Plasma Levels of Anabolic Hormones in Suckling Lambs are Affected by Late Gestational Nutrition

In this study, the effects of late gestational undernutrition (LGU) on plasma concentration of insulin-like growth factor 1 (IGF-I), leptin, insulin and glucose in subsequent sucking lambs was investigated. Ten twin-bearing ewes were fed either restrictedly (Restricted) or adequately (Control) during the last six weeks of gestation and were fed ad libitum after parturition. Blood samples were taken from subsequent suckling lambs at birth day, 7, 17 and 35 days of age. The average growth rate of restricted lambs was significantly lower than control lambs (292±21 vs. 216±19 g/d) during first two weeks of suckling period. Lambs in both groups were hypoglycemic (2.5±0.2 mmol/L) and had lowest level of leptin (0.6±0.08 ng/mL) at birth. Plasma glucose and leptin increased sharply by 7 days of age to 5.9 ± 0.2 mmol/L and to 0.6±0.08 ng/mL respectively. Late gestational undernutrition reduced plasma glucose in restricted (3.1±0.2 mmol/L) at birth but not in control lambs (2.1±0.3 mmol/L). Plasma insulin was the highest at 7 days of age (0.9±0.08 ng/mL). Restricted lambs had highly significant lower insulin values (0.6±0.1 vs. 1.3±0.1 ng/mL) and significantly higher ratio of glucose/insulin than control lambs. Insulin-like growth factor I values at birth was not affected by LGU. However, during suckling period restricted lambs had lower IGF-I than control lambs. In conclusion, LGU decreased insulin plasma concentration, changed the ratio of glucose to insulin, and decreased the concentration of IGF-I in subsequent offspring. Results also confirm the finding that circulating glucose rather than insulin is a determinant of leptin secretion in suckling lambs.