Diet digestibility and performance of dairy cows supplemented with live yeast

Dietary yeast supplementation may improve the digestive efficiency of ruminants, but responses depend on the yeast strain and the diet composition. Corn silage and citrus pulp arc usual carbohydrate sources for dairy cows in southeast Brazil. This study evaluated the supplementation of dairy cows fedding on corn silage-citrus pulp-based diets with Saccharomyces cerevisiae CNCM I-1077 (Lallemand SAS, Toulouse, France). Twenty multiparous, midlactation Holstein cows were assigned to two treatments in crossover design. Treatments were: live yeast on oyster meal capable of supplying a daily minimum of 1 X 10(10) CFU per cow or oyster meal top-dressed at 10 g to the morning meal. Diet contained (% of dry matter): 16.8% crude protein, 30.9% neutral detergent fiber, 43.9% corn silage, 2% tifton hay, 14.4% steam flaked corn, 16.9% citrus pulp and 21.7% soybean meal. Yeast supplementation increased daily yields of milk (29.4 vs. 28.5 kg, p = 0.11), protein (0.939 vs. 0.908 kg, p = 0.05), and lactose (1.294 vs. 1.241 kg, p = 0.06), but did not affect milk fat contents (p = 0.59). Daily dry matter intake was 21.4 with yeast: and 20.7 kg for the control (p = 0.11). Total tract apparent digestibility of the neutral detergent fiber was 48.1% with yeast and 43.2% for the control (p = 0.08). There was a trend for increased intake of digestible organic matter with yeast supplementation (p = 0.07). The positive milk protein yield response to yeast supplementation may have resulted from the increased fiber digestibility, but the response mechanism could not be elucidated.