Neuroendocrine and immune responses to acute endotoxemia in suckling and weaned piglets.

The objective of this study was to characterize effects of weaning stress on behavioural, endocrine and immune responses to acute peripheral lipopolysaccharide (LPS) challenge in neonatal pigs. Weaning in 28-day-old piglets was accompanied by a significant increase in ACTH concentrations (p = 0.0378) and an increase in basal cortisol level (p = 0.0135). There was also a significant suppressive effect on lymphocyte proliferation in response to concanavalin A (p = 0.0048) in newly weaned piglets. Peripheral administration of LPS induced vomiting, diarrhoea and somnolence in both suckling and weaned piglets. The frequency of these signs of sickness was significantly higher in weaned piglets compared with suckling piglets (p = 0.0049). Additionally, LPS significantly increased plasma concentrations of TNF-alpha, cortisol and ACTH. While weaned piglets reacted to LPS with a higher release of ACTH (p = 0.0239) and cortisol (p = 0.0015) than suckling piglets there was no significant effect of weaning on the magnitude of TNF-alpha. The present data indicate that weaning suppresses the lymphocyte function, causes changes in endocrine regulation and has a substantial effect on the behavioural and endocrine response to an acute peripheral LPS challenge; consequently it could increase disease susceptibility.