Effects of two yeast based direct fed microbials on performance of high producing dairy cows

•A yeast culture (XPC) or yeast/microbial culture (YST) were added to a Control (C).•Milk yield was higher with YST, but not XPC, and NE output was higher vs. C for both.•There were no impacts of YST or XPC on measures of rumen fermentation.•Lower digestion of organic matter and protein for YST vs. C occurred.•A post-ruminal YST effect improved gut health causing higher absorption efficiency. Our aim was to determine effects of two S. cerevisiae yeast based direct fed microbial (DFM) feed additives on the productive response of high producing early lactation dairy cows. The study consisted of three high producing Holstein cow pens (±315 cows/pen) in a 3×3 Latin square design experiment with 3 periods of 28 d each. The 3 treatments were: (1) Basal total mixed ration (Control), (2) Control supplemented with ‘XPC’ yeast culture at 14g/cow/d and, (3) Control supplemented with ‘Yeasture (YST)’ DFM at 10g/cow/d. Milk (P=0.01), milk true protein (P=0.01), lactose (P=0.01) and energy (P=0.02) outputs were higher for YST cows, and there was a tendency for milk fat (P=0.07) to increase compared to Control cows. In contrast, milk and component yields were not impacted by feeding XPC. Total net energy (NE) output was higher for both DFM treatments vs. Control (YST (P