Progesterone and behavior modification may be alternatives for a racehorse with an eye for the ladies

by Denise Steffanus

GOOD stallions make better geldings is what most horsemen will tell you about a racehorse whose libido takes his mind off racing or makes him a challenge to train.

But what if you want to preserve the stallion for breeding after his racing career has ended? It can be the ultimate Catch-22: Leave him intact and he probably will have a dismal racing career that makes him undesirable as a sire; geld him so he performs well on the track, and when his glory days are over, his only legacy will be a wall full of win photos.

Alternatives to castration exist--progesterone supplementation and behavior modification--but neither offers a quick fix, and the jury appears to be out on how effective progesterone is in getting the horse's libido under control.

Regu-Mate for stallions

In humans, convicted sex offenders in a handful of states now are given the option to serve a reduced sentence if they agree to chemical castration with Depo-Provera, a medroxyprogesterone acetate injection that reduces the sex drive. Studies in stallions using Regu-Mate (altrenogest), a man-made progesterone supplement used in mares to regulate estrus, have produced differing results.

Edward Squires, Ph.D., professor of biomedical sciences at Colorado State University, was presented the 2005 George Stubbs Award by the American Association of Equine Practitioners for his work in equine reproduction. In 1994, Squires studied the effects of a double dose of Regu-Mate in helping to manage aggressive performance stallions.

"Certainly, the majority of horses lost interest in mares and lost interest in ejaculating, so it seemed to be fairly effective," he said. More importantly, the regimen did not appear to cause any long-term detrimental effects.

"It takes about 120 days for the stallion to recover, but they did recover," Squires said. "The only disclaimer I would put in there is that these were all mature stallions. If you take weanlings or yearlings or maybe even two-year-olds and treat them [with Regu-Mate], you might cause some permanent effects. But once they have gone through puberty and are sexually mature, then I think you are just going to have temporary effects."

Stallions four years old and older would be considered sexually mature, he said.

Squires said that, as long as the owner does not intend the stallion to cover mares during the treatment, Regu-Mate is a viable option to subdue aggressiveness.

"If they are just trying to make the horse an athlete for a while and then make him a breeding horse later on, we certainly have had several horses we put into those categories," Squires said. "So, as long as you aren't trying to breed him at the same time that you're trying to suppress his reproduction, I think you're okay."

The stallions in Squires's study were placed on Regu-Mate for 240 days, but he said he would be reluctant to keep a stallion on progesterone for years. He suggested treating the performance stallion with Regu-Mate during the natural breeding season, when mares around him will be coming in and out of heat, and then giving the stallion a break from treatment in the winter when mares are not overtly showing heat.

"We did some research when I was at Texas A&M [University]," said Terry Blanchard, D.V.M., M.S., resident veterinarian at John G. Sikura's Hill 'n' Dale Farms in Lexington and 2006 Theriogenologist (reproductive specialist) of the Year. "We were using sexually experienced, older stallions that were at least four years of age. We did not find any alteration in their behavior in terms of interaction with people, interaction with other stallions, or interaction with mares. However, for a young horse that is in training, there are some people at Texas Tech [University] who think they have found some modification in behavior, kind of quieting down their male aggressiveness, so it might be something that can be considered, certainly for a young one."

In 1997, Heidi Brady, Ph.D., and her colleagues in the Department of Animal Science at Texas Tech administered a double dose of Regu-Mate for 57 days to ten Quarter Horse stallions, ranging from two to four years old. They reported: "Sexually aggressive behavior, as measured by a standardized teasing test, was significantly decreased in treated stallions. Further, poor libido at collection periods was observed in this group." However, eight weeks after the study ended, the stallions' scrotums still were decreased in circumference, and biopsies of the testicles revealed disorganized tissue, among other changes.

The researchers concluded: "In our study, it is unclear if a longer recovery period would have resulted in a return to pretreatment testicular and seminal measurements in this group of young stallions. Based on this study, further research is warranted to investigate the long-term effects of altrenogest [Regu-Mate] in the young stallion."

Behavior modification

Sue McDonnell, Ph.D., founding head of the Equine Behavior Program at the University of Pennsylvania's School of Veterinary Medicine at New Bolton Center, is considered the foremost authority on stallion

behavior. She said her clinical impression is that progesterone supplementation alone does not work, but it might give horsemen an edge when attempting to modify the horse's behavior through conditioning.

"My honest opinion is that most horses can be trained very satisfactorily to perform for you when you want and to forget the girls, but people just don't know how to do it, and they overdiscipline them, and they get into a battle with the horse."

