Effects of dry sugar cane yeast on the diet intake, digestibility and bovine rumen microbial populations

The objective of this research was to evaluate the effect of the dry sugar cane yeast (DSCY) protein addition on the intake, digestibility and rumen microbial population (bacteria, protozoa, and fungi) in zebu steers fed cotton seed processing residue (CSPR). Six Nellore steers, with rumen and duodenal cannulae were used. Data were analyzed according to a randomized block design, each one with three treatments: 0.0, 4.0 and 8.0% of DSCY as a percentage of supplied dietary dry matter. Parameters evaluated were: intake, digestibility and ruminal protozoa populations. In addition, the most probable numbers of rumen fungal and bacteria populations were estimated. The DM, OM, EE, NDF and ADF intakes and digestibilities were not influenced by different levels of DSCY, possibly because of the high value of the nitrogen C fraction of the CSPR (44.5% DM). Low levels of undegradable protein fraction from yeast did not provide an expected optimized synchronization energy/nitrogen in order to enhance the degradation rate. The presence of 4.0% DSCY in the diet significantly reduced fungal rumen population. There were no significant changes in fungal populations between the 4.0% and the 8.0% treatments. However, bacterial populations showed an increase when submitted to 8.0% DSCY compared to 4.0% in the diet. Protozoal populations did not vary significantly among the treatments. It was concluded that supplementation of DSCY to zebu steers did not affect the intake, digestibility and microbiological rumen populations.