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

Abstract

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 β 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 β 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 β cell function programmed during pregnancy may predispose foals to metabolic problems in later life.