The effects of maternal health and body condition on the endocrine responses of neonatal foals.

REASONS FOR PERFORMING THE STUDY

Chronic and acute alterations in maternal nutrient intake during pregnancy alter pancreatic and hypothalamo-pituitary-adrenal (HPA) axis function in the offspring, before and after birth. Little is known about these effects.

OBJECTIVE

To determine whether maternal nutrient restriction caused by natural infection with Streptococcus equi altered endocrine function in neonatal foals born from mares fed a maintenance or high plane of nutrition throughout pregnancy.

METHODS

Ten primiparous mares received either a diet to maintain moderate body condition score (Moderate, n = 5) or a near ad libitum feeding regime to maintain a high body condition score (High, n = 5) throughout pregnancy. All mares inadvertently became infected with Streptococcus equi in mid gestation and lost approximately 10% body mass.

RESULTS

Maternal insulin and glucose concentrations decreased (P < 0.05) during, and one month following, the weight loss period. High mares weighed more (P < 0.05) at parturition than Moderate mares; all foals were healthy. Gestational age, foal bodyweights, placental and clinical parameters after birth were no different between the 2 groups. Foal plasma cortisol and glucose responses to exogenous adrenocorticotrophic hormone and insulin, respectively, were similar for both groups. Insulin concentrations during glucose tolerance test were significantly higher (P < 0.05) in foals from Moderate than High mares and compared with foals studied previously from healthy, well-fed mares, suggesting that the beta cell sensitivity to glucose was enhanced in Moderate.

CONCLUSION

Acute nutrient restriction in mid gestation caused by maternal illness and inappetence, superimposed on a maintenance feed intake throughout pregnancy, enhanced insulin secretion to glucose in foals. Nutritional programming of pancreatic beta cells, but not the HPA axis, appeared to depend on the level of nutrition before and after the weight loss period.

POTENTIAL RELEVANCE

Disturbances in neonatal pancreatic beta cell function programmed during pregnancy may predispose foals to metabolic problems in later life.