THE INFLUENCE OF MATERNAL NUTRITION ON PLASMA HORMONE AND METABOLITE CONCENTRATIONS OF FOETAL LAMBS

Abstract

SUMMARY Merino ewes whose foetuses had surgically-implanted, indwelling vascular cannulae were used to determine the influence of maternal nutritional status on foetal plasma hormone levels during the last month of gestation. Observations were made during feeding of the ewes on a lucerne chaff diet ad libitum, during restricted feeding on the same diet and during fasting. Foetuses survived for an average of 31 days after the operation and seven out of the ten ewes lambed normally. In both ewes and foetuses, plasma concentrations of insulin were significantly higher 3–12 h after feeding than in prefeeding samples. Similar changes were seen with restricted and ad-libitum feeding. Fasting for 48 h caused significant decreases in insulin levels of both ewes and foetuses, but the decrease in foetal plasma insulin concentration was less than that in ewes. In agreement with earlier studies, foetal and maternal glucose concentrations were closely correlated and foetal fructose concentrations were closely related to foetal glucose concentrations. Foetal plasma insulin concentrations were closely correlated with glucose and fructose concentrations. Plasma growth hormone (GH) levels increased significantly in both ewes and foetuses during fasting. There were also significant increases during fasting in the plasma corticosteroid levels of the ewes, but not in those of their foetuses. Feeding did not cause significant changes in foetal plasma GH or corticosteroid concentrations although maternal GH concentrations were significantly increased and corticosteroid concentrations decreased 3–12 h after feeding on the restricted diet. The results suggest that alterations in foetal plasma hormone concentrations could play an important role in foetal adaptation to fluctuations in maternal nutrient supply during the last month of gestation.