same as the rearing house. Experiment 1. Three h u n d r e d dozen hatching eggs were o b t a i n e d from each of t w o commercial breeders to supply t w o well-known female line genotypes. Male day-old chicks of one g e n o t y p e were obtained t o m a t e at m a t u r i t y with t h e female lines. Fifteen chicks of t h e male line g e n o t y p e and 55 chicks of each of the female line genotypes, were r a n d o m l y assigned to two pens within each light z o n e . All stock was fed all-mash diets t h r o u g h o u t the experiment (Table 1). The low p r o t e i n (13.6%) and high protein (15.4%) breeder diets were assigned to each of t w o genotypes within each light z o n e . Skip-a-day feeding was commenced at 4 2 days of age and terminated at 154 days of age when feeding of breeder diets was c o m m e n c e d (Proudfoot and L a m o r e u x ,
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PROUDFOOT TABLE 2. Light treatments in Experiment Light period0 (hr)
1 2 3 4 5 6
24 27 24 27 27 24
14 14 10 + 2 10 + 2 14 14
Duration of special light t r e a t m e n t 0
ill
Treatment
Day cycle (hr)
la
10 13 9 + 3 12 + 3 13 10
(days)
(days)
168-448 168-214 168-448 168-214 168-448 168-448
280 46 280 46 280 280
10 + 2 under light and 9 + 3 under dark periods means lights were on 10 hr, off for 9 hr, on for 2 hr, and off for 3 hr ; similarly 10 + 2 and 12 + 3 means lights were on for 10 hr, off for 12 hr, on for 2 hr and off for 3 hr followed by a repeat of the cycles. When special light treatments were terminated they were reverted back to a 14L:10D day cycle.
days and terminated at 154 days of age when feeding of breeder diet c o m m e n c e d . The • breeder diet was fed according to the schedule described in Table 3. Birds received a 17-hr daylength from 1 to 14 days which was reduced by 10 min weekly until a 14-hr day was reached at 140 days of age. Morris (1973) provided evidence t h a t the 27-hr ahemeral p h o t o p e r i o d cycle resulted in performance which was either equal or superior to o t h e r ahemeral cycles among Leghorn stocks, and it was considered desirable to use this particular ahemeral cycle to c o m p a r e with t h e 24-hr cycle using b o t h constant and i n t e r m i t t e n t p h o t o p e r i o d s . Light t r e a t m e n t s
used in this e x p e r i m e n t were primarily designed t o estimate t h e effects of changing an intermittent light t r e a t m e n t (24-hr cycle) back to a 14L-.10D p h o t o p e r i o d at 238 days of age and to estimate the effects of switching from a 24-hr cycle with a 1 4 L : 1 0 D p h o t o p e r i o d to a 27-hr cycle with a 1 4 L : 1 3 D p h o t o p e r i o d at different ages with a constant age for reverting back to a 1 4 L : 1 0 D light t r e a t m e n t (Table 4 ) . T h e six p h o t o p e r i o d s used were initiated at 141 days of age using i n t e r m i t t e n t lighting of 10L-.9D:2L:3D t h r o u g h o u t t h e laying period as t h e c o n t r o l t r e a t m e n t similar to t r e a t m e n t 3 in Experiment 1 (Table 4 ) . A dim light ( < . l lx) was used t h r o u g h o u t t h e dark period of all
TABLE 3. Feed allotment schedule and dietary protein and energy levels" used during the laying period of Experiments 1 and 2
Frorr i
To
Feed/ bird/ day
155 162 169 176 183 190 197 281 288 309
161 168 175 182 189 196 280 287 308 448
109 118 127 136 145 150 154 150 145 140
Age (days)
Daily protein intake/bird protein diet ( 13.6%)
14.8 16.0 17.3 18.5 19.7 20.4 20.9 20.4 19.7 19.0
Daily ME
High protein diet (15.4%)
(kcal)
16.8 18.2 19.6 20.9 22.3 23.1 23.7 23.1 22.3 21.6
301 325 3 50 375 400 414 425 414 400 386
y&
The two breeder diets (1 3.6% and 15.4% protein) were isocalorie.
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Low intensity light (<1 lx) was used in service area on all treatments except treatment 1.
PROTEIN, PHOTOPERIOD, AND EGG PRODUCTION
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TABLE 4. Light treatments in Experiment 2 a
Treatment
Day cycle (hr)
Light cycle (hr)
1 2 3 4 5 6
24 24 27 27 27 27
10 + 2 10 + 2 14 14 14 14
Dark cycle (hr) 9+ 3 9 + 3 13 13 13 13
Duration of special light treatment' 3 (days)
(days)
140-448 140-238 140-210 158-210 168-210 178-210
308 98 70 52 42 32
treatment groups on a 27-hr cycle. During the adult period feed was allotted as shown in Table 3. The traits measured were the same for both experiments, except that fertility and hatchability were measured once in Experiment 1 and twice in Experiment 2 (Tables 5 and 7). Percentage mortality during the laying period was based on the number of birds housed at 140 days of age. Egg production was recorded on a pen basis throughout the laying period and mean henhoused egg production was calculated from 140 days of age to the end of the experiments. Hatching eggs were designated as suitable for hatching with a minimum individual weight of 47 g. Percentages of hatching eggs laid on 2 days each week were prorated with total eggs laid in each pen. The first day of the first 2 consecutive days that a female pen population reached 50% egg production was used as the age in days to 50% egg production. Feed efficiency was calculated as the kilograms of feed required to produce one dozen eggs. Fertility and hatchability of all eggs set were based on a sample of 150 to 180 eggs from each pen and were measured at 208 days in Experiment 1 and at 224 days and at 308 days in Experiment 2. Percent fertility was based on the candled, incubated eggs after 18 days of incubation and hatchability was calculated as eggs hatched from the number of eggs placed under incubation. The number of broiler chicks per female housed at 140 days was calculated by applying the percent hatchability of all eggs set to the number of hatching eggs produced. The calculation of mean egg weights was
based on weighing eggs laid on 2 consecutive days per week from each pen at 224, 308, and 448 days. Shell strength was measured as the specific gravity of each egg and was a discrete measurement made on a sample of 25 eggs selected at 224, 308, and 448 days of age. Birds were individually weighed at 224, 308, and 448 days of age in both experiments. Experiment 1 was designed as a 6 X 2 X 2 factorial with six photoperiod treatments, two adult dietary treatments, and two genotypes with two replicates. Experiment 2 was designed as a 6 x 4 factorial with six photoperiod treatments and four genotypes with two replicates. For the statistical analyses a split plot model was assumed. Pen means were used in the statistical analyses and percent data were transformed to angles. Standard errors of treatment and genotype means were calculated. RESULTS AND DISCUSSION Genotype Effects. The two genotypes used in Experiment 1 differed significantly for the traits: male mortality; hen-housed egg production; sexual maturity; hatching egg fertility; egg weight; egg specific gravity, and body weight at 308 days of age (Tables 5 and 6). In Experiment 2 the four genotypes differed significantly for hen-housed egg production, hatching egg production, sexual maturity, feed efficiency, hatchability of eggs at 308 days of age, egg weight, and shell strength as measured by the specific gravity method and body weight (Tables 7 and 8). The genotypic differences which occurred among female-line genotypes in both experiments provide evidence that highly divergent
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Light cycles 10 + 2 and dark cycle 9 + 3 means that lights were on for 10 hr, off for 9 hr, on for 2 hr, and off for 3 hr followed by a repeat of the cycle. Treatments 4, 5, and 6 were retained on the 14L:10D treatment until 27 hr cycles commenced; when light treatments were terminated they reverted to a 14L:10D day cycle.
