Postnatal function of the somatotrophic axis in pigs born naturally or by caesarian section

This study was designed to determine what effects the birth process would h ave on development of the somatotrophic axis in neonatal pigs. Eight crossb red sows were selected (n = 4 natural birth and n = 4 Caesarian section) fo r the present study. Blood and tissue samples from 38 pigs were collected a t birth. Twenty pigs were maintained with natural birth sows until sacrific ed for blood and tissue collection at 2 wk of age. Gestational age at birth did not differ (P > 0.16)between natural birth and C-section pigs. Average daily gain (ADG) from birth until 2 wk of age was reduced (P < 0.0001) by 39.3% in the C-section pigs as compared to the natural birth pigs. Serum gr owth hormone (GH) did not differ (P > 0.86) at birth, but was greater (P < 0.024) at 2 wk in C-section pigs. Serum insulin-like growth factor 1 (IGF-1 ) was greater at birth (P < 0.0025) and at 2 wk of age (P < 0.035) in the n atural birth pigs. Serum concentration of IGF-2 did not differ at birth (P > 0.8) but was greater (P < 0.043) in natural birth pigs at 2 wk of age. Pi tuitary content of GH mRNA and GH-releasing hormone receptor mRNA did not d iffer (P > 0.90) between groups regardless of age; however, expression of b oth mRNAs declined (P < 0.0003) from birth until 2 wk of age. There tended to be a birth type X age interaction (P < 0.082) for liver IGF-1 mRNA such that C-section pigs had a greater expression at 2 wk of age. Liver IGF-1 mR NA expression increased (P < 0.0001) in both groups from birth to 2 wk of a ge. Liver expression of GH receptor mRNA was greater in C-section pigs at b irth (P < 0.04) and 2 wk of age (P < 0.03). These data provide evidence tha t the natural birth process affects postnatal development and/or function o f the somatotrophic axis in the neonatal pig. (C) 2000 Elsevier Science Inc . All rights reserved.