Dietary polyphenols from shredded, steam-exploded pine particles mitigate the adverse effects of heat stress in...

The current study investigated the impact of supplementing polyphenols extracted from shredded, steam-exploded pine particles (PSPP) on the performance, gene expression, and gut metagenome of broilers exposed to cyclic heat stress (CHS). A total of 216 chickens were distributed into a 2 (temperature) by 3 (diets) design, with each treatment consisting of six replicates of six chickens. Specifically, chickens were fed diets containing 0% PSPP, 0.5% PSPP, and 1% PSPP and exposed to two temperature conditions: CHS (31°C) and Thermoneutral (NT, 21°C). The CHS was conducted for 6 hours every day for 7 consecutive days. Final body weight, average daily gain, and average daily feed intake (ADFI) were decreased, while feed conversion ratio and rectal temperature were increased in heat-exposed chickens. Dietary PSPP supplementation enhanced ADFI. The weight of the liver, bursa, and length of the jejunum and ileum were decreased in heat-exposed chickens. Plasma cholesterol was increased, and triglycerides were decreased in heat-exposed chickens. After heat exposure, gene expression of ZO1, ZO2, GLP2, NOX1, SOD, GPX, HSP70, HSP90, NRF2, TLR2, and TLR4 increased in the jejunum. GLP2 gene expression was similar in 1%PSPP exposed to HS in comparison to the entire NT-exposed chickens. Concerning microbiota analysis, alpha diversity indices, such as Shannon and Gini-Simpson, were increased following CHS exposure. Beta diversity, measured through unweighted and weighted UniFrac distances, showed temperature, dose, and interaction effects. The relative abundance of the phylum Candidatus Melainabacteria was increased, while Tenericutes populations were decreased in heat-exposed chickens. Furthermore, a total of thirty genera were identified as microbial biomarkers of CHS. Interestingly, the relative abundance of five pathogenic bacterial genera was found to be decreased in the 0.5%PSPP treatment. Overall, CHS negatively influences growth performance, modulates the expression of the gut antioxidant-related genes, and favors the colonization of pathogenic bacteria. However, 0.5% PSPP may mitigate CHS by reducing pathogen colonization in the gut of broilers.