Socialization, the Sequencing of Environmental Factors, and Their Effects on Weight Gain and Disease Resistance of Chickens

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1 Socialization, the Sequencing of Environmental Factors, and Their Effects on Weight Gain and Disease Resistance of Chickens W. B. GROSS and P. B. SIEGEL Virginia Polytechnic Institute and State University, Blacksburg, Virginia 246 (Received for publication April 3, 982) ABSTRACT Weight gain following a 6-hr fast was influenced ) by prior experiences of either a presence or an absence of a similar initial fast followed by either being moved to unfamiliar quarters or being fed corticosterone or 2) whether or not the chickens were socialized. Socialization, but not the environmental stresses, increased antibody response to erythrocyte antigens and increased resistance to Escherichia coli challenge. Although the experimental cockerels had increased heterophil/lymphocyte ratios following the feeding of corticosterone, their antibody response to erythrocyte antigen and their resistance to E. coli challenge were not altered. The presence or absence of water deprivation stress early in life failed to alter any results. (Key words-, socialization, environmental stresses, disease, resistance, antibodies, body weight) INTRODUCTION Environmental factors, the interactions among them, and the presence or absence of socialization influenced body weight gain and resistance to Staphylococcus aureus challenge (Gross and Siegel, 982a). A water deprivation stress during the st week after hatching influenced subsequent experimental results for at least 22 weeks (Gross and Siegel, 98). Chickens socialized to a human gained more weight, had higher blood protein levels, showed an increased feed efficiency, had a reduced standard deviation to all parameters, and were more resistant to Escherichia coli and Staphylococcus aureus infection (Gross and Siegel, 979, 982b) than those not socialized. The following experiments were conducted to determine the effects of a sequence of four environmental factors on cockerels of a commercial laying stock. MATERIALS AND METHODS Cockerels from the Dekalb -L stock of layers were obtained at two days of age. The chickens were started in small brooders in groups of about 35. When 4 weeks old, flocks of birds each were placed in cages of the Horsfall-Bauer type. At least 6 days were allowed for adaptation before the experiments were begun. The experimental cages were equipped with automatic waterers and contained a 5-day supply of feed. 983 Poultry Science 62: The chronology of stresses and infectious disease challenges during the two experiments appear in Table and the composition of experimental groups appears in Table 2. Environmental Stresses. The first and second fasts were administered by withholding feed for 48 hr except during the second fast of Experiment 2 when feed was withheld for 6 hr. For the second stress, one-third of the chickens were transferred to a range shelter (July and August) for 2 days where they were exposed to an unfamiliar environment and to unfamiliar chickens. During the second stressing period another one-third of the chickens were fed 3 ppm of corticosterone for 2 days. Response to Antigen. For determination of response to an antigen a. ml i.v. dose of a.5% suspension of either sheep, dog, swine, or human red blood cells was injected intravenously. Five days later plasma was collected and antibody titers determined by the microtiter agglutination testing method. Titers are expressed as log 2 of the reciprocal of the greatest dilution in which agglutination occurred. Mycoplasma gallisepticum Challenge. Mediagrown "W" strain (isolated from Winchester, VA) (Gross, 96) of M. gallisepticum stored at -7 C and having about 5 LD 5/ml for chicken air sacs was used. Chickens were challenged via the left posterior thoracic air sac with. ml of a ~ 3 dilution in tryptose broth. Fourteen days later, lesions were observed and graded on a scale from (no lesions) to 4 592

