Higher Intake of Milk-Replacer Pre-Weaning Enhances Post-Weaning Insulin-Like Growth Factor 1 Levels in Japanese Black Cattle

Alterations in early pre-natal nutrition of Japanese Black calves influence the glucose and lipid metabolism after weaning. However, the effects of early nutritional status on the endocrine system in later life stages in Japanese Black cattle are unknown. This study examined how post-weaning plasma levels of growth hormone (GH), insulin-like growth factor 1 (IGF-1), and blood insulin, which are hormones affecting growth and meat quality, and metabolites were affected by feeding 1800 g versus 500 g of milk replacer to Japanese Black cattle (5 per group) during nursing. Up to weaning (90 days post-birth), all calves received calf starter and hay ad libitum, and post-weaning, they received a concentrate feed and hay ad libitum. Plasma concentrations of GH and IGF-1 were greater at weaning in the high-milk-replacer group (P<0.1 and P<0.01, respectively), and elevated IGF-1 concentrations persisted until the study end (210 d) (P<0.05), suggesting that the levels were sustained independent of the influences of both GH and nutrient intake. Blood insulin and metabolites (plasma glucose, beta-hydroxybutyric acid, and non-esterified fatty acids) were not significantly different between the two groups. The results of this study suggest that feeding calves a high volume of milk replacer during nursing will increase IGF-1 secretion well beyond weaning.