Effect of a yeast culture (Saccharomyces cerevisiae) and monensin on ruminal fermentation and digestion in sheep

A metabolism trial was conducted to evaluate the effects of supplying a yeast culture containing Saccharomyces cerevisiae (Levucell) and monensin to sheep, on ruminal fermentation and digestibility of diets. Four Suffolk sheep (30 kg BW) with ruminal cannula were used in a Latin Square design, where treatments were control (C), 1 g/day of Levucell (L, 20 × 109 CFU/g), 25 mg/day of monensin (M) and a combination of L and M. Additives were dosed directly into the rumen. The diet was based on alfalfa hay (50%) and a concentrate containing sorghum grain (60%), molasses (24%), urea (2%) and soybean meal (14%). Digestibility of dry matter, neutral detergent fiber, and dry-matter intake were not affected (p > 0.05) by treatments. The ionophore alone or in combination, reduced (p < 0.05) the molar proportion of acetate from ≈71.2 to 66.2, and increased propionate from ≈18.6 to 24.4 without any effect on butyrate. Ruminal protozoa counts (organisms ×104) were greater (p < 0.05) in the control group (69.4) than with feed additives (15.9–39.7). No effects were detected in ruminal pH. Monensin and M + L increased propionate proportion, but no effects was observed with S. cerevisiae alone.