Net flux of nutrients across splanchnic tissues in wethers consuming grass hay with or without corn and alfalfa

Fourteen crossbred sheep (33 kg body weight, SE = 1; 9 months of age) were used in a 21 day experiment (2 × 2 factorial) to determine if dietary substitution of grain (ground corn; C) for ryegrass-wheat hay (72% neutral detergent fiber and 9% crude protein) alters effects of legume (alfalfa hay: 60% neutral detergent fiber and 15% crude protein; A) substitution on splanchnic tissue net flux of oxygen, alpha-amino nitrogen, urea and ammonia with ad-libitum consumption. Diets were approximately 100, 75, 75 and 50% grass, 0, 25, 0 and 25% C, and 0, 0, 25 and 25% A for control, C, A and CA treatments, respectively. Dietary inclusion of corn did not affect net fluxes or change effects of alfalfa. Alfalfa substitution did not alter dry matter intake, organic matter digestibility or oxygen consumption by the portal-drained viscera, liver or splanchnic bed. However, alfalfa increased digestible nitrogen intake (P < 0.01; 6.0, 5.9, 9.8 and 10.3 g per day), hepatic release of urea nitrogen (P = 0.04; 30.6, 22.5, 38.6 and 41.4 mM h−1) and hepatic uptake of ammonia nitrogen (P = 0.04; 12.1, 10.7, 19.3 and 17.6 mM h−1 for control, C, A and CA, respectively) and decreased energy expenditure as a percentage of digestible energy intake by the portal-drained viscera (P = 0.02; 10.8 versus 13.1%) and splanchnic bed (P = 0.08; 20.8 versus 23.3%). In conclusion, effects of substituting alfalfa for 25% of dietary grass, which was moderate to high in digestibility and moderate in nitrogen concentration, were not influenced by substitution of corn for grass.