Photoperiod
5.0 2.4 3.6
6.2
4.7 2.2 (1.5) 5.3 2.7 (1.5) 4.7 3.1 (1.5)
31.9 28.4 17.9
32.0
30.7 28.3 (4.2) 33.8 22.7 (1.6) 31.2 25.1 (1.6)
214
448 448
Female (%)
448 214 448
Male (%)
Mortality0 ( 1 4 0 - 4 4 8 days)
130 157 4.7 146 153 1.8 147 152 1.8
124 148 4.7 141 144 1.7 140 144 1.7 4.20 3.65 .18 3.83 3.74 .04 3.80 3.77 .04
3.83
154 155 153 140
3.66 3.69 3.69
145 148 146
egg p r o d u c e d (No.)
147
Feed per dozen eggs produced (kg)
.housed
Hen-housed hatching egg p r o d u c e d (No.)
Hen
177 176 1.1 179 176 .6 176 178 .6
180
176 177 179
Days age a egg p (No.)
genotype, and diet effects on mortality, egg production, feed e fertility, hatchability, of broiler chicks produced in Experiment I
HP, high p r o t e i n ; LP, low protein breeder diets.
SEM, standard error of t h e m e a n with t h e n u m b e r of observations in t h e m e a n s h o w n in parenthesis.
Mortality, fertility, and hatchability means are detransformed from angles t o p e r c e n t b u t standard error of m e a n s
Lower case " d " in 1 4 L : 1 0 D - d designates t h a t a c o n t i n u o u s dim light was not used in light t r e a t m e n t 1 and at 2 t o a 1 4 L ; 1 0 D light cycle. All light t r e a t m e n t s c o m m e n c e d at 1 6 8 days of age.
14L:10D-d 14L.13D 10L.-9D:2L: 3D 4 10L:12D: 2L:3D 5 14L:13D 6 14L:10D SEM ( 8 ) c Genotype A Genotype B SEM (24) Dietary t r e a t m e n t ' ' HP Dietary t r e a t m e n t LP SEM (24)
1 2 3
No.
Age at termination (days)
Light t r e a t m e n t s a
T A B L E 5. The pbotoperiod,
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448 214 448 214 448 448
Photoperiod
14L:10D-d 14L:13D 10L:9D:2L:3D 10L:12D:2L:3D 14L:13D 14L:10D
No.
1 2 3 4 5 6
.14
57.9 57.4
.14
59.5 55.8
.45
56.5 57.1 58.1 57.7 60.0 56.6
days
224
.20
.18
63.2 63.1
.18
65.1 61.2
.16
66.2 66.6
.16
68.7 64.2
.35
65.9 65.4 66.9 67.3 67.6 65.4
63.0 63.0 63.8 63.4 62.9 62.8 889 933 900 921 934 897 7 921 904 2 913 912 2
days
days
days ta\ W
224
448
308
Egg weight
852 842 868 864 868 849 8 862 852 2 857 857 2
days
308
Egg specific
HP, high protein; LP, low protein breeder diets.
SEM, standard error of the mean with the number of observations shown in parenthesis.
Multiply means by 10 —4 and add 1.0 to convert to specific gravity.
Lower case "d" in 14L:10D—d designates that a continuous dim light was not used with light treatment 1; at 214 a 14L:10D light cycle and all light treatments commenced at 168 days of age.
SEM(8) C Genotype A Genotype B SEM (24) Dietary treatment^ HP Dietary treatment LP SEM (24)
Age at termination (days)
Light treatments 3
TABLE 6. The photoperiod, genotype, and diet effects on egg weight, egg specific gravity, and fem
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Photoperiod
448 2 38 210 210 210 210
11.9 3.1 3.2 6.9 14.5 10.9 (4.3) 8.8 9.6 4.8 8.6 (4.3)
(%)
Male
3.2 4.3 6.7 7.3 4.9 7.9 (1.9) 5.8 4.0 8.1 4.8 (1.6)
(%)
Female
Mortality0 ( 1 4 0 - 4 4 8 days)
156 150 146 151 152 153 4.1 146 152 142 165 2.6
Hen-housed egg p r o d u c t i o n (No.) 148 142 139 143 144 146 4.1 135 146 140 154 2.7
Hen housed hatching egg p r o d u c t i o n (No.) 3.63 3.80 3.83 3.66 3.70 3.60 .11 3.83 3.70 3.88 3.41 .07
Feed per dozen leggs produced (kg)
SEM, standard error of the means with the number of observations shown in parenthesis.
Mortality, fertility, and hatchability means are detransformed from angles to percent but standard error of means
Light treatments 1, 2, and 3 commenced at 140 days of age and treatments 4, 5, and 6 commenced at 158, 16 to 14L:10D.
