INFLUENCE OF XYLANASE-SUPPLEMENTED FEED ON THE DEVELOPMENT OF SELECTED BACTERIAL GROUPS IN THE INTESTINAL-TRACT OF BROILER CHICKS

The colonization of Lactobacillus spp., enterobacteria and facultative ly anaerobic gram-positive cocci was monitored in intestinal samples o f growing broiler chicks from 24 h to 28 days of age. Rapid bacterial growth occurred within the first week, followed by stabilization and d ecline of colony forming units (CFU). Xylanase supplementation led to significantly lower CFU per gram of wet weight for total presumptive e nterobacteria and total gram-positive cocci in luminal and tissue samp les in the first 3 weeks. Lactobacillus spp. colony counts from tissue samples were higher for animals with the xylanase-supplemented diet, but luminal CFU were not. The composition of dominant Lactobacillus sp p. strains was different in duodenal and jejunal tissues, but distribu tion of Lactobacillus spp. colony forms was unaffected by xylanase tre atment. Mucosa-associated Enterococcus spp, displaced the dominant gra m-positive cocci in the jejunal samples. D- and L-lactic acid and acet ic acid concentrations were significantly higher in ileal samples from the control group on days 7 and 14, while butyric acid concentrations were higher in the xylanase-treated group. It is concluded that the l ess viscous intestinal environment caused by the xylanase slowed proli feration of gram-positive cocci and presumptive enterobacteria in enzy me-supplemented animals in the first 3 weeks of life.