Study links breeding goals, not just HSP70, to rooster heat tolerance
Bottom line
Commercial breeding for body weight may blunt heat resilience in red-feathered roosters, even when birds share the same HSP70 genotype, according to a new paper published June 22, 2026, in Animals. In the study, researchers compared four Taiwanese red-feathered rooster lines, all homozygous for the HSP70 BB genotype, during a one-hour heat challenge at 42 °C. The native trial line, TLRI-09, weighed far less than the three commercial lines, but it also had the best acute heat tolerance: no deaths, a lower final cloacal temperature, and a stronger respiratory response. Each commercial line had one death during the challenge, and birds in those groups exceeded the thermometer’s upper limit of 44 °C within an hour. The authors concluded that breeding objective, not just a putative heat-tolerance marker, remains a major determinant of thermal resilience. (mdpi.com)
Why it matters: For veterinary professionals working with poultry systems, the study is a reminder that single-gene selection may not be enough to protect flocks against heat stress, especially in fast-growing birds. Earlier work from the same Taiwan research group linked HSP70 polymorphisms with heat tolerance and found favorable associations for one genotype, but this new study suggests that performance-focused selection can still override some of that advantage at the whole-bird level. That fits with the broader poultry literature, which shows that heat stress response is shaped by body size, metabolic load, physiology, and multiple genes, not HSP70 alone. (tlri.gov.tw)
What to watch: The next question is whether TLRI-09’s apparent advantage holds under chronic field heat exposure and whether breeding programs can combine market weight with more reliable thermotolerance under commercial conditions. (mdpi.com)
Key facts
- Study type
- Comparative poultry study
- Publication date
- June 22, 2026
- Journal
- Animals
- Species
- Red-feathered roosters
- Lines compared
- Four Taiwanese lines
- Genotype
- HSP70 BB homozygous
- Heat challenge
- One hour at 42 °C
- Main finding
- Native line TLRI-09 had better acute heat tolerance than three commercial lines
- Sample size
- 10 birds per line
A new Animals study adds nuance to the search for heat-tolerant poultry genetics: sharing the same HSP70 BB genotype did not equalize thermal resilience across rooster lines. In a one-hour, 42 °C challenge, Taiwan’s native trial line TLRI-09 outperformed three commercially bred red-feathered lines selected for maximum body weight, with zero mortality and a lower end-point cloacal temperature, while each commercial line recorded one death. The paper was published June 22, 2026. (mdpi.com)
The work builds on years of Taiwanese research into HSP70 as a marker for heat tolerance in country chickens. A 2016 study from overlapping authors reported that HSP70 polymorphisms were associated with acute thermal tolerance and production traits, and identified a favorable genotype linked to better heat tolerance without clear production penalties in that dataset. Taiwan’s Livestock Research Institute has continued developing local lines with heat-stress resilience in mind, and separate institute research has also examined seasonal physiology in TLRI-09-type birds under cool and hot conditions. (tlri.gov.tw)
In the new experiment, the researchers evaluated four red-feathered rooster lines, 10 birds per line, all carrying the BB homozygous HSP70 genotype. Three lines, labeled F, T, and K, had been commercially bred for higher body weight, while TLRI-09 was developed through marker-assisted selection targeting that genotype. The body-weight gap was large: TLRI-09 averaged about 909 g, versus roughly 2,039 to 2,226 g in the commercial groups. After one hour at 42 °C, cloacal temperatures in the commercial groups rose past the thermometer’s measurable ceiling of 44 °C, while TLRI-09 averaged 42.8 °C. Respiratory rate increase was greatest in TLRI-09, and plasma T3 changes differed significantly among lines, with a significant post hoc difference reported between K and T. The authors said those findings point to breeding objective as an important determinant of acute thermal resilience. (mdpi.com)
That conclusion is consistent with broader poultry heat-stress research. Reviews and comparative studies have repeatedly found that thermotolerance is influenced by strain, growth rate, body mass, tissue-specific stress responses, and the interaction of multiple genes and management factors. In other words, HSP70 may still be useful as a biomarker or selection component, but it is unlikely to function as a stand-alone predictor of field performance under heat load. (mdpi.com)
No outside expert commentary specific to this paper was readily available as of June 24, 2026, but the surrounding literature supports the paper’s central caution. A recent poultry heat-stress review described heat stress as a major welfare and productivity constraint, while another review noted that rapid growth and increased body mass can worsen thermoregulatory challenges in commercial birds. Prior Taiwanese and international studies have also shown that native or slower-growing chickens often retain better heat tolerance than commercial counterparts, even when productivity traits favor the latter. (ijpsjournal.org)
Why it matters: For veterinarians, integrators, and breeding advisers, the study reinforces that heat resilience should be evaluated as a whole-animal trait, not inferred from a single favorable genotype. In practice, that affects how clinicians interpret flock risk during hot weather, how breeding programs balance growth with survivability, and how production systems plan ventilation, stocking density, and emergency heat-response protocols. For pet parents, this research may feel distant, but for the poultry sector it speaks directly to animal welfare, mortality risk, and productivity in a warming climate. (mdpi.com)
The study also has clear limits. It was small, with 10 birds per line, and tested an acute one-hour challenge rather than chronic commercial exposure. The authors themselves said the findings warrant validation under longer-term and production-relevant conditions. That matters because some lines may compensate differently over days or weeks, and management interventions can meaningfully change outcomes. (mdpi.com)
What to watch: Expect the next phase of work to focus on whether lines like TLRI-09 can maintain acceptable production traits while preserving heat resilience, and whether marker-assisted selection can be paired with broader genomic and phenotypic selection strategies for commercial use in subtropical poultry systems. (mdpi.com)