| Three experiments were designed in this study to investigate the effect of different doses and different components of bacilli (Bacillus licheniformis 19 and Bacillus licheniformis 15, abbreviated as BL19 and BL15) on growth performance, apparent digestibility of energy and crude protein, immune function and gastrointestinal microbial population of yellow chickens and propagation rate of bacilli in crop and in ileum.In experiment one, 150 yellow chickens (1 day old) were divided into five treatments (the doses of viable bacilli were 0, 105cfu/g, 10bcfu/g, 107cfu/g, 108cfu/g separately), and each treatment included 3 replication. The main goals of this experiment was to investigate the effect of the different doses of bacilli on growth performance, apparent digestibility of energy and crude protein, immune function and gastrointestinal microbial population of yellow chickens. The results were as follows:1. Viable bacilli increased the growth.performance of yellow chicken. In 107cfu/g treatment, the end weight (EW) increased by 6. 76%, average daily gain (ADG) increased by 7. 25%, feed consumed/gain dropped by 5. 28%, but the feed intake did not change significantly. None of the viable bacilli treatments improved apparent digestibility of crude protein in crop or ileum and all the viable bacilli treatments improved apparent digestibility of energy in crop or ileum. And in 107cfu/g treatment, the apparent digestibility of energy in crop and in ileum improved 51.87% and 7.68%, respectively.2. There was a linear relationship between total bacilli in feed and that in crop or between total bacilli in feed and that in ileum (P<0.05). And the total bacilli increased in crop and in ileum when the number of bacilli was increased in feed. Bacilli (total bacilli, spore, vegetative cell) proliferated in crop. The propagation rate of bacilli in crop dropped when the dose of feed improved. It also shows that when the dose of bacilli in feed changes one unit (106cfu/g), growth performance (EW, ADG and F/G) and immune function will change 0.2%-0. 3%. The number of lactobacilliin crop dropped markedly when viable bacilli were added in feed, but the number of lactobacilli in ileum did not change. No treatments influenced the number of coliform in crop and all treatment increased the number of coliform in ileum several times.3. Viable bacilli did not change the concentration of IgA, IgM and IgG (P>0.05) and increased bursa of fabricius index, thymus index, spleen index and the antibody titers to New Castle Disease Virus (NDV).In experiment two, 180 yellow chickens (1 day old) were divided into six treatments, and each treatment included 3 replications. The main goals of this experiments was to investigate the effect of the different components of bacilli on growth performance, apparent digestibility of energy and crude protein, immune function and gastrointestinal microbial population of yellow chickens. The results were as follows:1. The different components of bacilli increased the growth performance of yellow chicken. In the higher nonviable bacilli treatment, EW increased by 4.92%, ADG increased by 4. 92%, feed consumed/gain dropped by 4. 0%, and feed intake almost was the same. In metabolite treatment, EW increased by 4.92%, ADG increased by 4.08%, feed consumed/gain dropped by 3. 48%, the feed intake did not change markedly. At the same dose, the effect of viable was better than nonviable and the effect of nonviable was better than metabolite on the growth performance. None of nonviable bacilli and metabolite can improve the apparent digestibility of energy in crop or in ileum. Although nonviable bacilli and metabolite did not improve apparent digestibility of energy in crop, they improved the apparent digestibility of energy in ileum. The higher and the lower nonviable bacilli improved 6.06% and 6.69%, respectively, and metabolite improved 4.47%. From above results we can conclude that the effect of viable bacilli was better than nonviable bacilli and metabolite of bacilli on improvement of apparent digesti...
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