Approximately every four weeks, morphometric data were collected from all animals, including testes size, to monitor the effectiveness of GnRHa to suppress the reproductive axis. Scrotal length and circumference were measured with a tailor tape measure while sheep were held in a sitting-position. Testes size was calculated from the scrotal length × circumference and normalized to body weight. Testes size data at 28 (first breeding season), 44 (first anestrus), 81 (second breeding season) and 99 (second anestrus) weeks of age are presented, as these measurements were nearest to the dates of spatial maze performance assessment.