Hu and Wugu × Hu rams underwent scrotal insulation to simulate mild heat stress, resulting in a 3.0 ± 0.1 °C increase in scrotal surface temperature. Semen samples were collected every five days from day 11 to 56, and testis samples immediately after insulation. Both breeds experienced similar semen quality reductions and recovery trends, including reduced motility, concentration and the percentage of morphologically normal, but on days 41 and 46, Wugu-Hu rams exhibited significantly lower sperm motility than Hu rams (