Effect of melatonin on the reproductive cycle in female cats: a review of clinical experiences and previous studies.

Practical relevance Cat breeders aim to suppress the sexual cycle for a defined period. This is a challenge as most preparations available for this intention are orally administered progestins; however, these drugs may have side effects, especially when used over a long period of time. Long-acting gonadotropin-releasing hormone agonist implants have been used successfully to suppress the oestrous cycle in cats for a longer period. After removal of the implant, the duration of action was shortened; however, the re-occurrence of normal cyclicity cannot be foreseen. The search for alternatives is therefore ongoing. Clinical challenges Another possibility for oestrus control is orally administered melatonin preparations; however, previous studies have shown that the effect was not satisfactory. After subcutaneous application of a melatonin implant developed for induction of oestrus in sheep (Melovine; Ceva Santé Animale), duration of oestrus suppression was shown to differ highly in individuals and in some cases no effect was observed. Nevertheless, it is used for short-term oestrus suppression in female cats. Aims This article provides an overview of recent studies and clinical experiences of the use of melatonin as a contraceptive in cats. It explains the function of melatonin in cats, discusses previous studies, provides clinical experience with Melovine (27 cases) and elucidates advantages and disadvantages. Evidence base Information provided in this article is drawn from the published literature and the author's own clinical experience.