The influence of gestational housing on the behavior, physiology and welfare of the sow and her piglets.

摘要

The research presented in this thesis addresses some of the questions and challenges related to the group housing of sows. How group space size impacts the sows in a free-access system is unknown and the goal of the first research study was to investigate the effect of the group space size on the sow's health, productivity, behavior, and welfare.;The size of the group pen had very little effect on the health, physiology, or productivity of the sows. Dewclaw lesions tended to be reduced on sows with the smallest group spaces compared to sows with the largest group spaces (P = 0.06). Skin thickening in response to concanavalin A, a lymphocyte mitogen, was greater in sows with the smallest spaces compared to sows with the largest spaces (P < 0.05). No other measures of sow health, physiology, or production were affected by the group space size (P > 0.10). In contrast to health and physiology measures, the sows' behavior differed with pen size. Sows with the smallest spaces were observed more frequently in stalls (P < 0.05) and less frequently in the group space (P < 0.01) than sows in other pen sizes and they exhibited the smallest increase in group space use with time (P < 0.01). Sows with the smallest group space stood less at wk 2 and wk 5 than sows with the mid-sized pens (P ≤ 0.05), but the amount of time sows spent manipulating the pen and fixtures was not affected by space. Social interaction was reduced among sows with the smallest group space compared to sows with the largest space ( P < 0.05) and tended to be reduced compared to sows with a mid-sized pen (P = 0.99). Although the activity of the sows was unaffected by space allowance, space utilization and social interactions were restricted in the smallest group size. Overall, sow welfare in the two larger pens was better than in the smallest pen because there was greater ability to express normal behavior, but the welfare differences were small and did not impact the sow health, physiology, or productivity.;Increased maternal stress during gestation can prenatally stress developing fetuses which may alter offspring development. In rodents prenatal stress masculinizes female and feminizes male rodent offspring by altering reproductive development. In swine production regrouping gestating sows is a common stressful practice, but its impact on the reproductive potential of piglets is unknown. The second study examined the effects of regrouping gestating sows on the development of reproductive morphology in piglets. Sows were assigned to 1 of 3 treatments during mid-gestation: socially stable (Stable), hydrocortisone acetate (HCA) treatment, and mixed (Mixed). Each Mixed sow was penned with 2 companion sows (Companion). Mixed sows were regrouped on d 7 and d 14 of the 21 d treatment, by removing them from their current groups and placing them in pens with 2 different Companion sows. Stable and HCA sows were penned in groups of 3 by treatment and remained in their original group through the treatment. To simulate a physiological stress response, HCA sows were orally administered 70 mg HCA twice daily.;Mixing was stressful to the sows. At the end of the treatment, Companion sows weighed more than HCA and Mixed sows (P < 0.05) with Stable sows intermediate but not different than the other treatments. Cortisol concentration was greater in HCA sows (P = 0.0004) than sows in the other treatments. Mixed sows had greater head lesion scores than Stable and HCA sows (P < 0.05) with Companion sows intermediate. The sow's treatment did not affect farrowing rate, gestation length, litter size or sex ratio of the piglets (P > 0.10). The prenatal environment almost exclusively affected the male piglets. Pre-weaning mortality was higher among male piglets from HCA sows compared with males from Mixed sows (P = 0.04) with mortality in the other treatments intermediate. Male pigs from Mixed sows tended to have greater birth weights than males from Companion sows (P = 0.07), but there were no other differences during the lactation period. However, at 160 d of age, males from HCA sows weighed more than males from Stable sows (P = 0.01). Anogenital distance, a marker of fetal testosterone, was longer in male piglets born to Companion sows than male piglets from Mixed sows (P = 0.03) with the other treatments intermediate. Neither maternal social stress nor maternal HCA administration impacted the female offspring but they resulted in small changes in male piglets' sexual development, mortality, and body weight. (Abstract shortened by UMI.).