Testicular hyperthermia reduces testosterone concentrations and alters gene expression in testes of Nelore bulls

Abstract Increased testicular temperature reduces sperm motility, morphology and fertility. Our objectives were to characterize effects of testicular hyperthermia (scrotal insulation) on acute testosterone concentrations and gene expression in Bos indicus testes. Nelore bulls (n = 20), ∼27 mo of age, 375 kg, scrotal circumference >31 cm, with ≥30% motile sperm, were allocated into four groups (n = 5/group): non-insulated (Control) and insulation removed after 12, 24, or 48 h. Immediately after insulation, intratesticular temperatures (needle thermocouples) were coolest in Control bulls and warmest in 48-h bulls (mean ± SEM, 35.28 ± 0.31 vs 38.62 ± 0.57 °C, P