Performance of Egg Production Stocks Under Three Cage Densities1

Performance of Egg Production Stocks Under Three Cage Densities1 H. L. MARKS,2 L. D. TINDELL 3 AND R. H. LOWE4

United States Department of Agriculture (Received for publication February 21, 1970)

N

PROCEDURE

Six commercial egg production stocks

were evaluated in one-, two-, and five-bird cage units. There were 3600 layers involved in two trials with two replications per trial. For each replicate of each stock, there were 50 birds in 50 one-bird cages, 50 birds in 25 two-bird cages, and 50 birds in 10 fivebird cages. Pullet chicks from each stock were obtained in January 1966, and April 1967 (trials 1 and 2, respectively). Chicks from each stock were reared in replicate pens (2.5 X 8 meters) from hatching to 56 days of age. At this age 65 pullets from each replicate pen were placed in a third pen to provide additional floor space. All chicks were fed a nonmedicated starter diet (20% protein) for the first 35 days and a nonmedicated grower diet (15% protein) from 35 to 126 days. Vaccinations were for Newcastle and fowl pox at 10 and 126 days of age, respectively, and all birds were debeaked at 84 days. Pullets were exposed to natural daylight (0 to 140 days) and given increasing increments of artificial light at the onset of egg production. The photoperiod was held constant for the remainder of each trial after reaching 16 hours.

1

This investigation was conducted as part of the Southern Regional Poultry Breeding Project (S-57), a cooperative study involving agricultural experiment stations in the Southern Region and supported in part by Regional Research Funds and Poultry Research Branch Funds of the United States Department of Agriculture. University of Georgia, College of Agriculture Experiment Stations, Journal Paper Number 712, College Station, Athens. 2 Coordinator, Southern Regional Poultry Breeding Project, AH, ARS, USDA, Athens, Georgia 30601. 'Former Coordinator, Present address: Kimber Farms, Inc., Fremont, California. 4 Plant Superintendent, Southern Regional Poultry Genetics Laboratory, Athens, Georgia.

A house containing single tiers of cages arranged in three double rows with the cages back to back was utilized in this study. Partitions were removed between 20 cages in each row to obtain ten cages that were 50 X 45 cm. At eighteen weeks of age, 150 birds from each stock were divided into three 50-bird groups. They were then randomly assigned to rows with 50 placed in one-bird cages (25 X 45 cm.): 50 in 25 two-bird cages (25 X 45 cm.); 50 in 10 five-bird cages (50 X 45 cm.). Densities in the one-, two- and five-bird

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UMEROUS studies have been conducted to compare the performance of caged chickens maintained at different population densities (Shupe and Quisenberry, 1961; Bramhall et al., 1966; Logan, 1965; Lowe and Hewang, 1964; Moore et al., 1965; Magruder and Nelson, 1966; Owings et al, 1967; Marr et al, 1967; Tower et al., 1967). Although higher population densities per cage generally decreased the number of eggs per bird and increased mortality, only limited information is available to indicate whether strains differ in their ability to adapt to multiple bird cages. Cook and Dembnicki (1966) and Wilson et al. (1967) observed significant interactions for strain by cage type. The objective of the current investigation was to evaluate genotype by environment (strain by cage density) interactions when commercial egg production stocks are caged at different population densities.

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PRODUCTION AND CAGE DENSITY

STATISTICAL METHODS Analyses were based on means within trials. Stocks and replications were considered random effects while cage densities were considered as a fixed effect in the following statistical model:

TABLE 1.—Expectations of mean squares for the mixed model

Stock (S) Cage Density ( O * SC Rep (R) SR CR SCR Total

5 ^ 10 1 5 2

10 35

i = 1, 2, 3 cage densities j = 1, 2 replications XUj is the mean observation of the j t h replication (R) in the ith cage density (C) for the kth stock (S). The mean of the pop-

a2x.