10L:9D:2L:3D 10L:9D:2L:3D 14L:13D 14L:13D 14L:13D 14L:13D SEM ( 8 ) c Genotypes A Genotypes B Genotypes C Genotypes D SEM (12)
1 2 3 4 5 6
No.
Age at termination (days)
Light t r e a t m e n t s 3
TABLE 7. The photoperiod and genotype effects on mortality, egg production, feed efficiency, fertili broiler chicks per hen housed in Experiment 2
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Photoperiod
448 238 210 210 210 210
Age at termination (days)
177 177 176 172 176 171 2.0 178 175 178 169 1.0
Age at 50% egg proiduction (days)
.15
58.1 58.8 58.4 56.5
.34
58.0 58.2 57.6 57.5 57.4 57.4
.22
65.0 65.0 63.4 62.6
.36
64.5 64.4 64.4 63.7 63.1 63.9
(&>
.23
68.9 68.5 66.3 65.9
.37
68.6 67.6 67.3 66.6 67.3 67.2 884 873 911 914 902 908 4 909 908 900 877 4
days
days
days
days
Egg s
224
448
308
Egg weight 224
SEM, standard error of the mean with the number of observations shown in parenthesis.
Multiply means by 10 — * and add 1.0 to convert to specific gravity.
Light treatments 1,2, and 3 commenced at 140 days of age and treatments 4, 5, and 6 commenced at 158,168, a to 14L:10D.
10L:9D:2L:3D 10L:9D:2L:3D 14L:13D 14L:13D 14L:13D 14L:13D SEM (8) c Genotypes A Genotypes B Genotypes C Genotypes D SEM (12)
1 2 3 4 5 6
No.
Light treatments 3
TABLE 8. The photoperiod and genotypic effects on sexual maturity, egg weight, egg specific gravity, an
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PROUDFOOT
In the current study, hatchability and growth of broiler progeny were unaffected by the dietary protein level of breeder diets. Patel and McGinnis (1977) found that a high protein breeder diet had a depressing effect on hatchability and chick growth. However, their high protein diet contained 32% protein fed to a Leghorn population whereas the high protein diet evaluated here had a protein level of 15.4% and was fed to meat parent stock.
A diet x genotype interaction occurred for egg weight at 224 days, 44 day female body weights, and age at 50% egg production. A diet X photoperiod interaction occurred for feed consumed per dozen eggs produced and the specific gravity of eggs measured at 224 days of age. As these interactions appeared sporadically and were of low magnitude, they are considered of minor importance; as detrimental effects on egg size and shell strength were minimal, it is concluded that the low protein (13.6%) breeder diet supported performance equivalent to that of birds on the higher protein (15.4%) breeder diet when fed at the quantities described in Table 3. Photoperiod Effects. Mortality, egg production, age at sexual maturity, feed efficiency, and female body weights were unaffected by the different photoperiod treatments tested in the two experiments reported here (Tables 5, 6, 7, and 8). In Experiment 1, light treatment 1 differed from light treatment 6 only in that treatment 1 did not have a dim light (<1 Ix) on at all times to facilitate servicing the birds. As female mortality was lower and shell strength at 224 days and 448 days was stronger under light treatment 6, it appears that birds exposed to a continuous low intensity light (<.l lx) enhanced these two traits. As this does not agree with Morris (1973), further experimentation should be undertaken to test the repeatability of this phenomenon. In Experiment 1 the 27-hr ahemeral light treatments resulted in heavier initial egg weight compared with the 14L:10D photoperiods in treatments 1 and 6 which supports results reported by Morris (1973). However, there was no significant difference in initial egg weights between the 24-hr intermittent light treatment 3 (10L:9D:2L:3D) and the ahemeral light treatments. Further, this 24-hr intermittent light treatment was characterized by persistently resulting in larger egg size throughout the laying period of Experiment 2. A significant difference occurred in Experiment 1 among photoperiods for the specific gravity of eggs when measured at 224 days with eggs laid by birds under light treatments 2, 4, and 5 exhibiting significantly stronger egg shells compared with other treatment groups as measured by the specific gravity method. As shell strength of all treatment groups are well over acceptable levels at this age, this difference is of little practical importance. The 27-hr ahemeral treatments tested in
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female-line genotypes were used in these experiments which provided a sound basis for estimating interactions involving either photoperiod or dietary treatments. Dietary Effects. Despite the substantial difference in the protein levels of the two breeder diets used in Experiment 1, this difference in protein had no effect on the performance traits measured except female body weights at 224 and 308 days of age and egg weights at 224 days (Tables 5 and 6). Feeding the low protein diet resulted in lighter female body weights, lighter egg weights at 224 days of age, and heavier egg weights at 448 days. Ivy and Gleaves (1976), working with table egg production stocks, provided evidence that 15 g of protein and 299 kcal metabolizable energy (ME) per hen day was adequate for birds producing eggs at a rate of 80% or more, but as egg production declined to 70 and 50%, protein and energy requirements were reduced to 13.5 g protein, 269 kcal ME and 12.5 g protein and 250 kcal ME per hen day, respectively. More recently Gleaves et al. (1977) reported that average egg production was best with diets containing 19 g protein and 200 kcal ME per bird day. In Experiment 1, when the low protein (13.6%) breeder diet was fed, the dietary protein intake per hen per day ranged from 14.8 to 20.9 g and ME ranged from 301 to 425 kcal (Table 3). When the high protein (15.4%) breeder diet was fed, the protein intake per hen per day ranged from 16.8 to 23.7 g and ME ranged from 301 to 425 kcal. The protein and energy intake for the two breeder diets is as described in Table 3. For most traits it would appear that the protein and energy intake provided by the low protein breeder diet was adequate, although body weights were reduced compared with birds on the high protein regimen as was age at 50% egg production. These effects, however, could be considered an advantage. The only traits which were affected adversely by the feeding of the low protein breeder diet was egg weight at 224 days of age.
PROTEIN, PHOTOPERIOD, AND EGG PRODUCTION
ACKNOWLEDGMENT
The author acknowledges the advice and assistance freely given by K. McRae in the data
processing and statistical analysis of the data presented herein.
