Oral imipramine and intravenous xylazine for pharmacologically-induced ex copula ejaculation in stallions

Sue M. McDonnell, Ph.D.

    This study is part of ongoing work toward developing pharmacological methods for enhancing and inducing ejaculation in stallions with ejaculatory dysfunction or disabilities that interfere with normal breeding behavior.  The objective was to evaluate a treatment regimen involving oral imipramine followed by intravenous xylazine that, in uncontrolled field clinical trials, had shown promise for a higher rate of ejaculation and fewer side effects using a more easily obtained and administered form of imipramine.  Each stallion each underwent eight trials in which treatment consisted of imipramine hydrochloride (3mg/kg, orally in a small portion sweet feed) followed 2 h later by xylazine hydrochloride (0.66mg/kg, intravenously).  Trials were conducted with the stallion in a stall.  Semen was collected using a collection bag secured over the prepuce with a girth band.  Overall, 44 of the 64 attempts (68%) resulted in ejaculation.  Within-stallion ejaculation rated ranged from 3 to 7 of 8 attempts.  Interval from xylazine treatment to ejaculation ranged from 1.2 to 14 min.  As is typical for induced ejaculations in which imipramine is included in the treatment regimen, ejaculations were of low volume, high sperm concentration, and with a higher total number of sperm than for in copula ejaculates of these stallions.  These results represent modest improvement in rate of ejaculation over previous treatment regimens.