Cage density MS df for (SC-f-CR-SCR)MS denominator computed according to Satterthwaite (1946).

ulation is represented by |A and (scr)uj represents the random variation among subclass means. Expectations of mean squares for the mixed model are given in Table 1. Since there was no exact test of significance for cage density an appropriate divisor was developed (Table 1) with the degrees of freedom computed according to Satterthwaite (1946). RESULTS AND DISCUSSION Stocks. Average performance of stocks for body weight, egg production traits, and feed conversion are presented in Tables 2, 3 and 4. Mean squares from an analysis of variance for these traits are presented in Tables 5, 6 and 7. Differences among stocks for body weight were significant (P TABLE 2.—Mean body weights summarized by stock, age, cage density and trial Body Weight (g.) Stock

560--day

140-day

300-day

It

2

1

2

1

2

X

1472 1391 1435 1428 1444 1500 1445

1339 1267 1295 1278 1266 1414 1310

1890 1931 1921 1800 1924 2056 1920

1786 1755 1864 1732 1767 1986 1815

1941 2006 1977 1826 1998 2146 1982

1937 1936 2051 1827 1891 2171 1969

Cage Density 1-bird 2-bird 5-bird

1426 1435 1474

1319 1304 1306

1920 1909 1932

1820 1803 1823

2041 1961 1946

2010 1933 1959

where: h = 1, 2, • • • , 6 stocks

(T2ser + 3(r 2 8 r -r-6(7 2 , v scr
* F cage density ==

Xhij = M + Sh + Ci + Tj + (sc)hi + (sr)hj + {cr)ij + (scr)iuj

Expectations of mean squares

df

Source

1 2 3 4 5 6

t l = T r i a l 1; 2 = T r i a l 2.

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units were 1125, 562 and 450 cm.2 per bird, respectively. The second replication was housed similarly in the opposite end of the house. This procedure was repeated for all stocks in both trials. Starting at 18 weeks an all-mash layer diet (17% protein) was fed ad libitum. Feeding and watering space varied within cage treatments because of differences in bird densities. Egg production was recorded for fourteen 28-day periods beginning at 140 days. Sexual maturity was measured and defined as the age at 50% production and body weights were obtained at 140, 300 and 560 days of age. Average egg weight and specific gravity were obtained on one day's eggs from each cage type within stocks during each of the 14 periods. Albumen height data were obtained at three-month intervals and feed conversion (g. feed/g. egg) was measured for each period. Mortality was recorded, as the age in weeks at death, and post-mortem examinations were made to determine the cause of death. Birds that died were not replaced in any of the treatments.

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H. L. MARKS, L. D. TINDELL AND R. H. LOWE TABLE 3.—Means for various traits by stock, cage density and trial

