Researchers have identified regions of DNA linked to responses to high temperatures in a European pig breed, paving the way for breeders to select for heat stress resilience.
Pigs are highly vulnerable to heat stress due to having no functional sweat glands and small lungs. Such stress poses a global economic and welfare challenge to farmers, costing hundreds of millions of dollars in losses every year, and is a problem only increasing with climate change.
Creating a heat-stress mapping population
In their 18-month study, French scientists used the Large White, a breed originating in England, and Creole, which originates from Hispaniola. Creole pigs are considered more heat tolerant and Large White more productive, and the researchers hoped to combine these qualities.
They first crossbred the Large White and Creole, then mated this generation back to Large Whites to produce a backcross population. They did this to compare genomic regions where pigs have only Large White chromosome segments or one from both breeds, using the contrast to detect genes involved in managing heat stress.
Testing pigs under different climate conditions
For the heat stress testing, the team exposed 1,149 pigs to different temperature treatments. These represented temperate and tropical conditions, as well a temperate climate heated to 30°C for three weeks to represent acute heat stress. They recorded production and thermoregulation traits and carried out what is known as a genome-wide association study, where genetic variation is linked to specific traits in the animals.
Genetic signals of heat tolerance
They found that most of the specific regions of DNA associated with thermoregulation were associated with the Large White, with separation of susceptibility and resistance variants. During acute heat stress, the scientists identified 13 of the thermoregulation-associated DNA segments, four of which they also detected under chronic heat stress.
Breeding Opportunities for a Warmer Future
“The first striking outcome of our study is the large genetic variability that segregates in a European pig population for its response to heat stress, paving the way for substantial potential to select for response to heat,” the scientists wrote in the journal Genetics Selection Evolution.
Some of the DNA regions could be prioritised for breeding, they said, including one which regulates backfat thickness under heat stress. Research translating the results into real-world applications could come soon, but with the finding that some genomic regions were associated with only acute or chronic heat stress, there still are areas of uncertainty.
“Dedicated studies are needed to further decipher the underlying biological mechanisms that affect differences in resistance to each type of stress,” they added.
Key takeaways
- Heat stress causes major welfare and productivity losses in pig farming.
- Researchers identified DNA regions linked to thermoregulation under high temperatures.
- Large White and Creole pigs were crossbred to study heat resilience genetics.
- Some genetic variants were associated with acute, chronic, or both stress types.
- Findings could support breeding programmes for climate-resilient pigs.
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