Abstract

The objective of this study was to evaluate the net flux response of nitrogen compounds (alpha-amino N, ammonia N, urea N, essential amino acids) across the portal-drained viscera (PDV), liver and total splanchnic tissues of mature wethers to increasing level of dietary fishmeal (FM) supplementation. Four wethers (average body weight, 64 kg) with chronic indwelling catheters into the portal, hepatic and mesenteric veins and the abdominal aorta were used in a 4×4 Latin square design. A basal diet consisting of 0.7 hay and 0.3 concentrate was fed twice daily with a fixed amount at 1.4 times maintenance energy (1.3 kg/day on a dry matter basis). The supplementation proportion of FM as treatment was 0, 0.03, 0.06 and 0.09 to the amount of the basal diet to contain 119, 137, 154 and 170 g crude protein per kg dietary dry matter, respectively. Blood flows through PDV and liver did not differ (p>0.05) among the treatments. Both net PDV release and hepatic uptake of alpha amino acid N increased linearly (p<0.05) in response to increased dietary FM, which resulted in similar total splanchnic release of alpha-amino N among the treatments. Similarly, increased dietary FM increased net PDV absorption and hepatic removal of ammonia N linearly (p<0.05). Hepatic synthesis and total splanchnic release of urea N increased linearly (p<0.01) with increased dietary FM, but PDV uptake of urea N did not respond to increased dietary FM. Linear regression equations between the increases in FM N intake and PDV net flux indicated that 0.34 and 0.30 of FM N was absorbed in the form of alpha-amino N and ammonia N, respectively. The results demonstrated that FM supplementation provides more alpha-amino N than ammonia N to the liver, but the alpha-amino acid N absorption is less than the expected metabolizable protein N from FM supplementation. (Asian-Aust. J. Anim. Sci. 2005. Vol 18, No. 9 : 1255-1261)

Highlights

  • Fishmeal (FM) is characterized as a low ruminally degradable protein source for feeding of ruminants, and is abundant in methionine and lysine, two amino acid which are in low concentration in most of plant protein sources

  • Both N and dry matter (DM) intakes increased with FM supplementation as planned, but sheep fed FM9 refused to Linear effect Quadratic effect

  • In the studies of protein sources that differed in ruminal degradability with beef steers (Huntington, 1987) or sheep (Ferrell et al, 2001), plasma flows of the portal vein were greater when low ruminal undegraded protein (RUP) diets fed than when high RUP diets were fed

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Summary

Introduction

Fishmeal (FM) is characterized as a low ruminally degradable protein source for feeding of ruminants, and is abundant in methionine and lysine, two amino acid which are in low concentration in most of plant protein sources. Researchers who measured the net flux of alpha-amino nitrogen (AAN) by PDV did not detect significant differences among protein supplements with different Venoartical concentration differences were multiplied by blood (or plasma) flows to calculate net nutrient fluxes across PDV, liver and total splanchnic (TS) tissues.

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