A Comparative Study of Formic Acid, Herbal Mixture and Spirulina Powder as Antibiotic Alternatives in Broiler Diets: Effects on Growth, Carcass Traits, Blood Biochemistry and Microbial Load

BACKGROUND: Restrictions on antibiotic growth promoters in poultry production have driven the search for safe, natural alternatives. Organic acids, herbal additives and spirulina are promising options due to their antimicrobial, antioxidant and growth-enhancing effects. OBJECTIVES: The purpose of this experiment was to evaluate the effects of formic acid (FAc), herbal mixture (HMX) and spirulina powder (SPI) as potential antibiotic alternatives in broiler diets, specifically examining their impact on growth, carcass characteristics, blood biochemistry and intestinal microbial count. METHODS: FAc/kg diet); T5 (2 g HMX/kg diet); T6 (3 g HMX/kg diet); T7 (0.5 g SPI/kg diet); and T8 (1 g SPI/kg diet). RESULTS: Significant differences were detected in daily body weight gain (DBWG) and live body weight (LBW), with the spirulina-treated groups (T7 and T8) showing the highest values. Also, significant influences on feed intake (FI), feed conversion ratio (FCR) and performance index (PI), with the HMX groups showing the most favourable FCR and the highest PI. Blood biochemistry and antioxidant markers were influenced by the HMX and SPI treatments. The SPI groups showed reduced liver enzyme levels, while the HMX groups demonstrated improved protein profiles and enhanced antioxidant enzyme activity. Microbial analysis revealed that FAc and HMX treatments led to a reduction in pathogenic bacteria, with T3, T4 and T5 showing the lowest levels of Escherichia coli and Salmonella. CONCLUSION: These results suggest that FAc, HMX and SPI are promising dietary supplements for enhancing both the broiler chickens' growth rates and general health.