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Effects of Early Flock Assembly on Agonistic Behavior and Egg Production in Chickens1,2
Effects of Early Flock Assembly on Agonistic Behavior and Egg Production in Chickens12 M. R. CHOUDARY3 AND J. V. CRAIG Kansas State University, Manhattan, Kansas 66502 (Received for publication February 21, 1972)
POULTRY SCIENCE 5 1 :
INTRODUCTION
S
COTT and Fredericson (1951) defined "agonistic behavior" as behavior associated with fighting, escape, defensive and passive interactions between individuals. Observations on agonistic encounters between individuals in a flock led Schjelderup-Ebbe to discover the social hierarchy in domestic chickens in 1913 (see his summary, 1935). Sanctuary (1932), Guhl (1953), McBride (1958a, b) Tindell and Craig (1959, 1960), and Biswas and Craig (1971) discussed the advantages of hens high in the dominance or "peck" order and "This investigation is part of the Kansas contribution to the NC-89 Regional Poultry Breeding Project. " Contribution No. 847, Department of Dairy and Poultry Science, Kansas Agricultural Experiment Station, Manhattan, Kansas 66502. 'Present address: All India Project on Poultry for Eggs, Rajendranagar, Hyderabad-30, A.P., India.
1928-1937,
1972
phenotypic associations between social status and egg production. Heredity influences agonistic behavior as shown clearly by selection studies (Guhl et al., 1960; Siegel, 1960; and Craig et al., 1965) and by inbreeding effects (Craig and Baruth, 1965). Guhl (1953) reported that peck orders among birds raised together in small groups usually become established at about 8 weeks of age for males and 10 weeks for females. After establishment, the peck order is fairly stable in small groups. Guhl and Allee (1944) concluded that flocks socially integrated pecked less, gained more weight, consumed more feed, and laid more eggs than hens kept in a state of reorganization. However, Craig and Toth (1969), using a different experimental design, were unable to demonstrate loss of productivity associated with unstable flock membership during the early laying period.
1928
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ABSTRACT Pullets from high and low social-dominance strains of the White Leghorn (W.L.) and Rhode Island Red (R.I.R.) breeds were assembled in 32 flocks at 6 weeks of age; eight flocks per strain. At 19 weeks all birds were moved to strange pens; four flocks per strain were kept intact as to membership, whereas the other four were reassembled within strains so as to maximize number of strangers. Data were collected and analyzed for agonistic behavior from 19 to 31 and from 52 to 56 weeks, age at sexual maturity, egg weights at 32 and 55 weeks, hen-day rate of lay, henhoused production and mortality. Intra-flock variability was significantly greater for the W.L. high dominance strain for rate of lay and hen-housed production, whereas the W.L. low strain was more variable for age at first egg and egg weights. High dominance strain R.I.R. pullets were more variable for age at sexual maturity only. Analyses of variance, based on flock means, indicated pullets of the W.L. high strain to be significantly inferior in egg production, survival, and to have smaller eggs than the W.L. low strain. Within the R.I.R. breed, the high strain matured earlier. Age at final assembly of flocks had no long-term effects on agonistic activity levels. However, pullets in flocks reassembled at 19 weeks interacted at elevated frequencies from 19 to about 26 to 30 weeks of age. Productivity traits were not significantly influenced by final flock assembly at 6 as compared to 19 weeks of age. Results are discussed in terms of agonistic behavior, social stress and how both appear to relate to productivity traits.
AGE AT ASSEMBLY, BEHAVIOR AND PRODUCTION
The present investigation was designed to obtain information on agonistic behavior and egg production in high and low social dominance strains of Rhode Island Red and White Leghorn breeds as influenced by age. MATERIALS AND METHODS
18 or 19 chicks each. Each pen received approximately \ of its chicks, selected at random, from each of the 4 brooder pens so % of the flock members were strangers to any individual pullet. Four days after assembly all pens were checked for males (sexing errors) and sick birds which were removed. That procedure brought the lowest number of chicks per pen to 17. When the birds were 19 weeks old, half of the 8 flocks per strain were chosen at random to be continued as "stable" flocks, but were moved to different pens, with no change of flock membership. The number of birds in each flock was reduced to 17 by removal of excess birds. Birds from the other four flocks per strain chosen for reassembly were distributed to 4 different pens with restricted randomization, i.e., a maximum of 5 from any one pen. Excess pullets from stable flocks were used to bring a few pens up to 17 females. All pullets were debeaked a second time and wing badged at 19 weeks of age as they were moved from pen to pen. Behavioral observations: Observations of social behavior were begun when the birds were 6 weeks old. However, data presented are for observations after birds were 19 weeks of age. The pullets had been under observation for 13 weeks and were relatively undisturbed by the observer. Each of the 32 flocks was watched for two 10-minute periods per week. Sixteen pens were observed each day. All observations were made by the same person (M. R. Choudary) between noon and 4 p.m., 4 days a week. The first pen observed was randomly selected during each 2-day period and observations included 16 consecutive pens; on the next day the remaining 16 pens were observed. The observer would first enter each pen, move those hens in nests to the floor, and place wet mash in a 22 cm. diameter shallow bowl on top of an
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Genetic stocks: The strains of chickens used were produced by 5 generations of bidirectional selection for high and low social dominance from heterogeneous base populations of the White Leghorn (W.L.) and Rhode Island Red (R.I.R.) breeds (Craig et al., 1965, 1969). During 1968 selection was practiced for one additional generation, following four generations of relaxed selection. The inbreeding coefficient of all strains hatched during 1969 was approximately 0.20. The chicks used represented the first generation of relaxed selection after the 1968 generation of selection. Hatching eggs were obtained using 6 to 8 sires per strain. Each sire represented a different family of the previous generation and 8 to 33 females were assigned per male. Management and experimental procedure: Chicks of all strains were pedigree hatched in the same incubator October 27, 1969. They were sexed, wing banded, dubbed, and vaccinated for Newcastle disease and bronchitis at hatching. Males and females of high and low social dominance strains were mixed and kept in 4 brooder pens within each breed. Chicks were debeaked (^ to ^ of upper beak removed) at 3^ weeks of age to prevent or inhibit cannibalism. When the chicks were 6 weeks old, females were assembled separately by strains in laying house pens. The house had 32 pens (1.5 m. X 2.3 m.) arranged in 4 rows. Eight pens were chosen at random for each strain. Each laying house pen received 20 females of the same strain except for pens allotted to the R.I.R. high strain which had
