Increase in milk yield of commercial dairy herds fed a microbial and enzyme supplement.

A microbial and enzyme supplement fed at 21.2 g/d per cow to 46 Virginia dairy herds increased the milk yield of 31 herds (17 significantly) and decreased the milk yield of 15 herds (7 significantly). Effects of season were important but consistent with overall results. Herds began receiving the supplement, which contained dried fermentation products of Aspergillus oryzae, Bacillus subtilis, Lactobacillus acidophilus, and yeast culture, midway between the first and second monthly Dairy Herd Improvement tests and continued on the supplement through the 3rd mo. Entry of herds was staggered over 8 mo to reduce the influence of season. The trial involved 3417 cows with 5 test mo between 60 and 365 d in milk. Milk yield during mo 3 averaged 0.64 kg/d per cow more (+0.73 kg/d for first lactation cows and +0.56 kg/d for later lactation cows) than the mean milk yield during mo 1 and 5. Herds completing the study before summer responded similarly to all other herds, which included herds that were fed the product during summer and those that finished the study during summer. Fat and protein yields and protein percentage differed little with or without the supplement. Fat percentage decreased (0.10%). Twenty-one herds that were fed a yeast product prior to and during the study responded similarly to the 17 herds that were not fed a yeast product.