New Protocol Using Oxytocin to Induce Ejaculation in Penectomized Stallion

Background: Several reproductive diseases can prevent ejaculation by the traditional method of collection. Neoplasias as squamous cell carcinoma is the most common tumor of the external genitalia of horses and its lesions usually prevent copulation. The pharmacological induction of ejaculation is an important alternative technique to obtain and preserve the genetic material of stallions incapable of ejaculating by traditional methods of semen collection. However, the protocols currently used have shown questionable results and new protocols are needed in order to increase the success rates. The aim of this study is to report the success of a new protocol in inducing ejaculation when oral imipramine and intravenous oxytocin and detomidine were administrated in a Crioulo stallion. Case: A 9-year-old Crioulo stallion was admitted at the Veterinary Hospital of the Sao Paulo State University, FMVZ-UNESP, Botucatu, Brazil, with a history of a mass located on the glans and body of the penis. The histopathological exam confirmed the diagnostic of Squamous cell carcinoma and penectomy was performed. After 10 days of surgery the stallion was submitted to 5 different protocols with 3 days interval between the follow protocols: hnipramine+Xylazine; Imipramine+ Xylazine+Oxytocin; Imipramine+Detomidine and Imipramine+Detomidine+Oxytocin. Discussion: The traditional protocol of pharmacologically-induced ejaculation with imipramine hydrochloride (3 mg/kg/v.o) and xylazine hydrochloride (0.66 mg/kg/iv) was not successful even when oxytocin (20 UI/iv) was added to this protocol. Administration of imipramine hydrochloride (3 mg/kg/v.o) two hours prior to administration of detomidine hydrochloride (0.02 mg/kg/i.v) also did not result in ejaculation. However, administration of imipramine hydrochloride (3 mg/kg/v.o) 2 h prior to administration of detomidine hydrochloride (0.02 mg/kg/i.v) associated with oxytocin (20 U.I/i.v) resulted in ejaculation. The stallion was submitted to three seminal collections with a three-day interval between administration of the protocol and ejaculated in all the attempts after approximately 5 min of detomidine and oxytocin injection, presenting mean values of 50 mL of total volume (TV) and concentration of 80x10(6) spermatozoa/mL. The VT was higher and concentration was lower when compared to ejaculates obtained by pharmacological induction in previous studies, probably due to daily stimulation with estrus mare to induce penile exposure in order to allow antisepsis of the surgical wound. Thus, it is believed that the large amount of total volume of this stallion is due to the high production of gel by the accessory sex glands, with consequent reduction of ejaculate concentration. The sperm kinetics were evaluated by the computerized method CASA (HTMA-IVOS-12) with total motility (MT) of 84% and progressive (MP) of 38%, with 70% of rapid spermatozoa (RAP), being considered normal to the equine specie and similar to those observed by other authors in phamiacolocally-induced ejaculates. Post-thaw sperm kinetics presented 42% of MT, 21% of MP and 28% of RAP probably due to an intrinsic sensitivity of the stallion to the freezing process. Thus, this report concludes that the protocol associating imipramine, detomidine and oxytocin was efficient in the pharmacological induction of ejaculation, presenting normal and characteristic sperm parameters of the specie. Fresh and refrigerated semen presented good parameters for use in conventional artificial inseminations while frozen semen is indicated for deep horn inseminations or for use in intracytoplasmic sperm injection (ICSI) programs.