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Effect of early handling on growth, mortality and feed efficiency in White Leghorns
Applied Animal Behaviour Science, 34 (1992) 121-128
121
Elsevier Science Publishers B.V., Amsterdam
Effect of early handling on growth, mortality and feed efficiency in White Leghorns* Marry L. Leonard and R. Wayne Fairfull Animal Research Centre, Agriculture Canada, Ottawa, Ont., KI.4 0C6, Canada (Accepted 11 November 1991 )
ABSTRACT Leonard, M.L. and Fairfull, R.W., 1992, Effect of early handling on growth, mortality and feed efficiency in White Leghorns. Appl. Anita. Behav. Sci., 34: 121-128. The influence of early and regular handling on weight gain, mortality and feed efficiency was examined in four strains of White Leghorn chicks. Pens of approximately 60 chicks were assigned at random to one of three treatment groups: non-handled (NH), handled every, day (HED), and handled every 3 days (HE3D). The experiment began 4 days post-hatch and continued for 5 weeks. The mean weight and pattern of weight gain over four weighing periods did not differ significantly among the three treatment groups. However, the variation around the mean was significantly different at the second weighing period. Handling appeared not to affect overall mortality. However, more pens in the HE3D group had individuals die from cannibalism in the first 5 weeks than from either omphalitis or dehydration. Feed efficiency did not differ significantly among the treatment groups. Contrary to earlier studies, our results showed relatively minor, short-term effects of handling.
INTRODUCTION
Habituation to human handlers is thought to have a beneficial effect on animals. Early work suggested that habituation to humans accelerated growth and decreased fearfulness in rats and mice (Denenberg and Karas, 1959). More recently, the effects of habituation through early handling have been studied using domestic animals (e.g. Hemsworth et al., 1981; Gonyou et al., 1986; Hargreaves and Hutson, 1990). These studies indicated that handling may improve growth rate and reduce fear of humans in gilts (Hemsworth et al., 1981 ), increase learning ability in horses (Heird et al., 1986), and decrease fear responses in cattle (Boissy and Bouissou, 1988) and sheep (Hargreaves and Hutson, 1990). Thus the possibility of reducing stress and inCorrespondence to: M.L. Leonard, Centre for Food and Animal Research, Central Experimental Farm, Ottawa, Ont., K IA 0C6, Canada. *CFAR Contribution N u m b e r 1758.
© 1992 Elsevier Science Publishers B.V. All rights reserved 0168-1591/92/$05.00
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creasing productivity through socialization to humans may be important for modern domestic species subject to intensive farming practices. Regular handling of broiler and layer chicks has been shown to enhance growth (e.g. Jones and Hughes, 1981; Collins and Siegel, 1987), feed efficiency (e.g. Gross and Siegel, 1982), resistance to infection (e.g. Collins and Siegel, 1987), and i m m u n e responses (Gross and Siegel, 1982). However, some studies have found little or no effect of early handling (e.g. Reichmann et al., 1978 ) and in some cases a negative effect of handling has been reported (Hughes and Black, 1976; Freeman and Manning, 1979). These conflicting results may be related to differences in methodology among studies, especially differences between strains, stimulation rate or the age at the beginning of the treatment. The purpose of our study was to test the effect of early handling on weight gain, mortality and feed efficiency of four strains of White Leghorn. We wanted to ensure that if there was no treatment effect it was because of the birds' failure to respond to the treatment and not because of the experimental protocol (e.g. missing a sensitive period). Therefore we chose a relatively high stimulation rate that continued for an extended period of time and began when the chicks were very young. ,ANIMALS, MATERIALS AND METHODS
At hatch, 3000 White Leghorn females were assigned, in groups of approximately 60, to the top c o m p a r t m e n t of a Thornber, three tier brooder pen. Chicks were kept in the top tier for approximately 8 weeks and were then distributed equally among the three tiers. The chicks were brooded under dull emitter heat lamps and food and water were provided ad libitum. The photoperiod was from 06:00 to 14:00 h. The birds were from one selected and one control strain in each of two genetic bases. Strain 3 of Base 1 has undergone selection since 1950, while Strain 9 of Base 2 has been under selection since 1969. The control or random-bred strains have been maintained since 1950 (Strain 5, Base 1) and 1961 (Strain 7, Base 2 ). The selected strains have been selected for a variety of production traits (e.g. viability, egg production, fertility). In both bases, the selected and control strains differ significantly for many of these traits (e.g. age at first egg, egg production, egg weight). Forty-eight pens were randomly divided into three treatment groups: not handled ( N H ) , handled every day ( H E D ) , and handled every third day (HE3D). The last treatment was designed to identify a m i n i m u m handling rate. Chicks that were not handled were restricted to regular management activities only (i.e. a daily check of the pens by a single person). Among handled chicks, handling began when the chicks were 4 days old and continued until they were 37 days old. Handling consisted of gently removing each chick
EFFECT OF HANDLING ON WHITE LEGHORNS
123
from its pen and placing it in a large cardboard box. Once all the chicks had been removed they were individually returned to their home pen. Pens adjacent to, and across from a handled pen were covered during handling to prevent the chicks in those cages from seeing the procedure. It took approximately 10 rain to remove and replace all the chicks in a brooder. The birds were handled between 08:00 and 10:00 h by seven regular handlers. The chicks were exposed to all handlers equally. The order in which the pens were handled was randomized. All chicks were weighed at 3, 37, 78 and 121 days of age. Feed efficiency (weight of feed consumed/weight gained ) was measured between 79 and 121 days of age. During this time all feed was weighed into the feed trough. At the end of the test period the feed remaining in the trough was weighed to determine the total feed consumed per pen. Spillage was minimal. Mortality rate was also recorded and necropsies were performed to determine the cause of death.