REFERENCES Cooper, J. B., and B. D. Barnett, 1976. Ahemeral photoperiods for chicken hens. Poultry Sci. 55:1183-1187. Dorminey, R. W., 1974. Incidence of floor eggs as influenced by time of nest installation, artificial lighting and nest location. Poultry Sci. 53:1886— 1891. Foster, W. H., 1968. The effect of light-dark cycles of ahemeral length upon egg production. Brit. Poultry Sci. 9:273-284. Foster, W. H., 1969. Egg production under 24, 26 and 28-hr light-dark cycles. Brit. Poultry Sci. 10: 273-279. Gleaves, E. W., F. B. Mather, and M. M. Ahmad, 1977. Effects of dietary calcium, protein and energy on feed intake, egg shell quality and hen performance. Poultry Sci. 56:402-406. Ivy, R. E., and E. W. Gleaves, 1976. Effect of egg production level, dietary protein and energy on feed consumption and nutrient requirements of laying hens. Poultry Sci. 55:2166-2171. Morris, T. R., 1973. The effect of ahemeral light and dark cycles on egg production in the fowl. Poultry Sci. 52:423-445. Patel, M. B., and J. McGinnis, 1977. The effect of levels of protein and vitamin B 12 in hen diets on egg production and hatchability of eggs and on livability and growth of chickens. Poultry Sci. 56:45-53. Proudfoot, F. G., and W. F. Lamoreux, 1973. The bio-economic effect of nutrient restrictions during the rearing period and post "peak" egg production feed restrictions on four commercial meat-type parental genotypes. Poultry Sci. 52:1269-1282.
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Experiment 2, initiated at 140, 158, 168 and 178 days of age and terminated at 210 days of age, failed to enhance the performance of the parent meat breeders compared with the 24-hr intermittent control treatment (10L:9D: 2L:3D). There was, however, a tendency for egg production to increase as the age at initiating the ahemeral treatment was delayed. A significant genotype x photoperiod interaction occurred in Experiment 1 for 224 day female weight which is of some interest but of little practical importance since it did not persist into the later stages of the laying period. A genotype X light treatment interaction occurred for egg weight at 224 and 308 days but was of low magnitude and, therefore, of questionable importance. In both experiments birds on the 27-hr day cycle laid approximately 50% of their eggs on the floor. This is in agreement with Dorminey (1974) who concluded that lighting method can affect the incidence of floor eggs. It is concluded that an ahemeral lighting program for birds housed in floor pens is considered impractical because of the large number of eggs which were soiled. It is also concluded that the intermittent 24-hr treatment (10L:9D:2L:3D) supports performance which is equal or superior to all other treatments tested.
1267
1980 Poultry Science 59:1258-1267 INTRODUCTION There are a n u m b e r of reports in t h e literature involving t h e evaluation of diets with different protein levels fed to laying birds (Gleaves et al, 1 9 7 7 ; Patel and McGinnis, 1 9 7 7 ; Ivy and Gleaves, 1976). However, all of this research involved table egg p r o d u c t i o n stock and, t h u s , t h e results may n o t be applicable to meat parent g e n o t y p e s used for t h e p r o d u c t i o n of hatching eggs. F u r t h e r m o r e , these egg p r o d u c t i o n stocks were fed ad libitum during t h e laying period whereas the a m o u n t of feed offered m e a t parent stocks is restricted, being based o n gains in b o d y weights and egg p r o d u c tion. It has been reported t h a t ahemeral light-dark cycles can be used t o alter t h e p e r f o r m a n c e of t h e domestic fowl (Cooper and Barnett, 1 9 7 6 ; Foster, 1 9 6 8 , 1 9 6 9 ; and Morris, 1 9 7 3 ) . As much of t h e early e x p e r i m e n t a t i o n was conducted with commercial egg p r o d u c t i o n stocks, it was desirable to evaluate t h e effects of these
1
Contribution No. 1670.
ahemeral light-dark cycles on m e a t parent g e n o t y p e s . Foster ( 1 9 6 8 ) reported that egg p r o d u c t i o n was increased by t h e lengthening of the day cycle and Morris (1973) indicated t h a t initial egg size was increased and shell strength improved. Morris ( 1 9 7 3 ) also reported t h a t egg p r o d u c t i o n was decreased by increasing the length of t h e light-dark cycle. It would be of considerable advantage if early egg size and shell strength, particularly during the later stages of egg p r o d u c t i o n , could be improved for t h e p r o d u c t i o n of hatching eggs and the subseq u e n t p r o d u c t i o n of broiler chickens. T w o e x p e r i m e n t s were c o n d u c t e d . T h e objective of t h e first e x p e r i m e n t was to study t h e effects of feeding breeder diets with t w o calculated protein levels (13.6 and 15.4%) and to s t u d y the effects of c o n t i n u o u s and intermittent p h o t o p e r i o d s involving b o t h conventional and 27-hr ahemeral light-dark cycles. The objective of t h e second experiment was to extend t h e study of 24-hr cycled i n t e r m i t t e n t p h o t o p e r i o d s and c o m p a r e t h e m with 27-hr ahemeral light-dark cycles initiated at different ages and reverted back to 24-hr cycles at t h e same t i m e .
1258
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ABSTRACT Two experiments were undertaken to estimate the effect of: 1) two dietary protein levels (13.6 and 15.4%) in breeder diets fed to commercial meat parent genotypes; and 2) 6 photoperiods involving both 24-hr and 27-hr (ahemeral) day cycles with single stage and intermittent lighting for birds housed in floor pens. It was concluded that the 13.6% protein breeder diet, which provided from 14.8 to 20.9 g of protein per bird per day and from 301 to 425 kcal of ME per bird per day, was adequate to support optimum performance. The ahemeral light treatment 14L:13D used from 168 to 448 days had a depressing effect on egg production and feed efficiency compared with the conventional 24-hr day cycle with 14L:10D light treatment. The 14L:13D treatment, however, did result in increased egg size and improved shell strength. The intermittent light treatments, whether ahemeral or 24-hr cycle, resulted in improved egg weight and shell strength. The ahemeral intermittent treatment (10L:12D:2L:3D) had the effect of depressing fertility and hatchability, whereas the 24-hr intermittent photoperiod (10L:9D:2L:3D) resulted in fertility and hatchability equal to or better than other treatment. It was concluded that the 24-hr intermittent light treatment (10L:9D:2L:3D) supported performance which was equal to or better than other light treatments including the 27-hr ahemeral day cycles. Furthermore, ahemeral day cycles resulted in large numbers of eggs laid on the floor (Ca. 50%). First and second order interactions appeared to be of minor importance.
