Dose-dependent effects of hydrolysed yeast on gut microbial diversity, growth performance, antioxidant activity, and meat quality in densely stocked broilers
The search for effective alternatives to antibiotic growth promoters (AGP) has intensified due to increasing concerns regarding antimicrobial resistance and antibiotic residues in poultry products. Hydrolyzed yeast (HY) has emerged as a promising functional feed additive with potential benefits for growth performance, immune function, and product quality in broilers. This study evaluated the effects of graded dietary HY supplementation on growth performance, carcass characteristics, meat quality, oxidative stability, and gut microbial diversity in broilers reared under high stocking density. A total of 900 one-week-old male Ross 308 broilers were randomly allocated to 36 pens stocked at 25 birds per 1.2 meter squared. Birds were fed a standard diet without AGP (NCON), with 0.05 percent AGP (PCON), or NCON supplemented with 0.025 percent (HY25), 0.05 percent (HY50), 0.075 percent (HY75), or 0.1 percent HY (HY100). HY100 increased body weight gain during the starter phase, while HY25 improved body weight gain and feed conversion ratio during the finisher phase. Across the experimental period, HY supplementation enhanced breast muscle yield, and HY100 increased dressing percentage. Quadratic responses were observed for breast pH and thigh yellowness, whereas water-holding capacity and cooking loss were unaffected. HY supplementation reduced malondialdehyde concentrations without altering gut microbial diversity. Overall, low to moderate HY inclusion improved performance and carcass traits, supporting its potential as an AGP alternative under high stocking density conditions