Xylazine-induced ex copula ejaculation in stallions

This study is a part of ongoing work toward developing pharmacological methods of enhancing and inducing ejaculation in stallions with ejaculatory dysfunction. We evaluated ex copula ejaculatory response to treatment with the alpha-adrenergic agonist xylazine hydrochloride, with and without preliminary sexual stimulation. Twenty-eight mature stallions each reveived, in random order, one xylazine trial (0.3 mg/lb, i.v.) without preliminary sexual stimulation, one xylazine trial with 5 to 10 min of sexual prestimulation, and one control trial (equivalent volume sterile water injection). Trials were conducted in the animal stalls. Ejaculation occurred in 15 of 56 (27%) xylazine trials. No ejaculations occurred in the sterile water control trials. In trials with sexual prestimulation, ejaculation occurred in 39% compared with 14% in trials without prestimulation. This difference was significant (P < 0.05). Xylazine-induced ejaculates were collected into a plastic bag attached to a girth and were similar to those obtained by artificial vagina. Nine of the 15 ejaculations occurred within 2 min of injection.