Submitted to: Journal of Animal Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/14/1998
Publication Date: N/A
Interpretive Summary: Sickness and death continue to be significant problems in baby pigs and an animal's ability to respond to external stressors (e.g., environmental, managerial, social) has been linked to its overall performance and well-being. An inability to appropriately respond to or cope with external stressors results in poor performance. The natural birth process itself is sconsidered to be a stressful event on the dam as well as the newborn, and may be an important mediator of postnatal development and performance. Therefore, we evaluated the development and function of the stress axis in piglets born by caesarian section or by natural birth. We have found that, by eliminating the natural birth process, the postnatal development of the stress axis is altered in these young piglets. This alteration in the stress axis results in piglets that are more sensitive to an artificial stressor later in life than their natural birth counterparts. Thus, the stress associated with the natural birth process seems to play an essentia role in preparing the fetus for life outside of the uterus. This information will be useful to individuals in academia, government, and industry who have an interest in the effects of the natural birth process on neonatal biology.
Technical Abstract: Our objective was to determine if the natural birth process has a functional role in the postnatal development/function of the stress axis in pigs. Crossbred sows were selected for the present study (n=4 vaginal delivery and n=4 C-Section). Gestation length did not differ between vaginal delivery and C-Section piglets (113.6 +/ 0.1 and 113.2 +/ 0.3 d, respectively; P>.16). Blood and tissue samples from 38 piglets were collected at birth. Remaining piglets were sustained with vaginal delivery sows until 2 wk of age (n=39) at which time they were cannulated for blood sample collection to assess pituitary-adrenal responsiveness to corticotrophin-releasing hormone (CRH; 10ug/kg). Blood samples were collected at -30, -15, 0, 5, 10, 20, 40, 60, and 90 min. Animals were sacrificed immediately following the last blood sample. Packed cell volume was reduced in the C-Section piglets at birth (P<.001) and at 2 wk of age (P<.043) as compared to the vaginally delivered piglets. Basal ACTH was greater in C-Section than in vaginally delivered piglets at birth (P=.01) but did not differ at 2 wk of age. Basal cortisol (CS) was not different at birth but was greater in C-Section piglets at 2 wk of age (P<.04). Serum ACTH was not different between the two groups following the CRH challenge. However, serum CS was greater (P<.05) in C-Section piglets following the CRH challenge. ACTH receptor mRNA tended to be greater in C-Section piglets at birth (P<.063 ) and was greater in the C-Section piglets at 2 wk of age (P<.016). There was no difference in POMC mRNA between treatments; however, there was a developmental increase (P<.001) from birth to 2 wk of age. These data indicate that the birth process plays an important role in postnatal function of the stress axis in the young pig.