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Time-Limited Feeding of Leghorn Layers in California Open Housing1
Time-Limited Feeding of Leghorn Layers in California Open Housing1 D. R. KUNEY Cooperative Extension Service, University of California, Riverside, California 92521 HOWARD L. ENOS
(Received for publication March 30, 1979) ABSTRACT Ad libitum feeding of laying hens was compared with two 2-hr (2-2hr) and three 1-hr (3-lhr) feeding times per day in terms of rate of lay, feed efficiency, body weight, mortality, egg size, and quality. Two strains of commercial layers were housed in a conventional Californiatype open house at a density rate of three hens per 30.5 X 45.7 cm wire cage. The study continued through two lay cycles. Average feed restriction, relative to ad libitum-ied hens, was 11% and 8% during the first lay cycle and 12% and 10% during the second cycle for the 3-lhr and 2-2hr groups, respectively. Both time-limited feeding (TLF) programs significantly improved feed efficiency during each lay cycle. Average body weight gain for both TLF programs was less than ad libitum gain during the first lay cycle but greater during the second cycle. Unusually high mortality (cause undetermined) occurred during the first lay cycle but was not treatment related. Nonsignificant depressions in rate of lay among TLF groups were observed during both cycles. Decreased egg size, as measured by percent large, and an increased shell thickness due to TLF treatments occurred during both lay cycles. No egg quality differences were observed. Some strain differences were observed, which may indicate that strain should be considered along with environment, management, and flock health conditions when using TLF as a method of feed restriction. (Key words: layers, time-limited feeding, production, feed efficiency, open housing) 1980 Poultry Science 59:1824-1831 INTRODUCTION
Feed represents the major expense item in the total cost of egg production. With rising feed prices, producers are looking for new ways to reduce production costs and restore profit margins. Increasing feed efficiency through controlled feed intake may be one possibility. Although governed basically by their energy requirements, layers may under certain conditions overconsume, as reported by Andrews (1973), Balnave and Jackson (1973), Cherry (1959), Combs et al. (1961), Hannagan and Willis (1973), Johnston et al. (1972, 1973), Kari et al. (1977), Pope (1971), Sherwood and Milby (1961), Singsen et al. (1958), and Snetsinger et al. (1974). Overconsumption, in these
1 Published with the approval of the Director of the Colorado Agricultural Experiment Station as Scientific Series paper number 2438. Presented by the senior author in partial fulfillment of the requirements for the Master of Science Degree.
instances, occurs when birds fed ad libitum lay statistically at the same rate as restricted birds under similar conditions of temperature, age, type of feed, housing, and management. In efforts to minimize wasted feed through overconsumption, several researchers have studied the efficacy of physically limiting feed consumption by laying hens. Sherwood and Milby (1961) and Walter and Aitken (1961) reported decreased egg production as a result of feed restriction. Heywang (1940) restricted Single Comb White Leghorn pullets to 87.5 and 75.0% of the ad libitum control hens and observed a significant decrease in egg production. However, other workers have restricted laying hens as much as 15% without significantly lowering egg production (Dronawatt, 1968; Dronawatt and McGinnis, 1966; Johnston et al, 1973; Snetsinger et al., 1973; Watkins et al, 1973). In addition, all of these investigators reported improved feed efficiency as a result of the lowered feed consumption. In 1966, Dronawatt and McGinnis reported decreased egg size when laying hens were
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Department of Animal Sciences, Colorado State University, Fort Collins, Colorado 80523
TIME-LIMITED FEEDING OF LAYERS
EXPERIMENTAL PROCEDURE
Two commercial strains of Single Comb White Leghorn chickens were brooded and reared in the mild coastal climate of southern California. Conventional milo, corn, and soybean type rations were used. At 24 weeks of age the pullets were placed in a California open-type house at a density rate of three birds per cage. The 30.5 X 45.7 cm cages provided 465 cm2 of floor space per bird. The cages were oriented in a single row on each side of the house with a double row of back-to-back cages in the center. Lath siding partially protected the birds from wind and intense sunlight. The metal roof was not insulated. Feed troughs located at the front of each cage provided 10.2 cm of feeder space per bird. The waterers were continuous-flow type V-troughs which ran the length of each row at the rear of the cages. Three feeding treatments were imposed upon each strain of chicken. The first treatment consisted of three 1-hr (3-lhr) feeding periods per day (0700 to 0800 hr, 1300 to 1400 hr, and 1900 to 2000 hr). The second treatment allowed the birds to eat during two 2-hr (2-2hr) periods per day (0700 to 0900 hr and 1900 to 2100 hr). The third treatment served as a control and permitted the birds to feed ad libitum. Daylight was augmented artificially for a total of 17 hr of light per day (0500 to 1000 hr). For time-limited fed treatment groups, access was controlled mechanically by use of a
plywood lid hinged to the front of the feed through. A cord from each lid was attached to a central cable which, in turn, was connected to a hydraulic ram controlled by a 24-hr time clock. Trough lids opened or closed according to prescribed feeding treatments throughout the experiment. Two rations were fed during the test in accordance with seasonal temperature changes (Table 1). The winter ration, containing 16% crude protein and 2,756 kcal me/kg, was fed from October through May. The summer ration, with 17% crude protein and 2,695 kcal/kg, was fed from June to October. The experimental design, consisting of three feeding regimes and two strains, was a randomized complete block using six blocks. Each treatment replication consisted of 24 birds in an 8-cage section for a total of 864 hens. Data collections were started on February 20 when the hens were 24 weeks of age and continued through two lay cycles separated by a force-molt. The molt was accomplished at 64 weeks of age by removing the feed for 10 days, and the birds were returned to natural day lengths. Then the winter Phase I lay ration was reinstated as well as 17 hr lighting per day. Birds had water at all times during the molt period. Statistical analysis was performed on the data using the analysis of variance technique (Little and Hills, 1975) and multiple range test (Duncan, 1955). Duration of the experiment was 80 weeks, ending on August 29 of the second year. RESULTS
First Lay Cycle—Feed Consumption. Timelimited feeding (TLF) 3-lhr and 2-2hr groups had significantly reduced average feed con-
TABLE 1. Selected parameters calculated for the experimental rations Ingredients Metabolizable energy (kcal/kg) Crude protein (%) Methionine (%) Methionine plus cystine (%) Lysine (%) Calcium (%) Phosphorus (%)
Winter
Summer
2,756 16.0 .32
2,695 17.0 .34
.56 .64 3.70 .60
.59 .68 3.70 ..60
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restricted to 90% of control hens fed ad libitum. Other investigators also have observed losses in egg weight during feed restriction (Bell and Moreng, 1972; Jackson, 1970; Polin and Wolford, 1971). To the contrary, Johnston et al. (1972), Kari et al. (1977), and Snetsinger et al. (1973) found no significant decrease in egg weight. Mortality rate may be affected by feed restriction. Hannagan and Willis (1973), Singsen et al. (1958), and Snetsinger et al. (1973) report higher mortality among hens fed ad libitum than hens fed restrictively. This may be due to excess body fat accumulation, which was shown to be related to mortality by Singsen etal. (1958). The research being reported here is one of a series of experiments conducted to evaluate time-limited feeding in southern California, where the majority of egg-type poultry houses are of the open-type design.
