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Article: Vascular sources of amino acids for milk protein synthesis in goats at two stages of lactation
- Article from:
- Journal of Dairy Science
- Article date:
- April 1, 2002
- Author:
CopyrightCopyright American Dairy Science Association Apr 2002. Provided by ProQuest LLC. (Hide copyright information)
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ABSTRACT
An arteriovenous technique, combined with a 30-h i.v. infusion of [5- ^sup 13^CH^sub 3^]Met and [5,5,5-^sup 2^H]Leu, was used to monitor mammary uptake of free amino acid (AA) and to estimate the proportion of casein synthesized from circulating peptides in goats in early and late lactation. At both stages, kinetics was performed on the last day of consecutive 5.5-d periods. The first period was an i.v. infusion of saline and the second an i.v. infusion of lysine (8.9 g(h) plus methionine (2 g/h). Net uptake of essential AA and protein yields were higher in early than in late lactation. Uptake of free Met, His, and Pro was less than, uptake of Tyr and Lys was equal to, and uptake ...