The effect of Saccharomyces cerevisiae on ruminal fermentation in dairy cows

This study presents the results of an experiment in which the effect of addition of a yeast culture (Saccharomyces cerevisiae, Strain 47) on rumen fermentation was studied in thirty-six dairy cows of Holstein breed. The animals were divided into one control and five experimental groups. Each group involved 6 individuals. The animals received a diet consisting of good maize silage with a higher dry matter content (16 kg), clover-grass haylage (l6 kg), meadow hay (3 kg) and supplementary feed mixture (7.5 kg). The rations were fed to cows as total mixed ration (TMR). In experimental groups, the yeast culture was added into the feed mixture in amounts of 2, 4, 6, 8, 10 g per day and animal. Samples of rumen fluid were taken perorally 3–4 hours after feeding. The obtained results indicated that the addition of a Saccharomyces cerevisiae SC-47 culture in recommended doses showed a positive effect on ruminal digestion. As compared with control, the addition of all aforementioned amounts of the yeast culture into the feeding ration resulted in all cases in a statistically significant (P < 0.01) decrease in pH and fluctuated near the lower limit of the reference values. As compared with control, the yeast culture supplementation showed a positive effect (P < 0.01) on production of volatile fatty acids (VFA) (127.6 vs. 84.0 mmol/l). The utilisation of ammonia was higher (P < 0.01) in experimental groups (8.12, resp. 8.68 mmol/l) than in controls (9.06 mmol/l). The difference in protozoa numbers in rumens of dairy cows in the control and experimental groups was statistically highly significantly (P < 0.01) different. There was a close relationship between the dose of yeast culture on the one hand and the VFA content and protozoa numbers on the other. The regression analysis of dependence of dependent variable (i.e. pH of rumen fluid) on the independent one (i.e. the dose of yeast culture) revealed only a slight degree of dependence (r = 0.671).