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KUNEY AND ENOS
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TABLE 2. Effect of time-limited feeding on laying performance during the first lay cycle
Strain/ limitation
Feed consumption
Mortality
Reduction
Production
Hen-housed
Hen-day
(%)-
(g)
69.1a 69.2a 72.9a 70.4a 72.6a 70.8a 70.2a 71.2a
17.4A* 9.1B 17.4A 14.6A 10.7a 5.0b 7.1a 7.6B
12 106c* 8 lllb 0 120a 112A** 10lt> 10 8 103b 0 112a 105»
Average shell thickness (mm)
77.7 b 79 yab 81.8 a 79.7 A 57.la 62.4 a 65.8 a 61.8B
64.2a 66.0a 65.7a 65.3b 68.8a 68.9a 67.5a 68.4a
Feed efficiency (kg feed/ kg egg) 2.59 a 2.66 a 2.75 a 2.66 a 2.46 B 2.58AB 2.80 A 2.61 a
.384 A B .389 A .378 B .384 a .381 a .384 a .378 a .381 a
•Duncan's multiple range compares the three limitation treatments for each strain separately. Means with the same capital letter are not significantly different (P>,01). Means with the same lower case letter are not significantly different (P>.05). " S t r a i n means with the same capital letter are not significandy different (P>.001). Strain means with the same lower case letter are not significandy different (P>.05).
s u m p t i o n ( P < . 0 5 ) during t h e first lay cycle (Table 2). Because there were no significant strain-by-treatment interactions, d a t a for t h e t w o strains were combined. On t h e average, T L F g r o u p s resulted in an 11 and 8% reduction in feed c o n s u m p t i o n from the ad libitum control groups for t h e 3 - l h r and 2-2hr treatm e n t groups, respectively. Strain A consumed significantly more feed t h a n strain B ( P < . 0 0 1 ) . Scott et al. ( 1 9 7 1 ) state t h a t Single C o m b White Leghorn hens require 18 g of protein per day during Phase I (20 t o 4 2 weeks of age), 16 g during Phase II (from 4 2 weeks of age t o
a rate of lay of 65%), and 15 g of protein per day during Phase III (rate of lay below 65%). When using this rationale as a guideline for nutrient requirements, the 3-lhr and 2-2hr feeding t r e a t m e n t s did n o t allow birds to c o n s u m e an a d e q u a t e 18 g level of protein during Phase I (Table 3). During subsequent phases, however, t h e average daily protein intake would be considered sufficient according t o this interpretation. Body Weight and Weight Gain. Within b o t h strains, weight gain was reduced by T L F (Table 4). T h e strain A 3 - l h r and 2-2hr groups did n o t
TABLE 3. Average daily nutrient intake during the three phases of egg production during the first lay cycle Phase I ( 2 4 to 4 2 wk age)
Phase II (43 t o 60 w k age:)
Phase III (61 t o 64 w k age)
Strain/ limitation
Protein 1
Methio- Lynine' sine'
Calories 2
Protein 1
Methionine'
Lysine 1
Calories 2
Protein 1
Methionine 1
Lysine'
Calories 2
A Three 1-hr Two 2-hr ad libitum B Three 1-hr Two 2-hr ad libitum
17.2 17.8 19.1 17.0 16.6 18.3
.35 .36 .39 .35 .34 .38
291 299 319 286 278 308
18.1 18.6 20.6 16.7 17.6 19.1
.36 .38 .41 .33 .36 .38
.73 .76 .82 .66 .71 .75
287 299 324 263 282 298
17.6 18.8 20.4 16.2 17.3 18.3
.35 .40 .40 .31 .35 .36
.69 .76 .81 .63 .70 .72
299 340 348 270 301 310
.71 .72 .78 .70 .68 .74
1
Grams per hen per day.
2
Kilocalories metabolizable energy per hen per day.
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A Three 1-hr T w o 2-hr ad libitum Mean B Three 1-hr T w o 2-hr ad libitum Mean
Large Hen-housed eggs
TIME-LIMITED FEEDING OF LAYERS
1827
TABLE 4. Average body weights and weight gains throughout the two lay cycles
Initial
A Three 1-hr T w o 2-hr ad libitum Mean** B Three 1-hr T w o 2-hr ad libitum Mean**
1742a* 1773a 1787a 1767A 1644a* 1585a 1605a 1611B
First cycle final
First cycle gain
Postmolt
Second cycle final
1615B 1641AB 1827A 1694a 1570a 1601a 1660a 1610°
1804b 1841° 1974a 1843A 1694a 1739a 1782a 1706B
(%)
y&>
1736B 1772B 1937A 1815a 17 20 A 1677A 1789A 1729b
0 0 8 2.7 5 6 11 7.3
Second cycle gain
Total gain
(%)
(h>
12 12 8 10.7 8 9 7 8.0
3.6 3.8 10.5 4.3 3.0 9.7 11.0 5.9
'Duncan's multiple range compares the three limitation treatments for each strain separately. Means with the same capital letter are not significantly different (P>.01). Means with the same lower case letter are not significantly different (P>.05). " S t r a i n means with the same capital letter are not significandy different (P>.001). Strain means with the same lower case letter are not significantly different (P>.05).
gain weight during t h e first lay cycle, while t h e ad libitum controls gained an average of 8% over their initial b o d y weights. Strain B 3 - l h r and 2-2hr groups gained an average of 5 and 6%, respectively, whereas their ad libitum controls gained 1 1 % . These results are in agreement with t h e feed c o n s u m p t i o n data (Table 2), which showed marked reductions in feed intake by time-limited-fed groups. T h e fact t h a t neither time-limited-fed group of strain A gained weight during t h e first lay cycle indicates nutrient intake was critically close to their requirements under the conditions imposed. Although time-limited-fed groups of strain A did not gain weight, this strain was significantly heavier ( P « . 0 0 1 ) t h a n strain B t h r o u g h o u t t h e first lay cycle. Mortality. Higher than n o r m a l mortality was recorded t h r o u g h o u t t h e first 40-week lay cycle (Table 2), especially for strain A. The high mortality did n o t appear t o be caused by T L F , since it occurred within control groups as well as restricted groups. T h e cause was not identified. Egg Production. No significant differences a m o n g feeding regimes were d e t e c t e d ( P > . 0 5 ) in hen-day o r hen-housed egg p r o d u c t i o n within either of t h e t w o strains (Figs. 1 and 2). Strain A, however, laid significantly fewer eggs per hen-housed ( P < . 0 5 ) t h a n strain B, largely because of t h e higher mortality occurring within strain A (Table 2). Egg Size.