1929
1930
M. R. CHOUDARY AND J. V. CRAIG
Age at sexual maturity for an individual hen was determined by the week the first egg was laid. Average age at sexual maturity, based on individual pullet data, was calculated for each flock. Egg weights were recorded when pullets were 32 and 55 weeks of age. The first egg laid by each hen during the 3 trap-nest days of the week was weighed to the nearest gram. Egg weights were available only for hens that laid at least one egg during the 3 trap-nest days of the week. Average egg weight for each flock was calculated at each age. Hen-housed egg production was calculated on the basis of trap-nest records and number of pullets per flock at 19 weeks ,of age (17 birds). Hen-day rate of lay was'estimated from the first egg to the end of the period or to the date of death, but not calculated for pullets in production less than 10 trap-nest days. Both hen-housed egg production and rate of lay were expressed as percentages and calculated separately for 19 to 39 and for 39 to 59 weeks of age. Length of the first period corresponds approximately with the length of part-year records used by some breeders in selecting breeding stock. The period of 39 to 59 weeks was chosen arbitrarily to reflect long-term effects of age at flock assembly, not to represent residual production for the entire laying year. Calculations of laying house mortality were based on the number of birds at the beginning of each period. Analytical procedures: Within-flock individual variation in age at sexual maturity, 32-week egg weight, 55-week egg weight, hen-housed production for periods 1 and 2, and for hen-day rate of lay for both periods was calculated for each of the 32 flocks separately and then pooled within each strain. Intra-flock variances pooled within high and within low strains of each breed were then compared by the two-tailed Ftest. Hen-housed production and hen-day rate
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inverted bucket 30 cm. high in the center of the pen, after moving the regular tubetype feeder aside. Observations were made through wire screen, while sitting outside the pen in the aisle. Typically, most or all birds would approach the bowl of wet mash and engage in feeding for the first 2 or 3 minutes. Then the more dominant bird(s) would tend to stop feeding and start pecking and threatening subordinate birds at the feeder. Subsequently, birds low in the peck order usually would either go to a corner of the pen, the roost, or form a second circle waiting to reach the feed bowl. By the end of the 10minute observation period, feeding and agonistic activity usually had declined. The wet mash stimulus obviously increased frequency of social interactions. Social interactions recorded were: fighting, pecking with avoidance, threats with avoidance, and avoidance. Observations were from 19 to 31 weeks and from 52 to 56 weeks of age. Data on social behavior for those intervals were summarized biweekly. The total thus, was 8 biweekly periods. For convenience, each biweekly period was designated the age during the second week of each period, e.g. birds observed during the 19- to 21-week interval were designated 20 weeks old. Analysis of variance was calculated for number of 2-bird agonistic interactions per 10-minute observation period, using the mean number from four observations per flock taken within a biweekly period (age) as the unit of measure. Egg production traits and laying house mortality: Egg production was recorded from 19 to 59 weeks of age. Very few eggs were laid before 19 weeks of age. Trap-nest records were collected 3 days per week, and production data were based on trap-nest records only. Mortality was recorded daily. The 40-week production period was divided from 19 to 39 weeks and from 39 to 59 weeks.
1931
AGE AT ASSEMBLY, BEHAVIOR AND PRODUCTION
TABLE 1.—Mean squares from analyses of variance for frequency of agonistic behavior, hen-housed production, hen-day rate of lay; and mortality
D.F. 3 1 1 1 1 3 1 1 1 24 7 21 7 7 7 7 21 168
H . H . Production D.F.
M.S. 6.86" 18.86" 1.56 0.16 2.74 0.45 1.19 0.09 0.06 0.74 1.57" 0.20** 0.29" 0.22** 0.08 0.57" 0.07 0.07
3 1 1 1 1 3
1 1 1
24 1 3 1 1 1 1 3 24
M.S. 495.19** 469.97** 64.82 950.79** 1.06 2.34 0.58 0.14 0.99 70.86 276.93** 127.54** 90.13* 20.87 271.62** 5.96 1.42 16.22
H.D. Rate M.S. 194.09** 190.72* 25.90 365.65** 3.32 17.50 0.03 0.12 52.35 35.02 5287.83** 57.01** 35.76* 4.73 130.53** 0.27 9.22 10.81
Mortality M.S. 276.65** 88.67 20.48 722.00** 4.53 34.37 4.83 64.80 89.78 37.63 47.70 21.72 25.06 3.38 36.88 27.26 11.68 23.19
1 2
See text for description. Flocks'within genetic groups and age at assembly. Flocks within genetic groups, age at assembly and age or period. >*=P<0.05 **=P<0.01
3
of lay for each period were analyzed for intra-fiock variability and heterogeneity of variance, on the basis of percentages and again after transformation to arc sin values. Flock means were used as units of measure in analyses of variance. Breeds and strains within breeds constituted the term "Genetic Groups" with 3 degrees of freedom. Split-plot design was used for traits measured at different ages or periods but involving the same set of birds (Snedecor and Cochran, 1967, pp. 369-380). Fixed models were assumed for traits measured only once; thus the mean square for residual was used to test for significance due to other sources of variation (Snedecor and Cochran, 1967, pp. 275-279). Duncan's new multiple range test (Duncan, 1955) was used to test mean values for significant differences (P < 0.05).
many agonistic interactions as W. L. females after 19 weeks of age (Table 2). The frequency of interactions changed significantly with age (P < 0.01); tending to level off after the first few weeks at about half the early rates (Table 2 and Figure 1). Though reassembly at 19 weeks of age increased frequencies of agonistic encounters, the effect was temporary, as indicated by the highly significant age-at-assembly by age interaction, but absence of permanent age-at-assembly effect (Table 1). Figure 1 shows the relationship clearly. Differences in agonistic interaction frequencies of flocks assembled at 6 and at 19 weeks of age, though initially present, were no
TABLE 2.—Comparison of breeds and ages for number of agonistic interactions per bird per 10 minute periods during 10 to 31 and 52 to 56 weeks of age
RESULTS AND DISCUSSION
Agonistic behavior: The frequency of agonistic interactions for the periods 19 to 31 weeks and 52 to 56 weeks of age was significantly affected by several variables, Table 1. R.I.R. pullets had about twice as
Breed Mean Average age: Weeks Mean
R.I.R. 1.84 20 24 22 2.00 1.70 1.64
W.L. 0.76 26 28 30 55 53 1.34 1.16 0.96 0.90 0 . 7 4
Means not underscored by the: same line differ signi6cantly (P<0.05).
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Genetic groups (G) Breed (Br) H Vs. h: R.I.R. H Vs. L: W.L. Age at assembly (R) GXR BrXR (H Vs.L: R.I.R.) X R (H Vs. L: W.L.) X R Error A 2 Ages or Periods (A) GXA BrXA (H Vs.L: R . I . R . ) X A (H Vs. L : W.L.) X A RXA GXRXA Error B«
Productivity traits
Agonistic interaction frequency 1
Source
1932
M. R. CHOUDAEY AND J. V. CRAIG LOW
STRAINS
STRAINS ASSEMBLED: AT 19 WKS AT S WKS.
