SUMMARY

Background. Due to the harmful effects resulting from the addition of antibiotics to treat diseases affecting poultry and their use as growth promoter, it was necessary to have safe alternatives such as organic acids and probiotics, which work to provide an appropriate pH for activity of beneficial bacteria and reducing the numbers of harmful pathogenic bacteria. Objective. To assess the effects of dietary supplementation of probiotics, with or without organic acids (acetic, propionic, and benzoic) on growth performance, carcass quality, digestibility, intestinal development, gut microbiota, and serum parameters of broiler chicks. Methodology. A total number of 250 one-day old, unsexed Ross (308) broiler chicks, were equally assigned to five feeding treatments (50 birds/treatment, five replicates of ten birds/treatment) as follows: T1 (control); fed a basal diet (BD), T2; fed BD + 2g commercial probiotics (PRO)/kg diet, T3: fed BD + 2g PRO/ kg diet + 10 ml acetic acid/kg diet, T4: fed BD + 2g PRO/kg diet + 10 ml propionic acid/ kg diet, and T5: fed BD + 2g PRO/ kg diet + 10 ml benzoic acid / kg diet. The trial prolonged from day 1 to day 42 of age. Results. Compared to the control, the results revealed that body weight and body weight gain were significantly improved at 3 and 6 wks of age as a result of supplementing the diets with probiotics and organic acids (especially benzoic acid). The positive impacts of the supplements on FCR were more pronounced from 4-6 weeks and for the overall period (0-6 wks). No mortalities occurred when organic acids were supplemented. The tested supplements also decreased bacterial counts of ileal E. coli. Moreover, probiotics plus benzoic acid treatment (T5) significantly (P < 0.05) increased the ileal lactobacilli count. Carcass traits, internal organs and GIT histological parameters were positively affected by different treatments, especially probiotics plus benzoic acid treatment. The supplements improved ALT, AST and ALP activity and decreased cholesterol and triglycerides content in blood serum (P <0.05). Implications. The study showed that the addition of organic acids to probiotics led to an increase in the lactobacilli count. Conclusions. The tested feed supplements displayed beneficial impacts and positive role on broilers productive performance and improved their gut health and function through enhancement of the intestinal microbiota.