Effects of dietary fat type and xylanase supplementation to rye-based broiler diets on selected bacterial groups adhering to the intestinal epithelium, on transit time of feed, and on nutrient digestibility

Two experiments were conducted to examine the effects of different fat types, i.e., soybean oil (S) and beef tallow (T), in rye-based broiler diets, either unsupplemented (-) or supplemented (+) with xylanase (Avizyme 1300 at 1 g/kg diet), on selected bacterial groups adhering to the epithelium of crop, duodenum, jejunum, and ileum (Experiment 1, 16 d of age), on mean retention time (MRT) of digesta, and on digestibility of N and dry matter in successive segments of the digestive tract (Experiment 2, 24 d of age). Live weight of enzyme-treated and S-fed chickens was significantly higher than that for unsupplemented or T-fed birds, respectively, in both experiments. In Experiment 1, a reduction in bacterial colonization from crop to duodenum was followed by a continuous increase as far as the ileum. Xylanase supplementation significantly reduced enterobacteria and total anaerobe microbes with a similar trend for Gram-positive cocci and enterococci. The latter two groups were significantly enhanced in birds fed T. In Experiment 2, xylanase supplementation resulted in a decrease in MRT in several segments of the digestive tract. This effect was most pronounced in the small intestine, where MRT of 268, 217, 241, and 209 min in groups S-, S+, T-, and T+, respectively, were measured. Apparent digestibility of N and dry matter was slightly improved by xylanase supplementation in the jejunum and ileum. Nitrogen digestibility by the terminal ileum was 80.3, 83.7, 79.4, and 82.2% for the S-, S+, T-, and T+ groups, respectively, and dry matter digestibility amounted to 61.2, 65.5, 62.1, and 64.0%, respectively.