Only within strain A did T L F
t r e a t m e n t s significantly decrease t h e percent large eggs p r o d u c t i o n , although strain B had similar responses (Table 2). Strain A laid a significantly greater percentage of large eggs than strain B, presumably a genotypic response. T h e T L F had no significant effect ( P > . 0 5 ) o n egg quality as measured b y t h e Haugh unit (Haugh, 1937) in either of t h e t w o strains. Shell Thickness. Significant effects ( P < . 0 1 ) on shell thickness due to T L F were detected in strain A b u t n o t in strain B (Table 2). When strain data were c o m b i n e d , restricted hens laid eggs with significantly thicker shells t h a n ad libitum-ied hens ( P « . 0 5 ) between t h e t w o strains. Molt. Feed withdrawal and day length change as t h e force molting procedure successfully stopped p r o d u c t i o n , as 0% was recorded
^PRODUCTION
___
ADUIITUM THREE 1-HOUR TWO 2-HOUR
1
2
3
3
b
7
2SDArP£R!OOS
FIG. 1. Percent hen-day egg production during first lay cycle, Strain A.
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Strain/ limitation
KUNEY AND ENOS
1828
"PRODUCTION
70
!
3 28DAY PERIODS
FIG. 2. Percent hen-day egg production during first lay cycle, Strain B.
o n the 5th day of starvation t r e a t m e n t . Mortality was low, averaging . 9 3 % for the 28-day period in which t h e 10 days of feed deprivation started t h e period. Egg p r o d u c t i o n resumed on t h e 19th day after initiation of molt t r e a t m e n t . Second Lay Cycle—Feed Consumption. Average feed c o n s u m p t i o n during t h e second lay cycle was significantly affected by strain as well as T L F t r e a t m e n t s (Table 5), b u t there were no significant strain-by-treatment interactions. T h e 3 - l h r and 2-2hr limitation programs allowed statistically t h e same total feed c o n s u m p t i o n w h e n these t r e a t m e n t s for t h e t w o strains were averaged together. However, b o t h programs significantly reduced consumption from t h a t of t h e ad libitum control birds. Nutritional requirements for Single C o m b White Leghorns during t h e second lay cycle
Body Weight and Weight Gain. During the second lay cycle, weight gain (from b o d y weights t a k e n immediately following t h e force m o l t ) was less for ad libitum groups t h a n for time-limited g r o u p s (Table 4). Time-limited-fed birds exhibited greater weight losses during t h e force m o l t b u t compensated for that loss by gaining m o r e weight than ad libitum-fed birds during t h e interval of t h e second lay cycle. Mortality. Mortality was n o t affected by either strain or t r e a t m e n t during t h e second lay cycle (Table 5). Mortality occurred at a rate slightly greater than 1.0% per m o n t h (hen-
TABLE 5. Effect of time-limited feeding on laying performance during the second lay cycle
Feed c o n s u m p t i o n limitation
X
Reduction
Mortality Hen-housed
Production Hen-day
Hen-housed
Large eggs
(mm)
(g) A Three 1-hr Two 2-hr ad libitum Mean B Three 1-hr Two 2-hr ad libitum Mean
103A* 107A 120B 110A** 98A 99A 109B 102B
Average shell thickness
14 11 0 10 9 0
12.5a* 13.3a 12.5a 12.8a** 11.2a 9.0a 14.2a 11.5a
49.3a 52.8a 53.6a 51.9a 55.6a 54.9a 53.7a 54.7a
36.6b 44. l a 40.6ab 40.4B 45.8a 49.4a 45.3a 46.8A
94.6a 95.2a 96.5a 95.4A 86.0b 90.4ab 91.9a 89.4B
.389a .384ab ,381b .385a .384A .386A .371B .380b
efficiency (kg feed/ kg egg) 3.29ab 3.14b 3.46a 3.30A 2.92b 2.97b 3.26a 3.05B
•Duncan's multiple range compares the three limitation treatments for each strain separately. Means with the same capital letter are not significantly different (P>.01). Means with the same lower case letter are not significantly different (P>.05). "Strain means with the same capital letter are not significantly different (PX001). Strain means with the same lower case letter are not significantly different (P>.05).
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1
after a force m o l t have n o t yet b e e n established. However, o n e could a p p r o x i m a t e t h e d u r a t i o n of t h e t h r e e phases during t h e second cycle using a rationale similar to t h a t of Scott et al. ( 1 9 7 1 ) for t h e first lay cycle. F o r example, t h e period from t h e time t h e birds were given lay mash after t h e 10-day starvation period to t h e point where t h e y reached peak egg p r o d u c t i o n could correspond to Phase I. Phase II could represent t h e period from t h e end of Phase I t o t h e point where t h e hens were laying at a rate of 6 5 % . Phase III, as in the first cycle, would cover t h e period in which rate of lay fell below 6 5 % . If it is assumed t h e nutrient requirements during t h e t h r e e phases, as outlined by this rationale, are similar to t h o s e stated by Scott et al. ( 1 9 7 1 ) for t h e first cycle, a d e q u a t e a m o u n t s of total protein, methionine, and lysine were c o n s u m e d , o n t h e average, by all groups during each phase of t h e second lay cycle (Table 6).
TIME-LIMITED FEEDING OF LAYERS
1829
TABLE 6. Effect of time-limited feeding on nutrient intake during the three phases of egg production of the second lay cycle Phase I (65 t o 76 w k age) Protein 1
Methio- Lynine 1 sine 1
A Three 1-hr T w o 2-hr ad libitum B Three 1-hr T w o 2-hr ad libitum
18.8 18.9 22.1 18.6 18.4 20.0
.38 .38 .44 .37 .37 .40
.75 .76 .88 .74 .74 .80
Phase III (81 t o 104 w k age)
Calories 2
Protein 1
Methionine 1
Lysine 1
Calories 2
Protein 1
Methionine 1
Lysine
Calories 2
326 328 383 323 319 347
18.1 19.1 21.0 17.4 17.6 19.3
.36 .38 .42 .35 .35 .39
.73 .76 .84 .70 .70 .78
315 331 363 301 304 335
16.8 18.1 20.2 16.1 16.8 18.1
.34 .36 .40 .32 .34 .36
.67 .72 .81 .64 .67 .72
284 295 331 269 274 297
1
Grams per hen per day.
2
Kilocalories metabolizable energy per hen per day.
