EFFECTS OF PROBIOTICS BACILLUS SUBTILIS AND BACILLUS LICHENIFORMIS SUPPLEMENTATION ON GROWTH PERFORMANCE, NUTRIENT DIGESTIBILITY, CECAL MICROBIOTA AND SMALL INTESTINAL MORPHOLOGY IN BROILERS.
Abstract:
The experiment aims to investigate the effects of supplementing probiotics (Bacillus subtilis and Bacillus licheniformis) on growth performance, ileal digestibility, cecal microbiota and small intestinal morphology in broilers. Two hundred and eighty-eight, day-old female Ross-308 broiler chicks were randomly allotted to 4 treatments with six replicates of 12 birds on the basis of equal average BW in a completely randomized design. Dietary treatments were T1) basal diet (control), T2) basal diet supplemented with 200 ppm Amoxycillin, T3) basal diet supplemented with Bacillus subtilis and Bacillus licheniformis at the level of 2.5 x 107 CFU/kg feed and T4) basal diet supplemented with Bacillus subtilis and Bacillus licheniformis at the level of 5 x 107 CFU/kg feed. Jejunum was collected to investigate small intestinal morphology. In addition, growth performance, ileal digestibility, cecal microbiota and pH in jejunum were determined. Supplementation of Amoxycillin (T2) and probiotics (T3 and T4) improved (P < 0.05) average daily gain and feed conversion ratio but there was no significant difference in average daily feed intake (P>0.05) at d 42. Diet contained probiotics at the level of 5x107 CFU/kg feed increased ileal dry matter and protein digestibility (P<0.05). In addition, there was no difference in ileal fat digestibility among groups (P>0.05). At d 21 birds supplemented with Bacillus subtilis and Bacillus licheniformis in both groups showed the higher numbers of caecal Lactic acid bacteria and Lactobacillus: E. coli ratio. Moreover, at d 42 birds supplemented with probiotics at the level of 5x107 CFU/kg feed higher numbers of caecal Lactic acid bacteria, Bacillus spp and Lactobacillus: E. coli ratio in T3 and T4. In addition, caecal E. coli count was decreased (P< 0.05) in broilers fed diet supplemented with probiotics at the level of 5x107 CFU/kg feed. However, Salmonella spp. was not detected in all groups. Birds supplemented with the probiotics in both groups had higher villus height (P<0.05) than other groups. Moreover, supplementation of probiotics at the level of 5x107 CFU/kg feed increased (P < 0.05) villus height to crypt depth ratio in jejunum. No significant difference was detected (P> 0.05) for pH in jejunum. In conclusion, diets composed of probiotics (Bacillus subtilis and Bacillus licheniformis) at the level of 5x107 CFU/kg feed improve the balance of intestinal microbiota, small intestinal morphology and ileal digestibility. Moreover, there was no significant difference in growth performance between probiotics at both levels.