Statistics Because measures of individuals within pens were not independent, pen means were used in all analyses. We used a log transformation on the standard deviations to correct for non-normality. The results from the analyses for transformed and untransformed data were the same, therefore the latter are presented. The model to examine differences in body weight included differences among the three treatments (2 d.f. ) and among the four strains ( 3 d.f. ) and the interaction of treatment and strain (6 d.f.) all tested against pens within treatments (36 d.f.). We also used split-plot analyses to examine whether the relationship among the above factors changed over time. In this study we were interested in strain differences as they relate to treatment effects. Differences in strains with respect to weight gain, mortality etc. have been described elsewhere (Fairfull and Gowe, 1990). Therefore, we report statistics for strain × treatment interactions only. RESULTS
Within 2 weeks of the beginning of the study, most chicks in the HED group would approach the front of the cage when the handler arrived and peck the handler's hand and arms. During the same time period, the chicks in the HE3D group moved to the rear of the cage when the handler approached and did not attempt to peck or move toward the handler. After 5 weeks these differences were no longer apparent and both groups approached, pecked and climbed on the handler in a manner unlike the normal flightiness seen in these strains (R.W. Fairfull, personal observation, 1990). In an attempt to avoid inadvertent socialization, the NH group was not observed during this time.
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Weight The mean weights of the three treatment groups were not significantly different at the beginning of the study (Day 3, P = 0 . 6 9 ; Table 1 ), nor was there a significant interaction between strain and treatment ( P = 0.59 ). After handling, differences in the mean weight among the treatment groups remained non-significant (Day 37, P = 0 . 2 3 ; Day 78, P = 0 . 2 8 : Day 121, P = 0 . 2 5 ; Table 1 ). Likewise, the interaction between strain and treatment was not significant (Day 37, P = 0 . 8 4 ; Day 78, P = 0 . 3 8 ; Day 121, P = 0 . 5 9 ; Table 1 ). In addition, split-plot analyses to examine the pattern of weight gain over time showed that the relationship among treatment groups was consistent over the brooding period ( P = 0.38 ). Finally, the relationship between treatment and strain did not vary significantly over this time ( P = 0 . 6 3 ) . Although the mean weight among treatments was similar, the standard deviation about the means was significantly different at Day 37 ( P < 0.01 ; Table 1 ). At Day 78 this difference, although not significant ( P = 0 . 0 6 ; Table 1 ), was in the same direction. The results of a protected least square differences test indicated that the variation in the HED group was greater than that of the other two groups. This was not the result of initial differences in the standard deviation at Day 3 ( P = 0 . 5 5 ; Table 1 ). Standard deviations were not significantly different by Day 121 ( P = 0 . 8 5 ; Table 1 ). Strain by treatment interactions were not significant at any time (Day 37, P = 0 . 7 4 ; Day 78, P = 0 . 2 9 ; Day 121, P = 0 . 9 1 ). Finally, the relationship among the three treatment groups with respect to the standard deviations was not significantly different over time ( P = 0 . 7 9 ) nor was the interaction between treatment and strain over this time period ( P = 0 . 9 2 ) . TABLE I Mean body weights (g) and mean standard deviations o f the weights for each of the three treatment groups ~at Days 3, 37, 78 and 121 Age (days)
3 37 78 121
Mean
Standard deviation
NH
PIED
HE3D
NH
HED
HE3D
40.5 219.5 818.5 1180.7
40.3 217.7 797.9 1180.2
40.6 227.1 817.6 1190.9
3.2 37.0 76.1 100.9
3.3 42. l** 84.5 110.2
3.3 38.7 78.2 100.9
~NH. non-handled; HED, handled every day: HE3D, handled every third day. Each value is the mean of 16 pen means or 16 within-pen standard deviations based on approximately 60 birds per pen. **Significantly different from the other two treatments, P < 0.01.
