The Effects of Reduced Glutathione on Growth Performance, Intestinal Inflammation, and Gut Microbiota in Immune-Stressed Broiler Chickens

In intensive farming systems, broilers are exposed to various stressors that trigger immune stress. Reduced glutathione is known to play a crucial role in modulating immune function. This study investigated the effects of different doses of reduced glutathione on the growth performance, intestinal immune function, and gut microbiota of broilers under immune stress. One-day-old broilers were randomly assigned to five groups: group K (control), group L (lipopolysaccharide), and three glutathione supplementation groups, Y1 (50 mg/kg), Y2 (100 mg/kg), and Y3 (200 mg/kg). Each group had four replicates, with 11 broilers per replicate. On days 16, 18, and 20, broilers in groups L and Y1-Y3 received intraperitoneal injections of 0.5 mg/kg of lipopolysaccharide, while group K received an equal volume of saline. On day 16, the average daily weight gain and final body weight of group Y3 were significantly higher than those of groups K and L, whereas on day 21, the average daily weight gain of group Y3 was still significantly higher than that of group L. On day 21 broilers were slaughtered, and samples were collected. In the jejunal mucosa, group Y3 showed significantly reduced levels of IL-2, IL-4, IL-1β, and TNF-α compared to group L. Additionally, group Y3 exhibited reduced relative expression levels of <i>NF-κB</i>, <i>TLR4</i>, <i>IFN-γ</i>, <i>IL-1β</i>, <i>IL-6</i>, <i>IL-4</i>, <i>TNF-α</i>, and <i>IL-2</i> mRNA; a decreased abundance of <i>Enterococcus</i>, <i>Proteobacteria</i>, and <i>Actinobacteria</i>; and a restored abundance of <i>Ligilactobacillus</i>, <i>Turicibacter</i>, and <i>Firmicutes</i> to normal levels. These findings suggest that 200 mg/kg of reduced glutathione is the optimal dose for improving the gut microbiota composition and mitigating gut damage caused by immune stress by inhibiting the <i>TLR4/NF-κB</i> signaling pathway.