h o u s e d ) for strain A and slightly less t h a n 1.0% for strain B. Egg Production. Hen-day egg p r o d u c t i o n was n o t significantly altered by T L F during t h e second lay cycle within either of t h e t w o strains (Figures 3 and 4). T h e average values, 51.9 and 54.7% for strains A and B, respectively, include egg p r o d u c t i o n data during t h e m o l t period (Table 5). Although statistically nonsignificant ( P > . 0 5 ) , strain A birds fed ad libitum p r o d u c e d eggs at a slightly higher rate t h a n time-limitedfed birds. To t h e c o n t r a r y , within strain B, time-limited-fed hens produced eggs at a higher rate t h a n their ad libitum controls. Strain B showed a 6.4% hen-housed egg p r o d u c t i o n advantage over strain A. This advantage was d u e to t h e combined effects of a slightly higher p r o d u c t i o n rate and a slightly lower mortality rate (neither alone were statistically significant) during t h e second lay cycle o n t h e part of strain B. Egg Size. Egg size (as indicated by percent large) was significantly lowered by T L F within strain B b u t n o t strain A during t h e second lay cycle (Table 5). This finding was t h e reverse of t h e first lay cycle where egg size was significantly changed only within strain A. However, within b o t h strains we observed a trend of decreasing egg size as feed c o n s u m p t i o n decreased. As in t h e first lay cycle, strain A produced a greater percentage of large eggs. Shell Thickness. Within both strains hens fed ad libitum p r o d u c e d eggs with significantly t h i n n e r shells t h a n time-limited-fed hens (Table 5). Although shell thickness is shown to be a t r e a t m e n t response (Table 5), it is believed to be an indirect response to T L F and m o r e
directly related to egg size. Feed Efficiency. Feed efficiency improved as feed c o n s u m p t i o n decreased (Table 5). T h e only exception was t h e 3-lhr limitation group of strain A, which did n o t perform statistically different from its ad libitum control. Unlike t h e first lay cycle, strain B produced eggs with significantly greater ( P < . 0 0 1 ) feed efficiency t h a n strain A. DISCUSSION T h e use of controlled feeding m e t h o d s t o limit energy c o n s u m p t i o n normally would require fortification of t h e ration so t h a t with a restricted feed intake, deficiencies in protein, vitamins, and minerals do not occur. In this e x p e r i m e n t , with identical rations for all t r e a t m e n t groups, energy intake was successfully reduced by b o t h time-limited feeding programs. It is n o t k n o w n for certain w h e t h e r deficiencies in certain amino acids occurred during t h e first cycle of p r o d u c t i o n . Egg size
PRODUCTION
SO
_
ADUEITUM THREE 1-HOUR TW02-HOUR
••p"ASiS 2
'
|
"
3
4
| 5
6
7
8
9
1
0
11
28 0/TWR1OOS
FIG. 3. Percent hen-day production during the second lay cycle, Strain A.
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Strain/ limitation
Phase II (77 t o 80 w k age)
1830
KUNEY AND ENOS
70
* PRODUCTION
„•
'•-,
30
__
ADUSITUM
t w o strains. A n o t h e r possibility is t h a t the t w o restriction programs did n o t allow sufficient t i m e for strain A birds to c o n s u m e t h e same relative a m o u n t of feed as strain B. This last possibility might indicate different requirem e n t s for cage space a n d / o r , again, behavioral differences.
. . . . THREE 1-HOUR 30
TWOI-HOUR
was slightly depressed by T L F while rate or p r o d u c t i o n was not. In this instance, possibly a diet fortified with certain amino acids should have been fed t o prevent a possible deficiency. Although egg p r o d u c t i o n was not significantly lowered by t h e time-limited feeding programs, egg size and shell thickness were altered. Egg size appeared t o be closely related to feed intake in t h a t it was decreased w h e n feed intake was restricted. As egg size declined, shell thickness increased in m o s t cases. One possible explanation for this relationship between shell thickness and egg size is t h a t while calcium deposition by commercial egg-type chickens remains constant, increases in egg size will be accompanied by t h i n n e r egg shell (Roland et al, 1975). These results suggest that changes in feed intake can c o n t r i b u t e to significant changes in egg size and shell thickness w i t h o u t significantly altering egg p r o d u c t i o n . Also, egg size and shell thickness may be more sensitive to variations in nutrient intake t h a n average hen-day p r o d u c t i o n . T h e two strains responded similarly to time-limited feeding in terms of feed efficiency, egg size, and shell thickness. However, t h e t w o limitation programs imposed caused a greater feed restriction (relative t o ad libitum cons u m p t i o n ) for strain A t h a n strain B. For strain A, this greater restriction may have caused t h e nonsignificant depressions in egg p r o d u c t i o n . Restricted h e n s of strain B p r o d u c e d eggs at numerically higher rates t h a n their ad libitum controls, indicating the lower relative restriction imposed was probably not detrimental t o performance. Since b o t h strains were restricted t h e same n u m b e r of h o u r s and in t h e same m a n n e r , behavioral differences m a y exist b e t w e e n t h e
ACKNOWLEDGMENTS T h e experimental d a t a on which this study is based was supplied by t h e University of California Cooperative Extension Service. Special gratitude is expressed to Milo II. Swanson and Gary W. J o h n s t o n for assisting us with these data. Appreciation is also given to Carol J. A d a m s and Eleanor Beckwith for their assistance in t h e statistical analysis.
REFERENCES Andrews, D. K., 1973. Limited time feeding of commercial White Leghorn hens—a field trial. Poultry Sci. 52:1995. Balnave, D., and N. Jackson, 1973. The effect of quality of food offered and ad libitum feeding on metabolizable intakes and egg production responses of mature laying hens. World's Poultry Sci. J. 29:60. Bell, D. D., and R. E. Moreng, 1972. Intermittent feeding and lighting of mature Leghorn hens. Poultry Sci. 51:1783. Cherry, A. J. 1959. Restricted feeding time for the laying bird. World's Poultry Sci. J. 15:371-378. Combs, G. F., B. Cattis, and C. S. Shaffner, 1961. Studies with laying hens. 2. Energy restriction. Poultry Sci. 40:220-224. Dronawatt, N. S., 1968. Effect of feed restriction and of limiting feeding time on the performance of White Leghorn laying hens. Thesis, Washington State University, Pullman, WA. Dronawatt, N. S. and J. McGinnis, 1966. Effect of feed restriction and of limiting feeding time for laying hens on egg production, egg size and feed consumption. Poultry Sci. 45:1081. Duncan, D. B., 1955. Multiple range and multiple F test. Biometrics 11:1-42.
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FIG. 4. Percent hen-day production during second lay cycle, Strain B.
In the practice of controlled feeding, an end result should b e t h e minimizing of unnecessary energy c o n s u m p t i o n w i t h o u t creating deficiencies in o t h e r essential n u t r i e n t s and w i t h o u t sacrificing performance. It should be remembered t h a t t h e time-limited feeding m e t h o d restricts all n u t r i e n t s and n o t just energy. Finally, t h e a m o u n t of restriction for a successful feeding program logically d e p e n d s u p o n flock health, m a n a g e m e n t , environment, and possibly strain of bird. Optimally, these considerations should be m a d e o n an individual flock basis.
TIME-LIMITED FEEDING OF LAYERS
Pope, D. L., 1971. Limiting the feeding time of layers. Brookhurst Mill Rep. 19:1-4. Roland, D. A., Sr., D. R. Sloan, and R. H. Harms, 1975. The ability of hens to maintain calcium deposition in the egg shell and egg yolk as the hen ages. Poultry Sci. 54:1720-1723. Scott, M. L., M. C. Nesheim, and R. J. Young, 1971. Nutrition of the chicken. M. L. Scott and Associates, Ithaca, NY. Sherwood, D. H., and T. T. Milby, 1961. Controlled feeding of laying chickens. Poultry Sci. 40: 80-86. Singsen, E. P., L. D. Matterson, J. Tlustohowicz, and L. M. Potter, 1958. The effect of controlled feeding, energy intake, and type of diet on the performance of heavy-type laying hens. Poultry Sci. 37:1243-1244. Snetsinger, D. C , R. A. Zimmerman, and D. E. Greene, 1973. Limit feeding of egg strain layers. Poultry Sci. 52:2087. Snetsinger, D. C , R. A. Zimmerman, and D. E. Greene, 1974. Limited feeding of medium weight pullets and layers. Poultry Sci. 53:1980. Walter, E. F., and J. R. Aitken, 1961. Performance of laying hens subjected to restricted feeding during rearing and laying periods. Poultry Sci. 40: 345-354. Watkins, R. M., B. C. Dilworth, and E. J. Day, 1973. The effect of calcium source, particle size, level and restricted feeding time on shell strength and production parameters of commercial laying hens. Poultry Sci. 52:2100.