Stock

1

Cage Eggs per Den- Bird Housed sity (Birds) It 2

1 2 5

X

1

2

1

2

1

2

66.5 68.2 65.0 66.6

162 157 160 160

160 159 159 159

97 90 75 87

90 86 82 86

252 230 237 240

193 212 229 211

65.2 61.2 62.9 63.1

52.5 56.8 62.5 57.3

64.2 58.6 60.5 61.1

49.2 54.0 58.4 53.9

169 168 169 169

168 164 169 167

95 93 91 93

87 88 87 87

243 238 223 235

230 205 223 219

63.6 65.8 62.6 64.0

63.2 58.1 60.6 60.6

61.9 60.8 56.9 59.9

58.5 52.3 56.9 55.9

169 171 171 170

171 174 174 173

92 86 85 88

88 79 83 83

238 242 236 239

226 216 210 217

63.1 66.9 63.6 64.5

59.1 59.3 57.7 58.7

60.8 61.8 60.1 60.9

57.6 55.2 53.4 55.4

174 171 171 172

185 181 187 184

92 90 85 89

87 86 81 85

258 236 208 234

222 234 216 224

66.6 63.4 63.4 64.5

59.9 63.6 61.4 61.6

65.7 60.2 53.1 59.7

56.5 59.7 55.1 57.1

168 170 168 169

164 165 165 165

97 89 72 86

91 86 78 85

X

270 256 242 256

248 247 246 247

70.1 68.4 70.6 69.7

69.3 70.4 69.6 69.8

68.8 65.4 61.8 65.3

63.2 63.1 62.7 63.0

167 168 168 168

165 171 171 169

96 91 83 90

87 81 83 84

1 2 5

257 244 230

230 230 230

66.8 65.9 65.3

62.4 63.5 63.8

65.5 62.2 58.7

58.6 58.8 58.6

168 168 168

169 169 171

95 90 82

88 84 82

244

230

66.0

63.2

62.1

58.7

168

170

89

85

1 2 5 1 2 5 1 2 5 1 2 5 1 2 5

t l = T r i a l 1; 2 = Trial2

< .01) at all ages in both trials. Stock 6 was the heaviest stock at all ages in both trials, while stock 2 was the lightest stock at 140 days with stock 4 being smaller at 300 and 560 days of age. Stock differences were significant (P < .01) for sexual maturity, percent hen-day egg production and feed conversion in both trials, while significant (P < .01) in trial 2 for number of eggs per bird and percent hen-housed egg production (Table 6). Sexual maturity of stock 1 (Table 3) was approximately 10 days earlier (159 days) than other stocks. Stock 4 was the latest maturing stock, particularly in trial 2 (184

days). Egg production (Table 3) of stocks 1 and 6 was superior to the other four stocks while there was little difference between the other stocks with the exception of the performance of stock 2 in trial 2. Feed conversion (g. feed/g. egg) ranged from 2.59 to 2.89 and 2.36 to 2.86 in trials 1 and 2, respectively (Table 4). Stock 1 had the best conversion ratio and stock 2 the poorest in both trials. Differences between stocks for egg weight, specific gravity, albumen height and Haugh units were significant (P < .01) in both trials. Stock and trial means (averages for all periods) for these traits are presented in Table 4.

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Mean

2

71.3 66.6 59.5 65.8

X

6

1

70.2 72.6 71.1 71.3

X

5

% Adult Livability

72.3 69.8 68.5 70.2

X

4

Sexual Mat. (Days)

261 267 255 261

X

3

% Hen-housed egg prod.

280 261 233 258

X

2

% Hen-day egg prod.

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PRODUCTION AND CAGE DENSITY TABLE 4.—Means for egg weight, egg quality and feed conversion by trial and slock Feed Conversion g. feed/g. Stock egg

X

Specific Gravity

Albumen Height (mm.)

Haugh Units

It

2

1

2

1

2

1

2

1

2

2.59 2.89 2.84 2.70 2.83 2.75 2.77

2.36 2.86 2.74 2.62 2.65 2.55 2.63

61.7 60.9 60.9 62.8 60.9 61.6 61.5

59.8 58.8 59.9 62.5 58.7 61.6 60.2

1.082 1.082 1.084 1.083 1.086 1.084 1.084

1.082 1.082 1.084 1.083 1.086 1.081 1.083

6.23 6.55 5.94 5.59 6.98 5.82 6.19

6.10 6.58 6.35 6.00 7.36 6.46 6.48

77.3 79.8 75.4 72.2 82.8 74.3 77.0

77.2 80.8 79.0 75.3 85.9 79.0 79.5

t l = Trial l ; 2 = T r i a l 2 .

