A total of 608 Ross 308 broiler chickens of both sexes were studied to determine the effect of Lactococcus lactis 847 bacteria compared to probiotic bacteria Lactobacillus delbruecki 838 and Lactobacillus plantarum 837 on body weight, feed consumption and conversion, mortality, dressing percentage, postmortem carcass traits, composition of breast muscle tissue, and blood plasma traits. Feeding diets with bacteria to chickens did not increase body weight at 42 days of age or improve feed conversion compared to control chickens. It significantly reduced chicken mortality compared to the control group, from 3.3% to 1.4% (P<0.01). No significant differences were found in feed consumption and conversion. There were no significant differences in the weight of carcasses and their parts. Lactococcus lactis 847 and Lactobacillus plantarum 837 bacteria significantly increased dressing percentage (P<0.05). Lactococcus lactis 847 significantly increased liver weight (P<0.05). No significant differences were observed in carcass fatness, and in the dry matter, protein and fat content of breast muscles. Feeding diet with Lactobacillus plantarum 837 to chickens significantly decreased plasma triglyceride levels, and feeding diet with Lactobacillus delbruecki 838 and Lactobacillus plantarum 837 significantly decreased the level of high-density cholesterol (P<0.05). In conclusion, Lactococcus lactis 847 bacteria in diet significantly reduce losses due to digestive disorders while having no effect on the quantity and proportion of saleable cuts in the carcass, the composition of breast muscles and basic blood parameters.
