Effect of heat stress on jejunal epithelial barrier integrity in broilers divergently selected for high- and low-water efficiency.

Drought and water scarcity, exacerbated by global warming, are enormous threats to global food sustainability and security. Poultry, in particular, are highly impacted by adverse environmental stressors. As nutrient absorption and intestinal integrity are critical for growth and performance, understanding the impact on the broiler gastrointestinal tract is highly relevant. Here, we examined the effect of chronic cyclic heat stress (HS) on the jejunal expression profile of tight-junction, gap-junction, adherens, and desmosome genes in the 4th generation of broiler lines divergently selected for low (LWE)- and high-water efficiency (HWE). Male HWE and LWE broilers (n = 240/line) were allotted to 12 environmental chambers (2 floor pens/chamber, 6 chambers/line, 20 birds/pen) and were exposed to cyclic HS (36°C for 9h/day from 9:00 am to 6:00 pm) or thermoneutral conditions (25°C) from day 29 to 49 of age in a 2 × 2 factorial design. Growth performance and mortality were recorded. At day 49, jejunal tissues were collected for molecular analyses using real-time quantitative PCR and immunoblot. Jejunal gene expression of multiple gut integrity factors were higher (P < 0.05) in the HWE as compared to the LWE lines, including claudin 22 (CLDN22), -34, occluding (OCDN), zona-occludin-2 (ZO-2), gap junction alpha1 (GJA1), GJA3, GJC1, and cadherin 1 (CDH1). CLDN8, -20, -25, -4, GJC2, and GJD2 were also greater (P < 0.05) in HWE, but were additionally downregulated (P < 0.05) during HS. Conversely PALS1-associated tight junction protein (PATJ) and desmocollin 1 (DSC1) mRNAs were significantly downregulated in the HWE as compared to the LWE broilers. Significant interactions between the line and environment were seen in CLDN1, where the expression was decreased in the LWE but increased in the HWE in HS. Additionally, CLDN15 and -16 genes were greatest in the HWE under TN conditions, while catenin alpha 2 (CTNNA2) was highest in the HWE during HS. Overall, the jejunal expression profile of key genes associated with intestinal barrier integrity likely contributes to the water efficiency phenotype and the response of these birds to HS.