Effects of intramammary arterial infusion of non-essential amino acids and glucose in the lactating goat

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Abstract
Summary: Three experiments were carried out on 2 lactating goats, in which mammary arterial plasma amino-acid concentrations were elevated by the infusion of a solution of non-essential amino acids into a carotid artery supplying a transplanted mammary gland. In a fourth experiment a solution of glucose was similarly infused. In some cases the increased arterial concentrations of amino acids resulted in their increased mammary uptake, and in a depression of glucose uptake. However, infusions of neither amino acids nor glucose resulted in increased milk protein yield. Infusion of [U-14C]glutamic acid in one experiment demonstrated gluconeogenesis from glutamate carbon within the mammary gland. The results are discussed in relation to data obtained in another laboratory, from which it has been claimed that non-essential amino acid supply may limit milk protein synthesis. The present results provide no confirmation for the claim.