McDonnell said the solution is to teach the horse when it is acceptable to exhibit breeding behavior and when it is not.

"As bizarre as it sounds, one thing that is very helpful is to actually let these horses ejaculate so they learn when it's okay to breed and when it's not," McDonnell said. "That's pretty hard to orchestrate in a racetrack situation. If it were my horse with the problem, I'd have my jump mare on the trailer out in the parking lot, and I'd let him breed. It sort of takes the edge off and kind of builds a bond with the horse that you're not just saying, 'No, no, no.' You're saying, 'Now is the time to breed, and now is the time to perform.'

"Almost without exception, if we get trainers to buy into this, they come back saying, 'It's like a switch was flipped, and this horse now is really on our team; he seems to understand, and we're not fighting with him not to go after the ladies."

Conditioning a horse to teach him when breeding behavior is inappropriate differs with each horse, but McDonnell said some handlers overreact and make the situation worse.

"If the horse even has a prancing gait or screams out, they get into them really hard in the mouth, and fighting with a horse in his mouth actually provokes aggression," she said. "They are doing things they think are going to get the horse's attention, but they actually are elements of inter-male aggression, so they're provoking it."

McDonnell said in these situations, sometimes it is the handler who actually starts the fight, not the horse.

The University of Pennsylvania offers a short course for veterinarians, stallion managers, and owners at its New Bolton Center in Kennett Square that focuses on concepts and skills for safe, efficient handling and general management of breeding stallions. The course, "Just Stallion Handling," provides two days of basic skills and one day of advanced work during which a participant is permitted to bring his or her stallion to receive individualized coaching on how to handle the horse or cope with his specific behavioral problems.

To learn more about the stallion-handling short course, visit the University of Pennsylvania's website at www.vet.upenn.edu and enter "Just Stallion Handling" into its search engine.

The course is designed to enhance the ability of those who work on breeding farms, but McDonnell said the same skills are needed at the racetrack.

"We've certainly had people come to the course who have pointed out to us that they didn't realize they would be learning tips about horse behavior and what kinds of things inadvertently provoke the battles and how to peacefully address these issues," she said. "The reason we started this course is because we really didn't know where to send people for help.

"If people on the racetrack would learn how to handle stallions for breeding in a peaceful way, they'd be a whole lot better [at the racetrack]," she added.

Groundwork for young horses

McDonnell suggested working with a young horse on the farm before sending him to a racing trainer as a means to prepare the colt for the concentration of horses--including other stallions and females in heat--he will encounter at the training facility or racetrack.

"If it were my horse, I would work with him on the ground, even just lunging him, and bring fillies nearby, closer and closer, kind of titrating the distraction of the female and keeping the horse going and taking direction from humans," she said. "I have worked with people who are not all that skilled in working with horses, and doing this, they can gradually teach the horse that what you want is, when you're giving direction, [the horse] pays attention to you. You can even just walk them past female stimuli and just keep them moving and keep them taking direction from you while praising them for that. Just get closer and closer until you can get right up next to a female, and as long as they are in hand with you, they are paying attention to you."

No other solution

McDonnell advocates proper education for handlers in how to curb aggressive behavior in stallions as the best solution in most cases where the horse's inappropriate sexual behavior is causing a problem. The handler can learn what he or she has been doing wrong that is contributing to the problem and how to give the horse correct signals and reinforcement to modify the behavior.

McDonnell said that for some dangerous stallions, gelding may be the only solution, and sometimes even castration does not curtail aggressive behavior.

"There have been incidences of savage stallions, ones that are attacking people or going after other horses very savagely," McDonnell said, "and it is a reasonable step to try gelding--not that that's going to fix it, because there certainly are geldings that continue to do that--but it's a reasonable step."

Harold Snowden Jr. owned eventual seven-time champion John Henry when he was an unruly young stallion. Castrating the horse dampened his aggressive tendencies somewhat, yet he was left with a foul disposition that made other renegades seem like Mister Rogers by comparison.

"I hope he doesn't hold a grudge against me for castrating him because I've forgiven him for all of his misgivings and shortcomings," Snowden said during John Henry's 30th birthday celebration at the Kentucky Horse Park's Hall of Champions in Lexington. "I remember it vividly. It was so cold on the hill at Keeneland [Race Course], and I wanted to castrate this horse in February, but the vet kept telling me, 'It's too cold, wait until March, wait until it warms up some.' I didn't think March would ever come around!"

Denise Steffanus is a contributing editor of Thoroughbred Times who writes frequently on veterinary and farm management topics.