Dietary grape pomace mitigates high-NSP-induced inflammation and production loss via microbiome-SCFA-immune mediated pathways

The United States poultry industry is transitioning away from antibiotic growth promoters (AGP) to antibiotic-free programs, which may increase the risk of chronic intestinal inflammation due to exposure to multiple factors. Grape pomace (GP), a polyphenol-rich by-product, might be a promising candidate for mitigating such inflammation. This study investigated the fermented and non-fermented GP as potential substitutes for antibiotic growth promoters in broilers. A total of 126 broilers were divided into six treatment groups: (i) standard diet (STD), (ii) high non-starch polysaccharide diet (NSP), (iii) NSP + zinc bacitracin (AGP), (iv) NSP + 0.5% GP (GP), (v) NSP + 0.5% Lactobacillus casei fermented GP (LAB FGP), and (vi) NSP + 0.5% Saccharomyces cerevisiae fermented GP (YST FGP). NSP-fed birds exhibited reduced growth and increased TNF-α and IL-1β expression, indicating chronic inflammation. GP and FGP suppressed cytokine expression, modulated microbial homeostasis, and increased butyrate production, suggesting functional modulation of the cecal microbiome. Exploratory correlation identified the Lactobacillaceae-butyrate-IL-1β pathway, positively associated with growth, microbiome, and SCFA production, and negatively associated with inflammation. Overall, incorporating 0.5% of GP or FGP into the diet may serve as an effective alternative to AGPs in broiler production, with the added benefits of antioxidants and prebiotics.