Abstract
Background: Regarding animal welfare and reversible suppression of reproduction the need for alternatives to surgical castration like slow-release gonadotropin-releasing hormone implants is increasing.
Aim: In this study, we evaluated whether the onset of puberty can be suppressed by implantation of a slow-release gonadotropin-releasing hormone implant (4.7 mg deslorelin) in juvenile rams.
Methods: Seven juvenile rams (3-5.5 months) were treated with the gonadotropin-releasing hormone analogue deslorelin to analyse the effects on testicular development, sonographic findings of testicular tissue, testosterone concentration in the blood, spermatogenesis and sperm parameters from the epididymis after castration. Seven rams of the same age without an implant served as controls.
Results: Follow-up examinations were performed over five months, after which four rams per group were castrated. No significant group differences were found in the andrological parameters on the group level, but testicular development was suppressed in three rams in the treated group. Histological examination revealed spermatogenesis in the testicular tissue in three of four animals treated with a gonadotropin-releasing hormone analogue.
Conclusion: The onset of puberty in juvenile rams cannot be reliably suppressed by using the slow-release gonadotropin-releasing hormone implant Suprelorin ®.

Key words: Castration, Male, Hormonal Downregulation, Puberty, Sheep.