RESUMEN
The purpose of this research was to evaluate the effects of apple cider vinegar in diet on the growth performance, immune response, histomorphological changes of the small intestine and some serum biochemical factors in broilers. A total of 85 broiler chicks of Ross 308 were purchased and 64 well-conditioned chicks were selected and divided into four experimental groups with four replicates and four chicks per replicate. The diets of groups 2, 3 and 4 were mixed with 1, 2 and 3% of vinegar, respectively, and group 1 as the control group was fed by the standard diet. The results showed that body weight gain was higher in the groups fed vinegar than the control group. There were no significant changes in the feed conversion ratio between the treatment and control groups (p = .507). Vinegar intake through the diet did not change significantly the weight of Bursa of Fabricius (p = .369) and spleen (p = .122). Vinegar significantly reduced blood urea nitrogen levels in the treatment groups compared with the control group (p = .0052). There was a significant increase in the level of antibody titre against Newcastle disease virus by haemagglutination inhibition test in the groups receiving vinegar in comparison with control group (p = .0358). Compared with the control group, the villus height (p = .0022) and intestinal crypts depth (p = .0015) significantly increased in the groups receiving apple cider vinegar. In conclusion, dietary supplementation with apple cider vinegar has beneficial effects on performance, immune response and small intestine histomorphology in broilers.