PSVII-11 Monensin and supplementation level effects on ruminal parameters and in-situ disappearance of steers receiving bermudagrass

Abstract

Abstract The objective of this study was to evaluate the effects of monensin and supplementation level on bermudagrass (Cynodon dactylon) in situ disappearance and ruminal parameters. The experiment was conducted in Ona, FL. Treatments were the factorial arrangement of 2 supplementation levels [0.4 (low) or 4 kg/d (high)] and 2 monensin levels (20 mg/kg of the DM intake or no monensin) distributed in a latin square design. Four rumen-cannulated steers were used with 10-d adaptation and 3-d incubation and collection periods. Samples were incubated in the rumen with nylon bags and analyzed for DM, CP, and NDF disappearance. Rumen fluid was collected for 3 d during the incubation period and analyzed for pH, ammonia, propionate, lactate, and butyrate. There was no effect (P > 0.05) of monensin on potential DM, CP, and NDF disappearance; however, greater supplementation level increased (P < 0.03) potential DM disappearance (64 vs. 61%) and NDF disappearance (60 vs. 57%). Steers receiving greater supplementation level had greater (P = 0.01) total DMI (1.4 vs. 1.0% BW) but there was no difference in forage DMI (P = 0.72, mean = 1.0 ± 0.1% BW). There was a monensin × supplementation level interaction on ruminal propionate concentration. The interaction occurred because there was no effect (P = 0.64) of monensin with low supplementation (mean = 12 ± 1.2 mol/100 mol); however, monensin increased propionate on high supplementation from 15 to 19 mol/100 mol. There was an increase (P < 0.05) in ruminal ammonia (from 1.9 to 4.4 mg/100 ml) and lactate (from 60 to 64 mol/100 mol) from low to high supplementation. Rumen pH and butyrate were not affected by monensin or supplementation (P > 0.12). Monensin did not change forage disappearance parameters but increased ruminal propionate production in steers receiving greater amount of concentrate.