Supplementation of heat-killed probiotics mixture improves intestinal morphology, antioxidant capacity, and meat quality in broilers

Probiotics are widely used to improve intestinal health and production performance in the poultry industry. However, few studies have explored the effects of heat-killed probiotics. This study investigated the effects of a heat-killed probiotic mixture, comprising Bacillus subtilis (BS) and Lactobacillus plantarum 28 (LP28), on the growth performance, intestinal morphology, antioxidant capacity, and meat quality of broilers. A total of 300 Arbor Acres chicks were randomly assigned to four treatment groups (three replicates per group; 25 chicks per replicate): CON (basal diet), AB (basal diet + 10 ppm enramycin), LDP (basal diet + heat-killed LP28 and BS, 1.0 × 10⁸ cells/kg each), and HDP (basal diet + heat-killed LP28 and BS, 1.0 × 10⁹ cells/kg each). Feed intake was recorded daily, and body weight was recorded at the end of each growth phase. Twelve birds per treatment were used for intestinal morphology and antioxidant capacity analyses, and eight birds were used for meat quality analysis on day 35. One-way ANOVA followed by Tukey test was performed to perform statistical comparison among groups at p < 0.05. No significant intergroup difference was observed in growth performance. However, villus height and crypt depth were higher in the HDP group than in the CON and LDP groups (p < 0.05). The HDP group exhibited a stronger antioxidant capacity, higher hepatic glutathione peroxidase levels in the liver, and lower thiobarbituric acid reactive substance levels in breast meat than did the CON group (p < 0.05). The HDP group also exhibited better meat quality with lower shear force and higher gumminess and chewiness than did the CON group (p < 0.05). In summary, heat-killed probiotics may improve the intestinal morphology, antioxidant capacity, and meat quality of broilers and can be utilized in the poultry industry.