Effect of abomasal glucose infusion on alanine metabolism and urea production in sheep

Abstract

The effect of abomasal infusion of glucose (120 kJ/d per kg body weight (BW) 0×75 , 758 mmol/d) on urea production, plasma alanine-N¯ux rate and the conversion of alanine-N to urea was studied in sheep offered a low-N diet at limited energy intake (500 kJ/d per kg BW 0×75 ), based on hay and grass pellets. Glucose provision reduced urinary N (P = 0×040) and urea (P = 0×009) elimination but this was offset by poorer N digestibility. Urea-N production was signi®cantly reduced (822 v. 619 mmol/d, P = 0×024) by glucose while plasma alanine-N¯ux rate was elevated (295 v. 342 mmol/d, P = 0×011). The quantity of urea-N derived from alanine tended to be decreased by glucose (127 v. 95 mmol/d) but the fraction of urea production from alanine was unaltered (15 %). Plasma urea and alanine concentrations (plus those of the branched chain amino acids) decreased in response to exogenous glucose, an effect probably related to enhanced anabolic usage of amino acids and lowered urea production.

Effects of intraruminal propionate supplementation on nitrogen utilisation by the portal-drained viscera, the liver and the hindlimb in lambs fed frozen rye grass

“…When looking at the AA concentrations in the artery, a decrease in EAA and BCAA concentrations (2 16 and 2 21 % respectively between the control and P2 animals) occurred with the propionate treatment. Similar effects have been observed after glucose or propionate infusion in most studies (for example, Cappelli et al 1997;Nozière et al 2000;Obitsu et al 2000), in spite of a few conflicting data where no change (Balcells et al 1995) or an increase (Seal et al 1993;Seal & Parker, 1996) in EAA concentrations was observed. A decrease in AA concentrations in systemic blood would tend to indicate an increase in the utilisation of these AA by peripheral tissues (such as muscle), which was not confirmed by the net hindlimb fluxes measured.…”

“…The effects of propionate (or glucose) treatments on N metabolism (global N retention, protein synthesis in muscle and milk production) in ruminants have been studied extensively (Eskeland et al 1973(Eskeland et al , 1974Abdul-Razzaq & Bickerstaffe, 1989;Seal et al 1993;Huhtanen et al 1998;Moloney, 1998;Kim et al 1999;Ørskov et al 1999;Obitsu et al 2000). Whatever the mechanisms underlying this process (the role of insulin is indisputable), propionate or glucose infusions induce an increase in N retention in the muscle (Abdul-Razzaq & Bickerstaffe, 1989;Moloney, 1998) or an increase in milk production and protein content in the milk (Huhtanen et al 1998).…”

Increasing intravenous infusions of glucose improve body condition but not lactation performance in midlactation dairy cows

“…Additionally, the major blood metabolite of protein metabolism, BUN, showed numerically larger decreases in the GI group during the infusion period, even though the treatment × dose interaction was not significant for the latter. Together, this could be explained by a decrease in hepatic uptake and deamination of glucogenic AA, thereby promoting peripheral uptake of AA for protein synthesis (Obitsu et al, 2000).…”

Ammonia production, ammonia absorption, and urea recycling in ruminants. A review

“…Thus, MCP production in the rumen can be increased. Obitsu et al (2000) reported that abomasal infusion of glucose reduced urea production and urinary N excretion. This illustrates that increased glucose absorption from the small intestine may contribute to increased fl ow of AA to peripheral tissues and to reduced wastage as excretion of urinary N. As described above, it is necessary to maintain a suitable ratio of available energy and N to improve the utilization of recycled urea.…”