EFFECT OF HANDLING ON WHITE LEGHORNS
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TABLE 2 Mean ( +_SE) n u m b e r of deaths per pen for each of the three treatment groups ~during the experimental period (Days 0-37 ) and over the total brooding period ( Days 0-129 ) Treatment
N2
Experimental period
Brooding period
NH HED HE3D
16 16 16
1.44 +_0.32 1.31 +_0.29 1.13+_0.30
2.06 + 0.49 1.63+0.34 1.31 +_0.31
~NH, non-handled; HED, handled every day; HE3D, handled every third day. 2N, the n u m b e r of pens.
Mortality Handling did not appear to affect mortality during the treatment period (first 5 weeks). The number of deaths per pen during this time did not differ significantly among the three treatment groups ( P = 0.35; Table 2) and the interaction between strain and treatment was also not significant ( P = 0.35 ). Similarly mortality over the total brooding period (including the first 5 weeks ) showed no effect of handling treatment ( P = 0 . 2 9 ) and no interaction between strain and treatment ( P = 0.08 ). The cause of death was weakly related to treatment. Significantly more pens in the HE3D group had individuals die from cannibalism in the first 5 weeks than in the other two groups (Z= = 7.0, d.f. = 2, P < 0.05 ). However, this was not the case when the total brooding period was examined (X2= 1.52, d.f. = 2, P > 0.10 ). The other two major causes of death in the early period, omphalitis and dehydration, did not differ significantly among the three groups.
Feed efficiency Feed efficiency (amount of feed consumed/weight gained) did not differ significantly among treatment groups ( P = 0.76). Strain and treatment also did not interact significantly ( P = 0.84). DISCUSSION
In this experiment, using an intensive stimulation rate on several genetically diverse strains, early handling failed to produce the positive effects reported in many other studies (Thompson, 1976; Jones and Hughes, 1981; Gross and Siegel, 1983; Collins and Siegel, 1987). Although there were minor, short-term effects of handling, the apparent response of the experimental birds did not result in an increase in weight gain or a reduction in mortality compared with the control group. Some earlier studies also found a limited effect of handling (McPherson et
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al., 1961; Reichman et al., 1978). However, in both studies the birds were handled at most once a week and in the former study the treatment did not begin until the birds were 3 weeks (broilers) and 9 weeks (pullets) of age. Unlike these studies, our birds were handled every day for 5 weeks beginning at Day 4 post-hatch. This rate is comparable to studies in which a positive effect was reported. It is unlikely that the strains used in this study were not receptive to socialization. Again, because we used four strains it seems that at least one of the strains would have shown an effect if it existed. Layer stocks have responded positively to early handling (Jones and Hughes, 1981; Gross and Siegel, 1983 ), so it is not a response peculiar to broiler stocks. Two alternative possibilities may explain our results. All cages in the battery were assigned to each of the three treatment groups at random, so that handlers passed by all the cages every day. Although the NH and HE3D groups were not actually subject to daily handling, and could not see the HED birds being handled, they were exposed to this daily disturbance. This would have increased exposure to humans and possibly reduced any differences among the groups. If this is the case, then perhaps just the frequent presence of a stockperson may habituate the birds and ultimately produce the positive effects reported in other studies (Siegel, 1989). Alternatively, if handling had a positive effect on the i m m u n e response of these birds we might not detect it in our system, where the effects of disease on growth and mortality are minimal (Gowe and Fairfull, 1985). Thus an effect of handling on the i m m u n e system may only be beneficial under certain conditions. The increased variation in weight among individuals in the HED group is interesting, but difficult to interpret. It suggests that the benefit of daily handling may vary among individuals. Individuals that responded negatively to this treatment may not grow as quickly as those responding positively to the treatment. Because this effect was not obvious in the HE3D group, this result also suggests that there may be a threshold rate of handling necessary before the effect is detectable. Increased mortality from cannibalism during the first 5 weeks was associated with the HE3D treatment. A relationship between disturbance and cannibalism has been reported in poultry (Hughes and Duncan, 1972). Thus, this effect may be related to the regular, but infrequent disturbance involved with handling the birds every third day. Perhaps daily handling resulted in increased socialization, so that the disturbance had a limited negative effect. Increased variation in body weights within the HED group suggests that some individuals may benefit from regular handling. However, this effect is short-lived. Our results also suggest that regular, but infrequent handling may actually have negative effects in the short term (i.e. increased cannibalism). Further work obviously needs to be done to examine some of these possibili-
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ties. We are presently examining the effect of early handling on production traits in layers. ACKNOWLEDGMENTS
We thank David Fraser and Andy Horn for reading the manuscript and providing many helpful comments. We also thank Brian Thompson for help with the analyses and Bob Mumford and the staff of the CFAR poultry unit for their assistance with the experiment.
