Level of nutrition and splanchnic metabolite flux in young lambs

Splanchnic metabolite flux was measured in young lambs given access to a high-concentrate diet either ad libitum (ADLIB) or at a maintenance level (MAINT) for 21 d. Net fluxes of urea N (UN), ammonia N (NH3 N), alpha-amino N (AAN), amino acids, glucose (G), and lactate (L) across the liver and portal-drained viscera (PDV) were measured in 11 crossbred ram lambs (35 kg) surgically fitted with indwelling catheters in the portal, hepatic, and mesenteric veins and mesenteric artery. During the 21-d period, daily N and ME intakes were 24.6 and 10.7 g N/d and 3.02 and 1.28 Mcal/d, respectively, for ADLIB and MAINT lambs. Intakes, thus, were 42% lower for MAINT than for ADLIB lambs. Net portal fluxes of UN, NH3 N, AAN, and L in MAINT lambs were 46%, 84%, 50%, and 74%, respectively, of that in ADLIB lambs. Expressed as a percentage of N intake, the proportion of AAN absorbed by the PDV was higher in MAINT lambs (P less than .05) than in ADLIB lambs. There was no net portal glucose absorption in either group of lambs; however, net hepatic glucose production in MAINT lambs was 48% of that in ADLIB lambs. There was net utilization of glutamine by the PDV; net glutamine flux in MAINT lambs was 49% of that in ADLIB lambs. The liver utilized AAN and NH3 N and produced UN. Splanchnic tissues modulate metabolite flux following changes in feed intake in young ruminants.