PROTEIN, PHOTOPERIOD, AND EGG PRODUCTION
197 3). At 154 days of age each male p o p u l a t i o n was reduced at r a n d o m to a m a x i m u m of 5 males with up to 5 males in reserve. During t h e brooding and rearing period (1 t o 168 days) t h e p h o t o p e r i o d was decreased in weekly d e c r e m e n t s of 15 min from a 17-hr day until a 14-hr day was attained at 168 days of age, at which t i m e adult light t r e a t m e n t s were initiated. Six different adult p h o t o p e r i o d s were compared (Table 2). T r e a t m e n t s 1, 3, and 6 were all on 24-hr cycles with t r e a t m e n t s 1 and 6 differing only in t h a t birds u n d e r t r e a t m e n t 6 were exposed to a c o n t i n u o u s dim light ( < . l lx) and t r e a t m e n t 1 had a t o t a l black-out w h e n the main lights were off. Experiment 2. One h u n d r e d and fifty dozen hatching eggs were o b t a i n e d from each of four commercial breeders to supply four well-known female line genotypes. Male chicks of one g e n o t y p e were obtained t o mate at m a t u r i t y with the four female lines. Fifty-five female chicks from each of t h e four female-line genotypes and 14 male line chicks were r a n d o m l y assigned to one pen in each light controlled zone, so t h a t there were 12 pens of each female-line g e n o t y p e in t h e test building. All stock were given t h e same dietary regimen, using the low protein (13.6%) breeder diet (Table 1). Skip-a-day feeding was started at 4 2
TABLE 1. Composition of the starter, grower, and breeder diets Breeder diets Ingredients
Starter
Grower (%)
Ground corn Ground wheat Ground oats Ground barley Fishmeal (63%) Soybean meal (49%) Dehydrated alfalfa (16%) Ground limestone Dicalcium phosphate Salt (NaCl) Micro-nutrients 3 Calculated analyses: Crude protein ME kcal/kg
20 28 15 15 3 15 1.5 .75 .75 .5 .5 18.4 2885
20 30 20 20 5..5 1..5 .75 1..25 .5 .5
13. 3
Low protein
High protein
15 30 20 20 3 3 2 5 1
15 30 20 16 5 5 2 5 1
•
13.i 2760
15.4 2754
Amount for 1 kg of starter and grower diets contained 5,000 IU vitamin A; 1,000 ICU vitamin D, ; 1 rag vitamin K; 4 mg riboflavin; 20 mg niacin ; 5 mg d-calcium pantothenate; 1 rag folic acid; 5 Mg vitamin B, 2; 50 mg manganese; 40 mg zinc; 5 mg copper; 1 mg iodine. The supplement for the breeder diets was similar but contained 400 mg choline.
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MATERIALS AND METHODS A windowless brooding and rearing house containing 4 8 pens was used for b o t h experim e n t s . T h e t w o e x p e r i m e n t s were c o n d u c t e d concurrently. A service r o o m was located m i d w a y in t h e building and a central alleyway 1.83 m wide e x t e n d e d t h e length of the building with equal n u m b e r s of pens on each side of t h e alleyway. Each block of 4 pens constituted a light controlled zone. T h e general lay-out of the laying house was the same as the rearing house. Experiment 1. Three h u n d r e d dozen hatching eggs were o b t a i n e d from each of t w o commercial breeders to supply t w o well-known female line genotypes. Male day-old chicks of one g e n o t y p e were obtained t o m a t e at m a t u r i t y with t h e female lines. Fifteen chicks of t h e male line g e n o t y p e and 55 chicks of each of the female line genotypes, were r a n d o m l y assigned to two pens within each light z o n e . All stock was fed all-mash diets t h r o u g h o u t the experiment (Table 1). The low p r o t e i n (13.6%) and high protein (15.4%) breeder diets were assigned to each of t w o genotypes within each light z o n e . Skip-a-day feeding was commenced at 4 2 days of age and terminated at 154 days of age when feeding of breeder diets was c o m m e n c e d (Proudfoot and L a m o r e u x ,
1259
1260
PROUDFOOT TABLE 2. Light treatments in Experiment Light period0 (hr)
1 2 3 4 5 6
24 27 24 27 27 24
14 14 10 + 2 10 + 2 14 14
Duration of special light t r e a t m e n t 0
ill
Treatment
Day cycle (hr)
la
10 13 9 + 3 12 + 3 13 10
(days)
(days)
168-448 168-214 168-448 168-214 168-448 168-448
280 46 280 46 280 280
10 + 2 under light and 9 + 3 under dark periods means lights were on 10 hr, off for 9 hr, on for 2 hr, and off for 3 hr ; similarly 10 + 2 and 12 + 3 means lights were on for 10 hr, off for 12 hr, on for 2 hr and off for 3 hr followed by a repeat of the cycles. When special light treatments were terminated they were reverted back to a 14L:10D day cycle.