ASSEMBLED: AT 19 WKS. AT S WKS,
WL
a: I/) Z
O i-
u
<
01 hi tZ
(J IIS)
z O
< LL
O
6
53
55
20
22
24
26
28
30
55
AGE,WEEKS FIG. 1. Number of agonistic interactions per female per 10-minute observation, at 8 age intervals, for high and low social dominance strains of W.L. and R.I.R. breeds assembled at 6 and 19 weeks of age.
longer evident after about 26 to 30 weeks of age in any of the 4 strains. R.I.R. reassembled flocks interacted at relatively higher rates than W.L. flocks (Table 1 and Figure 1). The more rapid drop in agonistic activity following reassembly in W.L. flocks and the higher levels of agonistic activity with a more gradual drop in frequency for the R.I.R. reassembled flocks contributed to the significant interaction between age at flock assembly and breed. Craig et al. (1965, 1969) reported more frequent social interactions in the W.L. than in the R.I.R. breed utilizing chicks of the same strains as those compared in the present study. The differences in agonistic activity of the two breeds in the two studies may possibly be attributed to the presence or absence of wet mash stimulus in the
different studies. W.L. pullets were observed to retreat rapidly from the wet mash feeder when a socially superior bird(s) pecked or threatened them. They would try to reach the wet mash again only when dominant birds could be avoided. Contrarily, R.I.R. pullets were often observed to remain at the feeder despite repeated pecks and threats. Thus, a breed genotype-feeding stimulus interaction appears as a likely possibility. Pullets of high and low social dominance strains of the same breed were not found to differ for agonistic interaction frequencies, confirming previous studies with R.I.R. strains but not with W.L. strains (Craig et al. 1965, 1969). Moderately large scale comparisons in two earlier experiments indicated W.L. high-dominance-strain pullets to have 62 to 83 percent more frequent in-
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hi D.
AGE AT ASSEMBLY, BEHAVIOR AND PRODUCTION
1933
TABLE 3.—Intra-jlock individual variability in production traits for high and low strains of W.L. D.F.
Mean squares
F
Age at sexual maturity
Low High
125 126
11.96 5.12
2.34**
32-week egg weight
Low High
112 107
13.53 8.22
1.64*
55-week egg weight
Low High
106 67
23.90 14.01
1.71*
Hen-housed production (Period 1)
Low High
128 128
180.55 147.72
1.22
Hen-housed production (Period 2)
High Low
127 128
388.60 230.29
1.69*
Hen-day rate of production (Period 1)
High Low
123 120
123.54 91.93
1.34
Hen-day rate of production (Period 2)
High Low
109 112
253.68 135.51
1.87**
* = P<0.05 ** = P<0.01
teractions (P < .01) when kept in flocks (Craig et al., 1969). Indirect evidence from analysis of productivity traits suggests that the W.L. high strain pullets were under greater social stress than pullets of the W.L. low strain. Egg production and mortality: Intralock
variability. Intraflock estimates of individual variability were calculated for age at sexual maturity and for various egg production traits. Data were pooled within strains and comparisons were then made between strains within breeds (Tables 3 and 4). Hen-housed production and hen-day rate of
TABLE 4.—Intra-jlock individual variability in production traits for high and low strains of R.I.R. Strain
D.F.
Age at sexual maturity
High Low
126 123
5.19 2.76
32-week egg weight
High Low
118 112
13.42 13.22
1.02
55-week egg weight
High Low
79 89
28.37 18.82
1.51
Hen-housed production (Period 1)
Low High
128 128
150.42 127.26
1.18
Hen-housed production (Period 2)
Low High
125 124
287.16 207.34
1.38
Hen-day rate of production (Period 1)
Low High
123 125
77.26 56.53
1.36
Hen-day rate of production (Period 2)
Low High
113 114
115.24 80.38
1.43
Trait
** = P < 0 . 0 1
Mean square
F 1.88**
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Strain
Trait
1934
M. R. CHOUDARY AND j . V. CRAIG TABLE 5.—Mean squares from analyses of variance for age at sexual maturity and egg weights at 32 and 55 weeks Source
3 1 1 1 1 3 1 1 1 24
Age at sexual maturity
Egg weight (32 weeks)
Egg weight (55 weeks)
5.63** 8.42** 7.60** 0.92 0.54 0.71 0.94 0.88 0.30 0.80
11.664 0.004 2.214 32.774** 0.841 0.277 0.049 0.142 0.198 0.829
34.53** 13.69 0.03 89.87** 0.61 0.51 0.17 0.87 0.50 1.93
= P<0.01
lay, calculated as percentages, were analyzed before and after arc sin transformation, with similar results. The tabular results are from calculations based on percentages. Observations of agonistic behavior within flocks of high and low strains of the W.L. and R.I.R. breeds (Craig et al., 1969) indicated higher frequencies of social interactions, hence presumably greater social stress, within high strain W.L. flocks. McBride (1960, 1962, 1968) hypothesized that increased stress would decrease mean productivity, but contrarily would increase individual variability due to negative skewness of the frequency distribution. Significantly greater variability of individual performance was found for the high strain W.L. flocks (Table 3) for hen-day rate of production and hen-housed production during period 2, confirming the previous results of Craig and Toth (1969) and Biswas and Craig (1970). The results reported here are of particular interest because greater social stress was not indicated by frequencies of agonistic interactions within the W.L. high strain. They suggest social stress was in fact present, though undetected by that criterion (frequency of agonistic behavior).
Contrarily, the low strain W.L. was significantly more variable for age at sexual maturity and egg weights at 32 and 55 weeks of age. Higher variability among low-social-dominance W.L. flocks could be due to greater variance associated with higher mean values for those particular traits as usually expected (Snedecor and Cochran, 1967 pp. 62-64). Intra-flock variance of the R.I.R highsocial-dominance strain was significantly (P < 0.01) higher than in the low strain only for age at first egg, Table 4. Craig and Toth (1969) found no significant differences in variability between high and low strains of R.I.R. for various production traits. Such results are not unexpected since mean performance levels were similar for most traits and differences in frequency of agonistic behavior between pullets of the R.I.R. strains kept in flocks were not detected in the present study or in earlier comparisons (Craig et al., 1969). Egg weights: Egg weights at 32 and 55 weeks of age differed for strains within the W.L. breed only, Table 5. W.L. low strain pullets had heavier eggs at both 32 and 55 weeks of age. Heavier egg weight at 32 weeks of age for the W.L. low social dominance strain is in agreement with the find-
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Genetic groups (G) Breed (Br) High vs. low: R.I.R. High vs. low: W.L. Age at flock assembly (R) GXR BreedXR (Highw. low: R.I.R.)XR (Highw. low: W.L.)XR Flocks: G and R
D.F.
1935
AGE AT ASSEMBLY, BEHAVIOR AND PRODUCTION
6 and Figure 2 reveals these interactions are primarily due to the precipitous decline in performance of the W.L. high strain in the second 20-week period of egg production. Age at flock assembly did not have significant effects on either rate of lay or hen-housed production. The earlier sexual maturity of the R.I.R. high strain is in agreement with the data of Craig and Toth (1969). They also reported a tendency for their unstable flocks to mature earlier (P = .06). In this study age at flock assembly had no detectable effect on sexual maturity. The significantly poorer egg production and survival for the high social dominance strain of W.L. found in this study (Table 1) are in agreement with the findings of Craig and Toth (1969) and Biswas and Craig (1970). The W.L. high strain had the highest mortality (12%) as compared with an average of 4% for the other three strains. The present study did not show significant effects for age at flock assembly on any production trait, although frequency of social interactions was clearly elevated for several weeks in flocks reassembled at 19 weeks. Craig and Toth (1969) postulated
TABLE 6.—Comparison of breeds, strains and 20-week production periods on hen-housed production and hen-day rate of production Hen-housed Egg Production, Percentages Breed Mean Strain Mean Periods: weeks Mean Breed Mean Strain Mean Periods: weeks Mean
W.L. 53.0
R.I.R. 58.4 R.I.R.-High 59.9
W.L.-Low 58.5
W.L.-High 47.6
R.I.R.-Low 57.0
19 to 39 57.8
39 to 59 53.7
Hen-Day Rate of Production, Percentages W.L. R.I.R. 70.2 66.8 R.I.R.-Higl i R.I.R.-Low W.L.-Low 69.3 71.1 70.2 19 to 39 77.6
Means not underscored by the same line differ significantly (P<0.05).