Cage Densities. The only trait showing significance (P < .05) due to cage type was 560-day body weight in trial 2. The computation of the degrees of freedom for the denominator by the method of Satterthwaite (1946) yielded small values which did not allow a critical "F"-test of cage effect for several traits. Percentage livability in trial 1 was 95, 90 and 82 for one-,

two- and five-bird units, respectively, and yet not significantly different. Comparable values for livability in trial 2 were 88, 84 and 82 percent. Replications. The performance of birds in the two replications was similar as indicated by the lack of significant differences for this variable. The only significant (P < .01) replication differences observed

TABLE 5.—Mean squares for body weight 300-day

140-day

5 2 1 10 5 2 10

Stock (S) Cage (C) Rep (R) SC SR CR SCR

560-day

It

2

1

2

1

2

8,538** 7,673 83 718 216 2,552 778

19,891** 833 765 504 1,131* 89 261

40,650** 1,674 92 976 1,340 46 2,155

54,348** 1,477 2,278 1,522* 1,006 2,975* 338

64,448** 31,230 25 3,003 936 204 2,697

86,939** 18,268* 79 1,708 1,024 869 1,414

*P<.05. **P<.01. t l = T r i a l 1;2 ==Trial 2. TABLE 6.—Mean squares for production traits

Source

df

^ggs per Bird

It Stock (S) 5 Cage(C) 2 Rep (R) 1 SC 10 SR 5 CR 2 SCR 10

693 2,143 315 207 201 31 223

•P<.05. **P<.01. 1 1 = T r i a l 1; 2 = T r i a l 2.

2 2297** 2 121 270 173 4 175

% Hen-housed Production 1 45.12 139.45 20.47 13.46 13.10 2.04 14.51

2

Sexual Maturity 1

2

Livability 1

149.51** 116.20** 427.12** 36.4 .10 1.50 12.25 516.0 7.85 0.00 34.03 121.0 17.54 4.30 10.52 42.3 11.25 35.0 1.60 6.23 .29 28.36* 9.5 2.50 11.41 6.76 47.5 4.70

2 13.4 112.0 16.0 17.3 13.0 9.5 56.0

% Hen-day Production 1

2

Feed Conversion 1

2

57.55* 207.97** .0711** .1723** 7.20 7.28 .0350 .0118 .09 2.30 .0009 .0081 6.27 13.72 .0066 .0165 6.00 9.71 .0066 .0123 2.56 .25 .0031 .0040 6.21 10.70 .0092 .0117

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1 2 3 4 5 6

Egg Weight (g.)

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H. L. MARKS, L. D. TINDELL AND R. H. LOWE TABLE 7.—Mean squares for i

df -

Egg Weight

It Stock (S) Cage (C) Rep (R) SC SR CR SCR

5 2 1 10 S 2 10

3.2444** .8442 .6400 .2371 .2465 .3186 .4596

2 13.8622** .2099 .1178 .5209 .2328 .2070 .3916

! and egg quality traits

Specific Gravity 1

Albumen Height

2

1.5720** .1353 .4831 .0232 .0160 .0292 .0255

2

1

2

1

1197** 707* 345 480 14 56 48 31 77 56 4 15 42 52

Haugh Units

1.4164** .0492 .0711 .0144 .0351 .0548 .0189

88.45** 5.07 25.84** 1.55 1.06 .72 1.28

80.34** 3.03 3.36 .65 2.34 2.78 .81

were for albumen height and Haugh units in trial 1. Trials were analyzed separately since they were confounded with seasons, samples of stocks obtained (a different model was sampled from one breeder in trial 2), and possible genetic gains of stocks. Differences between trials for some traits appeared to be rather large, e.g., 140- and 300-day body weights, egg production, livability and feed conversion (Tables 2, 3 and 4). Since prolapse and pickouts were a problem in multiple bird units during trial 1, an attempt was made in trial 2 to restrict body weight by limiting feed consumption during the growing period. This procedure resulted in body weights at 140 days being 135 g. lighter in the second trial. The birds in trial 2 were also lighter at 300 days, however, by 560 days they had reached body weights similar to birds in the preceding trial. It is possible that the smaller body weights in trial 2 were related to smaller egg size and better feed conversion encountered in this trial. It is difficult to speculate if the restriction in body weight had any influence on the lower rate of egg production encountered in the second trial. First-order interactions. The stock by cage density interaction (SC) for 300-day body weight in trial 2 was significant (P < .05) while all other SC interactions were nonsignificant. The stock by replication in-

teraction (SR) was also significant (P < .05) in trial 2 for 140-day body weight, while the cage density by replication interaction (CR) was observed to be significant (P < .05) in trial 2 for 300-day body weight and sexual maturity. The lack of a significant SC interaction for egg production is contrary to the reports of Cook and Dembnicki (1966) and Wilson et al. (1967). Percentage hen-day egg production by stock and cage density is presented in Figure 1. While a significant interaction was not observed, there were some definite changes in the relative ranking of cage 75 1

