NET FLUX OF NUTRIENTS ACROSS SPLANCHNIC TISSUES IN SHEEP FED TROPICALVS TEMPERATE GRASS HAY OF MODERATE OR LOW QUALITIES

Crossbred wethers (18 months old; 44 +/- 0.7 kg body weight), with cat heters in a hepatic vein, the portal vein and a mesenteric vein and ar tery, consumed ad libitum tropical or temperate grass hay each of thre e different qualities or stages of maturity. Splanchnic tissue energy consumption was similar among tropical grass diets but increased as qu ality of temperate grass declined. Portal-drained viscera oxygen consu mption increased with increasing digestible energy intake and fecal ne utral detergent fiber excretion. Energy available to extra-splanchnic tissues with highest quality grass was greater for temperate than for tropical grass because of lower splanchnic tissue energy consumption r elative to digestible energy intake. Grass source, quality and nitroge n concentration did not significantly affect portal-drained viscera re lease of alpha-amino nitrogen. Hepatic uptake of Lu-amino nitrogen was greater for tropical than for temperate grass, presumably because of higher nitrogen concentration with greater hepatic ammonia nitrogen up take. Glucose uptake by the portal-drained viscera was greater for tro pical than for temperate grass, and the potential contribution of prop ionate to hepatic glucose release tended to be greatest for grass high est in quality. Grass quality appears more important to achieve maxima l energy availability to extra-splanchnic tissues with temperate than tropical grass.