Effect of supply of metabolizable protein on whole body and splanchnic leucine metabolism in lactating dairy cows.

摘要: The effect of the supply metabolizable protein (MP) on metabolism across splanchnic tissues was determined in six catheterized lactating Holstein cows. In a crossover design, two isonitrogenous (16.3% CP) diets balanced to provide low (Lo-MP) or high (Hi-MP) MP were fed over 35-d periods. After 24 d feeding, N balance 6-d period. On 33, [13C] sodium bicarbonate infused into one jugular vein for 6 h, and hourly breath samples collected. 34 35, L[1-(13)C] leucine vein, between 2 h infusion, blood taken from portal hepatic veins an artery. Isotopic enrichments plasma leucine, 4-methyl-2-oxopentanoate, expired CO2 calculation kinetics. Net absorption greater, either direct basis (leucine transfer only) corrected portal-drained viscera 4-methyl-2-oxopentanoate Hi-MP diet. There no effects diet net flux liver, and, thus, more available peripheral with Combined increment most essential AA, this led increased milk output, although it only represented 16% additional leucine. Whole body oxidation also greater diet, as used synthesis. Despite these changes, did not affect irreversible loss rate by liver; averaged 35 20% whole rate, respectively. These ratios confirm metabolic activity dairy cows, which are even than previously reported growing ruminants.