39 to 59 59.4
W.L.-High 63.4
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ings of Biswas and Craig (1970). Age at flock assembly had no effect on egg weights. Egg production and mortality: Variances between flock means within strain-treatment subclasses were calculated for age at sexual maturity, hen-housed production, and hen-day rate of lay. Bartlett's test as described by Snedecor and Cochran (1967, pp. 296-298) showed no heterogeneity for any of the traits. No heterogeneity was detected for variances of flock means within strain-treatment subclasses for mortality. Therefore flock means were used in analyses of variance. Age at sexual maturity was affected significantly (P < 0.01) by breed and by strains within the R.I.R breed, Table 5. The R.I.R. breed, on the average, matured 1 week earlier than the W.L. Within the R.I.R. breed the high strain matured earlier (22.4 vs. 23.8 weeks). Hen-housed production and hen-day rate of lay were affected significantly by breed, strains within the W.L. breed, and periods, Table 1. Interactions were significant for breed and period and also for strains within the W.L. and period. Examination of Table
1936
M. R. CHOUDAEY AND J. V. CRAIG KEY AC.C.FMRLED.WKS — HIGH — HIGH - LOW -
LOW
19 5 19 6
WEEKS
FIG. 2. Hen-housed production in percentages for high and low social dominance strains of W.L. and R.I.R. breeds, assembled at 6 and 19 weeks of age, at 20 biweekly periods from 19 to 59 weeks.
that higher rates of agonistic activity associated with flock reorganization may not always increase social stress; at least not for birds previously near the bottom of the social heirarchy. For such individuals, reassembly in new groups may allow some upward social mobility with reduced stress. A similar situation may be postulated for flocks reassembled shortly before sexual maturity. ACKNOWLEDGMENT The authors are grateful to Drs. Kenneth Kemp and Arthur Dayton for assistance in statistical analyses and interpretation of results. REFERENCES Biswas, D. K., and J. V. Craig, 1970. Genotype— environment interactions in chickens selected for high and low social dominance. Poultry Sci. 49:681-692. Biswas, D. K., and J. V. Craig, 1971. Social ten-
sion indexes and egg production traits in chickens. Poultry Sci. 50: 1063-1065. Craig, J. V., and R. A. Baruth, 1965. Inbreeding and social dominance ability in chickens. Animal Behav. 13: 109-113. Craig, J. V., and A. Toth, 1969. Productivity of pullets influenced by genetic selection for social dominance ability and by stability of flock membership. Poultry Sci. 48: 1729-1736. Craig, J. V., D. K. Biswas and A. M. Guhl, 1969. Agonistic behaviour influenced by strangeness, crowding and heredity in female domestic fowl. Animal Behav. 17 : 498-506. Craig, J. V., L. L. Ortman and A. M. Guhl, 1965. Genetic selection for social dominance ability in chickens. Animal Behav. 13: 114-131. Duncan, D. B., 1955. Multiple range and multiple F tests. Biometrics, 11: 1-42. Guhl, A. M., 1953. Social behavior of domestic fowl. Kansas Agr. Expt. Sta. Tech. Bull. 73. Guhl, A. M., and W.C. Allee, 1944. Some measurable effects of social organization in flocks of hens. Physiol. Zool. 17 : 320-347. Guhl, A. M., J. V. Craig and C. D. Mueller, 1960. Selective breeding for aggressiveness in chickens. Poultry Sci. 39: 970-980.
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AGE,
AGE AT ASSEMBLY, BEHAVIOR AND PRODUCTION McBride, G., 1958a. The relationship between aggressiveness and egg production in the domestic hen. Nature, 181: 858. McBride, G., 1958b. The relationship between aggressiveness, peck-order and some characters of selective significance in the domestic hen. Proc. Roy. Phys. Soc. Edin. 27: 56-60.
McBride, G., 1968. Behavioral measurement of social stress. In: Adaptation of Domestic Animals, ed. E.S.E. Hafez pp. 360-366. Lee and Febiger, Philadelphia. Sanctuary, W. C , 1932. A study of avian behavior to determine the nature and persistency of the order of dominance in the domestic fowl and to relate these to certain physiological reactions.
M. S. Thesis, Massachusetts State College, Amherst. Schjelderup-Ebbe, T., 1935. Social behavior of birds. Chap. X X In: Murchison's Handbook of Social Psychology, 947-972. Clark Univ. Press, Worcestor. Scott, J. P., and E. Fredericson, 1951. The causes of fighting in mice and rats. Physiol. Zool. 24: 273-309. Siegel, P. B., 1960. A method of evaluating aggressiveness in chickens. Poultry Sci. 39: 1046-1048. Snedecor, G. W., and W. G. Cochran, 1967. Statistical Methods, 6th Ed. Iowa State College Press, Ames. Tindell, D., and J. V. Craig, 1959. Effects of social competition on laying house performance in the chicken. Poultry Sci. 38: 95-105. Tindell, D., and J. V. Craig, 1960. Genetic variation in social aggressiveness and competition effects between sire families in small flocks of chickens. Poultry Sci. 39: 1318-1320.
Environmental Temperature and Dietary Lysine Effects on Free Amino Acids in Plasma J. D. MAY, 1 L. F. KUBENA, 1 F. N. REECE 2 AND J. W. DEATON 1 United States Department of Agriculture, A.R.S., State College, Mississippi 39762 (Received for publication February 25, 1972)
ABSTRACT Broiler chicks were reared to 5 weeks of age in environmental chambers maintained at 7.2°C. and 32.2°C. with dewpoints of 0° and 10°C, respectively. In 2 trials chicks were fed commercial broiler diets and in 3 trials they were fed diets supplying 60, 100 and 130 percent of the dietary lysine requirement. Free amino acids in plasma were measured. Chicks at 7.2°C. had reduced concentrations of alanine, arginine and tyrosine but had increased levels of cystine, ornithine and lysine, when compared to the values for chicks at 32.2°C. The increased plasma lysine could result from its relative difficulty of catabolism in comparison with the other amino acids. It is suggested that the high level of plasma lysine in chicks kept at 7.2°C. results in an increased breakdown of arginine to ornithine. POULTRY SCIENCE SI: 1937-1940, 1972
HRONIC exposure of animals to low environmental temperatures results in increased food consumption per unit of
C
1 Animal Science Research Division, Poultry Research Branch, South Central Poultry Research Laboratory, State College, Mississippi. 2 Agricultural Engineering Research Division, Farm Electrification Research Branch, South Central Poultry Research Laboratory, State College, Mississippi.
body weight. Many amino acids can be readily converted into carbohydrate and, therefore, they are a potential source of energy. The role of amino acids as an energy source is probably more important during cold weather. Klain et al. (1962) stimulated consumption of amino acid imbalanced diets by keepings rats at 7°C. and found that they grew as well as rats fed control diets and
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McBride, G., 1960. Poultry husbandry and the peck order. Brit. Poultry Sci. 1: 65-68. McBride, G., 1962. Behavior and a theory of poultry husbandry. Proc. X l l t h World's Poultry Congress (Symposia): 102-105.