REFERENCES Boissy, A. and Bouissou, M.-F., 1988. Effects of early handling on heifers' subsequent reactivity to humans and to unfamiliar situations. Appl. Anita. Behav. Sci., 20: 259-273. Collins, J.W. and Siegel, P.B., 1987. Human handling, flock size and responses to an E. coli challenge in young chickens. Appl. Anim. Behav. Sci., 19: 183-188. Denenberg, V.H. and Karas, G.G., 1959. Effects of differential infantile handling upon weight gain and mortality in the rat and mouse. Science, 130: 629-630. Fairfull, R.W. and Gowe, R.S., 1990. Egg production in chickens. In: R.D. Crawford (Editor), Poultry Breeding and Genetics. Elsevier, Amsterdam, pp. 705-759. Freeman, B.M. and Manning A.-C.C., 1979. Stressor effects of handling in the immature fowl. Res. Vet. Sci., 26: 223-226. Gonyou, H.W., Hemsworth, P.H. and Barnett, J.L., 1986. Effects of frequent interactions with humans on growing pigs. Appl. Anim. Behav. Sci., 16: 269-278. Gowe, R.S. and Fairfull, R.W., 1985. The direct response to long-term selection for multiple traits in egg stocks and changes in genetic parameters with selection. In: W.G. Hill, J.H. Manson and D. Hewitt (Editors), Poultry Genetics and Breeding. British Poultry Science. Symposium 18, pp. 125-146. Gross, W.B. and Siegel, P.B., 1982. Socialization as a factor in resistance to infection, feed efficiency and response to antigen in chickens. Am. J. Vet. Res., 43:2010-2021. Gross, W.B. and Siegel, P.B., 1983. Socialization, the sequencing of environmental factors, and their effects on weight gain and disease resistance of chickens. Poult. Sci., 62: 592-598. Hargreaves, A.L. and Hutson, G.D., 1990. The effect of gentling on heart rate, flight distance and aversion of sheep to a handling procedure. Appl. Anim. Behav. Sci., 26: 243-252. Heird, J.C., Whitaker, D.D., Bell, R.W., Ramsey, C.B. and Lokey, C.E., 1986. The effects of handling at different ages on the subsequent learning ability of 2-year-old horses. Appl. Anim. Behav. Sci., 15:15-25. Hemsworth, P.H., Barnett, J i . and Hansen, C., 1981. The influence of handling by humans on the behavior, growth and corticosteroids in the juvenile female pig. Horm. Behav., 15: 396403. Hughes, B.O. and Black, A.J., 1976. The influence of handling on egg production, egg shell quality and avoidance behaviour of hens. Br. Poult. Sci., 17:135-144. Hughes, B.O. and Duncan, I.J.H., 1972. The influence of strain and environmental factors upon feather pecking and cannibalism in fowls. Br. Poult. Sci., 13: 525-547. Jones, R.B. and Hughes, B.O., 1981. Effects of regular handling on growth in male and female chicks of broiler and layer strains. Br. Poult. Sci., 22:461-465. McPherson, B.N., Gyles, N.R. and Kan, J., 1961. The effects of handling frequency on 8-week body weight, feed conversion and mortality. Poult. Sci., 40: 1526-1527.
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Reichmann, K.G., Barram, K.M., Brock, I.J. and Standfast, N.F., 1978. Effects of regular handling and blood sampling by wing vein puncture on the performance of broilers and pullets. Br. Poult. Sci., 19: 97-99. Siegel, P.B., 1989. The genetic-behaviour interface and wellbeing of poultry. Br. Poult. Sci., 30: 3-13. Thompson, C.I., 1976. Growth in the Hubbard broiler: increased size following early handling. Dev. Psychol., 9: 459-464.
