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Dietary Energy Concentration Effect on Performance of White Leghorn Hens at Various Densities in Cages1
Dietary Energy Concentration Effect on Performance of White Leghorn Hens at Various Densities in Cages1 L. B. CAREW, JR., D. C. FOSS, and D. E. BEE2 Department of Animal Sciences, Bioresearch Laboratory, University of Vermont, Burlington, Vermont 05405 (Received for publication June 20, 1979)
1980 Poultry Science 59:1090-1098 INTRODUCTION It is generally observed t h a t egg p r o d u c t i o n declines as hen density in cages increases (Wilson et ai, 1 9 6 7 ; reviews by Hughes, 1 9 7 5 ; N o r t h , 1978). However, few researchers have studied t h e effect of dietary energy level on this p h e n o m e n o n (review, Carew et al., 1 9 7 6 ) . We showed previously (Carew et al., 1976) t h a t t h e decline in egg p r o d u c t i o n t h a t occurs as the density of hens in cages increases cannot be reversed by increasing t h e dietary energy concentration. T h u s , this lower egg p r o d u c t i o n cannot be a t t r i b u t e d simply t o c o m p e t i t i o n for feeding time or space. To t h e contrary, there was evidence t h a t increasing dietary energy from 2,737 o r 3,003 kcal/g to 3,322 kcal/g b y t h e addition of soybean oil caused consistently lower egg p r o d u c t i o n , particularly during t h e latter half of t h e 12-month layer experiment. In
1 Vermont Agricultural Experiment Station Journal Article No. 417. 2 Statistician, Vermont Agricultural Experiment Station. Present address, Department of Preventive Medicine and Community Health, University of Texas Medical Branch, Galveston, TX 77550.
t h a t e x p e r i m e n t we studied a crossbred, heavy, egg-type hen (Sex-Sal) popular in New England for b r o w n egg p r o d u c t i o n . However, since t h e majority of commercial hens in t h e US are of White Leghorn derivation, a breed t h a t is m u c h lighter in b o d y size and different in behavioral characteristics from t h e ones we had studied, we repeated our study using t h e White Leghorn hen. R e p o r t s o n t h e effects o f dietary energy per se on hen performance are confusing and contradictory. In m a n y of these studies t h e ratio b e t w e e n dietary energy and protein or n u t r i e n t density varied as energy level changed. Since food intake is controlled primarily by energy needs, intakes of protein and o t h e r nutrients also varied in these studies (Carew et al., 1976) and confounded t h e results. However, in studies where t h e p r o p o r t i o n of dietary energy to protein was held constant, increases in dietary energy usually did n o t affect hen performance (Maclntyre and Aitken, 1 9 5 7 ; Turk et al, 1 9 5 8 ; Davis et al., 1 9 5 8 ; T o u c h b u r n and Naber, 1 9 6 2 ; March and Biely, 1963). In the present s t u d y we held n u t r i e n t density constant in relation to dietary energy level.
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ABSTRACT White Leghorn hens housed at cage floor densities of 660, 440, or 330 cm 2 each (2,3, or 4 per cage) were fed diets with 2,737, 3,003, or 3,322 kcal/kg of metabolizable energy from 21 to 73 weeks of age. As density of hens per cage increased, hen-day egg production and efficiency of feed utilization were reduced, whereas mortality increased. Final body weight decreased most with 4 hens per cage. Feed intake, energy intake, and egg quality characteristics were little affected. Dietary energy level did not significantly affect overall hen-day egg production. However, the highest dietary energy consistently resulted in the lowest egg production during the latter part of the experiment. This decrease was most noticeable with hens housed 4 per cage. This confirms our earlier conclusion with heavy, egg-type hens that high dietary energy is not conducive to sustained egg production with high density housing of hens in cages. Increasing the dietary energy level decreased feed intake and consequently increased efficiency of feed utilization. However, energy intake/hen was similar with all diets. Total mortality as well as that caused just by traumatic events increased as dietary energy increased. Egg quality characteristics were little affected by dietary energy. In agreement with our earlier study with heavy, egg-type hens, we conclude that increasing dietary energy level for White Leghorn hens will not reverse the downward trend in egg production that occurs as hen density in cages increases. The only depressive effect of increasing hen density in cages that was partly reversible by increasing dietary energy was the decline in body weight.
DIETARY ENERGY, CAGE DENSITY, AND HEN PERFORMANCE
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TABLE 1. Composition of diets for laying hens Ingredients
Diet 1
Diet 2 y,a/
—- -
58.3875 15.40 10.00 2.70 .0125
Constant ingredients premix Fish meal (72% protein) Alfalfa meal (20% protein) Diealcium phosphate Limestone Salt Methionine hydroxy analogue Vitamin premix 3 Mineral premix a
13.50 (90.6% of diet 2 premix) 0
Calculated analysis: Crude protein, % ME, kcal/kg Kcal ME/kg % crude protein Ether extract, % Crude fiber, %
64.0875 18.00
49.6875 23.80
3.00 .0125
10.00 .0125
14.90 3.00 2.00 1.90 7.00
16.50 (110.7% of diet 2 premix) 0
.37 .03 .50 .10
15.50 2,737 177 5.60 5.20
17.00 3,003 177
6.00 2.30
18.80 3,322 177
12.60 2.20
Mineral and vitamin premixes supply the following to diet 2, in mg/kg of diet: manganese 60, iron 20, copper 2, iodine 1.2, cobalt .2, calcium 250, riboflavin 4.4, calcium pantothenate 8.8, niacin 20, choline 22, menadione 2, vitamin B12 .01; in units/kg of diet: vitamin A 4,875 IU, vitamin D 3 1,000 IU, vitamin E 4.4 IU. These quantities of "constant ingredients" supply the same proportions of ingredients as found in diet 2.
MATERIALS AND METHODS
The design of this experiment was similar to that reported earlier (Carew et al., 1976). The diets contained 2,737, 3,003, or 3,322 kcal/kg of metabolizable energy (Table 1). Energy levels were altered primarily by varying the amounts of corn, soybean oil, and oat hulls. The energy-to-protein ratio was held constant, and the proportion of other nutrients to energy was held constant by the use of a "constant ingredients" premix. By calculation, the essential amino acid balance of all diets was similar. Feed and water were consumed ad libitum throughout the study. Hecht's Single Comb White Leghorn pullets were used. They were debeaked and dubbed at the hatchery. From hatching to 6 weeks they were housed in heated brooder cages. Thereafter half were grown in cages and half in floor pens. Equal proportions of pullets from these two management systems were distributed among the layer treatments at 21 weeks of age. Commercial starter and grower rations were fed 0 to 8 and 8 to 21 weeks of age, respectively. The diets were supplemented with 400 g/ton of Terramycin from 35 to 45 days of age.
