Pharmacological methods of contraception can be effectively used to control the overpopulation of cats and long-term continuous GnRH administration has been used for this purpose. For how long puberty could be delayed in pre-pubertal cats, and the mechanism by which GnRH accomplishes its effect, remains to be investigated. This study investigates the effect of GnRH administration in pre-pubertal tomcats on the length of delay in puberty, their sexual behavior and testicular LHR expression. Three-month-old tomcats were either implanted with 4.7 mg Deslorelin (Suprelorin®, Virbac Animal Health, France) or left as controls (n = 6/group). Sexual behavior was monitored at 2-weekly intervals during the study period of 48 weeks. Semen was collected and evaluated only at the end of study period when all the cats were castrated; their testes fixed, wax-embedded and sectioned (5 µm) to analyze for LHR by immunohistochemistry. LHR expression was studied by image analysis and compared between the two groups using the general linear model.

No adverse reaction was noted on the general health of cats after Deslorelin implantation. Sexual behavior and semen production were absent in the Deslorelin-implanted cats but were present in the control group. LHR expression was significantly lower (p ≤ 0.05) in the implanted group compared to the controls (Figure 1). The data suggest that Deslorelin implantation in 3-month-old cats delays puberty at least for 48 weeks via suppression of testicular LHR expression. (Supported by the RGJ PhD program and the Department of Obstetrics, Gynaecology and Reproduction, Chulalongkorn University, Thailand).

Figure 1 The mean (± SEM) LHR expression in cats (n = 6/group) with or without Deslorelin implantation of 3-month-old cats for 48 weeks. Different letters on the bars indicate significant differences (p ≤ 0.05).