Acute Thermal Tolerance and Physiological Responses in Commercial and Native Red-Feathered Roosters Sharing the Same...

Taiwan's subtropical climate poses substantial heat stress challenges to poultry production. This study compared four red-feathered rooster lines (n = 10 per line, BB homozygous HSP70 genotype)-three commercially bred lines (F, T, K) selected for maximum body weight, and one native trial line (TLRI-09) developed through marker-assisted selection targeting the HSP70 BB genotype-during a one-hour acute heat challenge at 42 °C. A pre-specified statistical decision tree was applied: normality was assessed by the Shapiro-Wilk test for each group's change score (Δ = post - pre); one-way ANOVA with Tukey's HSD was used when all groups were normally distributed; Kruskal-Wallis with Dunn's post hoc test (Bonferroni correction) was used otherwise. Within-group pre-to-post changes were assessed by paired t-test. TLRI-09 showed a substantially lower body weight (909 ± 102 g vs. 2039-2226 g) and zero mortality, whereas each commercial line experienced one death (10%). Cloacal temperatures in F, T, and K groups exceeded the thermometer's upper limit (>44 °C) within one hour; TLRI-09 reached only 42.8 ± 0.1 °C. Respiratory rate increment was highest in TLRI-09 (Δ = 82.0 ± 8.4 breaths/min) and differed significantly among lines (p < 0.001). Plasma T₃ change differed among lines (p = 0.006); post hoc analysis identified a significant K vs. T contrast only (p = 0.019). These results indicate that, despite sharing the same HSP70 genotype, breeding objective is an important determinant of acute thermal resilience-an observation that warrants further validation under chronic and commercial production conditions.