Monensin and concentrate supplementation level affect forage ruminal measurements and forage in situ disappearance of bermudagrass fed to beef cattle

Abstract

The objective of this study was to evaluate the effects of monensin and concentrate supplementation levels on bermudagrass (Cynodon dactylon) in situ disappearance and ruminal measurements. The experiment was conducted in Ona, Florida, and treatments were the factorial arrangement of 2 supplementation levels [0.4 (low) or 4 kg/d (high)] and 2 monensin levels (0 or 20 mg/kg of the DMI) distributed in a Latin square design. The supplement was 17.1% CP and 79.1% TDN. Steers receiving the higher supplementation level had greater (P = 0.01) total DMI (1.4 vs. 1.0 ± 0.1% BW), but there was no difference in forage DMI (P = 0.72, mean = 1.0 ± 0.1% BW). Monensin did not affect total DMI or forage DMI (P ≤ 0.74). 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 (P = 0.01) propionate on the high supplementation level (19 vs. 15 ± 1.5 mol/100 mol). 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 and NDF disappearance. Monensin did not change forage disappearance measurements but increased ruminal propionate concentrations in steers receiving higher supplementation level. Higher supplementation level was effective to increase total DMI and forage DM and NDF disappearance.