EN
The aim of the study was the comparison of performance, mortality and quality of the carcasses of the broiler chickens fed feed mixtures without antibacterial additives (CON), with the antibiotics Flavomycine (ANT) and fumaric (FUA) or formic (FOA) acids. Birds in experimental groups (FUA, FOA) were fed with the addition of lactic acid bacteria (LAB) and mannan oligosaccharide (MOS). The studies were carried out on 600 broilers of the ROSS breed (four groups, each group in two replications for 75 birds). The investigation shows that fumaric and formic acids significantly increased broiler body weight in comparison to the control and antibiotic groups (P ≤ 0.01). Bird mortality was 2.5%; 1.3%; 0.0% and 1.3%, respectively. Feed consumption increased, but feed conversion ratio decreased significantly in experimental groups (P ≤ 0.01). The European Index of Production (EPI-index) was increased significantly in the experimental groups (P ≤ 0.01). Fumaric and formic acids significantly increased carcass weight (P ≤ 0.01). There was no significant differences in the digestic tract and muscle of pH after broilers. slaughter. There was also no difference in dry matter, crude protein and fat content in breast muscles. Metabolic parameters of the serum were at an average level for young birds. Glucose levels for birds receiving antibiotics was higher than for the other birds. Fumaric and formic acid increased Enterococcus, Streptococcus and Lactobacillus bacteria in the small intestine, but Enterococcus and Lactobacillus bacteria in the cecum. A small number of Bacillus spp. and Proteus mirabilis were detected in the small intestine and cecum, while Salmonella, Shigella and Campylobacter were not detected in the cecum.