The split plot design used was described previously. At 21 weeks of age, 1,080 hens were housed in Harford three-tier layer units with individual cages that measured 29 cm wide by 45.5 cm deep. At densities of 2, 3, or 4 hens/cage, the allotted floor area was 660, 440, or 330 cm /hen, respectively. Contiguous (side-by-side) units of 10 cages each, at any one of the three tiers in the cage units, were considered the experimental units. Six blocks of cages each contained six of the 10-cage units. Hens were housed at three densities — 2, 3, or 4 birds per cage — and fed one of the three diets. There were, therefore, nine treatments (3 densities x 3 diets) with 4 units of 10 cages per treatment. Since cage number was constant but hen density varied, 80 hens at 2 per cage, 120 hens at 3 per cage, and 160 hens at 4 per cage were fed each diet. The experiment was divided into thirteen 28-day periods, and egg production and feed consumption were measured for each period. Egg weight was measured for 3 consecutive days in all but the first period. Egg shell breaking strength, Haugh units, and meat and blood spots were measured for 3 consecutive days
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Ground yellow corn Soybean oil meal (49% protein) Oat hulls Soybean oil Ethoxyquin (100%)
Diet 3
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CAREW, JR., ET AL.
RESULTS AND DISCUSSION Increasing hen density resulted in a significant (P<.05) decline in egg production. This
amounted to a 2% decline for each additional bird added to the cage (Tables 2 and 3) and occurred consistently throughout the experiment (Fig. 1). This agrees with our previous results (Carewetal, 1976)when heavy, egg-type hens were increased from 2 to 3 birds per cage, and conforms to the conclusion of many others (Wilson et al, 1967; review, Grover et al., 1972). As we found previously, increasing dietary energy from 2,737 to 3,003 or 3,322 kcal/kg did not reverse the downward trend in egg production that occurred as hen density/cage increased (Table 2; and lack of C X D interaction, Table 3). This strengthens our earlier conclusion that the lower egg production that accompanies higher hen density is not simply a result of competition for limited feeder space or feeding time. Otherwise, if the least competitive hens were not being allowed sufficient feeding time by the other hens, the presence of a higher energy feed should allow them to meet their nutritional needs more readily on the same amount of feeding time. Among other factors that might influence performance of caged layers, Sefton (1976) has shown that a behavioral index called "fearfulness" increases
TABLE 2. Performance characteristics at differing hen densities and dietary energy levels Treatments Hens/ cage
Dietary energy levels (kcal/kg b )
Hen-day egg prod. 3
(%)
Feed intake/ day 3
Energy Intake/ day 3 (kcal)
Feed/ egga
Final body weight 3
Mortality Total
From traumatic events
(%)
74.4 73.7 73.7 72.0 72.5 71.7 70.0 71.4 68.3
106 99 86 107 98 88 105 100 87
289 297 285 292 294 293 288 300 290
142 134 116 148 135 123 147 140 128
(g) 1,913 1,959 1,891 1,867 1,850 1,950 1,754 1,788 1,797
10.0 11.2
0 1.2 2.5 .8 1.7 5.0 .6 3.1 5.0
74.0 72.0 69.9
97 98 98
290 293 293
131 135 138
1,921 1,889 1,780
3.3 4.7 8.9
1.2 2.5 2.9
Averages for dietary energy 2,737 kcal/kg 73.1 3,003 kcal/kg 72.5 3,322 k cal/kg 71.2
106 99 87
290 297 289
146 136 122
1,827 1,846 1,868
3.4 6.0 7.6
.5 2.0 4.2
2 2 2 3 3 3 4 4 4
2,737 3,003 3,322 2,737 3,003 3,322 2,737 3,003 3,322
Averages for hen density 2 hens/cage 3 hens/t:age 4 hens/cage
(g)
Values represent averages/hen from 21 to 73 weeks of age. Metabolizable energy.
(g)
3.7 1.2 5.0 .8 6.7 6.7 5.6
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during periods 2, 5, 8, and 11. Body weights were measured during periods 1, 4, 7,10, and 13. Average values for egg production, feed intake, feed/egg, and body weight were obtained for each 10-cage tier. Values for egg weight, shell breaking strength (determined by needle puncture), Haugh units, and meat and blood spots were obtained by averaging all data within 1 day for a given treatment. The experiment, which started in mid-October and continued through November of the following year, was conducted in a windowless research unit. Artificial lighting was supplied on a 14L:10D daily schedule. Room heat was derived largely from body heat. Air circulation design during winter was sufficient to maintain room temperature above 10 C except on the coldest days. During warm weather, room temperature was similar to that of the external air temperature. Bird density was kept constant throughout the experiment by replacing mortalities with hens from a surplus group that was fed the diet with 3,003 kcal/kg.
2 9 2 4 18 12 24 108 24 48 216
Hens/cage (C) Error! Diet (D) C XD Error 2 Period (P) CX P Error 3 D XP CXDXP Error 4
P<.01.
**
P<.05.
d.f.
Variable
1,924**
23 18
8,623**
11 13 14 8 10
10 9
30**
14,088**
76 78
25 96
Feed intake/day
109 76 44 43
468*
Hen-day egg prod.
2 9 2 4 18 12 24 108 24 48 216
d.f.
507
2,756*
gg
103 173 77 160
54,304** 208**
263 391
24,099**
e
Feed/
2 9 2 4 18 4 8 36 8 16 72
d.f.
388 359
101,450* 7,846 5,785 23,031** 4,677 1,504,517** 10,877** 1,127 1,597**
Final body weight 2 6 2 4 12 11 22 66 22 44 132
d.f.
.7 .7 .7 .6 .7
292.0
.8
11.6
.5 1.3
10.8
weigh
Egg
TABLE 3. Summary of mean square values obtained from statistical an
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_^_j 25
CAREW, JR., ETAL.
i 29
i 33
i 37
i 41
i 45
i 49
i 53
i 57
i 61
i 65
i 69
1_ 73
AGE IN WEEKS
as number of birds/cage increases, although this is not strongly related to changes in floor area/bird. As dietary energy increased, egg production did not change significantly overall (Table 2). However, after about the first third of the study, egg production with the highest energy level was consistently lowest (Fig. 2). This agrees with our earlier observation that showed that as they get older, heavy egg-type hens produce significantly fewer eggs when consuming a high energy level. Grover et al. (1972) observed a similar depression in egg production with increasing dietary energy (2,840 to 3,060 kcal/kg) when dietary energy-protein ratios varied. Our results show that a similar effect occurs when the energy-protein ratio is held constant, although it occurs only at a high dietary energy level (3,322 kcal/kg). The decline in egg production with increasing dietary energy in these studies demonstrates that small losses in egg production can be expected when high-energy, high-fat layer diets are used. This loss, although relatively small, should be incorporated into calculations of the economic value of using such rations for layers at high-cage densities. Kondra et al. (1968) reported that high energy rations depress egg production in certain strains of individually caged hens. Our results show that this effect can be seen in differing breeds of hens caged at high densities. Gleaves et al. (1968) proposed that high energy diets depress egg production because feed intake and hence protein intake are reduced. However, in our present study energy
Final body weight declined significantly (P<.05) with increasing hen density (Tables 2,3) in a pattern similar to that reported by us earlier with heavy egg-type hens. However, unlike previously, this reduction in body size was not accompanied by a decrease in feed or energy intake. This suggests that changes in body composition or caloric efficiency might have occurred as body weight dropped to account for the surplus energy intake. But the possibility cannot be ruled out that feed intake measurements were imprecise because of greater feed wastage with higher hen density. The significant (P<.01) cage-by-diet interaction for final body weight is caused by the fact that body weight increased only with the 3,003 kcal/kg dietary energy level at the density of 2 hens/cage, and only with the 3,322 kcal/kg dietary energy level at the density of 3 hens/ cage, but with both of these dietary energy levels at the density of 4 hens/cage (Table 2). There is, therefore, a tendency for the decrease in body weight concurrent with increasing hen density to be reversed by an increase in dietary energy. As dietary energy increased, the loss in body weight was fully reversed at a density of 3 hens/cage, but only partially so at 4 hens/ cage. The significant (P<.01) cage-by-period interaction is the result of a complex pattern of weight changes between hen densities at various periods during the experiment (Table 4). Increasing dietary energy did not significantly affect body weight overall (Tables 2 and 3), but there was a significant (P<.01) diet X period interaction, which reflects primarily the capacity
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FIG. 1. Hen-day egg production by White Leghorn hens housed at densities of 2 per cage •— •, 3 per cage o o, or 4 per cage A A.
