Role of Dietary Saccharomyces boulardii in Innate Immune Responses of Broiler Chickens Fed Diets Containing Different Nutrient Densities

The study was conducted to evaluate the influence of <i>Saccharomyces boulardii</i> (SB) supplementation on growth performance, meat quality, cecal volatile fatty acid (VFA) profile, immune parameters, and serum biochemistry in broiler chickens fed diets with varying nutrient densities. A total of 420 day-old male broiler chicks (Ross 308) were randomly allocated to 28 floor pens. A 2 × 2 factorial design was employed, with two factors: SB supplementation (none or 2.0 × 10¹⁰ CFU/ton), and optimal (OPT) and deficient nutrient density (DEF). The OPT diet significantly improved body weight gain and feed intake across all phases and enhanced the feed conversion ratio during the finisher and overall periods compared to the DEF diet (<i>p</i> < 0.05). However, SB supplementation decreased body weight gain during the starter and overall periods (<i>p</i> < 0.05). Serum levels of glutamic-oxaloacetic transaminase, glutamic-pyruvic transaminase, and triglyceride were elevated in chickens fed the OPT diet (<i>p</i> < 0.05). While SB supplementation did not affect meat quality or cecal VFA profiles, it interacted with nutrient density to influence alpha-1-acid glycoprotein and interferon-gamma concentrations in serum samples (<i>p</i> < 0.05). In conclusion, dietary supplementation with <i>S. boulardii</i> did not affect growth performance in broiler chickens regardless of nutrient density levels. However, it interacted with nutrient density to modulate the innate immune markers suggesting the immune-modulating role of <i>S. boulardii</i> in chickens.