Lactobacillus plantarum 4-2 alleviates cyclic heat stress-induced oxidative stress and damage in the ileum of laying hens via Keap1-Nrf2 pathway

The frequency and severity of heat stress in livestock production are increasing due to intensive farming practices and rising global temperatures. Due to the lack of sweat glands, poultry are highly susceptible to heat stress, especially in the intestinal tract. Therefore, it is crucial to find environmentally friendly, safe, and effective methods to alleviate heat stress. Probiotics have often been used to mitigate intestinal damage and maintain intestinal function. In this study, the efficacy and mechanism of action of Lactobacillus plantarum 4-2 on oxidative damage and inflammation induced by cyclic heat stress in laying hens were investigated. The results showed that addition of Lactobacillus plantarum 4-2 (≥1 × 10⁹ CFU/day/bird) significantly enhanced growth performance and improved the antioxidant capacity of the organism in cyclic heat-stressed laying hens. Meanwhile, ileum barrier damage was alleviated, expressions of intestinal tight junction proteins were elevated, and cyclic heat stress-induced decreases in ileum villus height and villus/crypt were ameliorated. Supplementation with Lactobacillus plantarum 4-2 resulted in a significant decrease in the expression of IFN-γ and IL-6 and an increase in IL-10 and TGF-β1, which attenuated the disruption of the ileum barrier and inflammatory damage by cyclic heat stress. Furthermore, Lactobacillus plantarum 4-2 decreased the level of Keap1 and increased the levels of Nrf2, NQO1, and HO-1, thereby alleviating cyclic heat stress-induced ileum oxidative stress. These results indicated that Lactobacillus plantarum 4-2 could enhance the antioxidant function, alleviate oxidative stress, and reduce ileum damage via Keap1-Nrf2 signaling pathway.

Cyclic heat stress; Ileum; Keap1-Nrf2 signaling pathway; Lactobacillus plantarum 4-2; Oxidative stress.