Supplementing Barley-Based Dairy Cow Diets with Saccharomyces cerevisiae1

Active dry yeast and yeast cultures based on Saccharomyces cerevisiae are widely used in commercial dairy production in North America and Europe to improve milk yield. These products have been extensively evaluated in corn-based diets, but their effectiveness may depend on the type of diet. The objective of this study was to determine the potential benefits of supplementing barley-based dairy diets with yeast for milk yield and production efficiency in dairy cows. Forty lactating Holstein dairy cows were randomly assigned to 1 of 2 treatments: 1) a control diet (no yeast) or 2) a yeast-supplemented diet. All cows were fed the control diet for 3 wk, followed by a 6-wk period on their assigned diets. The control diet consisted of 23% barley silage, 23% alfalfa silage, 6% alfalfa hay, and 48% of a ground barley-based concentrate (DM basis). For the treatment diet, an active dry yeast (Levucell SC-1077, Lallemand Animal Nutrition, Milwaukee, WI) was added to the concentrate to provide 0.5 g Levucell/d per animal (1 x 1010 cfu/d per animal). There was no difference in final BW (623 vs. 621 kg; P = 0.85), ADG (0.530 vs. 0.377 kg/d; P = 0.35), NE output (36.6 vs. 36.5 Mcal/d; P = 0.95), or efficiency of NE output (1.58 vs. 1.65 Mcal/kg DMI; P = 0.20) for cows on the control diet compared with those on the yeast-supplemented diet. There was also no difference (23.2 vs. 22.7 kg/d; P = 0.30) in DMI, 3.5% FCM (35.6 vs. 36.6 kg/d; P = 0.34), or efficiency of FCM production (1.55 vs. 1.64 kg FCM/kg DMI; P = 0.28) for yeast-supplemented cows compared with control cows. However, because FCM yield and efficiency of FCM production were numerically greater with yeast supplementation of the barley-based diet, the revenue over feed (including yeast) cost was increased by $0.77/d per animal compared with no supplementation.