Effects of live yeast on the rumen fermentation parameters and milk performance of Simmental dairy cows during the hot season

The effects of dietary supplementation with live yeast culture (LY) on the milk performance and rumen fermentation parameters of Simmental cows in the middle of lactation were examined under hot season conditions in 2019. The 28 cows, which were divided into two experimental groups of 14, were fed a controlled diet, with or without the addition of 5 g of LY per cow daily. The mean dry matter intake (DMI) and yield of milk in the LY group were greater by 0.25 kg/day and 0.42 kg/day, respectively, than for the control group. The yields of milk components and 4% fat corrected milk were also significantly greater in the LY group than in the control group, but LY supplementation did not significantly alter milk composition percentages. The acetate concentration in the rumen tended to be higher in cows fed LY but the ruminal pH, NH3-N, propionate and butyrate levels, and acetate/propionate ratio were similar in the two groups. It can be concluded that LY supplementation of the diet of Simmental dairy cows during the hot season improved milk production and ruminal fermentation performance to a limited degree.