2 ENVIRONMENT AND DISEASE RESISTANCE 593 TABLE. Days of stresses and infectious disease challenges Birds placed in experimental cages (4 weeks of age)- First fast in feed or moved to unfamiliar quarters Mycoplasma gallisepticum Second fast Newcastle disease Escherichia coli Lesions observed Experiment Days Experiment (maximum lesions) for four air sacs groups. The air sacs groups were ) left posterior, thoracic and lesser abdominal; 2) left greater abdominal; 3) right posterior thoracic and lesser Group TABLE 2. Composition of experimental groups st abdominal; and 4) right greater abdominal. The maximum possible score per bird was 6. Escherichia coli Challenge. Serotype :K of E. coli was grown for 8 hrs in tryptose broth. In Experiment, the culture was administered undiluted as an aerosol. In Experiment 2,. ml of a " dilution was inoculated into the left posterior thoracic air sac. Pericarditis and death were recorded 5 days later. Newcastle Disease Challenge. Egg propogated Bj strain having a ELD S was administered undiluted as an aerosol. Socialization of Chickens. Half of the chickens were gently handled during the brooding ( to 4 weeks of age) and experimental (4 to 8 weeks of age) periods. During the experimental period the birds were offered an open hand containing cracked corn once or twice each day (Gross, 982b). The other half of the chickens were ignored except for essential husbandry. Stress Early in Life. Chicks destined to be one-half of each experimental group were deprived of water for 8 hr each day between the 6th and th days after hatching. Treatments 2nd, Variable applied; blank, variable not applied; moved, moved among unfamiliar individuals.

3 594 GROSS AND SIEGEL Containing Feed. One hundred and twenty milligrams of corticosterone was dissolved in 2 ml of ethanol and mixed thoroughly in 4 kilo batches of feed to achieve a level of 3 ppm. After evaporation of the ethanol by air drying the medicated feed was fed for 2 days during the second stressing period. Chickens were also fed between 5 and 8 ppm day before and 5 days after being inoculated with erythrocyte antigens or E. coll Weight gain data were analyzed by analysis of variance with differences between means determined by the Duncan multiple range test. Disease challenge data were examined with a 2x2 contingency table. Antibody titers were examined by analysis of variance. RESULTS Socialization during the first experiment was achieved by about the 2st day after being placed in the experimental cages, whereas in the second experiment the birds became socialized by about the th day. None of the results were altered by the presence or absence of a stress early in life. Experiment. birds produced more antibody to human erythrocytes, administered after the second fasting period, than the nonsocialized birds (P<.). None of the environmental stressors influenced the antibody response to erythrocyte antibodies. The feeding of corticosterone before M, gallisepticum inoculation (Table 3) resulted in increased severity of air sac lesions (P<.5). These lesions were reduced in severity if the birds were also exposed to the first and second fasts. Neither socialization nor being moved into unfamiliar quarters influenced the severity of air sac lesions. The prevalence of pericarditis following E. coli aerosol challenge was 3% among socialized and % among nonsocialized birds (P<.5). The prevalence of pericarditis following E. coli aerosol challenge was % among those exposed to the second fast, whereas the unfasted birds had a 3% incidence (P<.5). The prevalence of pericarditis was 6% for nonsocialized birds subjected to the second fast and % for those which were socialized and not subjected to the second fast (P-C5). Experiment 2. During the first fasting period the average gain of fasted birds was 2 g and unfasted birds averaged a 43 g gain (P<.). birds gained less than nonsocialized birds (P<.5). The effects of being moved to unfamiliar quarters or of feeding corticosterone on body weight gain are recorded in Table 4. During the second stressing period both stressors resulted in decreased weight gain (P<.). Between the end of the first fasting period and the beginning of the second fasting period, those birds also subjected to the first fast had gained less (P<.) than unfasted birds. birds not subjected to the first fast gained more than fasted nonsocialized birds (P<.). The weight gain of those moved to unfamiliar quarters was intermediate between the controls and those fed corticosterone (P<.5). Weight gains during the second fasting period are summarized in Table 5. birds gained more than nonsocialized birds (P<), the difference being most apparent among birds subjected to both fasts. The probabilities that the stressors and socialization and TABLE 3. Effects of corticosterone, first fast, and second fast on air sac lesions resulting from E. coli aerosol exposure following myoplasma gallisepticum and Newcastle disease virus exposure Air sac lesion scores st 2nd socialized Average a 3.4 ab 3.7bc 4.3 C 3.2 ab a,b,c Means of values are different if followed by different letters (P<.5).

