Heat Stress Genetics in Poultry: Breeding for Thermal Resilience

Genetic selection for rapid growth in broiler chickens has inadvertently reduced thermal tolerance. Breeding programs that incorporate heat stress resilience markers offer a path to improved welfare in warming climates.

Key Facts

Modern broiler breeds have a thermoneutral zone of 18-22C; temperatures above 30C cause measurable heat stress
Heat stress-induced mortality in broilers costs the US poultry industry over $100 million annually
The naked neck (Naked Neck gene) naturally reduces heat stress by reducing plumage on the neck and breast
Genomic selection for heat tolerance markers can maintain growth rates while reducing heat-related mortality
Slower-growing breeds show greater thermal resilience than fast-growing commercial lines
Evaporative cooling systems combined with genetic selection provide the greatest welfare protection
Rising global temperatures make heat stress resilience an increasingly critical welfare and production issue

Welfare Considerations

Heat stress in poultry causes panting, reduced activity, suppressed feed intake, and in severe cases, rapid mortality. The combination of high stocking densities, poor ventilation, and genetic predisposition to heat sensitivity creates conditions of significant suffering during hot weather. Breeding programs that incorporate heat tolerance — whether through quantitative trait loci associated with thermoregulation or the use of more thermally resilient breeds — represent a meaningful welfare improvement. Slower-growing breeds with better heat tolerance also exhibit better overall welfare across multiple indicators.

What You Can Do

Support poultry welfare certification schemes that permit slower-growing breeds
Advocate for climate-adaptive poultry housing standards in agricultural policy
Choose chicken products certified by RSPCA Assured or Global Animal Partnership (steps 3+)
Support research into heat stress genomics and welfare-positive breeding programs
Reduce poultry consumption or shift to producers with documented heat stress management protocols