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Hannagan, M. J., and R. O. Willis, 1973. Practical observations on the restricted feeding of laying hens. World's Poultry Sci. J. 29:59-60. Haugh, R. R., 1937. The Haugh unit for measuring egg quality. US Egg and Poultry Mag. 4 3 : 5 5 2 - 5 5 5 ; 572-573. Heywang, B. W., 1940. The effect of restricted food intake on egg weight, egg production, and body weight. Poultry Sci. 19:29-34. Jackson, N., 1970. The effect of restricting the individual daily energy intake of caged layers on the efficiency of egg production. Brit. Poultry Sci. 11:93-102. Johnston, G. W., M. H. Swanson, and G. A. Salverson, 1972. A look at feed restriction in open houses. Pages 1 0 - 1 2 in Proc. 1972 Poultry Inst., Univ. California, Agr. Ext. Johnston, G. W., M. H. Swanson, and G. A. Salverson, 1973. Feed restriction through three lay cycles. Pages 8-13 in Proc. 1973 Poultry Inst. Univ. California, Agr. Ext. Kari, R. R., J. H. Quisenberry, and J. W. Bradley, 1977. Egg quality and performance as influenced by restricted feeding of commercial caged layers. Poultry Sci. 56:1914-1919. Little, T. M., and F. J. Hills, 1975. Statistical methods in agricultural research. Univ. California, Davis, CA. Polin, D., and J. H. Wolford, 1971. Egg production by W. L. adult females restricted in feed intake by limiting their time or allotted amount to eat. Poultry Sci. 50:1618.
1831
(Received for publication March 30, 1979) ABSTRACT Ad libitum feeding of laying hens was compared with two 2-hr (2-2hr) and three 1-hr (3-lhr) feeding times per day in terms of rate of lay, feed efficiency, body weight, mortality, egg size, and quality. Two strains of commercial layers were housed in a conventional Californiatype open house at a density rate of three hens per 30.5 X 45.7 cm wire cage. The study continued through two lay cycles. Average feed restriction, relative to ad libitum-ied hens, was 11% and 8% during the first lay cycle and 12% and 10% during the second cycle for the 3-lhr and 2-2hr groups, respectively. Both time-limited feeding (TLF) programs significantly improved feed efficiency during each lay cycle. Average body weight gain for both TLF programs was less than ad libitum gain during the first lay cycle but greater during the second cycle. Unusually high mortality (cause undetermined) occurred during the first lay cycle but was not treatment related. Nonsignificant depressions in rate of lay among TLF groups were observed during both cycles. Decreased egg size, as measured by percent large, and an increased shell thickness due to TLF treatments occurred during both lay cycles. No egg quality differences were observed. Some strain differences were observed, which may indicate that strain should be considered along with environment, management, and flock health conditions when using TLF as a method of feed restriction. (Key words: layers, time-limited feeding, production, feed efficiency, open housing) 1980 Poultry Science 59:1824-1831 INTRODUCTION
Feed represents the major expense item in the total cost of egg production. With rising feed prices, producers are looking for new ways to reduce production costs and restore profit margins. Increasing feed efficiency through controlled feed intake may be one possibility. Although governed basically by their energy requirements, layers may under certain conditions overconsume, as reported by Andrews (1973), Balnave and Jackson (1973), Cherry (1959), Combs et al. (1961), Hannagan and Willis (1973), Johnston et al. (1972, 1973), Kari et al. (1977), Pope (1971), Sherwood and Milby (1961), Singsen et al. (1958), and Snetsinger et al. (1974). Overconsumption, in these
1 Published with the approval of the Director of the Colorado Agricultural Experiment Station as Scientific Series paper number 2438. Presented by the senior author in partial fulfillment of the requirements for the Master of Science Degree.
instances, occurs when birds fed ad libitum lay statistically at the same rate as restricted birds under similar conditions of temperature, age, type of feed, housing, and management. In efforts to minimize wasted feed through overconsumption, several researchers have studied the efficacy of physically limiting feed consumption by laying hens. Sherwood and Milby (1961) and Walter and Aitken (1961) reported decreased egg production as a result of feed restriction. Heywang (1940) restricted Single Comb White Leghorn pullets to 87.5 and 75.0% of the ad libitum control hens and observed a significant decrease in egg production. However, other workers have restricted laying hens as much as 15% without significantly lowering egg production (Dronawatt, 1968; Dronawatt and McGinnis, 1966; Johnston et al, 1973; Snetsinger et al., 1973; Watkins et al, 1973). In addition, all of these investigators reported improved feed efficiency as a result of the lowered feed consumption. In 1966, Dronawatt and McGinnis reported decreased egg size when laying hens were
1824
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Department of Animal Sciences, Colorado State University, Fort Collins, Colorado 80523
TIME-LIMITED FEEDING OF LAYERS
EXPERIMENTAL PROCEDURE
Two commercial strains of Single Comb White Leghorn chickens were brooded and reared in the mild coastal climate of southern California. Conventional milo, corn, and soybean type rations were used. At 24 weeks of age the pullets were placed in a California open-type house at a density rate of three birds per cage. The 30.5 X 45.7 cm cages provided 465 cm2 of floor space per bird. The cages were oriented in a single row on each side of the house with a double row of back-to-back cages in the center. Lath siding partially protected the birds from wind and intense sunlight. The metal roof was not insulated. Feed troughs located at the front of each cage provided 10.2 cm of feeder space per bird. The waterers were continuous-flow type V-troughs which ran the length of each row at the rear of the cages. Three feeding treatments were imposed upon each strain of chicken. The first treatment consisted of three 1-hr (3-lhr) feeding periods per day (0700 to 0800 hr, 1300 to 1400 hr, and 1900 to 2000 hr). The second treatment allowed the birds to eat during two 2-hr (2-2hr) periods per day (0700 to 0900 hr and 1900 to 2100 hr). The third treatment served as a control and permitted the birds to feed ad libitum. Daylight was augmented artificially for a total of 17 hr of light per day (0500 to 1000 hr). For time-limited fed treatment groups, access was controlled mechanically by use of a