4 ENVIRONMENT AND DISEASE RESISTANCE 595 TABLE 4. Effects of socialization, first fast, unfamiliar environment, and feeding of corticosterone on weight gain (g) during the second stressing period and on weight gain between the end of the first fasting period and the beginning of the second fasting period Treatment socialized ed 4.5' Nonfasted 5.7' Weight gain during second stressing period Weight gain between end of st fasting period and beginning of 2nd fasting period. Second stress TABLE 5. Influence of stresses on weight gain (g) during the second fasting period 7 d a 9 d b 87 d ab F,' F 2 ' 92 e b -7Cb 66 c a -26 a a 75 cd a -9 a ab F F 2-9 c a -9 b a 2 a 67 d a 74 c a 77C d a socialized F> 64 d a 6 c a 63 c a F 2-76 a a 7bb -9 a b P.F. -23 b a -3 a a -2 a a ' ' ' ' Means in a row with different superscripts are different (P<.5). Means in a column with different subscripts are different (P<.5). 'F., ;F,, 2. their interactions affected on weight gain are recorded in Table 6. Most of the factors and their interactions did affect weight gain. The probabilities that the stressors and socialization and their interactions affected weight gain of chickens actually subjected to the second fast are recorded in Table 7. All of the environmental factors and almost all of their interactions did affect weight gain. Weight gains during the entire period of exposure to the environmental factors are recorded in Table 8. Chickens under the most favorable circumstances (socialized and not ) gained 72% more than those under the least favorable circumstances (ignored, subjected to both fasts and fed corticosterone). Birds subjected to the first fast and those moved to unfamiliar quarters tended to regain lost weights. The probabilities that the environmental factors and their interactions affected weight gain are recorded in Table 9. The number of significant values and their levels of significance were reduced as compared with those of the second fasting period (Table 6). Chickens fed corticosterone had a marked increase in heterophil/lymphocyte ratios of from.35 (at ppm) to 3.5 (at 5 ppm). The slope of the logs of H/L ratios related to ppm of corticosterone in the feed was.28 and the intercept log.495. The t value for significance of slope was 5.37 (P<). Even though the H/L ratio changes were highly significant there was no change in antibody response to sheep red blood cells. Response to E. coli challenge was not altered by the prior feeding of increasing levels of corticosterone. Following E. coli challenge after the second fasting period in the second experiment, socialized birds had a 26% incidence of pericarditis whereas nonsocialized birds had a 38% incidence (P<.). None of the other factors influenced the incidence of pericarditis.

5 596 GROSS AND SIEGEL TABLE 6. Probabilities that environmental factors influence weight loss during the second fasting period Factors Second stress period Movec Socialization st 2nd Socialization and st fast Socialization and 2nd fast st fast and 2nd fast Socialization and st fast and 2nd fast ' '.6543'.7.6 Probability of F values for each column was based on and 79 degrees of freedom. significant. DISCUSSION All of the stressors and socialization independently and as interactions influenced weight gain during the second fasting period (Tables 5, 6, 7). This indicates that the response of a chicken to an environmental change is influenced by its entire previous experience. It is possible that this effect would occur with other stocks of chickens, and that other stressors would also alter responses to other factors. That is, responses that occur later in life are influenced by the previous experiences of the chicken. Effects of short term weight losses in response to environmental stresses tended to be compensated with subsequent increased (as compared to the un control) weight gain. Each additional stress resulted in additional decreases in weight gain. TABLE 7. Probabilities that environmental factors influence weight gains of chickens fasted during the second fasting period Environmental factors Socialization st Move or corticosterone (M or C) Socialization and st fast Socialization and M or C st and M or C Socialization M or C and st fast significant. Probability of no effect * * *.75* Following exposure to environmental factors or the feeding of corticosterone the -L cockerels did not alter their response to erythrocyte antigens or their resistance to E. coli challenge. Previous experience with Cornell Randombred chickens indicated that they decreased antibody response to erythrocyte antigens and had increased resistance to E. coli challenge following environmental stress or the feeding of corticosterone (Gross and Siegel, 973; Gross et al, 98). Heterophil/lymphocyte ratios of both stocks could be increased by feeding higher doses of corticosterone (Gross et al., 98). Socialization appears to produce responses that differ from that of environmental and social stresses (McBride, 982). None of the stresses utilized in Experiment altered antibody response to the erythrocyte antigens. Antibody response was increased in socialized as compared to nonsocialized birds. In most stocks (Gross and Siegel, 973; Gross and Siegel, 982b) environmental stresses result in reduced antibody response whereas socialization results in increased antibody response. In Experiment 2 the second fast did not increase resistance to E, coli challenge. Other stocks when (Gross and Siegel, 98) had increased resistance to E. coli challenge. Resistance to E. coli challenge was increased by being socialized as compared to not being socialized. In other stocks, environmental stresses and socialization increased resistance to E. coli challenge (Gross and Siegel, 982a,b). Therefore, the responses of socialized birds are not only due to a reduced level of stress.