1937
POULTRY SCIENCE 5 1 :
INTRODUCTION
S
COTT and Fredericson (1951) defined "agonistic behavior" as behavior associated with fighting, escape, defensive and passive interactions between individuals. Observations on agonistic encounters between individuals in a flock led Schjelderup-Ebbe to discover the social hierarchy in domestic chickens in 1913 (see his summary, 1935). Sanctuary (1932), Guhl (1953), McBride (1958a, b) Tindell and Craig (1959, 1960), and Biswas and Craig (1971) discussed the advantages of hens high in the dominance or "peck" order and "This investigation is part of the Kansas contribution to the NC-89 Regional Poultry Breeding Project. " Contribution No. 847, Department of Dairy and Poultry Science, Kansas Agricultural Experiment Station, Manhattan, Kansas 66502. 'Present address: All India Project on Poultry for Eggs, Rajendranagar, Hyderabad-30, A.P., India.
1928-1937,
1972
phenotypic associations between social status and egg production. Heredity influences agonistic behavior as shown clearly by selection studies (Guhl et al., 1960; Siegel, 1960; and Craig et al., 1965) and by inbreeding effects (Craig and Baruth, 1965). Guhl (1953) reported that peck orders among birds raised together in small groups usually become established at about 8 weeks of age for males and 10 weeks for females. After establishment, the peck order is fairly stable in small groups. Guhl and Allee (1944) concluded that flocks socially integrated pecked less, gained more weight, consumed more feed, and laid more eggs than hens kept in a state of reorganization. However, Craig and Toth (1969), using a different experimental design, were unable to demonstrate loss of productivity associated with unstable flock membership during the early laying period.
1928
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ABSTRACT Pullets from high and low social-dominance strains of the White Leghorn (W.L.) and Rhode Island Red (R.I.R.) breeds were assembled in 32 flocks at 6 weeks of age; eight flocks per strain. At 19 weeks all birds were moved to strange pens; four flocks per strain were kept intact as to membership, whereas the other four were reassembled within strains so as to maximize number of strangers. Data were collected and analyzed for agonistic behavior from 19 to 31 and from 52 to 56 weeks, age at sexual maturity, egg weights at 32 and 55 weeks, hen-day rate of lay, henhoused production and mortality. Intra-flock variability was significantly greater for the W.L. high dominance strain for rate of lay and hen-housed production, whereas the W.L. low strain was more variable for age at first egg and egg weights. High dominance strain R.I.R. pullets were more variable for age at sexual maturity only. Analyses of variance, based on flock means, indicated pullets of the W.L. high strain to be significantly inferior in egg production, survival, and to have smaller eggs than the W.L. low strain. Within the R.I.R. breed, the high strain matured earlier. Age at final assembly of flocks had no long-term effects on agonistic activity levels. However, pullets in flocks reassembled at 19 weeks interacted at elevated frequencies from 19 to about 26 to 30 weeks of age. Productivity traits were not significantly influenced by final flock assembly at 6 as compared to 19 weeks of age. Results are discussed in terms of agonistic behavior, social stress and how both appear to relate to productivity traits.
AGE AT ASSEMBLY, BEHAVIOR AND PRODUCTION
The present investigation was designed to obtain information on agonistic behavior and egg production in high and low social dominance strains of Rhode Island Red and White Leghorn breeds as influenced by age. MATERIALS AND METHODS
18 or 19 chicks each. Each pen received approximately \ of its chicks, selected at random, from each of the 4 brooder pens so % of the flock members were strangers to any individual pullet. Four days after assembly all pens were checked for males (sexing errors) and sick birds which were removed. That procedure brought the lowest number of chicks per pen to 17. When the birds were 19 weeks old, half of the 8 flocks per strain were chosen at random to be continued as "stable" flocks, but were moved to different pens, with no change of flock membership. The number of birds in each flock was reduced to 17 by removal of excess birds. Birds from the other four flocks per strain chosen for reassembly were distributed to 4 different pens with restricted randomization, i.e., a maximum of 5 from any one pen. Excess pullets from stable flocks were used to bring a few pens up to 17 females. All pullets were debeaked a second time and wing badged at 19 weeks of age as they were moved from pen to pen. Behavioral observations: Observations of social behavior were begun when the birds were 6 weeks old. However, data presented are for observations after birds were 19 weeks of age. The pullets had been under observation for 13 weeks and were relatively undisturbed by the observer. Each of the 32 flocks was watched for two 10-minute periods per week. Sixteen pens were observed each day. All observations were made by the same person (M. R. Choudary) between noon and 4 p.m., 4 days a week. The first pen observed was randomly selected during each 2-day period and observations included 16 consecutive pens; on the next day the remaining 16 pens were observed. The observer would first enter each pen, move those hens in nests to the floor, and place wet mash in a 22 cm. diameter shallow bowl on top of an
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Genetic stocks: The strains of chickens used were produced by 5 generations of bidirectional selection for high and low social dominance from heterogeneous base populations of the White Leghorn (W.L.) and Rhode Island Red (R.I.R.) breeds (Craig et al., 1965, 1969). During 1968 selection was practiced for one additional generation, following four generations of relaxed selection. The inbreeding coefficient of all strains hatched during 1969 was approximately 0.20. The chicks used represented the first generation of relaxed selection after the 1968 generation of selection. Hatching eggs were obtained using 6 to 8 sires per strain. Each sire represented a different family of the previous generation and 8 to 33 females were assigned per male. Management and experimental procedure: Chicks of all strains were pedigree hatched in the same incubator October 27, 1969. They were sexed, wing banded, dubbed, and vaccinated for Newcastle disease and bronchitis at hatching. Males and females of high and low social dominance strains were mixed and kept in 4 brooder pens within each breed. Chicks were debeaked (^ to ^ of upper beak removed) at 3^ weeks of age to prevent or inhibit cannibalism. When the chicks were 6 weeks old, females were assembled separately by strains in laying house pens. The house had 32 pens (1.5 m. X 2.3 m.) arranged in 4 rows. Eight pens were chosen at random for each strain. Each laying house pen received 20 females of the same strain except for pens allotted to the R.I.R. high strain which had
1929
1930
M. R. CHOUDARY AND J. V. CRAIG
Age at sexual maturity for an individual hen was determined by the week the first egg was laid. Average age at sexual maturity, based on individual pullet data, was calculated for each flock. Egg weights were recorded when pullets were 32 and 55 weeks of age. The first egg laid by each hen during the 3 trap-nest days of the week was weighed to the nearest gram. Egg weights were available only for hens that laid at least one egg during the 3 trap-nest days of the week. Average egg weight for each flock was calculated at each age. Hen-housed egg production was calculated on the basis of trap-nest records and number of pullets per flock at 19 weeks ,of age (17 birds). Hen-day rate of lay was'estimated from the first egg to the end of the period or to the date of death, but not calculated for pullets in production less than 10 trap-nest days. Both hen-housed egg production and rate of lay were expressed as percentages and calculated separately for 19 to 39 and for 39 to 59 weeks of age. Length of the first period corresponds approximately with the length of part-year records used by some breeders in selecting breeding stock. The period of 39 to 59 weeks was chosen arbitrarily to reflect long-term effects of age at flock assembly, not to represent residual production for the entire laying year. Calculations of laying house mortality were based on the number of birds at the beginning of each period. Analytical procedures: Within-flock individual variation in age at sexual maturity, 32-week egg weight, 55-week egg weight, hen-housed production for periods 1 and 2, and for hen-day rate of lay for both periods was calculated for each of the 32 flocks separately and then pooled within each strain. Intra-flock variances pooled within high and within low strains of each breed were then compared by the two-tailed Ftest. Hen-housed production and hen-day rate
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inverted bucket 30 cm. high in the center of the pen, after moving the regular tubetype feeder aside. Observations were made through wire screen, while sitting outside the pen in the aisle. Typically, most or all birds would approach the bowl of wet mash and engage in feeding for the first 2 or 3 minutes. Then the more dominant bird(s) would tend to stop feeding and start pecking and threatening subordinate birds at the feeder. Subsequently, birds low in the peck order usually would either go to a corner of the pen, the roost, or form a second circle waiting to reach the feed bowl. By the end of the 10minute observation period, feeding and agonistic activity usually had declined. The wet mash stimulus obviously increased frequency of social interactions. Social interactions recorded were: fighting, pecking with avoidance, threats with avoidance, and avoidance. Observations were from 19 to 31 weeks and from 52 to 56 weeks of age. Data on social behavior for those intervals were summarized biweekly. The total thus, was 8 biweekly periods. For convenience, each biweekly period was designated the age during the second week of each period, e.g. birds observed during the 19- to 21-week interval were designated 20 weeks old. Analysis of variance was calculated for number of 2-bird agonistic interactions per 10-minute observation period, using the mean number from four observations per flock taken within a biweekly period (age) as the unit of measure. Egg production traits and laying house mortality: Egg production was recorded from 19 to 59 weeks of age. Very few eggs were laid before 19 weeks of age. Trap-nest records were collected 3 days per week, and production data were based on trap-nest records only. Mortality was recorded daily. The 40-week production period was divided from 19 to 39 weeks and from 39 to 59 weeks.