plywood lid hinged to the front of the feed through. A cord from each lid was attached to a central cable which, in turn, was connected to a hydraulic ram controlled by a 24-hr time clock. Trough lids opened or closed according to prescribed feeding treatments throughout the experiment. Two rations were fed during the test in accordance with seasonal temperature changes (Table 1). The winter ration, containing 16% crude protein and 2,756 kcal me/kg, was fed from October through May. The summer ration, with 17% crude protein and 2,695 kcal/kg, was fed from June to October. The experimental design, consisting of three feeding regimes and two strains, was a randomized complete block using six blocks. Each treatment replication consisted of 24 birds in an 8-cage section for a total of 864 hens. Data collections were started on February 20 when the hens were 24 weeks of age and continued through two lay cycles separated by a force-molt. The molt was accomplished at 64 weeks of age by removing the feed for 10 days, and the birds were returned to natural day lengths. Then the winter Phase I lay ration was reinstated as well as 17 hr lighting per day. Birds had water at all times during the molt period. Statistical analysis was performed on the data using the analysis of variance technique (Little and Hills, 1975) and multiple range test (Duncan, 1955). Duration of the experiment was 80 weeks, ending on August 29 of the second year. RESULTS
First Lay Cycle—Feed Consumption. Timelimited feeding (TLF) 3-lhr and 2-2hr groups had significantly reduced average feed con-
TABLE 1. Selected parameters calculated for the experimental rations Ingredients Metabolizable energy (kcal/kg) Crude protein (%) Methionine (%) Methionine plus cystine (%) Lysine (%) Calcium (%) Phosphorus (%)
Winter
Summer
2,756 16.0 .32
2,695 17.0 .34
.56 .64 3.70 .60
.59 .68 3.70 ..60
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restricted to 90% of control hens fed ad libitum. Other investigators also have observed losses in egg weight during feed restriction (Bell and Moreng, 1972; Jackson, 1970; Polin and Wolford, 1971). To the contrary, Johnston et al. (1972), Kari et al. (1977), and Snetsinger et al. (1973) found no significant decrease in egg weight. Mortality rate may be affected by feed restriction. Hannagan and Willis (1973), Singsen et al. (1958), and Snetsinger et al. (1973) report higher mortality among hens fed ad libitum than hens fed restrictively. This may be due to excess body fat accumulation, which was shown to be related to mortality by Singsen etal. (1958). The research being reported here is one of a series of experiments conducted to evaluate time-limited feeding in southern California, where the majority of egg-type poultry houses are of the open-type design.
1825
KUNEY AND ENOS
1826
TABLE 2. Effect of time-limited feeding on laying performance during the first lay cycle
Strain/ limitation
Feed consumption
Mortality
Reduction
Production
Hen-housed
Hen-day
(%)-
(g)
69.1a 69.2a 72.9a 70.4a 72.6a 70.8a 70.2a 71.2a
17.4A* 9.1B 17.4A 14.6A 10.7a 5.0b 7.1a 7.6B
12 106c* 8 lllb 0 120a 112A** 10lt> 10 8 103b 0 112a 105»
Average shell thickness (mm)
77.7 b 79 yab 81.8 a 79.7 A 57.la 62.4 a 65.8 a 61.8B
64.2a 66.0a 65.7a 65.3b 68.8a 68.9a 67.5a 68.4a
Feed efficiency (kg feed/ kg egg) 2.59 a 2.66 a 2.75 a 2.66 a 2.46 B 2.58AB 2.80 A 2.61 a
.384 A B .389 A .378 B .384 a .381 a .384 a .378 a .381 a
•Duncan's multiple range compares the three limitation treatments for each strain separately. Means with the same capital letter are not significantly different (P>,01). Means with the same lower case letter are not significantly different (P>.05). " S t r a i n means with the same capital letter are not significandy different (P>.001). Strain means with the same lower case letter are not significandy different (P>.05).
s u m p t i o n ( P < . 0 5 ) during t h e first lay cycle (Table 2). Because there were no significant strain-by-treatment interactions, d a t a for t h e t w o strains were combined. On t h e average, T L F g r o u p s resulted in an 11 and 8% reduction in feed c o n s u m p t i o n from the ad libitum control groups for t h e 3 - l h r and 2-2hr treatm e n t groups, respectively. Strain A consumed significantly more feed t h a n strain B ( P < . 0 0 1 ) . Scott et al. ( 1 9 7 1 ) state t h a t Single C o m b White Leghorn hens require 18 g of protein per day during Phase I (20 t o 4 2 weeks of age), 16 g during Phase II (from 4 2 weeks of age t o
a rate of lay of 65%), and 15 g of protein per day during Phase III (rate of lay below 65%). When using this rationale as a guideline for nutrient requirements, the 3-lhr and 2-2hr feeding t r e a t m e n t s did n o t allow birds to c o n s u m e an a d e q u a t e 18 g level of protein during Phase I (Table 3). During subsequent phases, however, t h e average daily protein intake would be considered sufficient according t o this interpretation. Body Weight and Weight Gain. Within b o t h strains, weight gain was reduced by T L F (Table 4). T h e strain A 3 - l h r and 2-2hr groups did n o t
TABLE 3. Average daily nutrient intake during the three phases of egg production during the first lay cycle Phase I ( 2 4 to 4 2 wk age)
Phase II (43 t o 60 w k age:)
Phase III (61 t o 64 w k age)
Strain/ limitation
Protein 1
Methio- Lynine' sine'
Calories 2
Protein 1
Methionine'
Lysine 1
Calories 2
Protein 1
Methionine 1
Lysine'
Calories 2
A Three 1-hr Two 2-hr ad libitum B Three 1-hr Two 2-hr ad libitum
17.2 17.8 19.1 17.0 16.6 18.3
.35 .36 .39 .35 .34 .38
291 299 319 286 278 308
18.1 18.6 20.6 16.7 17.6 19.1
.36 .38 .41 .33 .36 .38
.73 .76 .82 .66 .71 .75
287 299 324 263 282 298
17.6 18.8 20.4 16.2 17.3 18.3
.35 .40 .40 .31 .35 .36
.69 .76 .81 .63 .70 .72
299 340 348 270 301 310
.71 .72 .78 .70 .68 .74
1
Grams per hen per day.
2
Kilocalories metabolizable energy per hen per day.
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A Three 1-hr T w o 2-hr ad libitum Mean B Three 1-hr T w o 2-hr ad libitum Mean
Large Hen-housed eggs
TIME-LIMITED FEEDING OF LAYERS
1827
TABLE 4. Average body weights and weight gains throughout the two lay cycles
Initial
A Three 1-hr T w o 2-hr ad libitum Mean** B Three 1-hr T w o 2-hr ad libitum Mean**
1742a* 1773a 1787a 1767A 1644a* 1585a 1605a 1611B
First cycle final
First cycle gain
Postmolt
Second cycle final
1615B 1641AB 1827A 1694a 1570a 1601a 1660a 1610°
1804b 1841° 1974a 1843A 1694a 1739a 1782a 1706B
(%)
y&>
1736B 1772B 1937A 1815a 17 20 A 1677A 1789A 1729b
0 0 8 2.7 5 6 11 7.3
Second cycle gain
Total gain
(%)
(h>
12 12 8 10.7 8 9 7 8.0
3.6 3.8 10.5 4.3 3.0 9.7 11.0 5.9
'Duncan's multiple range compares the three limitation treatments for each strain separately. Means with the same capital letter are not significantly different (P>.01). Means with the same lower case letter are not significantly different (P>.05). " S t r a i n means with the same capital letter are not significandy different (P>.001). Strain means with the same lower case letter are not significantly different (P>.05).
