Investigating intestinal barrier integrity in heat-stressed modern broilers and their ancestor Jungle Fowl

Heat stress (HS) is devastating to poultry production sustainability from its adverse effects on bird welfare, health, growth, and mortality. Although modern broilers have greater gut mass and higher energy use efficiency than unselected birds, they are more vulnerable to HS that induces leaky gut syndrome. The aim of the present study was, therefore, to determine the effect of HS on gut barrier integrity in 3 modern broilers and in their ancestor Jungle Fowl. Four chicken populations: Giant Jungle Fowl, Athens Canadian Random Bred (1950s), 1995 Arkansas Random Bred, and Modern Random Bred (2015) were used. Day-old broiler chicks from each population were raised under thermoneutral conditions with feed and water intake measured daily. On d 28 the birds were subjected to 1 of 2 environment conditions: thermoneutral (24°C) or acute heat stress (2 h at 36°C). After the 2 h, samples from each section of the small intestine were harvested from 2 birds per line per treatment and flash frozen in liquid nitrogen. Gene expression was analyzed by 2-way ANOVA using real time quantitative PCR. At molecular levels in the duodenum, gene expression of HSP 70, 60, and 90, ZO-2, ZO-3, villin, PAT-J, cadherin, connexin-45, and calprotectin were shown to be significantly upregulated by heat stress. In the jejunum, gene expression of ZO-1, ZO2, and ZO-3 was significantly upregulated by heat stress, while occludin was downregulated. This data provides evidence for a mechanistic understanding of the gut physiology and how it can be influenced by growth-rate and heat stress.