Endocrine changes and circulating insulin-like growth factors in newborn calves fed colostrium, milk or milk replacer

Abstract

To examine whether colostral growth factors are transferred to the general circulation, concentrations of plasma cortisol, insulin, prolactin, growth hormone, insulin-like growth factors (IGF)-I and -II, IGF-binding proteins (IGFBP) and total protein were measured in newborn calves fed colostrum, milk or milk replacer before and after feeding at 12-h intervals during the first 2 days after birth. Plasma protein concentrations increased with time after birth, but this was apparent only in colostrum-fed calves. The mean protein concentration was greater in colostrum-fed than in milk- or milk replacer-fed calves. Plasma cortisol levels decreased after each feeding regardless of the type of diet, while insulin levels tended to increase. Mean concentrations of these hormones did not differ between dietary groups, nor did they change with time after birth. Plasma concentrations of prolactin and growth hormone did not differ between dietary groups and also did not change with time after birth or after feeding. Concentrations of IGF-I and IGF-II increased at the second feeding period, but these, as well as plasma IGFBP profiles, were not different between groups or before and after feeding. Results did not indicate significant transfer of colostral growth factors across the newborn ruminant small intestine.