Protein Synthesis in Jejunum and Liver of Neonatal Calves Fed Vitamin A and Lactoferrin

Abstract

Rates of protein synthesis (PS) and turnover are more rapid during the neonatal period than during any other stage of postnatal life. Vitamin A and lactoferrin (Lf) can stimulate PS in neonates. However, newborn calves are vitamin A deficient and have a low Lf status, but plasma vitamin A and Lf levels increase rapidly after ingestion of colostrum. Neonatal calves (n=6 per group) were fed colostrum or a milk-based formula without or with vitamin A, Lf, or vitamin A plus Lf to study PS in the jejunum and liver. l-[13C]Valine was intravenously administered to determine isotopic enrichment of free (nonprotein-bound) Val (APFree) in the protein precursor pool, atom percentage excess (APE) of protein-bound Val, fractional protein synthesis rate (FSR) in the jejunum and liver, and isotopic enrichment of Val in plasma (APEPla) and in the CO2 of exhaled air (APEEx). The APE, APFree, and FSR in the jejunum and liver did not differ significantly among groups. The APEEx increased, whereas APEPla decreased over time, but there were no group differences. Correlations were calculated between FSRJej and histomorphometrical and histochemical data of the jejunum, and between FSRLiv and blood metabolites. There were negative correlations between FSRLiv and plasma albumin concentrations and between FSRJej and the ratio of villus height:crypt depth, and there was a positive correlation between FSRJej and small intestinal cell proliferation in crypts. Hence, there were no effects of vitamin A and Lf and no interactions between vitamin A and Lf on intestinal and hepatic PS. However, FSRJej was correlated with histomorphometrical traits of the jejunum and FSRLiv was correlated with plasma albumin concentrations.