intake/hen/day was almost identical with either the lowest or highest energy diets (Table 2). Since the diets were isonitrogenous with nearly constant ratios between energy and all other nutrients, a reduction in nutrient intake did not occur and thus could not have caused lower egg production. Average energy intake/day over the entire experiment was similar in all treatments. Hens adjusted for increases in dietary caloric density by reducing their feed intake. Because of this, grams of feed required to produce an egg decreased with increasing caloric density. That is, efficiency of feed utilization increased (Table 2). However, efficiency of feed utilization decreased as hen density increased because feed intake remained similar as hen density/cage increased, but egg production declined. These changes in efficiency of feed utilization agree with our previous study.
DIETARY ENERGY, CAGE DENSITY, AND HEN PERFORMANCE
25
29
33
37
41
45
49
53
57
61
65
69
73
AGE IN WEEKS
of the hens fed the higher energy diets to gain more weight during the first phase of the experiment (Table 4). This difference and its overall effect were very small and should not be referred to as obesity. However, this result is consistent with earlier results obtained by ourselves and others (Carew et al., 1976) and demonstrates the tendency of hens fed high energy rations to weigh more. Mortality was not analyzed statistically. However, total mortality increased somewhat as either hen density or dietary energy level increased (Table 2). The highest mortality occurred with hens housed 4/cage and fed either of the higher dietary energy levels. This effect of hen density on mortality agrees with most work in this area (Lowe and Heywang, 1964; Wilson et al, 1967; Grover et al, 1972; Carew et al, 1976). However, dietary energy level affecting mortality usually has not been
observed (Berg and Bearse, 1956; Maclntyre and Aitken, 1957; Hochreich, et al, 1958; Peterson et al., 1960; Quisenberry and Bradley, 1962; March and Biely, 1963; Gleaves et al, 1968; Carew et al, 1976), although Heywang and Vavich (1962) observed greater mortality of White Leghorn hens as dietary energy increased. Of 71 total mortalities, 27% was caused by Leucosis or Marek's disease and 37% by traumatic events, primarily vent picking. The remaining 36% was the result of miscellaneous causes. Increasing the bird density in cages resulted in only a small increase in mortality because of traumatic events (Table 2). This increase is much less than reported by Lowe and Heywang (1964) and Wilson et al. (1967). Surprisingly, however, we found a definite increase in mortality as a result of trauma when dietary energy increased (Table 2). This effect occurred with hens at all densities but was more pronounced with either 3 or 4 hens/cage. There was a significant (P<.01) cage-by-diet interactive effect on egg weight (Tables 3 and 5), partly because eggs produced by hens at the highest cage density and fed the highest energy level were the heaviest whereas those produced by hens at the lowest cage density and fed the highest energy level were the lightest. The heavier egg weight correlates, in part, with lower egg production,as expected from extensive literature reports. Overall, differences in egg weights between cage and dietary treatments were small but statistically detectable due to the large number of observations. However, their practical importance is questionable. Shell-breaking strength was not significantly affected by the main effects, but there was a complicated three-way interaction (P<.05). The
TABLE 4. Effect of hen density and dietary energy level on periodic body weights3 Body weight (g)° Treatment
28 days
2. hens/cage 3 hens/cage 4 hens/cage
1,372 1,354 1,353
2,737 kcal/kg diet 3,003 kcal/kg diet 3,322 kcal/kg diet
1,358 1,357 1,343
112 days
196 days
(353) (385) (346)
1,725 1,739 1,699
(83) (82) (39)
1,808 1,821 1,738
(348) (357) (392)
1,706 1,714 1,735
(69) (65) (55)
1,775 1,779 1,790
Values represent averages/hen. Weight gain is shown in parenthesis.
280 days
364 days
(76) (33) (25)
1,884 1,854 1,763
(37) (35) (17)
1,921 1,889 1,780
(21) (41) (55)
1,796 1,820 1,845
(31) (26) (24)
1,827 1,846 1,869
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FIG. 2. Hen-day egg production by White Leghorn hens fed diets containing 3,322 kcal/kg o o, 3,003 kcal/kg o o, and 2,737 kcal/kg
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CAREW, JR., ETAL. TABLE 5. Effect of hen density and dietary energy level on egg quality characteristics Treatments
Hens/ cage
Dietary energy level (kcal/kgb)
Egg weight 3
Shellbreaking strength 3
Haugh units 3
Eggs showing any meat or blood spots
(%)
(kg) 13.3 13.9 13.8 13.9 13.3 13.7 14.1 13.4 14.0
85.5 85.9 87.3 86.7 86.2 86.1 85.4 85.2 83.5
11 16 19 9 11 10 10 9 10
Averages for hen density 2 hens/cage 3 hens/cage 4 hens/cage
59.4 59.6 60.0
13.7 13.6 13.8
86.2 86.3 84.7
15 10 10
Averages for dietary energy 2,737 kcal/kg 3,003 kcal/kg 3,322 kcal/kg
59.6 59.7 59.8
13.8 13.5 13.8
85.9 85.8 85.6
10 12 13
2 2 2 3 3 3 4 4 4
2,737 3,003 3,322 2,737 3,003 3,322 2.737 3,003 3,322
Values represent averages/hen from 21 to 73 weeks of age. Metabolizable energy.
