ABSTRACT The present study aimed to evaluate the influence of various levels of synbiotics on growth performance and intestinal morphology of fast-growing broilers during different phases. A total of 720, one-day-old straight run broilers (Ross 308) were randomly divided into 12 treatment groups according to a completely randomized design having three supplemented diets of synbiotics (a combination of probiotics and prebiotics) (0.5, 1, and 1.5%) reared at four phases [starter (1-11 days), grower (12-22 days), finisher (23-35 days), whole life (1-35 days)]. Every treatment was replicated six times with ten birds each. The parameters were evaluated in growth performance (feed intake, body weight, feed conversion ratio, and mortality) and intestinal morphology (Villus height, Crypt depth and Villus to Crypt ratio). Results of the present study revealed that growth performance, feed intake (p=0.0029), body weight (p=0.0001) and feed conversion ratio (p=0.0001) were improved with 1 percent synbiotics diet supplementation,while1.5 percent synbiotics level showed lower body weight. Crypt death (p=0.0529) has been marginally greater in the whole life. It can be inferred that a 1 % synbiotics supplemented diet has had a beneficial impact on growth and gut health throughout life.

ABSTRACT The aim of the present study was to investigate the influence of different growth promoters on broiler performance and intestinal morphology reared under various stocking densities. A total of 900 day old (Ross-308) straight run broilers were randomly divided into fifteen treatment groups according to a completely randomized design. A 5 × 3 factorial arrangement of treatment was employed. Treatments were consisted of four growth promoters (antibiotics, prebiotics, probiotics, and symbiotics) and a control group with three stocking densities (0.046, 0.056, 0.065m2). Each treatment was replicated 6 times with 10 birds in each. Regarding growth performance, feed intake (p=0.0008), body weight (p=0.0085) and feed conversion ratio (p=0.0001) were improved with the supplementation of symbiotic in the diet whereas lower body weight was noted in the control group. In terms of intestinal morphology, villus height (p=0.0011) and villus to crypt ratio (p=0.0001) were significantly higher in the symbiotics treatment groupas compared to the control group. Moreover, birds reared under 0.065m2 stocking density showed improvement in body weight, feed conversion ratio and livability as compared to the other treatment groups. It can be concluded that the supplementation of symbiotics in the diet of commercial broiler reared under 0.065m2 stocking density had a positive influence on overall growth performance and intestinal morphology.