Heat Stress Directly Affects Intestinal Integrity in Broiler Chickens

Area of Science:

• Animal Science
• Physiology
• Poultry Science

Background:

• Heat stress is a major challenge in poultry production, impacting bird health and performance.
• Reduced feed intake is a common consequence of heat stress, complicating the assessment of direct effects.
• Intestinal integrity is crucial for nutrient absorption and preventing pathogen translocation.

Purpose of the Study:

• To investigate whether heat exposure directly or indirectly (via reduced feed intake) causes intestinal mucosal damage and endotoxin permeability in broiler chickens.
• To differentiate the effects of heat stress from those of reduced feed intake on the broiler gut.
• To evaluate the temporal response of intestinal morphology and permeability to heat stress.

Main Methods:

• A pair-feeding technique was employed with male broiler chickens (Ross 308).
• Three treatment groups were established: thermo-neutral, heat stress, and pair-fed under thermo-neutral conditions.
• Two experiments assessed temporal changes (12, 24, or 72 hours) in intestinal morphology and plasma endotoxin concentration.

Main Results:

• Heat stress for 24 hours significantly reduced villus height to crypt depth ratio and proliferating cell nuclear antigen (PCNA)-positive cells in the duodenum, and increased plasma endotoxin.
• Pair-fed chickens did not exhibit these negative effects, indicating a direct impact of heat.
• Prolonged heat stress (72 hours) exacerbated intestinal damage and increased endotoxin permeability, effects absent in pair-fed controls.

Conclusions:

• Heat stress directly causes intestinal mucosal damage and increases gut permeability to endotoxin in broiler chickens.
• Reduced feed intake associated with heat stress is not the primary driver of these intestinal changes.
• Understanding these direct effects is critical for developing strategies to mitigate heat stress impacts on poultry gut health.