6 ENVIRONMENT AND DISEASE RESISTANCE 597 TABLE 8. Influences of stresses on weight gain (g) between the beginning of the first fasting period through the end of the second fasting period Second stress fast ing periods Fi F 2 F,F» socialized fasting period F. F F 2 F c a 36 c a 33 c a 328 c b 32bcb 262 b a 289 bc c 244 a b 98 a a 267 b b 247 a b 23 a a 34C a 328 b c a 39 c a 343 c c 3lbb 26 b a 29 a a 223 a a 97 a a 256 ab b 232 a ab 27 a a ' ' Means in a row with different superscripts are different (P<.5). Means in a column with different subscripts are different (P<.5). TABLE 9. Probabilities that environmental factors influence weight gain (g) between beginning of first fasting period through the end of the second fasting period Environmental factors Socialization st 2nd Socialization and st fast Socialization and 2nd fast st fast and 2nd fast Socialization, st fast and 2nd fast.9'.9977* : *.272* Second stress period '.7856' Probability of F values for each column was based on and 79 degrees of freedom. * significant. As compared to previously encountered experimental stocks, the -L cockerels were more difficult to socialize. More contact time was needed before the birds appeared to have confidence in the handlers. In Experiment 2, extra time was spent with the birds, particularly during the week after hatching and during the first week in the experimental cages. In both experiments, they did become well socialized. It should be noted that differences between the responses of experimental groups to environmental factors were often significant to the. to probability levels whereas the probabilities associated with E. coli challenges were usually less than.. This is because groups of birds tend to respond more uniformly to environmental stresses than to E. coli challenge. These results suggest that the presence or absence of environmental stresses can strongly affect growth rate. More factors are involved in determining resistance to E. coli challenge than.5883* *.478*.686* in determining response to environmental stresses. REFERENCES Gross, W. B., 96. The development of "air sac disease." Avian Dis. 5: Gross, W. B., and P. B. Siegel, 973. Effect of social stress and steroids on antibody production. Avian Dis. 7: Gross, W. B., and P. B. Siegel, 979. Adaptation of chickens to their handler and experimental results. Avian Dis. 23: Gross, W. B., and P. B. Siegel, 98. Effects of early environmental stresses on chicken body weight, antibody response to RBC antigens, feed efficiency and response to fasting. Avian Dis. 24: Gross, W. B and P. B. Siegel, 982a. Influences of sequences of environmental factors on the response of chickens to fasting and to Staphylococcus aureus infection. Am. J. Vet. Res. 43: Gross, W. B., and P. B. Siegel, 982b. Socialization as

7 598 GROSS AND SIEGEL a factor in resistance to infection, feed efficiency and response to antigen. Am. J. Vet. Res. 43: (In press). Gross, W. B., P. B. Siegel, and R. T. DuBose, 98. Some effects of feeding corticosterone to chickens. Poultry Sci. 59: McBride, G Adaptation and welfare at the mananimal interface. Pages 9598 in Behavior in Relation to Reproduction, Management, and Welfare of Farm Animals. M. Wodzicka-Tomaszewska et at, ed. Reviews in Rural Sci. No. IV. Univ. New England, Armidale, N.S.W., Australia.