In ovo quercetin and vitamin E synergistically reprogram the cecal microbiome and host transcriptome to enhance thermotolerance and gut resilience in broiler chickens

In this study, we evaluated the effects of in ovo embryonic injection of quercetin (Q), vitamin E (VE), and their combination (Q+VE) on the cecal microbiome, immune-metabolic responses, and intestinal morphology of broiler chickens exposed to cyclic heat stress (HS) . At embryonic day 12 (E12), viable eggs (n = 500) were randomly allocated into five experimental groups (100 eggs per group), each with four replicates (25 eggs per replicate). The treatment groups were as follows: Negative Control (NC): 0.2 mL of sterile deionized water; Positive Control (PC): 2.5 mg of Lactobacillus-based probiotic in 0.2 mL volume; Quercetin (Q): 4.5 mg of quercetin hydrate (>=95% purity) in 0.2 mL solution; Vitamin E (VE): 0.1 mL of a 60.4 IU/mL vitamin E solution; and Quercetin + Vitamin E (Q+VE): 4.5 mg quercetin hydrate + 0.1 mL vitamin E solution. Comprehensive metagenomic and metatranscriptomic sequencing revealed that Q+VE significantly restructured the cecal microbiota by enriching beneficial phyla including Bacteroidota, Bacillota, and Bifidobacterium, while reducing HS-associated Clostridium species.