days and terminated at 154 days of age when feeding of breeder diet c o m m e n c e d . The • breeder diet was fed according to the schedule described in Table 3. Birds received a 17-hr daylength from 1 to 14 days which was reduced by 10 min weekly until a 14-hr day was reached at 140 days of age. Morris (1973) provided evidence t h a t the 27-hr ahemeral p h o t o p e r i o d cycle resulted in performance which was either equal or superior to o t h e r ahemeral cycles among Leghorn stocks, and it was considered desirable to use this particular ahemeral cycle to c o m p a r e with t h e 24-hr cycle using b o t h constant and i n t e r m i t t e n t p h o t o p e r i o d s . Light t r e a t m e n t s
used in this e x p e r i m e n t were primarily designed t o estimate t h e effects of changing an intermittent light t r e a t m e n t (24-hr cycle) back to a 14L-.10D p h o t o p e r i o d at 238 days of age and to estimate the effects of switching from a 24-hr cycle with a 1 4 L : 1 0 D p h o t o p e r i o d to a 27-hr cycle with a 1 4 L : 1 3 D p h o t o p e r i o d at different ages with a constant age for reverting back to a 1 4 L : 1 0 D light t r e a t m e n t (Table 4 ) . T h e six p h o t o p e r i o d s used were initiated at 141 days of age using i n t e r m i t t e n t lighting of 10L-.9D:2L:3D t h r o u g h o u t t h e laying period as t h e c o n t r o l t r e a t m e n t similar to t r e a t m e n t 3 in Experiment 1 (Table 4 ) . A dim light ( < . l lx) was used t h r o u g h o u t t h e dark period of all
TABLE 3. Feed allotment schedule and dietary protein and energy levels" used during the laying period of Experiments 1 and 2
Frorr i
To
Feed/ bird/ day
155 162 169 176 183 190 197 281 288 309
161 168 175 182 189 196 280 287 308 448
109 118 127 136 145 150 154 150 145 140
Age (days)
Daily protein intake/bird protein diet ( 13.6%)
14.8 16.0 17.3 18.5 19.7 20.4 20.9 20.4 19.7 19.0
Daily ME
High protein diet (15.4%)
(kcal)
16.8 18.2 19.6 20.9 22.3 23.1 23.7 23.1 22.3 21.6
301 325 3 50 375 400 414 425 414 400 386
y&
The two breeder diets (1 3.6% and 15.4% protein) were isocalorie.
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Low intensity light (<1 lx) was used in service area on all treatments except treatment 1.
PROTEIN, PHOTOPERIOD, AND EGG PRODUCTION
1261
TABLE 4. Light treatments in Experiment 2 a
Treatment
Day cycle (hr)
Light cycle (hr)
1 2 3 4 5 6
24 24 27 27 27 27
10 + 2 10 + 2 14 14 14 14
Dark cycle (hr) 9+ 3 9 + 3 13 13 13 13
Duration of special light treatment' 3 (days)
(days)
140-448 140-238 140-210 158-210 168-210 178-210
308 98 70 52 42 32
treatment groups on a 27-hr cycle. During the adult period feed was allotted as shown in Table 3. The traits measured were the same for both experiments, except that fertility and hatchability were measured once in Experiment 1 and twice in Experiment 2 (Tables 5 and 7). Percentage mortality during the laying period was based on the number of birds housed at 140 days of age. Egg production was recorded on a pen basis throughout the laying period and mean henhoused egg production was calculated from 140 days of age to the end of the experiments. Hatching eggs were designated as suitable for hatching with a minimum individual weight of 47 g. Percentages of hatching eggs laid on 2 days each week were prorated with total eggs laid in each pen. The first day of the first 2 consecutive days that a female pen population reached 50% egg production was used as the age in days to 50% egg production. Feed efficiency was calculated as the kilograms of feed required to produce one dozen eggs. Fertility and hatchability of all eggs set were based on a sample of 150 to 180 eggs from each pen and were measured at 208 days in Experiment 1 and at 224 days and at 308 days in Experiment 2. Percent fertility was based on the candled, incubated eggs after 18 days of incubation and hatchability was calculated as eggs hatched from the number of eggs placed under incubation. The number of broiler chicks per female housed at 140 days was calculated by applying the percent hatchability of all eggs set to the number of hatching eggs produced. The calculation of mean egg weights was
based on weighing eggs laid on 2 consecutive days per week from each pen at 224, 308, and 448 days. Shell strength was measured as the specific gravity of each egg and was a discrete measurement made on a sample of 25 eggs selected at 224, 308, and 448 days of age. Birds were individually weighed at 224, 308, and 448 days of age in both experiments. Experiment 1 was designed as a 6 X 2 X 2 factorial with six photoperiod treatments, two adult dietary treatments, and two genotypes with two replicates. Experiment 2 was designed as a 6 x 4 factorial with six photoperiod treatments and four genotypes with two replicates. For the statistical analyses a split plot model was assumed. Pen means were used in the statistical analyses and percent data were transformed to angles. Standard errors of treatment and genotype means were calculated. RESULTS AND DISCUSSION Genotype Effects. The two genotypes used in Experiment 1 differed significantly for the traits: male mortality; hen-housed egg production; sexual maturity; hatching egg fertility; egg weight; egg specific gravity, and body weight at 308 days of age (Tables 5 and 6). In Experiment 2 the four genotypes differed significantly for hen-housed egg production, hatching egg production, sexual maturity, feed efficiency, hatchability of eggs at 308 days of age, egg weight, and shell strength as measured by the specific gravity method and body weight (Tables 7 and 8). The genotypic differences which occurred among female-line genotypes in both experiments provide evidence that highly divergent
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Light cycles 10 + 2 and dark cycle 9 + 3 means that lights were on for 10 hr, off for 9 hr, on for 2 hr, and off for 3 hr followed by a repeat of the cycle. Treatments 4, 5, and 6 were retained on the 14L:10D treatment until 27 hr cycles commenced; when light treatments were terminated they reverted to a 14L:10D day cycle.
Photoperiod
5.0 2.4 3.6
6.2
4.7 2.2 (1.5) 5.3 2.7 (1.5) 4.7 3.1 (1.5)
31.9 28.4 17.9
32.0
30.7 28.3 (4.2) 33.8 22.7 (1.6) 31.2 25.1 (1.6)
214
448 448
Female (%)
448 214 448
Male (%)
Mortality0 ( 1 4 0 - 4 4 8 days)
130 157 4.7 146 153 1.8 147 152 1.8
124 148 4.7 141 144 1.7 140 144 1.7 4.20 3.65 .18 3.83 3.74 .04 3.80 3.77 .04
3.83
154 155 153 140
3.66 3.69 3.69
145 148 146
egg p r o d u c e d (No.)
147
Feed per dozen eggs produced (kg)
.housed
Hen-housed hatching egg p r o d u c e d (No.)
Hen
177 176 1.1 179 176 .6 176 178 .6
180
176 177 179
Days age a egg p (No.)
genotype, and diet effects on mortality, egg production, feed e fertility, hatchability, of broiler chicks produced in Experiment I
HP, high p r o t e i n ; LP, low protein breeder diets.
