Illippangama, I.P.A.U.N.K.2021-03-242021-03-242016UWU/ANS/12/0016http://www.erepo.lib.uwu.ac.lk/bitstream/handle/123456789/6231/UWULD%20ANS%2012%200016-18042019085128.pdf?sequence=1&isAllowed=yAntibiotics are used in poultry industry as a growth promoter since late 1940s. However, due to public health concern on antimicrobial resistance, they were banned in the European Union devastating the European broiler industry. It was revealed later, necrotic enteritis caused by Clostridium perfringence is the cause of the economic damage. Thus, it is necessary to identify alternatives to antibiotics to withdraw them from animal feeds. Therefore, a study was conducted to determine the effects of Bacillus species as a probiotic on growth performance, meat quality traits and necrotic enteritis exposure in broiler chickens. C.perfringence inhibitory Bacillus species were identified in an in vitro study. Identified probiotics were then tested in vivo. Experimental diets were based on maize and soybean meal. Five dietary treatments were prepared by supplementing: i.no growth promoters ii.Bacillus licheniformis isolated from healthy poultry (>101°CFU/,,) iii.commercial probiotic preparation containing Bacillus species (>101°CFU/g), iv. a combination of Bacillus licheniformis, commercial probiotic, Lactobacillus spp. (>108CFU/g) and Saccharomyces spp. (105CFU/g) v.antibiotic (Zinc Bacitracin) into basal diet. The inclusion rate of growth promoters were 0.1 g/kg of basal diet. In fourth treatment all four probiotics combined at equal level: each at 0.025/0.1g of the combination. Each treatment replicated 6 times with 14 birds in each replicate pen. A total of 420, one-day-old broiler chicks (Cobb 500) were randomly assigned to the experimental design. The data were analysed with ANOVA and the Tukey's mean separation. Results revealed that when compare to birds fed without growth promoters, those fed with growth promoters, had higher (P>0.05) weight gain. Antibiotic and commercial probiotic fed ones had similar growth and feed conversion ratio: 2kg and 1.5, while the negative control had 1.8kg and 1.6 respectively. Antibody levels against alpha toxin were higher when fed without growth promoters compare to growth promoters supplemented indicating a aggravated C.perfringence infection. A better mouth feel, juiciness, texture and overall acceptance was identified in breast meat of broiler chickens fed the combination of probiotics compared to the breast meat from all other birds. In conclusion, Bacillus species incorporated probiotics can be used as an alternative to antibiotic growth promoters to gain similar growth performances and to better quality breastAneat. , ;words: Antibiotic, Bacillus species, Growth performance, Meat quality traits, Necrotic enteritisenAnimal Science Degree ProgrammeThesis