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Effect of early handling on growth, mortality and feed efficiency in White Leghorns* Marry L. Leonard and R. Wayne Fairfull Animal Research Centre, Agriculture Canada, Ottawa, Ont., KI.4 0C6, Canada (Accepted 11 November 1991 )
ABSTRACT Leonard, M.L. and Fairfull, R.W., 1992, Effect of early handling on growth, mortality and feed efficiency in White Leghorns. Appl. Anita. Behav. Sci., 34: 121-128. The influence of early and regular handling on weight gain, mortality and feed efficiency was examined in four strains of White Leghorn chicks. Pens of approximately 60 chicks were assigned at random to one of three treatment groups: non-handled (NH), handled every, day (HED), and handled every 3 days (HE3D). The experiment began 4 days post-hatch and continued for 5 weeks. The mean weight and pattern of weight gain over four weighing periods did not differ significantly among the three treatment groups. However, the variation around the mean was significantly different at the second weighing period. Handling appeared not to affect overall mortality. However, more pens in the HE3D group had individuals die from cannibalism in the first 5 weeks than from either omphalitis or dehydration. Feed efficiency did not differ significantly among the treatment groups. Contrary to earlier studies, our results showed relatively minor, short-term effects of handling.
INTRODUCTION
Habituation to human handlers is thought to have a beneficial effect on animals. Early work suggested that habituation to humans accelerated growth and decreased fearfulness in rats and mice (Denenberg and Karas, 1959). More recently, the effects of habituation through early handling have been studied using domestic animals (e.g. Hemsworth et al., 1981; Gonyou et al., 1986; Hargreaves and Hutson, 1990). These studies indicated that handling may improve growth rate and reduce fear of humans in gilts (Hemsworth et al., 1981 ), increase learning ability in horses (Heird et al., 1986), and decrease fear responses in cattle (Boissy and Bouissou, 1988) and sheep (Hargreaves and Hutson, 1990). Thus the possibility of reducing stress and inCorrespondence to: M.L. Leonard, Centre for Food and Animal Research, Central Experimental Farm, Ottawa, Ont., K IA 0C6, Canada. *CFAR Contribution N u m b e r 1758.
© 1992 Elsevier Science Publishers B.V. All rights reserved 0168-1591/92/$05.00
122
M.L. LEONARD AND R.W. FAIRFULL
creasing productivity through socialization to humans may be important for modern domestic species subject to intensive farming practices. Regular handling of broiler and layer chicks has been shown to enhance growth (e.g. Jones and Hughes, 1981; Collins and Siegel, 1987), feed efficiency (e.g. Gross and Siegel, 1982), resistance to infection (e.g. Collins and Siegel, 1987), and i m m u n e responses (Gross and Siegel, 1982). However, some studies have found little or no effect of early handling (e.g. Reichmann et al., 1978 ) and in some cases a negative effect of handling has been reported (Hughes and Black, 1976; Freeman and Manning, 1979). These conflicting results may be related to differences in methodology among studies, especially differences between strains, stimulation rate or the age at the beginning of the treatment. The purpose of our study was to test the effect of early handling on weight gain, mortality and feed efficiency of four strains of White Leghorn. We wanted to ensure that if there was no treatment effect it was because of the birds' failure to respond to the treatment and not because of the experimental protocol (e.g. missing a sensitive period). Therefore we chose a relatively high stimulation rate that continued for an extended period of time and began when the chicks were very young. ,ANIMALS, MATERIALS AND METHODS
At hatch, 3000 White Leghorn females were assigned, in groups of approximately 60, to the top c o m p a r t m e n t of a Thornber, three tier brooder pen. Chicks were kept in the top tier for approximately 8 weeks and were then distributed equally among the three tiers. The chicks were brooded under dull emitter heat lamps and food and water were provided ad libitum. The photoperiod was from 06:00 to 14:00 h. The birds were from one selected and one control strain in each of two genetic bases. Strain 3 of Base 1 has undergone selection since 1950, while Strain 9 of Base 2 has been under selection since 1969. The control or random-bred strains have been maintained since 1950 (Strain 5, Base 1) and 1961 (Strain 7, Base 2 ). The selected strains have been selected for a variety of production traits (e.g. viability, egg production, fertility). In both bases, the selected and control strains differ significantly for many of these traits (e.g. age at first egg, egg production, egg weight). Forty-eight pens were randomly divided into three treatment groups: not handled ( N H ) , handled every day ( H E D ) , and handled every third day (HE3D). The last treatment was designed to identify a m i n i m u m handling rate. Chicks that were not handled were restricted to regular management activities only (i.e. a daily check of the pens by a single person). Among handled chicks, handling began when the chicks were 4 days old and continued until they were 37 days old. Handling consisted of gently removing each chick
EFFECT OF HANDLING ON WHITE LEGHORNS
123
from its pen and placing it in a large cardboard box. Once all the chicks had been removed they were individually returned to their home pen. Pens adjacent to, and across from a handled pen were covered during handling to prevent the chicks in those cages from seeing the procedure. It took approximately 10 rain to remove and replace all the chicks in a brooder. The birds were handled between 08:00 and 10:00 h by seven regular handlers. The chicks were exposed to all handlers equally. The order in which the pens were handled was randomized. All chicks were weighed at 3, 37, 78 and 121 days of age. Feed efficiency (weight of feed consumed/weight gained ) was measured between 79 and 121 days of age. During this time all feed was weighed into the feed trough. At the end of the test period the feed remaining in the trough was weighed to determine the total feed consumed per pen. Spillage was minimal. Mortality rate was also recorded and necropsies were performed to determine the cause of death.
