Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 6/26/1999
Publication Date: N/A
Technical Abstract: Stress during the neonatal period alters (both enhances and diminishes) the hypothalamic-pituitary-adrenal (HPA) response to stress later in life. Lack of consistent results is likely due to variation in stressors, timing of stressor application, and(or) species and genetic differences. Our previous research showed that calves separated from their dams and allowed to suckle once daily between 20 and 40 d of age had greater heart rates an plasma cortisol (CS) and had slower CS clearance rates in response to restraint stress at 150 d of age. A practice that has become common in swine production is segregated early weaning (SEW). This involves weaning the pig at 10 d of age and moving it to an offsite facility. Because weaning is stressful, we designed an experiment to determine whether early weaning (EW) altered aspects of the HPA axis as compared to pigs weaned at 28 d of age (CON). At 165 d of age pigs were transported to an abattoir and housed overnight. Adrenal and pituitary glands were collected at slaughter for quantification of mRNA for the ACTH receptor and POMC. The EW and CON pigs had similar weights at slaughter. Plasma CS for EW and CON pigs did not differ. Pituitary and adrenal gland weights did not differ between the EW and CON pigs. Adrenal gland expression of mRNA specific for the ACTH receptor did not differ between EW and CON pigs. However, mRNA expression for POMC was greater in the EW pigs compared to CON. There was no correlation between mRNA for the ACTH receptor and POMC in EW pigs but there was a strong correlation for these parameters in CON pigs (r=.89, P<.02). These data along with that of others indicating altered hypothalamic glucocorticoid receptors suggest that altered physiology due to neonatal stress may be due to a disregulation of the HPA axis.