Elżbieta Bogusławska-Wąs

The aim of this research was to assess the influence of partially substituting post-extraction soybean meal with distillers dried yeast on the efficiency of broiler chicken fattening and the intestinal microflora.I Inactive distillers dried yeast Saccharomyces cerevisiae, cultivated on wheat extract, was employed in the study. The research was conducted on 112 Ross 308 line cockerels subjected to a 35-day fattening period, during which they were fed Starter (days 1–10), Grower (days 11–27), and Finisher (days 28–35) diets. Broiler chickens were randomly divided into four groups: control and three experimental groups with varying levels of distillers dried yeast—3%, 6%, and 9%. Cockerels in the control group (Starter diet) exhibited higher feed consumption compared to those receiving 3% yeast in their diet. Cockerels in the group receiving 3% yeast (Grower diet) demonstrated better feed conversion compared to those receiving 9% yeast in their diet. The study revealed that regardless of the broiler chicken fattening period, there was a decrease in the overall number of isolated microorganisms in the feces with an increase in the proportion of distillers dried yeast in the diet. This was confirmed by the total number of bacteria, anaerobic bacteria, Enterobacteriaceae, E. coli, Enterococcus sp., and S. aureus. Based on cluster analysis (dendrogram), it was observed that only a 9% addition of yeast to the diet significantly influenced the quantitative and qualitative composition of the fecal microbiota of broiler chickens. In summary, a properly balanced feed with distillery yeast can be used as a good source of energy and protein in feed mixtures for broilers, serving as a cost-effective alternative to soybean meal. However, for optimal production results and feed costs, the inclusion of yeast in the feed should not exceed 3%.