Statistics Because measures of individuals within pens were not independent, pen means were used in all analyses. We used a log transformation on the standard deviations to correct for non-normality. The results from the analyses for transformed and untransformed data were the same, therefore the latter are presented. The model to examine differences in body weight included differences among the three treatments (2 d.f. ) and among the four strains ( 3 d.f. ) and the interaction of treatment and strain (6 d.f.) all tested against pens within treatments (36 d.f.). We also used split-plot analyses to examine whether the relationship among the above factors changed over time. In this study we were interested in strain differences as they relate to treatment effects. Differences in strains with respect to weight gain, mortality etc. have been described elsewhere (Fairfull and Gowe, 1990). Therefore, we report statistics for strain × treatment interactions only. RESULTS
Within 2 weeks of the beginning of the study, most chicks in the HED group would approach the front of the cage when the handler arrived and peck the handler's hand and arms. During the same time period, the chicks in the HE3D group moved to the rear of the cage when the handler approached and did not attempt to peck or move toward the handler. After 5 weeks these differences were no longer apparent and both groups approached, pecked and climbed on the handler in a manner unlike the normal flightiness seen in these strains (R.W. Fairfull, personal observation, 1990). In an attempt to avoid inadvertent socialization, the NH group was not observed during this time.
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M.L. LEONARDAND R.W. FAIRFULL
Weight The mean weights of the three treatment groups were not significantly different at the beginning of the study (Day 3, P = 0 . 6 9 ; Table 1 ), nor was there a significant interaction between strain and treatment ( P = 0.59 ). After handling, differences in the mean weight among the treatment groups remained non-significant (Day 37, P = 0 . 2 3 ; Day 78, P = 0 . 2 8 : Day 121, P = 0 . 2 5 ; Table 1 ). Likewise, the interaction between strain and treatment was not significant (Day 37, P = 0 . 8 4 ; Day 78, P = 0 . 3 8 ; Day 121, P = 0 . 5 9 ; Table 1 ). In addition, split-plot analyses to examine the pattern of weight gain over time showed that the relationship among treatment groups was consistent over the brooding period ( P = 0.38 ). Finally, the relationship between treatment and strain did not vary significantly over this time ( P = 0 . 6 3 ) . Although the mean weight among treatments was similar, the standard deviation about the means was significantly different at Day 37 ( P < 0.01 ; Table 1 ). At Day 78 this difference, although not significant ( P = 0 . 0 6 ; Table 1 ), was in the same direction. The results of a protected least square differences test indicated that the variation in the HED group was greater than that of the other two groups. This was not the result of initial differences in the standard deviation at Day 3 ( P = 0 . 5 5 ; Table 1 ). Standard deviations were not significantly different by Day 121 ( P = 0 . 8 5 ; Table 1 ). Strain by treatment interactions were not significant at any time (Day 37, P = 0 . 7 4 ; Day 78, P = 0 . 2 9 ; Day 121, P = 0 . 9 1 ). Finally, the relationship among the three treatment groups with respect to the standard deviations was not significantly different over time ( P = 0 . 7 9 ) nor was the interaction between treatment and strain over this time period ( P = 0 . 9 2 ) . TABLE I Mean body weights (g) and mean standard deviations o f the weights for each of the three treatment groups ~at Days 3, 37, 78 and 121 Age (days)
3 37 78 121
Mean
Standard deviation
NH
PIED
HE3D
NH
HED
HE3D
40.5 219.5 818.5 1180.7
40.3 217.7 797.9 1180.2
40.6 227.1 817.6 1190.9
3.2 37.0 76.1 100.9
3.3 42. l** 84.5 110.2
3.3 38.7 78.2 100.9
~NH. non-handled; HED, handled every day: HE3D, handled every third day. Each value is the mean of 16 pen means or 16 within-pen standard deviations based on approximately 60 birds per pen. **Significantly different from the other two treatments, P < 0.01.