1931
AGE AT ASSEMBLY, BEHAVIOR AND PRODUCTION
TABLE 1.—Mean squares from analyses of variance for frequency of agonistic behavior, hen-housed production, hen-day rate of lay; and mortality
D.F. 3 1 1 1 1 3 1 1 1 24 7 21 7 7 7 7 21 168
H . H . Production D.F.
M.S. 6.86" 18.86" 1.56 0.16 2.74 0.45 1.19 0.09 0.06 0.74 1.57" 0.20** 0.29" 0.22** 0.08 0.57" 0.07 0.07
3 1 1 1 1 3
1 1 1
24 1 3 1 1 1 1 3 24
M.S. 495.19** 469.97** 64.82 950.79** 1.06 2.34 0.58 0.14 0.99 70.86 276.93** 127.54** 90.13* 20.87 271.62** 5.96 1.42 16.22
H.D. Rate M.S. 194.09** 190.72* 25.90 365.65** 3.32 17.50 0.03 0.12 52.35 35.02 5287.83** 57.01** 35.76* 4.73 130.53** 0.27 9.22 10.81
Mortality M.S. 276.65** 88.67 20.48 722.00** 4.53 34.37 4.83 64.80 89.78 37.63 47.70 21.72 25.06 3.38 36.88 27.26 11.68 23.19
1 2
See text for description. Flocks'within genetic groups and age at assembly. Flocks within genetic groups, age at assembly and age or period. >*=P<0.05 **=P<0.01
3
of lay for each period were analyzed for intra-fiock variability and heterogeneity of variance, on the basis of percentages and again after transformation to arc sin values. Flock means were used as units of measure in analyses of variance. Breeds and strains within breeds constituted the term "Genetic Groups" with 3 degrees of freedom. Split-plot design was used for traits measured at different ages or periods but involving the same set of birds (Snedecor and Cochran, 1967, pp. 369-380). Fixed models were assumed for traits measured only once; thus the mean square for residual was used to test for significance due to other sources of variation (Snedecor and Cochran, 1967, pp. 275-279). Duncan's new multiple range test (Duncan, 1955) was used to test mean values for significant differences (P < 0.05).
many agonistic interactions as W. L. females after 19 weeks of age (Table 2). The frequency of interactions changed significantly with age (P < 0.01); tending to level off after the first few weeks at about half the early rates (Table 2 and Figure 1). Though reassembly at 19 weeks of age increased frequencies of agonistic encounters, the effect was temporary, as indicated by the highly significant age-at-assembly by age interaction, but absence of permanent age-at-assembly effect (Table 1). Figure 1 shows the relationship clearly. Differences in agonistic interaction frequencies of flocks assembled at 6 and at 19 weeks of age, though initially present, were no
TABLE 2.—Comparison of breeds and ages for number of agonistic interactions per bird per 10 minute periods during 10 to 31 and 52 to 56 weeks of age
RESULTS AND DISCUSSION
Agonistic behavior: The frequency of agonistic interactions for the periods 19 to 31 weeks and 52 to 56 weeks of age was significantly affected by several variables, Table 1. R.I.R. pullets had about twice as
Breed Mean Average age: Weeks Mean
R.I.R. 1.84 20 24 22 2.00 1.70 1.64
W.L. 0.76 26 28 30 55 53 1.34 1.16 0.96 0.90 0 . 7 4
Means not underscored by the: same line differ signi6cantly (P<0.05).
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Genetic groups (G) Breed (Br) H Vs. h: R.I.R. H Vs. L: W.L. Age at assembly (R) GXR BrXR (H Vs.L: R.I.R.) X R (H Vs. L: W.L.) X R Error A 2 Ages or Periods (A) GXA BrXA (H Vs.L: R . I . R . ) X A (H Vs. L : W.L.) X A RXA GXRXA Error B«
Productivity traits
Agonistic interaction frequency 1
Source
1932
M. R. CHOUDAEY AND J. V. CRAIG LOW
STRAINS
STRAINS ASSEMBLED: AT 19 WKS AT S WKS.
ASSEMBLED: AT 19 WKS. AT S WKS,
WL
a: I/) Z
O i-
u
<
01 hi tZ
(J IIS)
z O
< LL
O
6
53
55
20
22
24
26
28
30
55
AGE,WEEKS FIG. 1. Number of agonistic interactions per female per 10-minute observation, at 8 age intervals, for high and low social dominance strains of W.L. and R.I.R. breeds assembled at 6 and 19 weeks of age.
longer evident after about 26 to 30 weeks of age in any of the 4 strains. R.I.R. reassembled flocks interacted at relatively higher rates than W.L. flocks (Table 1 and Figure 1). The more rapid drop in agonistic activity following reassembly in W.L. flocks and the higher levels of agonistic activity with a more gradual drop in frequency for the R.I.R. reassembled flocks contributed to the significant interaction between age at flock assembly and breed. Craig et al. (1965, 1969) reported more frequent social interactions in the W.L. than in the R.I.R. breed utilizing chicks of the same strains as those compared in the present study. The differences in agonistic activity of the two breeds in the two studies may possibly be attributed to the presence or absence of wet mash stimulus in the
different studies. W.L. pullets were observed to retreat rapidly from the wet mash feeder when a socially superior bird(s) pecked or threatened them. They would try to reach the wet mash again only when dominant birds could be avoided. Contrarily, R.I.R. pullets were often observed to remain at the feeder despite repeated pecks and threats. Thus, a breed genotype-feeding stimulus interaction appears as a likely possibility. Pullets of high and low social dominance strains of the same breed were not found to differ for agonistic interaction frequencies, confirming previous studies with R.I.R. strains but not with W.L. strains (Craig et al. 1965, 1969). Moderately large scale comparisons in two earlier experiments indicated W.L. high-dominance-strain pullets to have 62 to 83 percent more frequent in-
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hi D.