data on periodic shell-breaking strength are presented in Table 6, but no definite trends are evident. Haugh units were not significantly affected by cage or dietary treatment (Tables 3 and 5), but they decreased significantly (P<.01) with age, as expected. Average Haugh unit measurements over all treatments at periods 2, 5, 8, and 11 were 91.9, 86.0, 83.3, and 81.8, respectively. The presence of meat and blood spots in eggs were not significantly affected by hen density or dietary treatment. However, we observed that age significantly (P<.05) affected meat and blood spots; this represents an increase in these defects with age, particularly between the first half and last half of the study. Our observation that hen density has little effect on egg quality agrees generally with that of others (Wilson et al, 1967; Al-Rawi et al., 1976; Moore et al, 1977). In summarizing our present and previous studies on hen density and dietary energy level, we have found that increasing the density of either White Leghorn or heavy, egg-type hens in cages results in a decline in egg production, a decrease in efficiency of feed utilization, a decrease in body weight primarily at the highest
density, and an increase in mortality. Egg weight, shell-breaking strength, Haugh units, and meat and blood spots are little affected. Increasing dietary energy level to 3,322 kcal/kg by adding fat consistently causes a small decline in egg production of light or heavy breeds during the latter part of a laying year. This decline is observed most consistently with hens housed at the greatest densities (440 cm for the heavy breed and 330 cm 2 for Leghorns). This small decrease in egg production may be relatively unimportant economically if the cost.of dietary fats is favorable. Hens on the highest energy level weigh slightly more, but not to the extent of being considered obese. This change is accompanied by an increase in energy intake only in heavy hens. An unexpected observation with White Leghorn hens was that mortality as a result of cannibalism increases as dietary energy level increases, • an event that remains to be confirmed. Egg quality characteristics and egg weight are little affected by dietary energy level, with the exception in heavy hens that the highest energy level caused a small increase in egg weight during the mid-part of the study. The unfavorable effect on egg production,
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(g) 59.5 59.8 59.0 59.9 59.2 59.8 59.4 60.1 60.6
DIETARY ENERGY, CAGE DENSITY, AND HEN PERFORMANCE
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TABLE 6. Effect of hen density and dietary energy level on periodic shell-breaking strength Treatments
Kilograms of pressure (Period of measurement^
Hens/cage
Dietary energy level
2
5
8
11
2 2 2
2,737 3,003 3,322
13.1 13.5 13.6
12.1 12.6 14.2
14.1 14.8 14.0
13.9 14.5 13.3
3 3 3
2,737 3,003 3,322
14.0 13.5 13.2
13.8 14.0 13.9
13.6 13.7 14.7
14.2 12.1 13.0
4 ' 4 4
2,737 3,003 3,322
13.5 13.8 13.0
15.1 13.8 14.7
14.6 13.3 15.2
13.0 12.7 13.2
efficiency of feed utilization, or m o r t a l i t y as a result of increasing hen density was n o t reversed b y increasing t h e dietary energy level. But t h e reduction in b o d y weight t h a t accompanied increasing hen density was fully or partially reversible by increasing dietary energy depending o n t h e cage density of t h e hens. ACKNOWLEDGMENTS We appreciate t h e assistance of Gerard Shrewsbury and t h e technical staff. We are grateful to A b b o t t Laboratories, Commercial Solvents Corporation, Hoffmann-LaRoche, Merck and Co. Inc., Monsanto Chemical Co., Morton Salt Co., Syntex Agribusiness Inc., and T h o m p s o n - H a y w a r d Chemical Co., for supplying materials.
REFERENCES Al-Rawi, B., J. V. Craig, and A. W. Adams, 1976. Agonistic behavior and egg production of caged layers: genetic strain and group-size effects. Poultry Sci. 55:796-807. Berg, L. R., and G. E. Bearse, 1956. The effect of water-soluble vitamins and energy level of the diet on the performance of laying pullets. Poultry Sci. 35:945-951. Carew, Jr., L. B., D. C. Foss, and D. E. Bee, 1976. Effect of dietary energy concentration on performance of heavy egg-type hens at various densities in cages. Poultry Sci. 55:1057—1066. Davis, B. H., W. S. Wilkinson, and A. B. Watts, 1958. A study of the relationship of energy and protein in caged layer nutrition. Poultry Sci. 37:1197. Gleaves, E. W., L. V. Tonkinson, J. D. Wolf, C. K. Harman, R. H. Thayer, and R. D. Morrison, 1968. The action and interaction of physiological
food intake regulators in the laying hen. Poultry Sci. 4 7 : 3 8 - 6 7 . Grover, R. M., D. L. Anderson, R. A. Damon, Jr., and L. H. Ruggles, 1972. The effects of bird density, dietary energy, light intensity, and cage level on the reproductive performance of heavy type chickens in wire cages. Poultry Sci. 51:565—575. Heywang, B. W., and M. G. Vavich, 1962. Energy level of a sixteen percent protein diet for layers in a semiarid, subtropical climate. Poultry Sci. 4 1 : 1389-1393. Hochreich, H. J., C. R. Douglas, I. H. Kidd, and R. H. Harms, 1958. The effect of dietary protein and energy levels upon production of Single Comb White Leghorn hens. Poultry Sci. 37:949-953. Hughes, B. O., 1975. The concept of an optimum stocking density and its selection for egg production. Pages 271—298 in Economic factors affecting egg production. B. M. Freeman, and K. N. Boorman, ed. Brit. Poultry Sci. Ltd., Edinburgh. Kondra, P. A., S. H. Choo, and J. L. Sell. 1968. Influence of strain of chicken and dietary fat on egg production traits. Poultry Sci. 47; 1290-1296. Lowe, R. W., and B. W. Heywang, 1964. Performance of single and multiple caged White Leghorn layers. Poultry Sci. 43:801-805. Maclntyre, T. M., and J. R. Aitken, 1957. The effect of high levels of dietary energy and protein on the performance of laying hens. Poultry Sci. 36:1211-1216. March, B. E., and J. Biely, 1963. The effects of dietary fat and energy levels on the performance of caged laying birds. Poultry Sci. 42:20-24. Moore, D. J., J. W. Bradley, and T. M. Ferguson, 1977. Radius breaking strength and egg characteristics of laying hens as affected by dietary supplements and housing. Poultry Sci. 56:189-192. North, M. O., 1978. Commercial chicken production manual. AVI Publ. Co., Inc., Westport, CT. Peterson, C. F., E. A. Sauter, D. H. Conrad, and C. E. Lampman, 1960. Effect of energy level and laying house temperature on the performance of
Downloaded from http://ps.oxfordjournals.org/ at NERL on May 17, 2015
See text for number of measurements made.
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White Leghorn pullets. Poultry Sci. 39: 1010-1018. Quisenberry, J. H., and J. W. Bradley, 1962. Effects of dietary protein and changes in energy levels on the laying house performance of egg production stocks. Poultry Sci. 41:717-724. Sefton, A. E., 1976. The interactions of cage size, cage level, social density, fearfulness, and production of Single Comb White Leghorns. Poultry Sci. 55:1922-1926.
Touchburn, S. P., and E. C. Naber, 1962. Effect of nutrient density and protein-energy interrelationships on reproductive performance of the hen. Poultry Sci. 41:1481-1488. Turk, D. E., H. R. Bird, and M. L. Sunde, 1958. Effect of fats on replacement pullets and laying hens. Poultry Sci. 37:1249. Wilson, H. R., J. E. Jones, and R. W. Dorminey, 1967. Performance of layers under various cage regimens. Poultry Sci. 46:422-425.
