Biotechnological Feed Additives: Alternatives to Antibiotics as Growth Promoters in Broiler Chicken Farming

Abstract

The restriction of antibiotic growth promoters in poultry production has grown due to concerns about antimicrobial resistance and food safety. Phytogenic and probiotic feed additives are considered promising candidates for modulating gut health, immune responses, and growth performance in broiler chickens. The present study aimed to assess the effects of dietary supplementation with the probiotic Kluyveromyces marxianus strain (KluActive), either alone or in combination with encapsulated hydrolyzable tannins, on innate immune responses and growth performance in antibiotic-free-fed broiler chickens. Sixty broiler chickens, each 15 days old at the start, were used in a 27-day experiment. Broiler chickens were randomly assigned to four dietary treatments, including a control group fed a standard antibiotic-free diet (G1), a group that was fed the standard diet with KluActive at 0.04% (G2), and two groups fed a combination of KluActive with encapsulated tannins at 0.04% (G3) and 0.06% (G4). Phagocytic activity, phagocytic index, phagocytic number, serum bactericidal activity, and serum lysozyme activity were assessed on days 28 and 42. Growth performance parameters, including average daily gain and average body weight gain, were recorded over 42 days. Supplementation with the probiotic and tannins enhanced selected serum innate immune parameters in broiler chickens. In particular, serum bactericidal activity was significantly increased at the higher inclusion level (0.6%), by 12.5% on day 28 and 16.7% on day 42 compared with the control group. Phagocytic activity parameters were consistently elevated in broiler chickens across all experimental groups. The best improvement in feed conversion ratio was observed in the G3 group. The current findings indicated that probiotic-tannin combinations were a promising nutritional alternative to enhance immune function and performance in antibiotic-free broiler chicken production.