Abstract

Objective: This experiment was conducted to investigate and compare the effects of probiotic supplements containing Bacillus subtilis and Enterococcus faecium on growth performance, intestinal morphology, and gastrointestinal microbial population of Arian strain broiler chickens. Given the benefits of adding probiotic supplements to the diet, a more detailed understanding of the mechanisms of action and comparative effects of these two probiotics can lead to targeted diet adjustment to improve feed efficiency, body weight gain, and reduce disease incidence in Arian strain broiler chickens.

Method: In this study, 500 mixed-sex Arian broiler chicks were utilized in a Completely Randomized Design (CRD) consisting of five experimental treatments and five replicates, with 20 chicks per replicate, from day 1 to 42 of age. The experimental treatments were as follows: (1) Control (corn-soybean meal-based diet without additives); (2) Control + Lincomycin antibiotic (500 mg/kg diet); (3) Control + Probiotic Supplement A (1 g/kg diet containing Bacillus subtilis and Bacillus licheniformis); (4) Control + Probiotic Supplement B (1 g/kg diet containing Lactobacillus spp. and Enterococcus faecium); and (5) Probiotic Supplement C (1 g/kg diet containing Saccharomyces cerevisiae yeast). The 42-day rearing period was conducted in three phases using diets formulated according to the Arian breed nutritional guidelines. On day 38, blood serum biochemical parameters were analyzed. On day 42, jejunal histological indices, including villus height, villus width, crypt depth, villus-to-crypt ratio, and absorptive surface area, were measured. Total bacterial count, lactic acid bacteria (LAB), Escherichia coli, and coliform populations in the feces were determined using the drop plate method.

Results: Birds receiving Lincomycin and probiotic supplements A and B exhibited significantly higher live body weight compared to the control group (P>0.05). The effect of experimental treatments on feed intake was not significant. The feed conversion ratio (FCR) was significantly lower in birds fed diets supplemented with either Lincomycin or probiotics than in the control group (P>0.05). Relative ileal length was significantly increased in probiotic-supplemented birds compared to the Lincomycin treatment group (P>0.05). Regarding small intestine morphology, the relative jejunal weight was higher in the Lincomycin group and lower in the group receiving probiotic supplement B (P>0.05). Crypt depth was highest in the Lincomycin-treated birds and lowest in those receiving probiotic supplements A and B (P>0.05). Furthermore, the addition of Lincomycin and probiotic supplement B significantly reduced the total aerobic bacterial count in the small intestine (P>0.05).

Conclusions: The results demonstrated that probiotic supplements containing Bacillus subtilis and Enterococcus faecium improved the growth performance of broiler chickens by enhancing body weight, feed conversion ratio, and intestinal morphological indices. Consequently, these probiotics could serve as effective alternatives to antibiotic growth promoters.