AGE AT ASSEMBLY, BEHAVIOR AND PRODUCTION
1933
TABLE 3.—Intra-jlock individual variability in production traits for high and low strains of W.L. D.F.
Mean squares
F
Age at sexual maturity
Low High
125 126
11.96 5.12
2.34**
32-week egg weight
Low High
112 107
13.53 8.22
1.64*
55-week egg weight
Low High
106 67
23.90 14.01
1.71*
Hen-housed production (Period 1)
Low High
128 128
180.55 147.72
1.22
Hen-housed production (Period 2)
High Low
127 128
388.60 230.29
1.69*
Hen-day rate of production (Period 1)
High Low
123 120
123.54 91.93
1.34
Hen-day rate of production (Period 2)
High Low
109 112
253.68 135.51
1.87**
* = P<0.05 ** = P<0.01
teractions (P < .01) when kept in flocks (Craig et al., 1969). Indirect evidence from analysis of productivity traits suggests that the W.L. high strain pullets were under greater social stress than pullets of the W.L. low strain. Egg production and mortality: Intralock
variability. Intraflock estimates of individual variability were calculated for age at sexual maturity and for various egg production traits. Data were pooled within strains and comparisons were then made between strains within breeds (Tables 3 and 4). Hen-housed production and hen-day rate of
TABLE 4.—Intra-jlock individual variability in production traits for high and low strains of R.I.R. Strain
D.F.
Age at sexual maturity
High Low
126 123
5.19 2.76
32-week egg weight
High Low
118 112
13.42 13.22
1.02
55-week egg weight
High Low
79 89
28.37 18.82
1.51
Hen-housed production (Period 1)
Low High
128 128
150.42 127.26
1.18
Hen-housed production (Period 2)
Low High
125 124
287.16 207.34
1.38
Hen-day rate of production (Period 1)
Low High
123 125
77.26 56.53
1.36
Hen-day rate of production (Period 2)
Low High
113 114
115.24 80.38
1.43
Trait
** = P < 0 . 0 1
Mean square
F 1.88**
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Strain
Trait
1934
M. R. CHOUDARY AND j . V. CRAIG TABLE 5.—Mean squares from analyses of variance for age at sexual maturity and egg weights at 32 and 55 weeks Source
3 1 1 1 1 3 1 1 1 24
Age at sexual maturity
Egg weight (32 weeks)
Egg weight (55 weeks)
5.63** 8.42** 7.60** 0.92 0.54 0.71 0.94 0.88 0.30 0.80
11.664 0.004 2.214 32.774** 0.841 0.277 0.049 0.142 0.198 0.829
34.53** 13.69 0.03 89.87** 0.61 0.51 0.17 0.87 0.50 1.93
= P<0.01
lay, calculated as percentages, were analyzed before and after arc sin transformation, with similar results. The tabular results are from calculations based on percentages. Observations of agonistic behavior within flocks of high and low strains of the W.L. and R.I.R. breeds (Craig et al., 1969) indicated higher frequencies of social interactions, hence presumably greater social stress, within high strain W.L. flocks. McBride (1960, 1962, 1968) hypothesized that increased stress would decrease mean productivity, but contrarily would increase individual variability due to negative skewness of the frequency distribution. Significantly greater variability of individual performance was found for the high strain W.L. flocks (Table 3) for hen-day rate of production and hen-housed production during period 2, confirming the previous results of Craig and Toth (1969) and Biswas and Craig (1970). The results reported here are of particular interest because greater social stress was not indicated by frequencies of agonistic interactions within the W.L. high strain. They suggest social stress was in fact present, though undetected by that criterion (frequency of agonistic behavior).
Contrarily, the low strain W.L. was significantly more variable for age at sexual maturity and egg weights at 32 and 55 weeks of age. Higher variability among low-social-dominance W.L. flocks could be due to greater variance associated with higher mean values for those particular traits as usually expected (Snedecor and Cochran, 1967 pp. 62-64). Intra-flock variance of the R.I.R highsocial-dominance strain was significantly (P < 0.01) higher than in the low strain only for age at first egg, Table 4. Craig and Toth (1969) found no significant differences in variability between high and low strains of R.I.R. for various production traits. Such results are not unexpected since mean performance levels were similar for most traits and differences in frequency of agonistic behavior between pullets of the R.I.R. strains kept in flocks were not detected in the present study or in earlier comparisons (Craig et al., 1969). Egg weights: Egg weights at 32 and 55 weeks of age differed for strains within the W.L. breed only, Table 5. W.L. low strain pullets had heavier eggs at both 32 and 55 weeks of age. Heavier egg weight at 32 weeks of age for the W.L. low social dominance strain is in agreement with the find-
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Genetic groups (G) Breed (Br) High vs. low: R.I.R. High vs. low: W.L. Age at flock assembly (R) GXR BreedXR (Highw. low: R.I.R.)XR (Highw. low: W.L.)XR Flocks: G and R
D.F.
1935
AGE AT ASSEMBLY, BEHAVIOR AND PRODUCTION
6 and Figure 2 reveals these interactions are primarily due to the precipitous decline in performance of the W.L. high strain in the second 20-week period of egg production. Age at flock assembly did not have significant effects on either rate of lay or hen-housed production. The earlier sexual maturity of the R.I.R. high strain is in agreement with the data of Craig and Toth (1969). They also reported a tendency for their unstable flocks to mature earlier (P = .06). In this study age at flock assembly had no detectable effect on sexual maturity. The significantly poorer egg production and survival for the high social dominance strain of W.L. found in this study (Table 1) are in agreement with the findings of Craig and Toth (1969) and Biswas and Craig (1970). The W.L. high strain had the highest mortality (12%) as compared with an average of 4% for the other three strains. The present study did not show significant effects for age at flock assembly on any production trait, although frequency of social interactions was clearly elevated for several weeks in flocks reassembled at 19 weeks. Craig and Toth (1969) postulated
TABLE 6.—Comparison of breeds, strains and 20-week production periods on hen-housed production and hen-day rate of production Hen-housed Egg Production, Percentages Breed Mean Strain Mean Periods: weeks Mean Breed Mean Strain Mean Periods: weeks Mean
W.L. 53.0
R.I.R. 58.4 R.I.R.-High 59.9
W.L.-Low 58.5
W.L.-High 47.6
R.I.R.-Low 57.0
19 to 39 57.8
39 to 59 53.7
Hen-Day Rate of Production, Percentages W.L. R.I.R. 70.2 66.8 R.I.R.-Higl i R.I.R.-Low W.L.-Low 69.3 71.1 70.2 19 to 39 77.6
Means not underscored by the same line differ significantly (P<0.05).