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1980 Poultry Science 59:1090-1098 INTRODUCTION It is generally observed t h a t egg p r o d u c t i o n declines as hen density in cages increases (Wilson et ai, 1 9 6 7 ; reviews by Hughes, 1 9 7 5 ; N o r t h , 1978). However, few researchers have studied t h e effect of dietary energy level on this p h e n o m e n o n (review, Carew et al., 1 9 7 6 ) . We showed previously (Carew et al., 1976) t h a t t h e decline in egg p r o d u c t i o n t h a t occurs as the density of hens in cages increases cannot be reversed by increasing t h e dietary energy concentration. T h u s , this lower egg p r o d u c t i o n cannot be a t t r i b u t e d simply t o c o m p e t i t i o n for feeding time or space. To t h e contrary, there was evidence t h a t increasing dietary energy from 2,737 o r 3,003 kcal/g to 3,322 kcal/g b y t h e addition of soybean oil caused consistently lower egg p r o d u c t i o n , particularly during t h e latter half of t h e 12-month layer experiment. In
1 Vermont Agricultural Experiment Station Journal Article No. 417. 2 Statistician, Vermont Agricultural Experiment Station. Present address, Department of Preventive Medicine and Community Health, University of Texas Medical Branch, Galveston, TX 77550.
t h a t e x p e r i m e n t we studied a crossbred, heavy, egg-type hen (Sex-Sal) popular in New England for b r o w n egg p r o d u c t i o n . However, since t h e majority of commercial hens in t h e US are of White Leghorn derivation, a breed t h a t is m u c h lighter in b o d y size and different in behavioral characteristics from t h e ones we had studied, we repeated our study using t h e White Leghorn hen. R e p o r t s o n t h e effects o f dietary energy per se on hen performance are confusing and contradictory. In m a n y of these studies t h e ratio b e t w e e n dietary energy and protein or n u t r i e n t density varied as energy level changed. Since food intake is controlled primarily by energy needs, intakes of protein and o t h e r nutrients also varied in these studies (Carew et al., 1976) and confounded t h e results. However, in studies where t h e p r o p o r t i o n of dietary energy to protein was held constant, increases in dietary energy usually did n o t affect hen performance (Maclntyre and Aitken, 1 9 5 7 ; Turk et al, 1 9 5 8 ; Davis et al., 1 9 5 8 ; T o u c h b u r n and Naber, 1 9 6 2 ; March and Biely, 1963). In the present s t u d y we held n u t r i e n t density constant in relation to dietary energy level.
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ABSTRACT White Leghorn hens housed at cage floor densities of 660, 440, or 330 cm 2 each (2,3, or 4 per cage) were fed diets with 2,737, 3,003, or 3,322 kcal/kg of metabolizable energy from 21 to 73 weeks of age. As density of hens per cage increased, hen-day egg production and efficiency of feed utilization were reduced, whereas mortality increased. Final body weight decreased most with 4 hens per cage. Feed intake, energy intake, and egg quality characteristics were little affected. Dietary energy level did not significantly affect overall hen-day egg production. However, the highest dietary energy consistently resulted in the lowest egg production during the latter part of the experiment. This decrease was most noticeable with hens housed 4 per cage. This confirms our earlier conclusion with heavy, egg-type hens that high dietary energy is not conducive to sustained egg production with high density housing of hens in cages. Increasing the dietary energy level decreased feed intake and consequently increased efficiency of feed utilization. However, energy intake/hen was similar with all diets. Total mortality as well as that caused just by traumatic events increased as dietary energy increased. Egg quality characteristics were little affected by dietary energy. In agreement with our earlier study with heavy, egg-type hens, we conclude that increasing dietary energy level for White Leghorn hens will not reverse the downward trend in egg production that occurs as hen density in cages increases. The only depressive effect of increasing hen density in cages that was partly reversible by increasing dietary energy was the decline in body weight.
DIETARY ENERGY, CAGE DENSITY, AND HEN PERFORMANCE
1091
TABLE 1. Composition of diets for laying hens Ingredients
Diet 1
Diet 2 y,a/
—- -
58.3875 15.40 10.00 2.70 .0125
Constant ingredients premix Fish meal (72% protein) Alfalfa meal (20% protein) Diealcium phosphate Limestone Salt Methionine hydroxy analogue Vitamin premix 3 Mineral premix a
13.50 (90.6% of diet 2 premix) 0
Calculated analysis: Crude protein, % ME, kcal/kg Kcal ME/kg % crude protein Ether extract, % Crude fiber, %
64.0875 18.00
49.6875 23.80
3.00 .0125
10.00 .0125
14.90 3.00 2.00 1.90 7.00
16.50 (110.7% of diet 2 premix) 0
.37 .03 .50 .10
15.50 2,737 177 5.60 5.20
17.00 3,003 177
6.00 2.30
18.80 3,322 177
12.60 2.20
Mineral and vitamin premixes supply the following to diet 2, in mg/kg of diet: manganese 60, iron 20, copper 2, iodine 1.2, cobalt .2, calcium 250, riboflavin 4.4, calcium pantothenate 8.8, niacin 20, choline 22, menadione 2, vitamin B12 .01; in units/kg of diet: vitamin A 4,875 IU, vitamin D 3 1,000 IU, vitamin E 4.4 IU. These quantities of "constant ingredients" supply the same proportions of ingredients as found in diet 2.
MATERIALS AND METHODS
The design of this experiment was similar to that reported earlier (Carew et al., 1976). The diets contained 2,737, 3,003, or 3,322 kcal/kg of metabolizable energy (Table 1). Energy levels were altered primarily by varying the amounts of corn, soybean oil, and oat hulls. The energy-to-protein ratio was held constant, and the proportion of other nutrients to energy was held constant by the use of a "constant ingredients" premix. By calculation, the essential amino acid balance of all diets was similar. Feed and water were consumed ad libitum throughout the study. Hecht's Single Comb White Leghorn pullets were used. They were debeaked and dubbed at the hatchery. From hatching to 6 weeks they were housed in heated brooder cages. Thereafter half were grown in cages and half in floor pens. Equal proportions of pullets from these two management systems were distributed among the layer treatments at 21 weeks of age. Commercial starter and grower rations were fed 0 to 8 and 8 to 21 weeks of age, respectively. The diets were supplemented with 400 g/ton of Terramycin from 35 to 45 days of age.
