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

K. Rufibach^*,1, N. Stefanoni, V. Rey-Roethlisberger, P. Schneiter, M. G. Doherr, L. Tappy and J. W. Blum^*,2,3

^* Division of Animal Nutrition and Physiology, Institute of Animal Genetics, Nutrition and Housing, Vetsuisse-Faculty, University of Bern, CH-3012 Bern, Switzerland
Institute of Physiology, Centre Hospitalier Universitaire Vaud, University of Lausanne, CH-1005 Lausanne, Switzerland
Department of Clinical Veterinary Medicine, Vetsuisse-Faculty, University of Bern, CH-3012 Bern, Switzerland

² Corresponding author: juerg.blum{at}physio.unibe.ch

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 (AP_Free) 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 (APE_Pla) and in the CO₂ of exhaled air (APE_Ex). The APE, AP_Free, and FSR in the jejunum and liver did not differ significantly among groups. The APE_Ex increased, whereas APE_Pla decreased over time, but there were no group differences. Correlations were calculated between FSR_Jej and histomorphometrical and histochemical data of the jejunum, and between FSR_Liv and blood metabolites. There were negative correlations between FSR_Liv and plasma albumin concentrations and between FSR_Jej and the ratio of villus height:crypt depth, and there was a positive correlation between FSR_Jej 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, FSR_Jej was correlated with histomorphometrical traits of the jejunum and FSR_Liv was correlated with plasma albumin concentrations.

Key Words: neonatal calf • lactoferrin • protein synthesis • vitamin A