No CrossRef data available.
Published online by Cambridge University Press: 21 November 2017
During lactation the ruminant mammary gland removes relatively large quantities of circulating amino acids (AA) to meet the requirements for milk protein synthesis but arterio-venous uptake studies in dairy cows (1) have indicated that the uptake of certain AA may be insufficient to account for their output as milk protein. The apparent deficit may be accounted for by the use of AA supplied to the gland as small peptides or proteins. A dual-labelled tracer approach involving infusion of [13C]-labelled peptides into the external pudic artery which supplies blood directly to the mammary gland demonstrated that dipeptide-bound AA can be utilised as direct precursors for milk casein synthesis in lactating dairy goats (2). However, previous studies using vascular infusion of [13C]-labelled free AA (3) have provided equivocal data on involvement of non-labelled extra-mammary derived peptides/proteins in vivo in the biosynthesis of milk protein.