Contraceptive implants used by cat breeders in France: a study of 140 purebred cats

Objectives Deslorelin 4.7 mg and melatonin 18 mg subcutaneous implants were studied in purebred male and female cats, via questionnaires sent to French cat breeders, to assess breed, age, duration of the contraceptive effect, fertility after use, changes in behaviour and side effects. Methods Reproductive data were collected in 57 tom cats and 41 queens implanted with deslorelin 4.7 mg, and 42 queens implanted with melatonin 18 mg, for a total of 140 purebred cats, from 38 different catteries, representing 18 breeds. Results Using deslorelin (Suprelorin 4.7 mg; Virbac), sexual behaviour in males was inhibited for a mean +/- SD of 13.4 +/- 3.2 (range 8-21) months in 37/57 cats. Of these, 24/37 mated successfully and produced litters at a mean of 15.5 +/- 3.6 (range 9-20) months. Inhibition lasted 11 +/- 1.1 (range 9-12; n = 6), 13.2 +/- 2.4 (range 12-18; n = 6) and 15 +/- 3.5 (range 9-18; n = 6) months in Norwegian Forest Cat, Singapura and Ragdoll males, respectively. In 26/41 females implanted with deslorelin 4.7 mg, oestrus was inhibited for a mean of 16.0 +/- 5.7 (8-38) months; 12/26 went on to produce a litter. Of the side effects specific to females: two presented persistent oestrus, leading to the removal of the implant; two developed lactation; one had fibroadenomatosis; and one was sterilised owing to cystic endometrial hyperplasia. Using melatonin (Melovine 18 mg; Ceva), 33/42 females had oestrus inhibited for a mean of 86 +/- 50 (range 21-277) days after implantation with a peak return to oestrus in March, and 12/33 had a subsequent litter. No side effects were reported. Conclusions and relevance This study is the first to collect a large amount of field data, in 140 purebred male and female cats where a deslorelin 4.7 mg or a melatonin 18 mg implant was used. These field results may allow for more accurate clinical advice and open up new avenues of research.