Trial I

70 = o

65-

U

»

1-bird 2-bird 5-bird

60 55

3

50

4

Stock

75

Trial II -V

70 c

65

••'
V

;

60

\\

/ ------"**-*-^-^

•

7

55 50 1

2

3

4

5

Stock

FIG. 1. Percent hen-day egg production.

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* P<.05. ** P < . 0 1 . t l = T r i a I l ; 2 = Trial2.

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PRODUCTION AND CAGE DENSITY TABLE 8.—Period means by trial for measures of egg weight and egg quality Period Trait

1 It

Egg weight (g.)i Specific gravity 1 Albumen height (mm.) 2 Haugh units 2

1

2

52.8 53.2 1.088 1.092 7.1 7.7 86.1 89.4

2

3

2

1

57.0 57.7 1.085 1.088 6.7 7.0 81.6 83.0

4 2

59.8 61.4 1.085 1.083 6.2 6.1 76.6 76.5

1

5 2

63.2 6 2 . 3 1.084 1.082 5.7 5.8 72.5 73.9

1

7

6

2

1

64.3 63.1 1.083 1.079 5.2 5.7 68.4 72.3

2

64.7 63.2 1.083 1.078 — — — —

1

2

64.5 6 4 . 4 1.079 1.076

1 2

Each period represents a two-month summary. Measurements taken at three-month intervals, t 1-Trial l;2=Tria!2.

Mortality. Summarized in Table 9 are the causes of laying mortality by stock and trial. While there were only minor differences in livability between trials (89% versus 85%), the actual causes of mortality for the two trials are quite different. In trial 1, autopsy reports showed no mortality due to cage fatigue, while in the second trial 49 birds died of this condition. Similarily, 31 deaths were due to leukosis in trial 1, while 104 deaths were attributable to this disease in trial 2. Prolapse and pickouts (actually blowouts, prolapse, cannibalism and pickouts) were responsible for 88 and 44 deaths in trial 1 and 2, respectively. Since only five birds in the single-bird cages fell into this classification for

TABLE 9.—Causes of laying mortality

Stock

Fatty Liver Syndrome

Internal Layei:& Peritonitis

Cage Layer Fatigue

Prolapse and Pickouts

2

1

2

5 5 8 4 12 10

4 7 9 4 3 4

17 17 17 23 5 25

2 5 6 7 7 2

2 4 8 4 11 5

3 21 64

3 16 25

10 11 10

36 36 32

8 12 9

11 11 12

88 50

44 16

31 18

104 38

29 16

34 13

2

1

2

1

2

1

2* 0 1 0 2 0

7 4 3 5 1 2

7 1 6 6 2 2

1 3 5 3 5 3

0 0 0 0 0 0

11 5 8 9 11 S

18 4 13 10 26 17

1-bird 2-bird S-bird

0 1 4

8 10 4

S 6 13

5 8 7

0 0 0

8 17 24

Total Percentft

5 3

22 8

24 13

20 7

0 0

49 18

* Number of birds. t l=TriaIl;2=Trial2. ft % of total mortality due to each cause.

Other

1

It 1 2 3 4 5 6 Cage Density

Leukosis 2

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types among stocks. These same trends, however, were not present in both trials. The influences of age and/or season on egg quality traits are shown in Table 8. For egg weight and specific gravity each period in this table represents a two-month summary, while albumen height and Haugh units are measurements taken at threemonth intervals. Egg weights increased up to period 4 and then leveled off, while specific gravity and albumen height showed a constant decline with age. Significant stock by period interactions were present for albumen height (trial 1) and egg weight and feed conversion in trial 2. Since these interactions were not consistent in both trials their importance is not clear.

