The present study was conducted to investigate the effect of dietary supplementation of probiotic and drinking water (DW) supplemented with different levels of vinegar on performance, meat yields, immune responses, and small intestine histology of broiler chickens. Three hundred thirty day-old Ross 308 male broiler chicks assigned to six treatments in a completely randomised design experiment with a factorial arrangement (2×3) and five replicates of 11 chicks each. The treatments included two levels of dietary probiotic supplementation (zero and 1×1010 CFU lactic acid/kg of diet) and three levels (zero, 1 and 2%) of DW supplemented with vinegar (5% acetic acid concentration). The study lasted from 1-42 d. Growth performance, meat yields and lymphoid organs relative weight, humoral and cellular immune responses, and small intestine histomorphometry were measured. The average daily feed intake (ADFI) and feed conversion ratio (FCR) during 1-10 days of age significantly decreased in the birds that fed supplemented diet with probiotic and drunk supplemented water with vinegar than the birds fed and drunk free of any additive. Experimental treatments did not have a significant effect on performance during other growth periods, carcass yields, and lymphoid organs relative weight. Drinking water supplemented with vinegar significantly increased villus height (VH), crypt depth (CD) and decreased small intestine muscular thickness (MT) and abdominal fat. Dietary supplementation of probiotic significantly improved immune response to sheep red blood cell (SRBC) inoculation. In conclusion, this study confirms beneficial effects of probiotic and vinegar on 1- 10d performance, immune and intestine health of broiler chickens.

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