Effects of Heat Stress on Semen Quality and Reproductive Performance of Crossbred Boars with Different Maternal Origins

This study investigated whether maternal origin affects boar semen thermotolerance and its seasonal reproductive performance. Crossbred boars with different maternal origins were evaluated (K and KD boars with Meishan-derived cytoplasm and DK boars with Duroc-derived cytoplasm). Heat stress treatment (42 and 39 °C) on semen samples significantly reduced sperm viability and acrosome/membrane integrity while increasing mitochondrial damage. Notably, the decline in semen quality under heat stress was significantly lower (p < 0.05) in K and KD boars than in DK boars. The farrowing rates during the hot season were significantly higher (p < 0.05) in the K and KD breed compared with the DK breed. No significant differences among groups were observed during the cool season. Collectively, these findings indicate that maternal origin may contribute to mitochondrial stability and semen resilience under tropical heat stress, thereby influencing reproductive performance in hot seasons. Maternal inheritance should therefore be considered in breeding strategies of improving heat tolerance in pigs.