1100

H. L. MARKS, L. D. TINDELL AND R. H. LOWE

SUMMARY

Stock differences were significant for all traits studied. Cage density differences were present in trial 1, however, differences due to this source were nonsignificant except for 560-day body weight in trial 2. Differences due to replication were unimportant. The stock by cage density interaction (SC) for 300-day body weight in trial 2 was significant (P < .05) while all other SC interactions were nonsignificant. Significant interactions were not present for egg production, however, there were definite

changes in the relative ranking of stocks among cage densities. These results indicate that stock by cage density interactions are of minor importance in one,- two- and five-bird cage units. ACKNOWLEDGMENT

The authors gratefully acknowledge the efforts of Dr. S. P. Wilson for his assistance in the design of this study. REFERENCES Bramhall, E. L., W. F. Rooney and D. D. Bell, 1966. How many hens in a cage? University of California Agr. Ext. Bui. AXT-191. Cook, R. E., and E. F. Dembnicki, 1966. Performance and interactions of seven egg production stocks in three cage housing regimes. Poultry Sci. 45: 17-21. Logan, V. A., 1965. Influence of cage versus floor, density and dubbing on laying house performance. Poultry Sci. 44: 974-979. Lowe, R. W., and B. W. Heywang, 1964. Performance of single and multiple caged White Leghorn layers. Poultry Sci. 43: 801-805. Magruder, N. D., and J. W. Nelson, 1966. Effects of type and cage and cage density of laying performance. Poultry Sci. 45: 1101. Marr, J. E., D. W. Candin, D. E. Greene and J. L. Williamson, 1967. Evaluation of cage density for laying hens. Poultry Sci. 46: 1289. Moore, B. W., R. Plumley and H. M. Hyre, 1965. A cage density study of laying hens. Poultry Sci. 44: 1399. Owings, W. J., S. L. Balloun, W. W. Marion and J. M. J. Ning, 1967. The influence of dietary protein level and bird density in cages on egg production and liver fatty acids. Poultry Sci. 46: 1303. Satterthwaite, F. E., 1946. An approximate distribution of estimates of variance components. Biometrics, 2 : 110-114. Shupe, W. D., and J. H. Quisenberry, 1961. Effect of certain rearing and laying house environments on performance of incross egg production type pullets. Poultry Sci. 40: 1165-1171. Tower, B. A., A. J. Olinde, F. R. Baker and E. P. Roy, 1967. Performance of layers confined in single versus colony cages. Poultry Sci. 46: 1330. Wilson, H. R., J. E. Jones and R. W. Dorminey, 1967. Performance of layers under various cage regimes. Poultry Sci. 46: 422-425.

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both trials, it is obvious that this mortality loss was greater in multiple bird units, especially the five-bird units. It appears that the growth restriction of birds during the growing period (as indicated by smaller body weights at 140 days—Table 2), resulted in considerably less mortality due to prolapse and pickouts in trial 2. This may have also been responsible for a smaller spread in livability in trial 2 between cage types (82 to 95 in trial 1 versus 82 to 88 in trial 2). Post-mortem examinations both within and between trials were not performed by the same individual. It is possible, therefore, that causes of mortality may be confounded with the autopsist. These differences in causes of mortality between two trials conducted at the same location are of interest in regard to possible causes of genotype by environment interactions. A cursory review of environments for these two trials with regard to mortality would indicate a rather uniform response, however, examination of actual causes of mortality reveal that entirely different "subenvironmental" factors were present. The interrelationships of these "sub-environmental" factors operating under a seemingly constant environment may be responsible for the significant location by trial interactions that are often observed in genotypeenvironment studies.