gain weight during t h e first lay cycle, while t h e ad libitum controls gained an average of 8% over their initial b o d y weights. Strain B 3 - l h r and 2-2hr groups gained an average of 5 and 6%, respectively, whereas their ad libitum controls gained 1 1 % . These results are in agreement with t h e feed c o n s u m p t i o n data (Table 2), which showed marked reductions in feed intake by time-limited-fed groups. T h e fact t h a t neither time-limited-fed group of strain A gained weight during t h e first lay cycle indicates nutrient intake was critically close to their requirements under the conditions imposed. Although time-limited-fed groups of strain A did not gain weight, this strain was significantly heavier ( P « . 0 0 1 ) t h a n strain B t h r o u g h o u t t h e first lay cycle. Mortality. Higher than n o r m a l mortality was recorded t h r o u g h o u t t h e first 40-week lay cycle (Table 2), especially for strain A. The high mortality did n o t appear t o be caused by T L F , since it occurred within control groups as well as restricted groups. T h e cause was not identified. Egg Production. No significant differences a m o n g feeding regimes were d e t e c t e d ( P > . 0 5 ) in hen-day o r hen-housed egg p r o d u c t i o n within either of t h e t w o strains (Figs. 1 and 2). Strain A, however, laid significantly fewer eggs per hen-housed ( P < . 0 5 ) t h a n strain B, largely because of t h e higher mortality occurring within strain A (Table 2). Egg Size.
Only within strain A did T L F
t r e a t m e n t s significantly decrease t h e percent large eggs p r o d u c t i o n , although strain B had similar responses (Table 2). Strain A laid a significantly greater percentage of large eggs than strain B, presumably a genotypic response. T h e T L F had no significant effect ( P > . 0 5 ) o n egg quality as measured b y t h e Haugh unit (Haugh, 1937) in either of t h e t w o strains. Shell Thickness. Significant effects ( P < . 0 1 ) on shell thickness due to T L F were detected in strain A b u t n o t in strain B (Table 2). When strain data were c o m b i n e d , restricted hens laid eggs with significantly thicker shells t h a n ad libitum-ied hens ( P « . 0 5 ) between t h e t w o strains. Molt. Feed withdrawal and day length change as t h e force molting procedure successfully stopped p r o d u c t i o n , as 0% was recorded
^PRODUCTION
___
ADUIITUM THREE 1-HOUR TWO 2-HOUR
1
2
3
3
b
7
2SDArP£R!OOS
FIG. 1. Percent hen-day egg production during first lay cycle, Strain A.
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Strain/ limitation
KUNEY AND ENOS
1828
"PRODUCTION
70
!
3 28DAY PERIODS
FIG. 2. Percent hen-day egg production during first lay cycle, Strain B.
o n the 5th day of starvation t r e a t m e n t . Mortality was low, averaging . 9 3 % for the 28-day period in which t h e 10 days of feed deprivation started t h e period. Egg p r o d u c t i o n resumed on t h e 19th day after initiation of molt t r e a t m e n t . Second Lay Cycle—Feed Consumption. Average feed c o n s u m p t i o n during t h e second lay cycle was significantly affected by strain as well as T L F t r e a t m e n t s (Table 5), b u t there were no significant strain-by-treatment interactions. T h e 3 - l h r and 2-2hr limitation programs allowed statistically t h e same total feed c o n s u m p t i o n w h e n these t r e a t m e n t s for t h e t w o strains were averaged together. However, b o t h programs significantly reduced consumption from t h a t of t h e ad libitum control birds. Nutritional requirements for Single C o m b White Leghorns during t h e second lay cycle
Body Weight and Weight Gain. During the second lay cycle, weight gain (from b o d y weights t a k e n immediately following t h e force m o l t ) was less for ad libitum groups t h a n for time-limited g r o u p s (Table 4). Time-limited-fed birds exhibited greater weight losses during t h e force m o l t b u t compensated for that loss by gaining m o r e weight than ad libitum-fed birds during t h e interval of t h e second lay cycle. Mortality. Mortality was n o t affected by either strain or t r e a t m e n t during t h e second lay cycle (Table 5). Mortality occurred at a rate slightly greater than 1.0% per m o n t h (hen-
TABLE 5. Effect of time-limited feeding on laying performance during the second lay cycle
Feed c o n s u m p t i o n limitation
X
Reduction
Mortality Hen-housed
Production Hen-day
Hen-housed
Large eggs
(mm)
(g) A Three 1-hr Two 2-hr ad libitum Mean B Three 1-hr Two 2-hr ad libitum Mean
103A* 107A 120B 110A** 98A 99A 109B 102B
Average shell thickness
14 11 0 10 9 0
12.5a* 13.3a 12.5a 12.8a** 11.2a 9.0a 14.2a 11.5a
49.3a 52.8a 53.6a 51.9a 55.6a 54.9a 53.7a 54.7a
36.6b 44. l a 40.6ab 40.4B 45.8a 49.4a 45.3a 46.8A
94.6a 95.2a 96.5a 95.4A 86.0b 90.4ab 91.9a 89.4B
.389a .384ab ,381b .385a .384A .386A .371B .380b
efficiency (kg feed/ kg egg) 3.29ab 3.14b 3.46a 3.30A 2.92b 2.97b 3.26a 3.05B
•Duncan's multiple range compares the three limitation treatments for each strain separately. Means with the same capital letter are not significantly different (P>.01). Means with the same lower case letter are not significantly different (P>.05). "Strain means with the same capital letter are not significantly different (PX001). Strain means with the same lower case letter are not significantly different (P>.05).
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1
after a force m o l t have n o t yet b e e n established. However, o n e could a p p r o x i m a t e t h e d u r a t i o n of t h e t h r e e phases during t h e second cycle using a rationale similar to t h a t of Scott et al. ( 1 9 7 1 ) for t h e first lay cycle. F o r example, t h e period from t h e time t h e birds were given lay mash after t h e 10-day starvation period to t h e point where t h e y reached peak egg p r o d u c t i o n could correspond to Phase I. Phase II could represent t h e period from t h e end of Phase I t o t h e point where t h e hens were laying at a rate of 6 5 % . Phase III, as in the first cycle, would cover t h e period in which rate of lay fell below 6 5 % . If it is assumed t h e nutrient requirements during t h e t h r e e phases, as outlined by this rationale, are similar to t h o s e stated by Scott et al. ( 1 9 7 1 ) for t h e first cycle, a d e q u a t e a m o u n t s of total protein, methionine, and lysine were c o n s u m e d , o n t h e average, by all groups during each phase of t h e second lay cycle (Table 6).
