Effects of an Organic Acid Blend on Growth Performance, Redox Homeostasis, and Intestinal Microbiota of Broilers in an Antibiotic‐Free Production System Under Winter Environmental Challenges

ABSTRACT This study was conducted to evaluate the effects of an organic acid blend on growth performance, redox homeostasis, and intestinal microbiota of broilers raised in an antibiotic‐free system during the winter season in China, with low ambient temperatures and reduced ventilation. A total of 1080 1‐day‐old male broilers were randomly assigned to one of three treatment groups, with 18 replicates of 20 broilers each. All broilers were fed the same basal diet and provided either water (control, CON), water with antibiotics (ABx), or water with an organic acid blend (OA) for 5 weeks. The results showed that both ABx (+2.69–2.75%) and OA (+2.95–3.98%) treatments significantly increased body weight gain from Days 1 to 35 and body weight on Day 35 compared to the CON group. OA treatment also upregulated the mRNA expression of key immune‐related markers in the jejunum, including cytokines and transcription factors (IL‐1β and NF‐κB), tight junction proteins (ZO‐1 and occludin), and host defense peptides (AvBD‐1 and cathelicidin‐1). Furthermore, OA treatment significantly reduced serum LPS concentrations ( p < 0.05). Microbial analysis using principal coordinates analysis (PCoA) revealed significant differentiation ( p < 0.05) between the CON and the ABx or OA groups. LEfSe analysis identified 22 discriminative microbial features across the groups. Both ABx and OA treatments significantly increased the abundance of Intestinimonas , Bryobacter , and Rhodanobacter compared to the CON group. Additionally, ABx treatment significantly increased Lachnospiraceae FCS020, whereas OA treatment significantly increased Lachnospiraceae NK4A136 compared to ABx, with no significant difference observed compared to the CON group. In conclusion, the organic acid blend positively influenced broiler growth performance and microbial composition, suggesting its potential as a viable alternative to antibiotics for promoting growth and health in antibiotic‐free production systems.