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United States Department of Agriculture

Agricultural Research Service

Research Project: SAFEGUARDING WELL-BEING OF FOOD PRODUCING ANIMALS Title: Growth and reproductive development of male piglets are more vulnerable to mid-gestation maternal stress than that of female piglets

Authors
item Mack, L -
item Lay, Jr, Donald
item Eicher, Susan
item Johnson, Anna -
item Richert, Brian -
item Pajor, Edmund -

Submitted to: Journal of Animal Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: December 16, 2013
Publication Date: March 25, 2014
Citation: Mack, L.A., Lay Jr., D.C., Eicher, S.D., Johnson, A.K., Richert, B.T., Pajor, E.A. 2014. Growth and reproductive development of male piglets are more vulnerable to mid-gestation maternal stress than that of female piglets. Journal of Animal Science. 92:530-548.

Interpretive Summary: Fetal pigs are exposed to stress when gestating sows are regrouped. The ensuing rise in sow aggression and glucocorticoid (a stress hormone) synthesis may be persistent and impair feed intake of low ranked sows especially if competitively fed. Such prenatal stress can alter reproductive development of fetal rodents and sheep, and possibly swine. The effects of prenatal stress on swine reproductive development are not as well elucidated. This study examined the effects of regrouping gestating sows on the growth and external reproductive morphology of piglets. Sows were placed in 1 of 3 treatments: socially stable (Stable), hydrocortisone acetate (HCA to simulate a stress), or mixed (one sow mixed into a group of 2 ‘companions’). Sow social rank was assessed weekly during feeding. After the 21 day experimental period, all sows were housed in gestation stalls for the duration of pregnancy. Companion sows gained more weight than HCA and Mixed sows with Stable sows intermediate. High ranked sows gained more weight than middle and low ranked sows. Mixed sows had greater head lesions from fighting than Stable and HCA sows with Companion sows intermediate. Head lesions increased with decreased social rank. The sow’s treatment did not affect farrowing rate, litter size, or sex ratio. Social rank also had no effect on farrowing, but social rank affected total litter size. High ranked sows bore and weaned more live females than low ranked sows, in part due to differential preweaning mortality among female pigs. Only male pigs were affected by sow treatment. Preweaning mortality was higher among male pigs from HCA sows than from Mixed sows with other treatments intermediate. Despite no weight differences in the preweaning period, at 160 days of age males from HCA sows weighed more than males from Stable sows with other treatments intermediate. Male pigs born to Companion sows had longer relative anogenital distances, a marker of fetal testosterone and masculinization, than males from Mixed sows with other treatments intermediate. The prenatal environment did influence piglet development. Most important was the strong evidence of differential prenatal effects on the male and female piglets. Additionally, these results provide evidence that acutely elevated stress hormones can have long term effects on the growth of offspring and support the possibility that maternal nutrition may alter reproductive function of male offspring. This is important to recognize as producers move to group housing management and the associated stress and welfare considerations of the fighting that is inherent in this system.

Technical Abstract: In many mammalian species, prenatal stress masculinizes female and feminizes male offspring impairing their reproductive capacity. Regrouping gestating sows is a common, stressful production practice, but its impact on the sow’s developing piglets is not fully known. This study examined the effects of regrouping gestating sows on the growth and external reproductive morphology of piglets. At 37.2 ± 0.26 d of gestation, 6 cohorts of 18 sows (N = 108) were placed in 1 of 3 treatments: socially stable (Stable), hydrocortisone acetate (HCA), or mixed (Mixed). The HCA sows were administered 70 mg HCA, a synthetic glucocorticoid, twice daily during the 21 d experimental period. Each Mixed sow was penned with 2 companion sows (Companion) and regrouped on d 7 and 14 with 2 different Companion sows in a new pen each time. Stable and HCA sows were penned in treatment groups of 3 sows. Sow social rank was assessed weekly during feeding. After the 21 d experimental period, all sows were housed in gestation stalls for the duration of pregnancy. During the 21 d, Companion sows gained more weight than HCA and Mixed sows (P < 0.05) with Stable sows intermediate. High ranked sows gained more weight than middle and low ranked sows (P < 0.05). Mixed sows had greater head lesion scores than Stable and HCA sows (P < 0.05) with Companion sows intermediate. Head lesions increased with decreased social rank (P < 0.001). The sow’s treatment did not affect farrowing rate, litter size, or sex ratio (P > 0.10). Social rank also had no effect on farrowing rate (P > 0.10), but social rank affected total litter size (P = 0.03). High ranked sows bore and weaned more live females than low ranked sows (P < 0.05), in part due to differential preweaning mortality among female pigs (P = 0.01). Only male pigs were affected by sow treatment. Preweaning mortality was higher among male pigs from HCA sows than from Mixed sows (P = 0.04) with other treatments intermediate. Despite no weight differences in the preweaning period, at 160 d of age males from HCA sows weighed more than males from Stable sows (P = 0.01) with other treatments intermediate. Male pigs born to Companion sows had longer relative anogenital distances, a marker of fetal testosterone, than males from Mixed sows (P = 0.03) with other treatments intermediate. The prenatal environment affected the piglets in a sex-specific manner altering the growth and reproductive morphology of the males more than that of the females.

Last Modified: 10/26/2014
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