EFFECT OF HANDLING ON WHITE LEGHORNS
125
TABLE 2 Mean ( +_SE) n u m b e r of deaths per pen for each of the three treatment groups ~during the experimental period (Days 0-37 ) and over the total brooding period ( Days 0-129 ) Treatment
N2
Experimental period
Brooding period
NH HED HE3D
16 16 16
1.44 +_0.32 1.31 +_0.29 1.13+_0.30
2.06 + 0.49 1.63+0.34 1.31 +_0.31
~NH, non-handled; HED, handled every day; HE3D, handled every third day. 2N, the n u m b e r of pens.
Mortality Handling did not appear to affect mortality during the treatment period (first 5 weeks). The number of deaths per pen during this time did not differ significantly among the three treatment groups ( P = 0.35; Table 2) and the interaction between strain and treatment was also not significant ( P = 0.35 ). Similarly mortality over the total brooding period (including the first 5 weeks ) showed no effect of handling treatment ( P = 0 . 2 9 ) and no interaction between strain and treatment ( P = 0.08 ). The cause of death was weakly related to treatment. Significantly more pens in the HE3D group had individuals die from cannibalism in the first 5 weeks than in the other two groups (Z= = 7.0, d.f. = 2, P < 0.05 ). However, this was not the case when the total brooding period was examined (X2= 1.52, d.f. = 2, P > 0.10 ). The other two major causes of death in the early period, omphalitis and dehydration, did not differ significantly among the three groups.
Feed efficiency Feed efficiency (amount of feed consumed/weight gained) did not differ significantly among treatment groups ( P = 0.76). Strain and treatment also did not interact significantly ( P = 0.84). DISCUSSION
In this experiment, using an intensive stimulation rate on several genetically diverse strains, early handling failed to produce the positive effects reported in many other studies (Thompson, 1976; Jones and Hughes, 1981; Gross and Siegel, 1983; Collins and Siegel, 1987). Although there were minor, short-term effects of handling, the apparent response of the experimental birds did not result in an increase in weight gain or a reduction in mortality compared with the control group. Some earlier studies also found a limited effect of handling (McPherson et
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al., 1961; Reichman et al., 1978). However, in both studies the birds were handled at most once a week and in the former study the treatment did not begin until the birds were 3 weeks (broilers) and 9 weeks (pullets) of age. Unlike these studies, our birds were handled every day for 5 weeks beginning at Day 4 post-hatch. This rate is comparable to studies in which a positive effect was reported. It is unlikely that the strains used in this study were not receptive to socialization. Again, because we used four strains it seems that at least one of the strains would have shown an effect if it existed. Layer stocks have responded positively to early handling (Jones and Hughes, 1981; Gross and Siegel, 1983 ), so it is not a response peculiar to broiler stocks. Two alternative possibilities may explain our results. All cages in the battery were assigned to each of the three treatment groups at random, so that handlers passed by all the cages every day. Although the NH and HE3D groups were not actually subject to daily handling, and could not see the HED birds being handled, they were exposed to this daily disturbance. This would have increased exposure to humans and possibly reduced any differences among the groups. If this is the case, then perhaps just the frequent presence of a stockperson may habituate the birds and ultimately produce the positive effects reported in other studies (Siegel, 1989). Alternatively, if handling had a positive effect on the i m m u n e response of these birds we might not detect it in our system, where the effects of disease on growth and mortality are minimal (Gowe and Fairfull, 1985). Thus an effect of handling on the i m m u n e system may only be beneficial under certain conditions. The increased variation in weight among individuals in the HED group is interesting, but difficult to interpret. It suggests that the benefit of daily handling may vary among individuals. Individuals that responded negatively to this treatment may not grow as quickly as those responding positively to the treatment. Because this effect was not obvious in the HE3D group, this result also suggests that there may be a threshold rate of handling necessary before the effect is detectable. Increased mortality from cannibalism during the first 5 weeks was associated with the HE3D treatment. A relationship between disturbance and cannibalism has been reported in poultry (Hughes and Duncan, 1972). Thus, this effect may be related to the regular, but infrequent disturbance involved with handling the birds every third day. Perhaps daily handling resulted in increased socialization, so that the disturbance had a limited negative effect. Increased variation in body weights within the HED group suggests that some individuals may benefit from regular handling. However, this effect is short-lived. Our results also suggest that regular, but infrequent handling may actually have negative effects in the short term (i.e. increased cannibalism). Further work obviously needs to be done to examine some of these possibili-
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ties. We are presently examining the effect of early handling on production traits in layers. ACKNOWLEDGMENTS
We thank David Fraser and Andy Horn for reading the manuscript and providing many helpful comments. We also thank Brian Thompson for help with the analyses and Bob Mumford and the staff of the CFAR poultry unit for their assistance with the experiment.
