Effect of fermented soybean meal supplementation and birth weight of broiler on performance, hematochemical parameters, and lactic acid bacteria composition under tropical conditions.

Fermented soybean meal (FSBM) is considered a potential protein source, yet its efficacy under tropical conditions requires further investigation. This study evaluated the effects of fermented soybean meal supplementation and initial body weight on growth performance, gut environment, and hematochemical parameters of broiler chickens raised under tropical conditions. A total of 1,080 male Ross 308 broilers were categorized into two hatch weight groups high (43 g) and low (33 g). Birds within each weight category were randomly assigned to diets containing 0%, 2.5%, or 5% FSBM during the starter phase (1-21 d) in a 2 × 3 factorial design. Performance data, gut health markers (lactic acid bacteria populations, cecal pH), and hematochemical profiles were analyzed. Dietary supplementation with 2.5% FSBM significantly (P < 0.05) improved overall average daily gain and feed conversion ratio compared with the control group, while the 5% inclusion level yield intermediate results. Although initial body weight significantly (P < 0.05) affected early growth performance, birds in the low weight group demonstrated compensatory growth during the finisher phase, resulting in comparable final performance between hatch weight groups. Furthermore, FSBM supplementation significantly (P < 0.05) increased lactic acid bacteria populations in both fecal and cecal samples from day 10 to day 36, accompanied by a reduction in cecal pH, indicating a more favorable intestinal environment. Fecal scores remained within acceptable ranges; however, the 5% inclusion level caused a transient increase in fecal moisture during the first week. Hematochemical parameters remained within normal physiological ranges across all treatments, indicating that FSBM supplementation did not adversely affect bird health. In conclusion, supplementation with 2.5% FSBM during the starter phase improves growth performance, enhances beneficial gut microbiota, and maintains physiological health in broilers raised under tropical conditions. These findings suggest that FSBM can be utilized as an effective nutritional strategy to improve productivity and intestinal health in tropical broiler production systems.