Abstract
Objectives The aim of the study was to evaluate the efficacy of a 4.7 mg deslorelin implant in tom cats. Methods Nine mature male cats were included in the deslorelin group and five cats in the control group. Before the study started, all cats were confirmed to have distinct sexually dimorphic behaviour. Blood samples were taken on the implantation day, at day 7 and at day 15, then monthly, in order to measure serum dihydrotestosterone (DHT) and 17beta(β)-oestradiol concentrations. The deslorelin group (n = 9) was divided into two subgroups: five cats (cats 1-5) were neutered in the postimplantation period during suppression of sexually dimorphic behaviour, and four cats (cats 6-9) were neutered after re-expression of sexually dimorphic behaviour. The control group cats (n = 5) were castrated without administration of the implant. Results Sexually dimorphic behaviours ceased within a mean ± SD of 13-58 days (23.30 ± 14.17) after implantation. DHT concentration decreased within 30 days. The mean duration of suppression was 26.5 ± 7.42 months and reactivation coincided with increased DHT values reaching preimplantation concentrations within 1 month. 17β-oestradiol concentrations significantly correlated with DHT concentrations ( P <0.01). For cats castrated during suppression of sexual behaviour, the length of the long axes of the nuclei of Leydig cells, the diameter of seminiferous tubules and the height of the epithelium of the seminiferous tubules did not change until 3-6 months after implantation, whereas at 12 and 32 months the measured values were even lower than in the control group. For cats castrasted after reactivation, the length of long axes of the nuclei of Leydig cells and the diameter of seminiferous tubules approached the values of the control group between 4 and 6 months after reactivation. Conclusions and relevance A deslorelin implant (4.7 mg) suppresses sexually dimorphic behaviour in tom cats without any side effects and with full reversibility; however, duration of suppression is highly individual.