|GALLOWAY SR, D|
Submitted to: Journal of Animal Science Supplement
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/9/1996
Publication Date: N/A
Interpretive Summary: Grass consumption often results in insufficient energy or specific nutrients for desired levels of performance by growing ruminants. Legumes can be ingested with grass in mixed swards or added in harvested diets to enhance performance. Likewise, cereal grains frequently are included in grass diets to increase production. Factors in addition to absorbed energy may influence splanchnic tissue mass and heat production, including digesta mass and the profile of nutrients presented to splanchnic tissues, which vary among supplemental feedstuffs. Therefore, the objective of this experiment was to determine interactions between dietary inclusion of ground corn and alfalfa in a basal grass diet on splanchnic net flux of nutrients in growing wethers with ad libitum consumption. Corn and alfalfa substitution each for 25% of dietary grass, moderate to high in digestibility and moderate in nitrogen concentration, did not interact in digestible energy intake or net fluxes of oxygen and nitrogenous compounds across splanchnic tissues in growing wethers. Alfalfa decreased splanchnic bed energy consumption as a proportion of digestible energy intake and increased the difference between splanchnic tissue heat energy production and digestible energy intake regardless of corn presence. Likewise, increases in portal-drained viscera release of ammonia and urea nitrogen release by the liver were not modified by dietary corn presence. In conclusion, under these experimental conditions dietary presence of corn should not influence effects of alfalfa inclusion, or vice versa, on performance.
Technical Abstract: Crossbred sheep (14, 33 +/- 1 kg body weight and 9 mo of age) were used in a 21-d experiment to determine interactions between dietary inclusion of grain (ground corn; C) and legume (alfalfa hay: 60% neutral detergent fiber and 15% crude protein; A) in a basal grass (ryegrass-wheat hay; 72% neutral detergent fiber and 9% crude protein) diet on splanchnic tissue net flux of nutrients. 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. Dry matter intake (0.86, 0.93, 0.97 and 1.10 kg/d; SE 0.092) and organic matter digestibility (67, 70, 70 and 72% for Control, C, A and CA, respectively; SE 2.0) were similar among treatments (P>0.10). Oxygen consumption by the portal-drained viscera, liver and splanchnic bed did not differ among treatments (P>0.10); however, energy consumption as percentages of digestible energy intake by the portal-drained viscera (13.1 and 10.8%; P=0.02) and splanchnic bed (23.3 and 20.8%, respectively; P=0.08) were greater without than with A. Alfalfa increased (P=0.04) hepatic release of urea nitrogen (30.6, 22.5, 38.6 and 41.4 mM/h) hepatic uptake of ammonia nitrogen (12.1, 10.7, 19.3 and 17.6 mM/h for Control, C, A and CA, respectively). In conclusion, C and A substitution for 25% of grass, which was moderate to high in digestibility and moderate in nitrogen concentration, did not interact in net fluxes of nutrients across splanchnic tissues in growing wethers.