Efficacy of natural alternatives to antibiotic on the growth performance, gut microbial population, intestinal morphology, and serum biochemical metabolites of broiler chickens

The present study investigated the effects of different feed additives on growth performance, carcass characteristics, gut microbial population, intestinal morphology, and blood metabolites of broiler chickens. A total of 540, day-old Ross 308 male chicks were randomly distributed into 6 dietary treatments with 6 replicate pens per treatment for 35 days. The birds fed on a basal diet without feed additive (CON) or the basal diet supplemented with 0.25 g/kg antibiotic as growth promoter (AGP), 1 g/kg essential oils (EO), 1.7 g/kg synbiotic (SYN), 3 g/kg medium-chain fatty acids (MCFA), and 1 mL/L essential oils in drinking water (EOW). The additives improved the body weight gain (p = .004) and feed conversion ratio (p = .02) compared to the CON group during the whole trial. The serum concentration of cholesterol was lower in the birds fed the MCFA diet and serum concentration of low-density lipoprotein cholesterol (LDL) decreased in MCFA and SYN groups. The relative weight of spleen was the greatest in MCFA group (p = .01). Feeding birds diets containing different additives decreased the population of coliform (p = .002) and Clostridium perfringens (p = .01) while Lactobacillus population was greater in broilers offered EOW, SYN, and MCFA supplements (p = .02). The jejunal villus height enhanced in the broiler chickens which received AGP and MCFA additives (p = .008). It is concluded that EOW, SYN, MCFA, and EO as alternatives for AGP improved the growth performance and intestinal morphometric indices and reduced the caecal pathogenic bacteria in broiler chickens.Highlights Adding MCFA to diet and EO to the drinking water improved BWG and FCR in broiler chickens. Dietary supplementation of MCFA decreased serum total cholesterol, increased caecal LAB population, and improved intestinal villus height. All supplements as AGP alternatives had beneficial effects on suppressing the pathogenic bacteria.