Saccharomyces cerevisiae and Aspergillus oryzae, used alone or in combination, as a feed supplement for beef and dairy cattle

The effects of addition of direct-fed microbials prepared from Saccharomyces cerevisiae (SC) and Aspergillus oryzae (AO) to ruminant diets was examined in two experiments. Experiment 1 was designed to study the effects of microbial supplements on ruminal and total tract digestibility, ruminal fermentation, bacterial counts and bacterial colonization of fibrous feed, in eight ruminally cannulated steers. The steers were used in a factorial arrangement within a replicated, concurrently run 4 × 4 Latin square design. Treatments were: (1) 60% rolled barley + 40% timothy hay (C); (2) C + 10 g head−1 d−1 of SC; (3) C + 3 g head−1 d−1 of AO fermentation extract; (4) C + 10 g head−1 d−1 of a mixture of SC and AO. In exp. 2, milk yield and composition were monitored following the addition of microbial supplements to the diets described above and fed to dairy cows. The addition of AO, alone or in combination with SC, stimulated (P < 0.10) ruminal fermentation with higher concentrations of acetate (P < 0.01), propionate (P = 0.07), and total VFA (P < 0.01) when sampled prior to feeding. Accordingly, ruminal pH was lower (P < 0.01) in animals receiving AO, alone or combined with SC. Aspergillus oryzae, when supplemented alone, tended (P > 0.10) to increase ruminal NH3-N concentration. These changes in ruminal fermentation did not affect DMI or ruminal and total tract digestibility. The addition of direct-fed microbials did not affect bacterial counts or bacterial colonization of roughage in the rumen. Milk yield, milk composition and feed intake were not affected by the addition of SC to the diet of dairy cows. However, supplementation of the diet with AO alone or in combination with SC increased (P < 0.05) the ratio of milk yield/DMI. Key words: Direct-fed microbials, Saccharomyces cerevisiae, Aspergillus oryzae, ruminal fermentation, milk production, beef, dairy cattle