Twenty-four primiparous Holstein cows were fed corn silage:grain (1:1, DM basis) and hay (.9 kg/d) beginning 30 d prepartum and through wk 18 of lactation. Ten grams of Biomate Yeast Plus (5 X 10(9) cfu of Saccharomyces cerevisiae/g) were top-dressed on the a.m. allotment of corn silage:grain fed to 12 cows. Corn silage:grain was restricted during prepartum and thereafter fed for ad libitum intake. Cows fed supplemental yeast peaked earlier and had a higher milk yield compared with control cows (wk 7, 29.5 kg/d vs. wk 11, 28.7 kg/d). Digestibilities of protein and cellulose were improved in cows fed supplemental yeast, contributing to a greater DMI during the first 6 wk of lactation and a higher average milk yield through wk 18 of lactation compared with control cows (27.2 vs. 26.0 kg/d).

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