Oxygen consumption by splanchnic tissues in wethers consuming ad libitum different proportions of bermudagrass and...

Crossbred wethers (n = 18, 7.5 month of age and 31 +/- 0.8 kg) were used in a 23-day experiment to determine effects of ad libitum consumption of diets differing in proportions of coarsely chopped bermudagrass and ryegrass-wheat hay (0, 33, 67 and 100%) on oxygen consumption by splanchnic tissues. Bermudagrass and ryegrass-wheat were 9 and 13% CP and 78 and 71% NDF, respectively. Intake of dry matter (1.03, 0.92, 0.92 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 and cubically (P < 0.05) as bermudagrass level increased. Consumption of oxygen by the portal-drained viscera tended to decrease linearly (P = 0.14) with increasing bermudagrass (182, 154, 156 and 137 mM/h), and hepatic oxygen consumption decreased linearly (P < 0.05) and changed cubically (P = 0.07; 150, 113, 116 and 103 mM/h for 0, 33, 67 and 100% bermudagrass, 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 affected energy use by the splanchnic bed, and as a percentage of digestible energy intake splanchnic bed energy consumption increased with increasing dietary bermudagrass level and decreasing digestible energy intake.