Effect of Heat Stress and Stocking Density onGrowth Performance, Breast Meat Quality,and Intestinal Barrier Function...

The present experiment was conducted to investigate the effect of heat stress (HS) andstocking density (SD) on growth performance, breast meat quality, and intestinal barrier functionin broiler chickens. Experimental treatments included two different ambient temperatures (20 °C:thermoneutral conditions, or 27.8 °C: HS conditions) and two different SD (low: 9 birds/m2 andhigh: 18 birds/m2) in a 2 × 2 factorial arrangement. A total of 1140 21-day-old broiler chickens wereallotted 1 of 4 treatments with five replicates. At the end of the experiment (35 days of age), twobirds per replicate were euthanized for sample collections. The results indicated no interactionsbetween HS and SD for all measurements. For main effects, HS decreased (p < 0.05) the growthperformance of broiler chickens. Similarly, high SD also decreased (p < 0.05) body weight gain andfeed intake. HS decreased (p < 0.01) jejunal trans-epithelial electric resistance (TER), whereas highSD did not affect TER. Neither HS nor high SD affected jejunal tight junction-related geneexpressions; however, high SD reduced (p < 0.05) occludin expression. In conclusion, HS and highSD are key environmental factors decreasing broiler performance; however, the interactive effectsof HS and high SD are not significant under the current conditions.