TIME-LIMITED FEEDING OF LAYERS
1829
TABLE 6. Effect of time-limited feeding on nutrient intake during the three phases of egg production of the second lay cycle Phase I (65 t o 76 w k age) Protein 1
Methio- Lynine 1 sine 1
A Three 1-hr T w o 2-hr ad libitum B Three 1-hr T w o 2-hr ad libitum
18.8 18.9 22.1 18.6 18.4 20.0
.38 .38 .44 .37 .37 .40
.75 .76 .88 .74 .74 .80
Phase III (81 t o 104 w k age)
Calories 2
Protein 1
Methionine 1
Lysine 1
Calories 2
Protein 1
Methionine 1
Lysine
Calories 2
326 328 383 323 319 347
18.1 19.1 21.0 17.4 17.6 19.3
.36 .38 .42 .35 .35 .39
.73 .76 .84 .70 .70 .78
315 331 363 301 304 335
16.8 18.1 20.2 16.1 16.8 18.1
.34 .36 .40 .32 .34 .36
.67 .72 .81 .64 .67 .72
284 295 331 269 274 297
1
Grams per hen per day.
2
Kilocalories metabolizable energy per hen per day.
h o u s e d ) for strain A and slightly less t h a n 1.0% for strain B. Egg Production. Hen-day egg p r o d u c t i o n was n o t significantly altered by T L F during t h e second lay cycle within either of t h e t w o strains (Figures 3 and 4). T h e average values, 51.9 and 54.7% for strains A and B, respectively, include egg p r o d u c t i o n data during t h e m o l t period (Table 5). Although statistically nonsignificant ( P > . 0 5 ) , strain A birds fed ad libitum p r o d u c e d eggs at a slightly higher rate t h a n time-limitedfed birds. To t h e c o n t r a r y , within strain B, time-limited-fed hens produced eggs at a higher rate t h a n their ad libitum controls. Strain B showed a 6.4% hen-housed egg p r o d u c t i o n advantage over strain A. This advantage was d u e to t h e combined effects of a slightly higher p r o d u c t i o n rate and a slightly lower mortality rate (neither alone were statistically significant) during t h e second lay cycle o n t h e part of strain B. Egg Size. Egg size (as indicated by percent large) was significantly lowered by T L F within strain B b u t n o t strain A during t h e second lay cycle (Table 5). This finding was t h e reverse of t h e first lay cycle where egg size was significantly changed only within strain A. However, within b o t h strains we observed a trend of decreasing egg size as feed c o n s u m p t i o n decreased. As in t h e first lay cycle, strain A produced a greater percentage of large eggs. Shell Thickness. Within both strains hens fed ad libitum p r o d u c e d eggs with significantly t h i n n e r shells t h a n time-limited-fed hens (Table 5). Although shell thickness is shown to be a t r e a t m e n t response (Table 5), it is believed to be an indirect response to T L F and m o r e
directly related to egg size. Feed Efficiency. Feed efficiency improved as feed c o n s u m p t i o n decreased (Table 5). T h e only exception was t h e 3-lhr limitation group of strain A, which did n o t perform statistically different from its ad libitum control. Unlike t h e first lay cycle, strain B produced eggs with significantly greater ( P < . 0 0 1 ) feed efficiency t h a n strain A. DISCUSSION T h e use of controlled feeding m e t h o d s t o limit energy c o n s u m p t i o n normally would require fortification of t h e ration so t h a t with a restricted feed intake, deficiencies in protein, vitamins, and minerals do not occur. In this e x p e r i m e n t , with identical rations for all t r e a t m e n t groups, energy intake was successfully reduced by b o t h time-limited feeding programs. It is n o t k n o w n for certain w h e t h e r deficiencies in certain amino acids occurred during t h e first cycle of p r o d u c t i o n . Egg size
PRODUCTION
SO
_
ADUEITUM THREE 1-HOUR TW02-HOUR
••p"ASiS 2
'
|
"
3
4
| 5
6
7
8
9
1
0
11
28 0/TWR1OOS
FIG. 3. Percent hen-day production during the second lay cycle, Strain A.
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Strain/ limitation
Phase II (77 t o 80 w k age)
1830
KUNEY AND ENOS
70
* PRODUCTION
„•
'•-,
30
__
ADUSITUM
t w o strains. A n o t h e r possibility is t h a t the t w o restriction programs did n o t allow sufficient t i m e for strain A birds to c o n s u m e t h e same relative a m o u n t of feed as strain B. This last possibility might indicate different requirem e n t s for cage space a n d / o r , again, behavioral differences.
. . . . THREE 1-HOUR 30
TWOI-HOUR
was slightly depressed by T L F while rate or p r o d u c t i o n was not. In this instance, possibly a diet fortified with certain amino acids should have been fed t o prevent a possible deficiency. Although egg p r o d u c t i o n was not significantly lowered by t h e time-limited feeding programs, egg size and shell thickness were altered. Egg size appeared t o be closely related to feed intake in t h a t it was decreased w h e n feed intake was restricted. As egg size declined, shell thickness increased in m o s t cases. One possible explanation for this relationship between shell thickness and egg size is t h a t while calcium deposition by commercial egg-type chickens remains constant, increases in egg size will be accompanied by t h i n n e r egg shell (Roland et al, 1975). These results suggest that changes in feed intake can c o n t r i b u t e to significant changes in egg size and shell thickness w i t h o u t significantly altering egg p r o d u c t i o n . Also, egg size and shell thickness may be more sensitive to variations in nutrient intake t h a n average hen-day p r o d u c t i o n . T h e two strains responded similarly to time-limited feeding in terms of feed efficiency, egg size, and shell thickness. However, t h e t w o limitation programs imposed caused a greater feed restriction (relative t o ad libitum cons u m p t i o n ) for strain A t h a n strain B. For strain A, this greater restriction may have caused t h e nonsignificant depressions in egg p r o d u c t i o n . Restricted h e n s of strain B p r o d u c e d eggs at numerically higher rates t h a n their ad libitum controls, indicating the lower relative restriction imposed was probably not detrimental t o performance. Since b o t h strains were restricted t h e same n u m b e r of h o u r s and in t h e same m a n n e r , behavioral differences m a y exist b e t w e e n t h e
ACKNOWLEDGMENTS T h e experimental d a t a on which this study is based was supplied by t h e University of California Cooperative Extension Service. Special gratitude is expressed to Milo II. Swanson and Gary W. J o h n s t o n for assisting us with these data. Appreciation is also given to Carol J. A d a m s and Eleanor Beckwith for their assistance in t h e statistical analysis.
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FIG. 4. Percent hen-day production during second lay cycle, Strain B.
In the practice of controlled feeding, an end result should b e t h e minimizing of unnecessary energy c o n s u m p t i o n w i t h o u t creating deficiencies in o t h e r essential n u t r i e n t s and w i t h o u t sacrificing performance. It should be remembered t h a t t h e time-limited feeding m e t h o d restricts all n u t r i e n t s and n o t just energy. Finally, t h e a m o u n t of restriction for a successful feeding program logically d e p e n d s u p o n flock health, m a n a g e m e n t , environment, and possibly strain of bird. Optimally, these considerations should be m a d e o n an individual flock basis.
TIME-LIMITED FEEDING OF LAYERS
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