Submitted to: Journal of Animal Science Supplement
Publication Type: Abstract Only
Publication Acceptance Date: 7/31/1998
Publication Date: N/A
Technical Abstract: A study was conducted to compare the development of the hypothalamic-pituitary-adrenal (HPA) axis in piglets born by natural birth or Cesarean-Section. Eight crossbred sows were selected for the study (n=4 natural birth and n=4 C-Section). Gestation length did not differ between natural birth and C-Section piglets (113.6 +/ .14 and 113.2 +/ .27 d, respectively; P>.16). Blood and tissue samples from 38 piglets were collected at birth. Remaining piglets were sustained with natural birth sows until 2 wks of age. Piglets were canulated for blood sample collection to assess pituitary-adrenal responses to an injection of corticotrophin releasing hormone (CRH; 10 ug/kg). Blood samples were collected at -30, -15, 0, 5, 10, 20, 40, 60, and 90 min, piglets received CRH or saline at time 0, and tissue samples were collected following the last blood sample. Serum adrenocorticotrophic-releasing hormone (ACTH) and cortisol (CS) were determined by RIA. Total RNA was isolated from the right adrenal and level of ACTH receptor and 28S ribosomal RNA were determined by slot-blot hybridization. Basal concentration of ACTH was greater in C-Section than natural birth piglets at birth (P=.01) but did not differ at 2 wks of age (P=.42). Basal concentration of CS was not different at birth (P=.86) but was greater in C-Section piglets at 2 wks of age (P>.04). Serum ACTH was not different between C-Section and natural birth piglets following the CRH challenge (P>.99). However, serum concentration of CS was greater in C-Section than natural birth piglets following the CRH challenge (P<.05). Expression of ACTH receptor mRNA relative to 28S rRNA was greater in C-Section piglets (P=.04). These data indicate that the birth process plays an important role in post-natal function of the HPA axis.