39 to 59 59.4
W.L.-High 63.4
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ings of Biswas and Craig (1970). Age at flock assembly had no effect on egg weights. Egg production and mortality: Variances between flock means within strain-treatment subclasses were calculated for age at sexual maturity, hen-housed production, and hen-day rate of lay. Bartlett's test as described by Snedecor and Cochran (1967, pp. 296-298) showed no heterogeneity for any of the traits. No heterogeneity was detected for variances of flock means within strain-treatment subclasses for mortality. Therefore flock means were used in analyses of variance. Age at sexual maturity was affected significantly (P < 0.01) by breed and by strains within the R.I.R breed, Table 5. The R.I.R. breed, on the average, matured 1 week earlier than the W.L. Within the R.I.R. breed the high strain matured earlier (22.4 vs. 23.8 weeks). Hen-housed production and hen-day rate of lay were affected significantly by breed, strains within the W.L. breed, and periods, Table 1. Interactions were significant for breed and period and also for strains within the W.L. and period. Examination of Table
1936
M. R. CHOUDAEY AND J. V. CRAIG KEY AC.C.FMRLED.WKS — HIGH — HIGH - LOW -
LOW
19 5 19 6
WEEKS
FIG. 2. Hen-housed production in percentages for high and low social dominance strains of W.L. and R.I.R. breeds, assembled at 6 and 19 weeks of age, at 20 biweekly periods from 19 to 59 weeks.
that higher rates of agonistic activity associated with flock reorganization may not always increase social stress; at least not for birds previously near the bottom of the social heirarchy. For such individuals, reassembly in new groups may allow some upward social mobility with reduced stress. A similar situation may be postulated for flocks reassembled shortly before sexual maturity. ACKNOWLEDGMENT The authors are grateful to Drs. Kenneth Kemp and Arthur Dayton for assistance in statistical analyses and interpretation of results. REFERENCES Biswas, D. K., and J. V. Craig, 1970. Genotype— environment interactions in chickens selected for high and low social dominance. Poultry Sci. 49:681-692. Biswas, D. K., and J. V. Craig, 1971. Social ten-
sion indexes and egg production traits in chickens. Poultry Sci. 50: 1063-1065. Craig, J. V., and R. A. Baruth, 1965. Inbreeding and social dominance ability in chickens. Animal Behav. 13: 109-113. Craig, J. V., and A. Toth, 1969. Productivity of pullets influenced by genetic selection for social dominance ability and by stability of flock membership. Poultry Sci. 48: 1729-1736. Craig, J. V., D. K. Biswas and A. M. Guhl, 1969. Agonistic behaviour influenced by strangeness, crowding and heredity in female domestic fowl. Animal Behav. 17 : 498-506. Craig, J. V., L. L. Ortman and A. M. Guhl, 1965. Genetic selection for social dominance ability in chickens. Animal Behav. 13: 114-131. Duncan, D. B., 1955. Multiple range and multiple F tests. Biometrics, 11: 1-42. Guhl, A. M., 1953. Social behavior of domestic fowl. Kansas Agr. Expt. Sta. Tech. Bull. 73. Guhl, A. M., and W.C. Allee, 1944. Some measurable effects of social organization in flocks of hens. Physiol. Zool. 17 : 320-347. Guhl, A. M., J. V. Craig and C. D. Mueller, 1960. Selective breeding for aggressiveness in chickens. Poultry Sci. 39: 970-980.
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AGE,
AGE AT ASSEMBLY, BEHAVIOR AND PRODUCTION McBride, G., 1958a. The relationship between aggressiveness and egg production in the domestic hen. Nature, 181: 858. McBride, G., 1958b. The relationship between aggressiveness, peck-order and some characters of selective significance in the domestic hen. Proc. Roy. Phys. Soc. Edin. 27: 56-60.
McBride, G., 1968. Behavioral measurement of social stress. In: Adaptation of Domestic Animals, ed. E.S.E. Hafez pp. 360-366. Lee and Febiger, Philadelphia. Sanctuary, W. C , 1932. A study of avian behavior to determine the nature and persistency of the order of dominance in the domestic fowl and to relate these to certain physiological reactions.
M. S. Thesis, Massachusetts State College, Amherst. Schjelderup-Ebbe, T., 1935. Social behavior of birds. Chap. X X In: Murchison's Handbook of Social Psychology, 947-972. Clark Univ. Press, Worcestor. Scott, J. P., and E. Fredericson, 1951. The causes of fighting in mice and rats. Physiol. Zool. 24: 273-309. Siegel, P. B., 1960. A method of evaluating aggressiveness in chickens. Poultry Sci. 39: 1046-1048. Snedecor, G. W., and W. G. Cochran, 1967. Statistical Methods, 6th Ed. Iowa State College Press, Ames. Tindell, D., and J. V. Craig, 1959. Effects of social competition on laying house performance in the chicken. Poultry Sci. 38: 95-105. Tindell, D., and J. V. Craig, 1960. Genetic variation in social aggressiveness and competition effects between sire families in small flocks of chickens. Poultry Sci. 39: 1318-1320.
Environmental Temperature and Dietary Lysine Effects on Free Amino Acids in Plasma J. D. MAY, 1 L. F. KUBENA, 1 F. N. REECE 2 AND J. W. DEATON 1 United States Department of Agriculture, A.R.S., State College, Mississippi 39762 (Received for publication February 25, 1972)
ABSTRACT Broiler chicks were reared to 5 weeks of age in environmental chambers maintained at 7.2°C. and 32.2°C. with dewpoints of 0° and 10°C, respectively. In 2 trials chicks were fed commercial broiler diets and in 3 trials they were fed diets supplying 60, 100 and 130 percent of the dietary lysine requirement. Free amino acids in plasma were measured. Chicks at 7.2°C. had reduced concentrations of alanine, arginine and tyrosine but had increased levels of cystine, ornithine and lysine, when compared to the values for chicks at 32.2°C. The increased plasma lysine could result from its relative difficulty of catabolism in comparison with the other amino acids. It is suggested that the high level of plasma lysine in chicks kept at 7.2°C. results in an increased breakdown of arginine to ornithine. POULTRY SCIENCE SI: 1937-1940, 1972
HRONIC exposure of animals to low environmental temperatures results in increased food consumption per unit of
C
1 Animal Science Research Division, Poultry Research Branch, South Central Poultry Research Laboratory, State College, Mississippi. 2 Agricultural Engineering Research Division, Farm Electrification Research Branch, South Central Poultry Research Laboratory, State College, Mississippi.
body weight. Many amino acids can be readily converted into carbohydrate and, therefore, they are a potential source of energy. The role of amino acids as an energy source is probably more important during cold weather. Klain et al. (1962) stimulated consumption of amino acid imbalanced diets by keepings rats at 7°C. and found that they grew as well as rats fed control diets and
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McBride, G., 1960. Poultry husbandry and the peck order. Brit. Poultry Sci. 1: 65-68. McBride, G., 1962. Behavior and a theory of poultry husbandry. Proc. X l l t h World's Poultry Congress (Symposia): 102-105.
1937