A Stallion as a Problem Breeder

We purchased a stallion for breeding at nine years of age. He had bred before, but curiously had very few offspring for his impeccable credentials. He was a lovely stallion, very well-behaved, and a perfect gentleman to work around. When we bought him we were advised that he was an over-enthusiastic breeder and that we should breed him by natural cover at pasture at the beginning of the breeding season.

So for his first mare, we proceeded as advised, putting the stallion and mare together in a small paddock where we could intervene if necessary. We rapidly realized that we had a problem breeder. This horse would get so excited that prior to ever penetrating the mare, he would flower and his already large penis would become dinner plate-sized. He was then physically unable to enter the mare. It looked as if this had been a long-standing problem for him as he was obviously incredibly frustrated by this. The harder he would try, the more frustrated, excited, and angry he would get, until he would be running that mare down, teeth bared, and viciously trying to attack her. The mare was so frightened by him she was gumming at him in submission. Needless to say, he was removed.

We tried breeding him in-hand and found that he was pretty much uncontrollable to hand breed. He would rear up and lunge uncontrollably and frantically at the mare and try repeatedly and unsuccessfully to penetrate her and would not back off when directed.

So, we decided to approach this problem methodically. We did a lot of work with him at halter so that he learned to listen to us. We would work him quite hard before we bred him (e.g., free lunged at a strong canter or gallop for 20 minutes or so) to work the edge off and get him breathing fairly heavily. This really helped to tone down his sexual excitement. We felt that if he was a bit short of breath, he would be more concerned about getting air to breathe as opposed to being rough on the mare.

We ended up breeding him with a cavesson on so that he could mouth the mare, but not bite her viciously. We would lead him up to the mare. If he became erect and flowered, he got backed up/and or led away again. Only when he approached the mare semi-flaccid would we let him mount her. On the way up, he would become erect, and we could help him with penetrating the mare just before he began to flower. If we let him mount while erect, he would already be flowering on the way up and couldn't penetrate. So we would lead him away and start over. This worked well, but was time-consuming and labor-intensive.

We could finally use him for live cover, but only with good-sized mares that had foaled before and could accommodate his size. So as not to restrict his breeding potential, we decided to train him for AI using semen collection with a dummy mount. This has gone extremely well. He is now lovely to breed with, well-behaved, and has taken to the process like a duck to water. However, even with collecting semen, the old nemesis of premature flowering still occurs. We are careful to wash him with fairly cool (not cold) water with minimal penis stimulation when cleaning. If warm water is used, he will begin to thrust and flower almost immediately. He is led up to the dummy, and if he flowers before mounting, is led away again, and left to stand till he settles. He accepts all of this very well.

My question to you is twofold.

First, how would a problem such as this have been created in the first place? In the pasture situation, he was aggressive to the point of running the mare down, viciously grabbing her by the withers, forcing her into a corner, and raping her.

Second, even though we have things fairly under control at the moment, do you have any suggestions or tips on how to manage this stallion? I did read in your articles about gently directing the penis toward the back legs when a horse thrusts and flowers during washing, and we will try this.

As to why your stallion has this problem, it would be easy to assume that the intense groping arousal came first, and the premature flowering and inability to insert were consequences of that. An alternate interpretation for a horse with this history is that the premature flowering (tumescence of the glans penis), possibly together with some other subtle neurologic deficits in his ability to couple up and orient his penis for insertion, were the root problems. The wild urgency to breed and the aggressive scrambling might have developed secondary to that. This hypothesis comes from experience working with clinical case stallions that we knew while they developed neurologic disease, or research stallions that were treated with certain drugs that cause premature glans tumescence so we could observe their breeding behavior change.

Why would this particular stallion have this tendency to flower early? Glans tumescence is a neural reflex that naturally occurs in two stages, with a stage of moderate flowering when the penis is stimulated upon contacting the warm vagina, and a second stage of intense flowering (dinner plate-size, as you describe it) just as ejaculation commences. The initial flowering can occur before insertion due to tactile or thermal stimulation of the glans outside the vagina, for example during washing of the penis with warm water, or sometimes when the stallion's aim is slow and the glans momentarily contacts the vulva during "seeking thrusts." Even contact of the glans to the stallion's abdomen can elicit this initial reflex. This can occur from time to time in any stallion. But when the problem is persistent or when the full dinner plate tumescence occurs before insertion, we have interpreted this as an aberration of the control of the delicately coordinated erectile and ejaculatory neurovascular events.

A few things that can cause disturbances of the fine neural control of the erection and ejaculation processes that then result in premature flowering (often along with other subtle neurologic signs such as delayed detumescence or loss of erection of the penis) include abnormal curvatures of the penis, urine seepage into the semen from the bladder neck during ejaculation, atypical number and rhythm of ejaculatory pulses, and anal sphincter laxity during thrusting. Medications that can cause premature flowering are neuroactive agents (such as diazepam or fluphenazine). Any adverse effects usually disappear once medication is discontinued, so that's not likely a factor for your stallion even if he ever encountered those drugs.

Trauma and diseases (such as equine protozoal myeloencephalitis or EPM) can also result in disturbances of neural control necessary for normal breeding. For example, in some instances, disturbances of erection, mounting, thrusting, and ejaculation are the first or maybe the only recognized signs of neurologic disease.

As for further tips and suggestions, manual semen collection can work well for many horses with premature flowering. Just the hands, rather than an artificial vagina, support the penis during thrusting. Most stallions respond well, and most people get good at it with practice. It can be done with the horse standing on the ground or mounted. Since the penis is not inserted into an artificial vagina, the size of the glans is not as problematic. Details of this procedure can be found in a 1990 paper available at www3.vet.upenn.edu/labs/equinebehavior//publixs/Papers/man90.pdf.

You might still need to try to limit the amount of tumescence to the initial level of flowering before stimulating thrusting, since ejaculation is sometimes impeded once the full flowering has occurred.

Ground semen collection, rather than mounted, might more effectively enable titration of the stallion's arousal to avoid flowering. You might even be able to reliably use an artificial vagina if you do ground collection in his stall or a wash rack without a mare, dummy, or the breeding area to heighten his arousal.

About the Author

Sue McDonnell, PhD, Certified AAB

Sue M. McDonnell, PhD, is a certified applied animal behaviorist and the founding head of the equine behavior program at the University of Pennsylvania's School of Veterinary Medicine. She is also the author of numerous books and articles about horse behavior and management.

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