SEM, standard error of t h e m e a n with t h e n u m b e r of observations in t h e m e a n s h o w n in parenthesis.
Mortality, fertility, and hatchability means are detransformed from angles t o p e r c e n t b u t standard error of m e a n s
Lower case " d " in 1 4 L : 1 0 D - d designates t h a t a c o n t i n u o u s dim light was not used in light t r e a t m e n t 1 and at 2 t o a 1 4 L ; 1 0 D light cycle. All light t r e a t m e n t s c o m m e n c e d at 1 6 8 days of age.
14L:10D-d 14L.13D 10L.-9D:2L: 3D 4 10L:12D: 2L:3D 5 14L:13D 6 14L:10D SEM ( 8 ) c Genotype A Genotype B SEM (24) Dietary t r e a t m e n t ' ' HP Dietary t r e a t m e n t LP SEM (24)
1 2 3
No.
Age at termination (days)
Light t r e a t m e n t s a
T A B L E 5. The pbotoperiod,
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448 214 448 214 448 448
Photoperiod
14L:10D-d 14L:13D 10L:9D:2L:3D 10L:12D:2L:3D 14L:13D 14L:10D
No.
1 2 3 4 5 6
.14
57.9 57.4
.14
59.5 55.8
.45
56.5 57.1 58.1 57.7 60.0 56.6
days
224
.20
.18
63.2 63.1
.18
65.1 61.2
.16
66.2 66.6
.16
68.7 64.2
.35
65.9 65.4 66.9 67.3 67.6 65.4
63.0 63.0 63.8 63.4 62.9 62.8 889 933 900 921 934 897 7 921 904 2 913 912 2
days
days
days ta\ W
224
448
308
Egg weight
852 842 868 864 868 849 8 862 852 2 857 857 2
days
308
Egg specific
HP, high protein; LP, low protein breeder diets.
SEM, standard error of the mean with the number of observations shown in parenthesis.
Multiply means by 10 —4 and add 1.0 to convert to specific gravity.
Lower case "d" in 14L:10D—d designates that a continuous dim light was not used with light treatment 1; at 214 a 14L:10D light cycle and all light treatments commenced at 168 days of age.
SEM(8) C Genotype A Genotype B SEM (24) Dietary treatment^ HP Dietary treatment LP SEM (24)
Age at termination (days)
Light treatments 3
TABLE 6. The photoperiod, genotype, and diet effects on egg weight, egg specific gravity, and fem
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Photoperiod
448 2 38 210 210 210 210
11.9 3.1 3.2 6.9 14.5 10.9 (4.3) 8.8 9.6 4.8 8.6 (4.3)
(%)
Male
3.2 4.3 6.7 7.3 4.9 7.9 (1.9) 5.8 4.0 8.1 4.8 (1.6)
(%)
Female
Mortality0 ( 1 4 0 - 4 4 8 days)
156 150 146 151 152 153 4.1 146 152 142 165 2.6
Hen-housed egg p r o d u c t i o n (No.) 148 142 139 143 144 146 4.1 135 146 140 154 2.7
Hen housed hatching egg p r o d u c t i o n (No.) 3.63 3.80 3.83 3.66 3.70 3.60 .11 3.83 3.70 3.88 3.41 .07
Feed per dozen leggs produced (kg)
SEM, standard error of the means with the number of observations shown in parenthesis.
Mortality, fertility, and hatchability means are detransformed from angles to percent but standard error of means
Light treatments 1, 2, and 3 commenced at 140 days of age and treatments 4, 5, and 6 commenced at 158, 16 to 14L:10D.
10L:9D:2L:3D 10L:9D:2L:3D 14L:13D 14L:13D 14L:13D 14L:13D SEM ( 8 ) c Genotypes A Genotypes B Genotypes C Genotypes D SEM (12)
1 2 3 4 5 6
No.
Age at termination (days)
Light t r e a t m e n t s 3
TABLE 7. The photoperiod and genotype effects on mortality, egg production, feed efficiency, fertili broiler chicks per hen housed in Experiment 2
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Photoperiod
448 238 210 210 210 210
Age at termination (days)
177 177 176 172 176 171 2.0 178 175 178 169 1.0
Age at 50% egg proiduction (days)
.15
58.1 58.8 58.4 56.5
.34
58.0 58.2 57.6 57.5 57.4 57.4
.22
65.0 65.0 63.4 62.6
.36
64.5 64.4 64.4 63.7 63.1 63.9
(&>
.23
68.9 68.5 66.3 65.9
.37
68.6 67.6 67.3 66.6 67.3 67.2 884 873 911 914 902 908 4 909 908 900 877 4
days
days
days
days
Egg s
224
448
308
Egg weight 224
SEM, standard error of the mean with the number of observations shown in parenthesis.
Multiply means by 10 — * and add 1.0 to convert to specific gravity.
Light treatments 1,2, and 3 commenced at 140 days of age and treatments 4, 5, and 6 commenced at 158,168, a to 14L:10D.
10L:9D:2L:3D 10L:9D:2L:3D 14L:13D 14L:13D 14L:13D 14L:13D SEM (8) c Genotypes A Genotypes B Genotypes C Genotypes D SEM (12)
1 2 3 4 5 6
No.
Light treatments 3
TABLE 8. The photoperiod and genotypic effects on sexual maturity, egg weight, egg specific gravity, an
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1266
PROUDFOOT
In the current study, hatchability and growth of broiler progeny were unaffected by the dietary protein level of breeder diets. Patel and McGinnis (1977) found that a high protein breeder diet had a depressing effect on hatchability and chick growth. However, their high protein diet contained 32% protein fed to a Leghorn population whereas the high protein diet evaluated here had a protein level of 15.4% and was fed to meat parent stock.
