Seasonal Effects of Castration on the Male Gonads in Elk Deer (Cervus canadensis)

Elk deer (Cervus canadensis) is an economically important species valued for its antlers.The aim of this study is to evaluate the effects of castrating season on antler development in elk deer.The testes were surgically collected from the following four groups of six-year-old captive bulls during the non-mating season: in March, before casting of the antler stump; in April, after casting, that is, 50 days into the period of early velvet growth; in June, during antler removal when the antler growth peaked, that is, 85 days into the velvet antler period; and in October, during slaughter.The testis size and weight increased during the velvet antler growth period, from April to October, whereas, in April, the testis weight decreased significantly.Furthermore, the sperm concentration and motility increased significantly from March to October.There was no significant difference in the plasma testosterone concentration between the pre-and post-castration groups, although it was slightly higher in the precastration group.The plasma testosterone concentration in the castrated animals was lower than 0.025 ng mL -1 , whereas that in the control group was much higher (10.53 ng mL -1 ).Therefore, our results suggest a possible correlation between the velvet antler growth and castration timing in elk deer.