OXYGEN-CONSUMPTION BY SPLANCHNIC TISSUES IN WETHERS CONSUMING AD-LIBITUM DIFFERENT PROPORTIONS OF BERMUDAGRASS AND RYE GRASS-WHEAT

Crossbred wethers (n = Is, 7.5 month of age and 31 +/- 0.8 kg) were us ed in a 23-day experiment to determine effects of an libitum consumpti on of diets differing in proportions of coarsely chopped bermudagrass and ryegrass-wheat hay (0, 33, 67 and 100%) on oxygen consumption by s planchnic tissues. Bermudagrass and ryegrass-wheat were 9 and 13% CP a nd 78 and 71% NDF, respectively. Intake of dry matter (1.03, 0.92, 0.9 2 and 0.76 kg/d) and digestible energy (13.5, 10.7, 10.6 and 8.2 MJ/d for 0, 33, 67 and 100% bermudagrass, respectively) changed linearly an d cubically (P<0.05) as bermudagrass level increased. Consumption of o xygen by the portal-drained viscera tended to decrease linearly (P=0.1 4) with increasing bermudagrass (182, 154, 156 and 137 mM/h), and hepa tic oxygen consumption decreased linearly (P<0.05) and changed cubical ly (P=0.07; 150, 113, 116 and 103 mM/h for 0, 33, 67 and 100% bermudag rass, respectively). Splanchnic tissue energy consumption expressed as a percentage of digestible energy intake increased linearly (P=0.08) with increasing bermudagrass (24.0, 27.6, 28.6 and 33.2% for 0, 33, 67 and 100% bermudagrass, respectively). In conclusion, the level rather than presence alone of different grass sources consumed ad libitum af fected energy use by the splanchnic bed, and as a percentage of digest ible energy intake splanchnic bed energy consumption increased with in creasing dietary bermudagrass level and decreasing digestible energy i ntake.