Effect of monensin and/or probiotics on feed intake, apparent digestibility, ruminal, serum and urinary variables, and nitrogen balance of steers

The objective of the present study was to evaluate the association of Bacillus toyonensis, Saccharomyces cerevisiae var. boulardii, and sodium monensin on feed intake, apparent digestibility, ruminal, urinary, and serum variables in the diet of steers. Four Angus × Nellore crossbred steers, with 403.0 ± 75.5 kg of BW, rumen cannulated and housed individually were used. The animals were submitted to a 4 ×4 Latin square design, receiving the following treatments: monensin only (MO); monensin + B. toyonensis (MBT); monensin + S. cerevisiae boulardii (MSB); and B. toyonensis + S. cerevisiae boulardii (BTSB). Treatments with monensin (MO, MBT and MSB) presented lower DM intake than BTSB, but similar apparent digestibility between treatments. No difference was observed between treatments for ruminal pH, but BTSB presented higher NH₃-N concentration than MBT and MSB and did not differ from MO. All concentrations in the blood serum and urinary variables were found within the physiological range or close to normal, and no difference was observed in the retained nitrogen. The BTSB treatment showed potential as a feed additive for cattle, by controlling rumen pH and similar concentrations of NH₃-N, total SCFA, and retained nitrogen to MO treatment, but when probiotics were combined with monensin no beneficial effect was observed under the studied conditions.