LAUSR

ABSTRACT The experiment aimed to investigate the effects of probiotic (Bacillus subtilis KMP-BCP-1 and Bacillus licheniformis KMP-9) supplementation on growth performance, ileal digestibility, jejunal histomorphology, colonic ammonia-nitrogen (NH3-N) and blood parameters in broiler chickens. A total of 288, one-day-old female Ross-308 broilers were randomly allotted into 4 treatments with 6 replicates of 12 birds. Treatments were (T1) basal diet (BD), (T2) BD with 200 ppm amoxicillin, (T3) and (T4) BD with probiotics at the levels of 2.5 × 107 and 5.0 × 107 cfu/kg feed, respectively. Supplementation of amoxicillin or probiotics improved (P < 0.05) average daily gain (ADG) and feed conversion ratio (FCR) on d 42. Compared to those fed with T1, broilers fed with T4 increased (P < 0.05) the ratio of jejunal villus height to crypt depth, and improved (P < 0.05) ileal digestibility of dry matter and protein. They also had the highest numbers of lactic acid bacteria (LAB) and Bacillus spp. as well as the ratio of LAB to Escherichia coli (P < 0.05). Probiotics at the level of 5.0 × 107 cfu/kg feed improved the growth performance of broilers in a tropical region by enhancing the balance of caecal bacteria, jejunal histomorphology and ileal digestibility.