The split plot design used was described previously. At 21 weeks of age, 1,080 hens were housed in Harford three-tier layer units with individual cages that measured 29 cm wide by 45.5 cm deep. At densities of 2, 3, or 4 hens/cage, the allotted floor area was 660, 440, or 330 cm /hen, respectively. Contiguous (side-by-side) units of 10 cages each, at any one of the three tiers in the cage units, were considered the experimental units. Six blocks of cages each contained six of the 10-cage units. Hens were housed at three densities — 2, 3, or 4 birds per cage — and fed one of the three diets. There were, therefore, nine treatments (3 densities x 3 diets) with 4 units of 10 cages per treatment. Since cage number was constant but hen density varied, 80 hens at 2 per cage, 120 hens at 3 per cage, and 160 hens at 4 per cage were fed each diet. The experiment was divided into thirteen 28-day periods, and egg production and feed consumption were measured for each period. Egg weight was measured for 3 consecutive days in all but the first period. Egg shell breaking strength, Haugh units, and meat and blood spots were measured for 3 consecutive days
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Ground yellow corn Soybean oil meal (49% protein) Oat hulls Soybean oil Ethoxyquin (100%)
Diet 3
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CAREW, JR., ET AL.
RESULTS AND DISCUSSION Increasing hen density resulted in a significant (P<.05) decline in egg production. This
amounted to a 2% decline for each additional bird added to the cage (Tables 2 and 3) and occurred consistently throughout the experiment (Fig. 1). This agrees with our previous results (Carewetal, 1976)when heavy, egg-type hens were increased from 2 to 3 birds per cage, and conforms to the conclusion of many others (Wilson et al, 1967; review, Grover et al., 1972). As we found previously, increasing dietary energy from 2,737 to 3,003 or 3,322 kcal/kg did not reverse the downward trend in egg production that occurred as hen density/cage increased (Table 2; and lack of C X D interaction, Table 3). This strengthens our earlier conclusion that the lower egg production that accompanies higher hen density is not simply a result of competition for limited feeder space or feeding time. Otherwise, if the least competitive hens were not being allowed sufficient feeding time by the other hens, the presence of a higher energy feed should allow them to meet their nutritional needs more readily on the same amount of feeding time. Among other factors that might influence performance of caged layers, Sefton (1976) has shown that a behavioral index called "fearfulness" increases
TABLE 2. Performance characteristics at differing hen densities and dietary energy levels Treatments Hens/ cage
Dietary energy levels (kcal/kg b )
Hen-day egg prod. 3
(%)
Feed intake/ day 3
Energy Intake/ day 3 (kcal)
Feed/ egga
Final body weight 3
Mortality Total
From traumatic events
(%)
74.4 73.7 73.7 72.0 72.5 71.7 70.0 71.4 68.3
106 99 86 107 98 88 105 100 87
289 297 285 292 294 293 288 300 290
142 134 116 148 135 123 147 140 128
(g) 1,913 1,959 1,891 1,867 1,850 1,950 1,754 1,788 1,797
10.0 11.2
0 1.2 2.5 .8 1.7 5.0 .6 3.1 5.0
74.0 72.0 69.9
97 98 98
290 293 293
131 135 138
1,921 1,889 1,780
3.3 4.7 8.9
1.2 2.5 2.9
Averages for dietary energy 2,737 kcal/kg 73.1 3,003 kcal/kg 72.5 3,322 k cal/kg 71.2
106 99 87
290 297 289
146 136 122
1,827 1,846 1,868
3.4 6.0 7.6
.5 2.0 4.2
2 2 2 3 3 3 4 4 4
2,737 3,003 3,322 2,737 3,003 3,322 2,737 3,003 3,322
Averages for hen density 2 hens/cage 3 hens/t:age 4 hens/cage
(g)
Values represent averages/hen from 21 to 73 weeks of age. Metabolizable energy.
(g)
3.7 1.2 5.0 .8 6.7 6.7 5.6
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during periods 2, 5, 8, and 11. Body weights were measured during periods 1, 4, 7,10, and 13. Average values for egg production, feed intake, feed/egg, and body weight were obtained for each 10-cage tier. Values for egg weight, shell breaking strength (determined by needle puncture), Haugh units, and meat and blood spots were obtained by averaging all data within 1 day for a given treatment. The experiment, which started in mid-October and continued through November of the following year, was conducted in a windowless research unit. Artificial lighting was supplied on a 14L:10D daily schedule. Room heat was derived largely from body heat. Air circulation design during winter was sufficient to maintain room temperature above 10 C except on the coldest days. During warm weather, room temperature was similar to that of the external air temperature. Bird density was kept constant throughout the experiment by replacing mortalities with hens from a surplus group that was fed the diet with 3,003 kcal/kg.
2 9 2 4 18 12 24 108 24 48 216
Hens/cage (C) Error! Diet (D) C XD Error 2 Period (P) CX P Error 3 D XP CXDXP Error 4
P<.01.
**
P<.05.
d.f.
Variable
1,924**
23 18
8,623**
11 13 14 8 10
10 9
30**
14,088**
76 78
25 96
Feed intake/day
109 76 44 43
468*
Hen-day egg prod.
2 9 2 4 18 12 24 108 24 48 216
d.f.
507
2,756*
gg
103 173 77 160
54,304** 208**
263 391
24,099**
e
Feed/
2 9 2 4 18 4 8 36 8 16 72
d.f.
388 359
101,450* 7,846 5,785 23,031** 4,677 1,504,517** 10,877** 1,127 1,597**
Final body weight 2 6 2 4 12 11 22 66 22 44 132
d.f.
.7 .7 .7 .6 .7
292.0
.8
11.6
.5 1.3
10.8
weigh
Egg
TABLE 3. Summary of mean square values obtained from statistical an
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1094
_^_j 25
CAREW, JR., ETAL.
i 29
i 33
i 37
i 41
i 45
i 49
i 53
i 57
i 61
i 65
i 69
1_ 73
AGE IN WEEKS
as number of birds/cage increases, although this is not strongly related to changes in floor area/bird. As dietary energy increased, egg production did not change significantly overall (Table 2). However, after about the first third of the study, egg production with the highest energy level was consistently lowest (Fig. 2). This agrees with our earlier observation that showed that as they get older, heavy egg-type hens produce significantly fewer eggs when consuming a high energy level. Grover et al. (1972) observed a similar depression in egg production with increasing dietary energy (2,840 to 3,060 kcal/kg) when dietary energy-protein ratios varied. Our results show that a similar effect occurs when the energy-protein ratio is held constant, although it occurs only at a high dietary energy level (3,322 kcal/kg). The decline in egg production with increasing dietary energy in these studies demonstrates that small losses in egg production can be expected when high-energy, high-fat layer diets are used. This loss, although relatively small, should be incorporated into calculations of the economic value of using such rations for layers at high-cage densities. Kondra et al. (1968) reported that high energy rations depress egg production in certain strains of individually caged hens. Our results show that this effect can be seen in differing breeds of hens caged at high densities. Gleaves et al. (1968) proposed that high energy diets depress egg production because feed intake and hence protein intake are reduced. However, in our present study energy
Final body weight declined significantly (P<.05) with increasing hen density (Tables 2,3) in a pattern similar to that reported by us earlier with heavy egg-type hens. However, unlike previously, this reduction in body size was not accompanied by a decrease in feed or energy intake. This suggests that changes in body composition or caloric efficiency might have occurred as body weight dropped to account for the surplus energy intake. But the possibility cannot be ruled out that feed intake measurements were imprecise because of greater feed wastage with higher hen density. The significant (P<.01) cage-by-diet interaction for final body weight is caused by the fact that body weight increased only with the 3,003 kcal/kg dietary energy level at the density of 2 hens/cage, and only with the 3,322 kcal/kg dietary energy level at the density of 3 hens/ cage, but with both of these dietary energy levels at the density of 4 hens/cage (Table 2). There is, therefore, a tendency for the decrease in body weight concurrent with increasing hen density to be reversed by an increase in dietary energy. As dietary energy increased, the loss in body weight was fully reversed at a density of 3 hens/cage, but only partially so at 4 hens/ cage. The significant (P<.01) cage-by-period interaction is the result of a complex pattern of weight changes between hen densities at various periods during the experiment (Table 4). Increasing dietary energy did not significantly affect body weight overall (Tables 2 and 3), but there was a significant (P<.01) diet X period interaction, which reflects primarily the capacity
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FIG. 1. Hen-day egg production by White Leghorn hens housed at densities of 2 per cage •— •, 3 per cage o o, or 4 per cage A A.
