Protein and energy affect splanchnic and mammary metabolisms and drive amino acid use in dairy cows
Résumé
Balancing rations for essential amino acids (AA) to improve efficiency of utilisation (Eff) of N requires a better knowledge of AA use by different tissues under various nutritional conditions. Effects of infusion of AA (AAinf) and glucose (Glcinf), in a 2×2 factorial arrangement, were tested using 5 cows in a 4×4 Latin Square plus one cow. At the end of each period, splanchnic, mammary and other peripheral tissue metabolisms of AA were measured. There was no AAinf×Glcinf interaction on most of the measured parameters. Milk protein yield (MPY) increased with AAinf and Glcinf. With AAinf, catabolism by portal-drained viscera (PDV) and mammary gland of group 2 AA (Ile, Leu, Lys, and Val) increased leading to a decreased Eff. In contrast, with Glcinf, liver removal of His + Met + Phe (HMP) decreased, improving their Eff.