Inclusion of yeast and saccharides based-product to replace monensin in the diet of confined steers: performance, rumen environment, metabolism, animal health, and meat quality.

The present study aimed to evaluate a blend of yeast and saccharides based-product fed via diet to feedlot cattle on performance, health, meat quality, and rumen metabolism when compared to monensin. Twenty-four non-castrated crossbred male steers (Charolais x Nellore) were divided into control (n = 12), receiving the basal diet with monensin (215 mg/animal/day) and treatment (n = 12) receiving the basal diet with the blend of yeast and saccharides based-product (17.2 g/animal/day). Animals were weighed on days 1, 20, and 113, and on days 20, 70, and 113, blood and rumen fluid were collected, which was also used to determine the genera of bacteria present in the rumen and to quantify protozoa. Total feces were collected to determine apparent total tract digestibility from days 108 to 112 of the experiment. There was no treatment effect for weight gain, feed intake, or feed efficiency. There was a gain in the loin eye area in the control group (P = 0.05) and greater subcutaneous fat thickness in the loin and rump cap control group (P = 0.01). In the ruminal fluid, there was higher protozoa count in the treatment group on day 113 (P = 0.03) and a higher proportion of propionic acid in the treatment group on day 70 (P = 0.03). Total short-chain fatty acids were lower in steers in the treatment group. There was no treatment effect on the ruminal microbiota. There were lower counts of lymphocytes and granulocytes in the blood of steer in the treatment group (P < 0,05). A significant increase in the concentrations of immunoglobin A (IgA) and others heavy-chain immunoglobulins (IgM, IgG, IgM and IgE) were observed in the treatment group. There was an effect of treatment on glutathione S-transferase (GST) activity on days 70 and 113 (P = 0.02). Likewise, high GST activity in the liver was identified in the treatment group (P = 0.01). For fatty acid profile in meat, oleic acid presented higher proportion in the treatment group (P = 0.04), in contrast to docis-5,8,11,14,17-eicosapentaenoic acid, which was lower in the same group (P = 0.05). It is concluded that the blend of yeast and saccharides based-product played a role similar to monensin's in productive performance, demonstrating a potential to substitute monensin. Furthermore, the inclusion of yeast and saccharides in the diet stimulated the humoral immune response and antioxidant action without affecting meat quality.