Assessment of body and scrotal thermoregulation and semen quality of hair sheep rams throughout the year in a tropical environment

•Morada Nova and Santa Inês rams maintained homeothermy even under heat challenge.•Their efficient scrotal thermoregulation favored testicular thermal gradient.•The rams maintained testicular integrity and high semen quality throughout the year.•Their systemic and gonadal thermoregulation contributed to more viable spermatozoa.•The genotypes have desirable characteristics for use in tropical environments.