intake/hen/day was almost identical with either the lowest or highest energy diets (Table 2). Since the diets were isonitrogenous with nearly constant ratios between energy and all other nutrients, a reduction in nutrient intake did not occur and thus could not have caused lower egg production. Average energy intake/day over the entire experiment was similar in all treatments. Hens adjusted for increases in dietary caloric density by reducing their feed intake. Because of this, grams of feed required to produce an egg decreased with increasing caloric density. That is, efficiency of feed utilization increased (Table 2). However, efficiency of feed utilization decreased as hen density increased because feed intake remained similar as hen density/cage increased, but egg production declined. These changes in efficiency of feed utilization agree with our previous study.
DIETARY ENERGY, CAGE DENSITY, AND HEN PERFORMANCE
25
29
33
37
41
45
49
53
57
61
65
69
73
AGE IN WEEKS
of the hens fed the higher energy diets to gain more weight during the first phase of the experiment (Table 4). This difference and its overall effect were very small and should not be referred to as obesity. However, this result is consistent with earlier results obtained by ourselves and others (Carew et al., 1976) and demonstrates the tendency of hens fed high energy rations to weigh more. Mortality was not analyzed statistically. However, total mortality increased somewhat as either hen density or dietary energy level increased (Table 2). The highest mortality occurred with hens housed 4/cage and fed either of the higher dietary energy levels. This effect of hen density on mortality agrees with most work in this area (Lowe and Heywang, 1964; Wilson et al, 1967; Grover et al, 1972; Carew et al, 1976). However, dietary energy level affecting mortality usually has not been
observed (Berg and Bearse, 1956; Maclntyre and Aitken, 1957; Hochreich, et al, 1958; Peterson et al., 1960; Quisenberry and Bradley, 1962; March and Biely, 1963; Gleaves et al, 1968; Carew et al, 1976), although Heywang and Vavich (1962) observed greater mortality of White Leghorn hens as dietary energy increased. Of 71 total mortalities, 27% was caused by Leucosis or Marek's disease and 37% by traumatic events, primarily vent picking. The remaining 36% was the result of miscellaneous causes. Increasing the bird density in cages resulted in only a small increase in mortality because of traumatic events (Table 2). This increase is much less than reported by Lowe and Heywang (1964) and Wilson et al. (1967). Surprisingly, however, we found a definite increase in mortality as a result of trauma when dietary energy increased (Table 2). This effect occurred with hens at all densities but was more pronounced with either 3 or 4 hens/cage. There was a significant (P<.01) cage-by-diet interactive effect on egg weight (Tables 3 and 5), partly because eggs produced by hens at the highest cage density and fed the highest energy level were the heaviest whereas those produced by hens at the lowest cage density and fed the highest energy level were the lightest. The heavier egg weight correlates, in part, with lower egg production,as expected from extensive literature reports. Overall, differences in egg weights between cage and dietary treatments were small but statistically detectable due to the large number of observations. However, their practical importance is questionable. Shell-breaking strength was not significantly affected by the main effects, but there was a complicated three-way interaction (P<.05). The
TABLE 4. Effect of hen density and dietary energy level on periodic body weights3 Body weight (g)° Treatment
28 days
2. hens/cage 3 hens/cage 4 hens/cage
1,372 1,354 1,353
2,737 kcal/kg diet 3,003 kcal/kg diet 3,322 kcal/kg diet
1,358 1,357 1,343
112 days
196 days
(353) (385) (346)
1,725 1,739 1,699
(83) (82) (39)
1,808 1,821 1,738
(348) (357) (392)
1,706 1,714 1,735
(69) (65) (55)
1,775 1,779 1,790
Values represent averages/hen. Weight gain is shown in parenthesis.
280 days
364 days
(76) (33) (25)
1,884 1,854 1,763
(37) (35) (17)
1,921 1,889 1,780
(21) (41) (55)
1,796 1,820 1,845
(31) (26) (24)
1,827 1,846 1,869
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FIG. 2. Hen-day egg production by White Leghorn hens fed diets containing 3,322 kcal/kg o o, 3,003 kcal/kg o o, and 2,737 kcal/kg
1095
1096
CAREW, JR., ETAL. TABLE 5. Effect of hen density and dietary energy level on egg quality characteristics Treatments
Hens/ cage
Dietary energy level (kcal/kgb)
Egg weight 3
Shellbreaking strength 3
Haugh units 3
Eggs showing any meat or blood spots
(%)
(kg) 13.3 13.9 13.8 13.9 13.3 13.7 14.1 13.4 14.0
85.5 85.9 87.3 86.7 86.2 86.1 85.4 85.2 83.5
11 16 19 9 11 10 10 9 10
Averages for hen density 2 hens/cage 3 hens/cage 4 hens/cage
59.4 59.6 60.0
13.7 13.6 13.8
86.2 86.3 84.7
15 10 10
Averages for dietary energy 2,737 kcal/kg 3,003 kcal/kg 3,322 kcal/kg
59.6 59.7 59.8
13.8 13.5 13.8
85.9 85.8 85.6
10 12 13
2 2 2 3 3 3 4 4 4
2,737 3,003 3,322 2,737 3,003 3,322 2.737 3,003 3,322
Values represent averages/hen from 21 to 73 weeks of age. Metabolizable energy.
