Peptide and amino acid metabolism in the gastro-intestinal tract of yak

摘要

The present experiment was conducted to quantify the net fluxes of both free (FAA) and peptide amino acids (PAA) across the mesenteric and stomach portions of the portal-drained viscera (PDV) of three yak cows (weighing 172.3 ± 18.6 kg) fitted with sampling catheters in the portal vein, mesenteric artery and mesenteric vein prior to its convergence with the gastrosplenic vein. Blood flow was determined by measuring the dilution of para-aminohippurate (PAH) infused constantly into a distal mesenteric vein. Amino acids in the deproteinised plasma were analysed before and after acid hydrolysis. The increased amino acids after acid hydrolysis were considered as PAA. Portal blood flow was 389 L/h or 2.32 L/h kg body weight (BW), of which 37% was contributed by the mesenteric vein. There was net appearance of a large quantity of PAA across PDV, which accounted for 92% of the total nonprotein amino acid flux. Net release of PAA and FAA in stomach-drained viscera (SDV) accounted for 78% and 42% of the net release in PDV, respectively. These results suggest that, in yak, the peptide possibly to be the primary form of amino acid absorption, and that the stomach area probably to be the major site of peptide absorption.