A diet x genotype interaction occurred for egg weight at 224 days, 44 day female body weights, and age at 50% egg production. A diet X photoperiod interaction occurred for feed consumed per dozen eggs produced and the specific gravity of eggs measured at 224 days of age. As these interactions appeared sporadically and were of low magnitude, they are considered of minor importance; as detrimental effects on egg size and shell strength were minimal, it is concluded that the low protein (13.6%) breeder diet supported performance equivalent to that of birds on the higher protein (15.4%) breeder diet when fed at the quantities described in Table 3. Photoperiod Effects. Mortality, egg production, age at sexual maturity, feed efficiency, and female body weights were unaffected by the different photoperiod treatments tested in the two experiments reported here (Tables 5, 6, 7, and 8). In Experiment 1, light treatment 1 differed from light treatment 6 only in that treatment 1 did not have a dim light (<1 Ix) on at all times to facilitate servicing the birds. As female mortality was lower and shell strength at 224 days and 448 days was stronger under light treatment 6, it appears that birds exposed to a continuous low intensity light (<.l lx) enhanced these two traits. As this does not agree with Morris (1973), further experimentation should be undertaken to test the repeatability of this phenomenon. In Experiment 1 the 27-hr ahemeral light treatments resulted in heavier initial egg weight compared with the 14L:10D photoperiods in treatments 1 and 6 which supports results reported by Morris (1973). However, there was no significant difference in initial egg weights between the 24-hr intermittent light treatment 3 (10L:9D:2L:3D) and the ahemeral light treatments. Further, this 24-hr intermittent light treatment was characterized by persistently resulting in larger egg size throughout the laying period of Experiment 2. A significant difference occurred in Experiment 1 among photoperiods for the specific gravity of eggs when measured at 224 days with eggs laid by birds under light treatments 2, 4, and 5 exhibiting significantly stronger egg shells compared with other treatment groups as measured by the specific gravity method. As shell strength of all treatment groups are well over acceptable levels at this age, this difference is of little practical importance. The 27-hr ahemeral treatments tested in
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female-line genotypes were used in these experiments which provided a sound basis for estimating interactions involving either photoperiod or dietary treatments. Dietary Effects. Despite the substantial difference in the protein levels of the two breeder diets used in Experiment 1, this difference in protein had no effect on the performance traits measured except female body weights at 224 and 308 days of age and egg weights at 224 days (Tables 5 and 6). Feeding the low protein diet resulted in lighter female body weights, lighter egg weights at 224 days of age, and heavier egg weights at 448 days. Ivy and Gleaves (1976), working with table egg production stocks, provided evidence that 15 g of protein and 299 kcal metabolizable energy (ME) per hen day was adequate for birds producing eggs at a rate of 80% or more, but as egg production declined to 70 and 50%, protein and energy requirements were reduced to 13.5 g protein, 269 kcal ME and 12.5 g protein and 250 kcal ME per hen day, respectively. More recently Gleaves et al. (1977) reported that average egg production was best with diets containing 19 g protein and 200 kcal ME per bird day. In Experiment 1, when the low protein (13.6%) breeder diet was fed, the dietary protein intake per hen per day ranged from 14.8 to 20.9 g and ME ranged from 301 to 425 kcal (Table 3). When the high protein (15.4%) breeder diet was fed, the protein intake per hen per day ranged from 16.8 to 23.7 g and ME ranged from 301 to 425 kcal. The protein and energy intake for the two breeder diets is as described in Table 3. For most traits it would appear that the protein and energy intake provided by the low protein breeder diet was adequate, although body weights were reduced compared with birds on the high protein regimen as was age at 50% egg production. These effects, however, could be considered an advantage. The only traits which were affected adversely by the feeding of the low protein breeder diet was egg weight at 224 days of age.
PROTEIN, PHOTOPERIOD, AND EGG PRODUCTION
ACKNOWLEDGMENT
The author acknowledges the advice and assistance freely given by K. McRae in the data
processing and statistical analysis of the data presented herein.
REFERENCES Cooper, J. B., and B. D. Barnett, 1976. Ahemeral photoperiods for chicken hens. Poultry Sci. 55:1183-1187. Dorminey, R. W., 1974. Incidence of floor eggs as influenced by time of nest installation, artificial lighting and nest location. Poultry Sci. 53:1886— 1891. Foster, W. H., 1968. The effect of light-dark cycles of ahemeral length upon egg production. Brit. Poultry Sci. 9:273-284. Foster, W. H., 1969. Egg production under 24, 26 and 28-hr light-dark cycles. Brit. Poultry Sci. 10: 273-279. Gleaves, E. W., F. B. Mather, and M. M. Ahmad, 1977. Effects of dietary calcium, protein and energy on feed intake, egg shell quality and hen performance. Poultry Sci. 56:402-406. Ivy, R. E., and E. W. Gleaves, 1976. Effect of egg production level, dietary protein and energy on feed consumption and nutrient requirements of laying hens. Poultry Sci. 55:2166-2171. Morris, T. R., 1973. The effect of ahemeral light and dark cycles on egg production in the fowl. Poultry Sci. 52:423-445. Patel, M. B., and J. McGinnis, 1977. The effect of levels of protein and vitamin B 12 in hen diets on egg production and hatchability of eggs and on livability and growth of chickens. Poultry Sci. 56:45-53. Proudfoot, F. G., and W. F. Lamoreux, 1973. The bio-economic effect of nutrient restrictions during the rearing period and post "peak" egg production feed restrictions on four commercial meat-type parental genotypes. Poultry Sci. 52:1269-1282.
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Experiment 2, initiated at 140, 158, 168 and 178 days of age and terminated at 210 days of age, failed to enhance the performance of the parent meat breeders compared with the 24-hr intermittent control treatment (10L:9D: 2L:3D). There was, however, a tendency for egg production to increase as the age at initiating the ahemeral treatment was delayed. A significant genotype x photoperiod interaction occurred in Experiment 1 for 224 day female weight which is of some interest but of little practical importance since it did not persist into the later stages of the laying period. A genotype X light treatment interaction occurred for egg weight at 224 and 308 days but was of low magnitude and, therefore, of questionable importance. In both experiments birds on the 27-hr day cycle laid approximately 50% of their eggs on the floor. This is in agreement with Dorminey (1974) who concluded that lighting method can affect the incidence of floor eggs. It is concluded that an ahemeral lighting program for birds housed in floor pens is considered impractical because of the large number of eggs which were soiled. It is also concluded that the intermittent 24-hr treatment (10L:9D:2L:3D) supports performance which is equal or superior to all other treatments tested.
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