data on periodic shell-breaking strength are presented in Table 6, but no definite trends are evident. Haugh units were not significantly affected by cage or dietary treatment (Tables 3 and 5), but they decreased significantly (P<.01) with age, as expected. Average Haugh unit measurements over all treatments at periods 2, 5, 8, and 11 were 91.9, 86.0, 83.3, and 81.8, respectively. The presence of meat and blood spots in eggs were not significantly affected by hen density or dietary treatment. However, we observed that age significantly (P<.05) affected meat and blood spots; this represents an increase in these defects with age, particularly between the first half and last half of the study. Our observation that hen density has little effect on egg quality agrees generally with that of others (Wilson et al, 1967; Al-Rawi et al., 1976; Moore et al, 1977). In summarizing our present and previous studies on hen density and dietary energy level, we have found that increasing the density of either White Leghorn or heavy, egg-type hens in cages results in a decline in egg production, a decrease in efficiency of feed utilization, a decrease in body weight primarily at the highest
density, and an increase in mortality. Egg weight, shell-breaking strength, Haugh units, and meat and blood spots are little affected. Increasing dietary energy level to 3,322 kcal/kg by adding fat consistently causes a small decline in egg production of light or heavy breeds during the latter part of a laying year. This decline is observed most consistently with hens housed at the greatest densities (440 cm for the heavy breed and 330 cm 2 for Leghorns). This small decrease in egg production may be relatively unimportant economically if the cost.of dietary fats is favorable. Hens on the highest energy level weigh slightly more, but not to the extent of being considered obese. This change is accompanied by an increase in energy intake only in heavy hens. An unexpected observation with White Leghorn hens was that mortality as a result of cannibalism increases as dietary energy level increases, • an event that remains to be confirmed. Egg quality characteristics and egg weight are little affected by dietary energy level, with the exception in heavy hens that the highest energy level caused a small increase in egg weight during the mid-part of the study. The unfavorable effect on egg production,
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(g) 59.5 59.8 59.0 59.9 59.2 59.8 59.4 60.1 60.6
DIETARY ENERGY, CAGE DENSITY, AND HEN PERFORMANCE
1097
TABLE 6. Effect of hen density and dietary energy level on periodic shell-breaking strength Treatments
Kilograms of pressure (Period of measurement^
Hens/cage
Dietary energy level
2
5
8
11
2 2 2
2,737 3,003 3,322
13.1 13.5 13.6
12.1 12.6 14.2
14.1 14.8 14.0
13.9 14.5 13.3
3 3 3
2,737 3,003 3,322
14.0 13.5 13.2
13.8 14.0 13.9
13.6 13.7 14.7
14.2 12.1 13.0
4 ' 4 4
2,737 3,003 3,322
13.5 13.8 13.0
15.1 13.8 14.7
14.6 13.3 15.2
13.0 12.7 13.2
efficiency of feed utilization, or m o r t a l i t y as a result of increasing hen density was n o t reversed b y increasing t h e dietary energy level. But t h e reduction in b o d y weight t h a t accompanied increasing hen density was fully or partially reversible by increasing dietary energy depending o n t h e cage density of t h e hens. ACKNOWLEDGMENTS We appreciate t h e assistance of Gerard Shrewsbury and t h e technical staff. We are grateful to A b b o t t Laboratories, Commercial Solvents Corporation, Hoffmann-LaRoche, Merck and Co. Inc., Monsanto Chemical Co., Morton Salt Co., Syntex Agribusiness Inc., and T h o m p s o n - H a y w a r d Chemical Co., for supplying materials.
REFERENCES Al-Rawi, B., J. V. Craig, and A. W. Adams, 1976. Agonistic behavior and egg production of caged layers: genetic strain and group-size effects. Poultry Sci. 55:796-807. Berg, L. R., and G. E. Bearse, 1956. The effect of water-soluble vitamins and energy level of the diet on the performance of laying pullets. Poultry Sci. 35:945-951. Carew, Jr., L. B., D. C. Foss, and D. E. Bee, 1976. Effect of dietary energy concentration on performance of heavy egg-type hens at various densities in cages. Poultry Sci. 55:1057—1066. Davis, B. H., W. S. Wilkinson, and A. B. Watts, 1958. A study of the relationship of energy and protein in caged layer nutrition. Poultry Sci. 37:1197. Gleaves, E. W., L. V. Tonkinson, J. D. Wolf, C. K. Harman, R. H. Thayer, and R. D. Morrison, 1968. The action and interaction of physiological
food intake regulators in the laying hen. Poultry Sci. 4 7 : 3 8 - 6 7 . Grover, R. M., D. L. Anderson, R. A. Damon, Jr., and L. H. Ruggles, 1972. The effects of bird density, dietary energy, light intensity, and cage level on the reproductive performance of heavy type chickens in wire cages. Poultry Sci. 51:565—575. Heywang, B. W., and M. G. Vavich, 1962. Energy level of a sixteen percent protein diet for layers in a semiarid, subtropical climate. Poultry Sci. 4 1 : 1389-1393. Hochreich, H. J., C. R. Douglas, I. H. Kidd, and R. H. Harms, 1958. The effect of dietary protein and energy levels upon production of Single Comb White Leghorn hens. Poultry Sci. 37:949-953. Hughes, B. O., 1975. The concept of an optimum stocking density and its selection for egg production. Pages 271—298 in Economic factors affecting egg production. B. M. Freeman, and K. N. Boorman, ed. Brit. Poultry Sci. Ltd., Edinburgh. Kondra, P. A., S. H. Choo, and J. L. Sell. 1968. Influence of strain of chicken and dietary fat on egg production traits. Poultry Sci. 47; 1290-1296. Lowe, R. W., and B. W. Heywang, 1964. Performance of single and multiple caged White Leghorn layers. Poultry Sci. 43:801-805. Maclntyre, T. M., and J. R. Aitken, 1957. The effect of high levels of dietary energy and protein on the performance of laying hens. Poultry Sci. 36:1211-1216. March, B. E., and J. Biely, 1963. The effects of dietary fat and energy levels on the performance of caged laying birds. Poultry Sci. 42:20-24. Moore, D. J., J. W. Bradley, and T. M. Ferguson, 1977. Radius breaking strength and egg characteristics of laying hens as affected by dietary supplements and housing. Poultry Sci. 56:189-192. North, M. O., 1978. Commercial chicken production manual. AVI Publ. Co., Inc., Westport, CT. Peterson, C. F., E. A. Sauter, D. H. Conrad, and C. E. Lampman, 1960. Effect of energy level and laying house temperature on the performance of
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See text for number of measurements made.
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White Leghorn pullets. Poultry Sci. 39: 1010-1018. Quisenberry, J. H., and J. W. Bradley, 1962. Effects of dietary protein and changes in energy levels on the laying house performance of egg production stocks. Poultry Sci. 41:717-724. Sefton, A. E., 1976. The interactions of cage size, cage level, social density, fearfulness, and production of Single Comb White Leghorns. Poultry Sci. 55:1922-1926.
Touchburn, S. P., and E. C. Naber, 1962. Effect of nutrient density and protein-energy interrelationships on reproductive performance of the hen. Poultry Sci. 41:1481-1488. Turk, D. E., H. R. Bird, and M. L. Sunde, 1958. Effect of fats on replacement pullets and laying hens. Poultry Sci. 37:1249. Wilson, H. R., J. E. Jones, and R. W. Dorminey, 1967. Performance of layers under various cage regimens. Poultry Sci. 46:422-425.
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