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Effects of pre-natal stress
on piglet behavior and immunological response to weaning
M.J. Toscano1, K.A. Scott1, D.C. Lay 1, Jr. and H.K. Smith2
1Livestock Behavior Research Unit – Agriculture Research Service, USDA West Lafayette, USA; 2Purdue University, West
Exposing a pregnant sow to stress has been shown to have negative effects on resulting offspring. However, little knowledge exists regarding the mechanisms of this process or the effects due to specific stressful events. In this study, sows received one of two treatments once a week during d 35 to d 77 of gestation: injections of ACTH (i.v., 1 IU/kg BW) (ACTH, n=10), or forcefully moved up and down an alley and received 3 shocks from a standard electric prod over a 10 minute period (ROU, n=11). A third group served as a control and received no treatment (CONT, n=6). At weaning animals were blocked for weight and sex after which ten groups of six pigs were formed with 2 pigs from each treatment group. Each group of six pigs was then placed in one of ten individual nursery pens. To assess the behavioral effects of treatments, all behaviors were recorded for 6 d post-weaning using video cameras mounted above each pen. Recorded video was then analyzed for duration, initiator, and recipient of each fight/play bout. To assess the effect of treatments on hematological cell profiles, blood was collected every other day for 10 d after weaning. Statistical analysis using analysis of variance procedures revealed that duration (pooled mean ± SE; 25.9 ± 1.7 s; P < .25) and interactions of fight/play bouts (P < .50) were similar regardless of treatment, though the results of the hematocrit and hemoglobin for CONT were less than for the ACTH and ROU treatments, respectively (hematocrit: P < .03; treatment mean ± SE; 24.9 ± .62, 26.6 ± .62 , 28.0 1 ± .63; hemoglobin: P < .04; 7.72 ± .22, 8.26 ± .22 , 8.79 ± .22). Our results suggest that pre-natal stress can influence the pig’s physiological state during the post-weaning period. The effect of these parameters on the stress response during weaning and whether these treatment differences are maintained throughout the animal’s lifetime remain important welfare issues and require investigation.
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