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 Sacchar omyces cerevisiae (SC) and Aspergillus oryzae (AO) to ruminant diets w as examined in two experiments. Experiment 1 was designed to study the effects of microbial supplements on ruminal and total tract digestibi lity, ruminal fermentation, bacterial counts and bacterial colonizatio n of fibrous feed, in eight ruminally cannulated steers. The steers we re used in a factorial arrangement within a replicated, concurrently r un 4 x 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 h ead(-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 i n combination with SC, stimulated (P < 0.10) ruminal fermentation with higher concentrations of acetate (P < 0.01), propionate (P = 0.07), a nd total VFA (P < 0.01) when sampled prior to feeding. Accordingly, ru minal pH was lower (P < 0.01) in animals receiving AO, alone or combin ed 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 digestibil ity. The addition of direct-fed microbials did not affect bacterial co unts or bacterial colonization of roughage in the rumen. Milk yield, m ilk composition and feed intake were not affected by the addition of S C 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.