Protocol for Pharmacologically-Induced Ejaculation
in the Stallion using Imipramine and Xylazine
(there are other protocols)

Sue M. McDonnell, PhD

Equine Behavior Laboratory at New Bolton Center
University of Pennsylvania School of Veterinary Medicine, Kennett Square, PA 19348
610-444-5800 x2221       Fax 610-925-8124       suemcd@vet.upenn.edu

1. Pre-treat with 0.8 - 1.0 mg/lb imipramine hydrochloride (imipramine HCl) orally.  So, for the 1000 lb horse this would be 800 to 1000 mg.  Imipramine HCl is available from human pharmacies or drug supplies in 50 mg tablets, in bottles of 100.
   
   
2. Optional preteasing (increases success, but horse should be calm and quiet in the stall at the time of IV xylazine treatment).  Return the horse to the stall to be quiet and calm well before the next steps.
   
   
3. About 2 hours after the imipramine was given:
   •  Quietly attach a collection device over the prepuce and wait for the horse to quiet (an attached collected device usually reduces the disturbance of the horse).
   •  Quietly administer 0.2 to 0.3 mg/lb xylazine intravenously.  So, for the 1000lb stallion, this would be 200 to 300 mg.  Within this range, the particular dose of xylazine given to the stallion should be based un achieving a gradual sedation with the head dropping slowly at about 1 to 2 minutes after administration with the horse well sedated, but not visibly wobbly or dropping the nose to the floor.  This should last about 15 minutes before the horse regains alertness, raises his head, or begins nibbling.
   •  Quietly leave the stall and watch for ejaculation which typically occurs as the horse is just becoming sedate at 1 to 5 minutes after xylazine or as he regains alertness at about 15-20 minutes.
   
   
4. When ejaculation occurs, immediately snip off the bottom of the collection bag and process semen.  This avoids cold and light shock or contamination with belly hairs from disturbing the girth of the collection apparatus.
   
   
5. We have repeated this protocol for a total of two attempts per day with 4 hours rest interval after failure before beginning again with imipramine pretreatment.  Repeated success has been higher with as long an interval between procedures as possible (2-3 days between collections).
   
   
6. Semen is typically lower volume, more concentrated with a higher total number.  This is due to imipramine reducing accessory sex gland contraction and enhancing ampullae contraction.