Contribution of essential amino acids to glucose metabolism and lactose secretion in late lactation dairy cows
Résumé
Increased protein supply is known to increase both milk and milk lactose yields as well as whole body rate of appearance (Ra) of glucose (Lapierre et al., 2010). However, despite earlier observations reporting that arterial glucose would not be the only precursor of milk lactose (Bickerstaffe et al., 1974), little attention has been paid to the potential contribution of amino acids (AA) to mammary lactose synthesis. Although, Bequette et al. (2006) recently demonstrated in vitro that some essential AA could contribute to mammary lactose synthesis, no in vivo study has examined the contribution of essential AA to milk lactose secretion and if that contribution would be altered by AA provision. Therefore, the objective of this study was to examine if increased supply of essential AA, in excess of requirement, would affect the contribution of glucose to lactose synthesis in lactating dairy cows.