REFERENCES Boissy, A. and Bouissou, M.-F., 1988. Effects of early handling on heifers' subsequent reactivity to humans and to unfamiliar situations. Appl. Anita. Behav. Sci., 20: 259-273. Collins, J.W. and Siegel, P.B., 1987. Human handling, flock size and responses to an E. coli challenge in young chickens. Appl. Anim. Behav. Sci., 19: 183-188. Denenberg, V.H. and Karas, G.G., 1959. Effects of differential infantile handling upon weight gain and mortality in the rat and mouse. Science, 130: 629-630. Fairfull, R.W. and Gowe, R.S., 1990. Egg production in chickens. In: R.D. Crawford (Editor), Poultry Breeding and Genetics. Elsevier, Amsterdam, pp. 705-759. Freeman, B.M. and Manning A.-C.C., 1979. Stressor effects of handling in the immature fowl. Res. Vet. Sci., 26: 223-226. Gonyou, H.W., Hemsworth, P.H. and Barnett, J.L., 1986. Effects of frequent interactions with humans on growing pigs. Appl. Anim. Behav. Sci., 16: 269-278. Gowe, R.S. and Fairfull, R.W., 1985. The direct response to long-term selection for multiple traits in egg stocks and changes in genetic parameters with selection. In: W.G. Hill, J.H. Manson and D. Hewitt (Editors), Poultry Genetics and Breeding. British Poultry Science. Symposium 18, pp. 125-146. Gross, W.B. and Siegel, P.B., 1982. Socialization as a factor in resistance to infection, feed efficiency and response to antigen in chickens. Am. J. Vet. Res., 43:2010-2021. Gross, W.B. and Siegel, P.B., 1983. Socialization, the sequencing of environmental factors, and their effects on weight gain and disease resistance of chickens. Poult. Sci., 62: 592-598. Hargreaves, A.L. and Hutson, G.D., 1990. The effect of gentling on heart rate, flight distance and aversion of sheep to a handling procedure. Appl. Anim. Behav. Sci., 26: 243-252. Heird, J.C., Whitaker, D.D., Bell, R.W., Ramsey, C.B. and Lokey, C.E., 1986. The effects of handling at different ages on the subsequent learning ability of 2-year-old horses. Appl. Anim. Behav. Sci., 15:15-25. Hemsworth, P.H., Barnett, J i . and Hansen, C., 1981. The influence of handling by humans on the behavior, growth and corticosteroids in the juvenile female pig. Horm. Behav., 15: 396403. Hughes, B.O. and Black, A.J., 1976. The influence of handling on egg production, egg shell quality and avoidance behaviour of hens. Br. Poult. Sci., 17:135-144. Hughes, B.O. and Duncan, I.J.H., 1972. The influence of strain and environmental factors upon feather pecking and cannibalism in fowls. Br. Poult. Sci., 13: 525-547. Jones, R.B. and Hughes, B.O., 1981. Effects of regular handling on growth in male and female chicks of broiler and layer strains. Br. Poult. Sci., 22:461-465. McPherson, B.N., Gyles, N.R. and Kan, J., 1961. The effects of handling frequency on 8-week body weight, feed conversion and mortality. Poult. Sci., 40: 1526-1527.
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Reichmann, K.G., Barram, K.M., Brock, I.J. and Standfast, N.F., 1978. Effects of regular handling and blood sampling by wing vein puncture on the performance of broilers and pullets. Br. Poult. Sci., 19: 97-99. Siegel, P.B., 1989. The genetic-behaviour interface and wellbeing of poultry. Br. Poult. Sci., 30: 3-13. Thompson, C.I., 1976. Growth in the Hubbard broiler: increased size following early handling. Dev. Psychol., 9: 459-464.