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Anabolic steroids - uses and abuses


After administration of ABS to geldings and mares, stallion-like behavior was observed.

At a time when alleged abuses of performance-enhancing anabolic steroids (ABS) are making headlines in many professional and Olympic sports, questions about their use in horses also are coming to the forefront.

Based on a number of hearings, Congress appears close to legislating a ban on anabolic steroids in horseracing. The Jockey Club is seeking a crackdown to clean up the integrity of the sport and in recent months more than a dozen state racing jurisdictions have enacted or are considering controls on ABS in racing horses.

Most are adopting in some fashion the Racing Medication and Testing Consortium's (RMTC) updated model rules on anabolic and androgenic steroids (ANS), which it considers Class 4 drugs, "comprised primarily of therapeutic medications routinely used in racehorses. These may influence performance, but generally have a more limited ability to do so."

The Thoroughbred Owners and Breeders Association (TOBA) asked all racing jurisdictions with graded stakes races to begin testing in January for anabolic steroids.

Meanwhile, Keeneland and Fasig-Tipton, two major Thoroughbred auction sales companies, have adopted the American Association of Equine Practitioners (AAEP) guideline on the use of ABS in sales horses in Kentucky, "that no exogenous ABS be administered within 45 days of sale."

The various ABS and ANS drugs include boldenone, stanozolol, nandrolone and testosterone (TES), and "have been employed extensively in equine practice over the past 25 years," says Larry Soma, VMD, dipl. ACVA, professor of anesthesia and Marylin M. Simpson professor of veterinary medicine at the University of Pennsylvania School of Veterinary Medicine.

"Their usefulness is largely dependent on subjective opinion, as only minimal studies have been carried out in horses," Soma explains.

"As with most things, anabolic steroids are useful when used appropriately," says Larry Bramlage, DVM, MS, dipl. ACVS, at Rood & Riddle Equine Hospital in Lexington Ky., a member of the AAEP Task Force on Medication Issues at Public Auction.

The AAEP task force guidelines say anabolic steroids "may be therapeutic for normal health care, but should have cleared the horse's system and should have no detectable level at the time of sale."

"I think they can be valuable in treating some problems, in people and in the horse, but the problem comes with abuse," Bramlage says.

"I don't think it's appropriate to have any anabolic steroids in the system of a horse when it is presented for sale. I think you could make a case for not having anabolic steroids on board for any stakes races, and for any filly races. Geldings are a tougher problem. Castration removes the natural source of anabolic steroids for the training gelding. They sometimes need it. That makes a case for use — but not for abuse."

Their effects on horses

The purported beneficial effects of ABS in improving racing performance are anecdotal at best, though there is evidence as to their effects on behavior and reproduction.

"The benefits of the therapeutic use of ABS remain questionable and numerous side effects have been reported," says Soma. Possible therapeutic value of ABS described in the older veterinary literature include correction of the tissue-depleting process after systemic disease, malnutrition, parasitism or wasting disease of old age; enhancing tissue repair post-surgery or injury; and increasing appetite and vigor.

Though veterinarians use them, few modern studies, if any, are available to show that they enhance tissue repair.

"Many veterinarians attest to gains in physical strength, stamina and mental attitude of performance horses," Soma says. "This is especially true of horses that have gone off feed and have a "stale" or "sour" attitude. The apparent improvement in athletic performance may be more of a change in behavior and aggressiveness than any specific effects in physiologic para-meters that affect performance."

"I think the therapeutic value is one that's been around for a period of time," says Kevin Dunlavy, DVM, equine practitioner at Churchill Downs, Ky., and at the Fairgrounds Racecourse in New Orleans.

For racehorses, the primary goal "hopefully is to enhance red-cell count, to help blood counts and increase appetite, " Dunlavy says. "You can take a horse that is a slight individual and hopefully get him to eat more; if you can do that, you increase his plane of nutrition and can get him to lay down more muscle mass. In racehorses, we don't want bulky, bodybuilder-looking horses, but you do want those horses to be lean, with good muscle mass."

Many racehorses have ulcers that affect their appetite. With many ulcer medications available, there may not be a need for ABS to enhance appetite if one can cure appetite depression with ulcer medication. "A veterinarian made that statement to me," says Soma. "Probably the cheapest way to do it (improve appetite) is to give them ABS, but the better way is to get rid of the ulcers. That veterinarian's statement is absolutely correct," Soma says.

There is some evidence regarding ABS and metabolic recovery. ABS do appear to increase the rate of muscle-glycogen repletion after exercise or a race. "They may have recovered a little faster after racing, but the data didn't say that we have a bunch of horses that ran and we gave them ABS and they were able to run them back in two weeks vs. three weeks," says Soma. "That kind of data is not available."

Effects on geldings

Because geldings have little endogenous testosterone, some feel that exogenous ABS may be beneficial to level the playing field with intact colts that have large amounts of endogenous testosterone.

"However, evidence to substantiate these anecdotal observations was not substantive," Soma says.

"The ABS have testosterone-like effects on geldings, anabolic effects that are more pronounced than testosterone itself," says Dickson Varner, DVM, MS, dipl. ACT, reproductive specialist at Texas A&M University Veterinary School.

"I had a gelding that was out in the paddock with a mare, and another gelding was turned out with them," Varner notes. "The other gelding got to kicking him quite a bit, and so I gave him a little shot of boldenone just so he could stand his own ground. In response to the ABS, he was very aggressive toward that other gelding and started mounting the mare."

"It will have an immediate effect on geldings, so that they are then less trustworthy when on ABS," Varner says. "I don't know if they're more aggressive (per se), but they do have a psychological change when on ABS, and they 'think' they are stallions. It's difficult to say what effect it has on metabolic activity in the horse, other than that."

"Regarding ABS and a gelding racehorse I had, the last thing I ever thought he needed was to get any ABS," says Stuart Brown II, DVM, reproduction specialist at Hagyard-Davidson-McGee in Lexington.

"Being that size (>17 hands), he didn't need to be carrying any more mass on that limb structure. I think all too often the anecdotal evidence about geldings needing ABS has taken precedence over what people see and judge in terms of the way individuals do, or perform, or how they mature."

Effects on behavior

ABS may trigger an increase in pre-race aggressive behavior in many horses.

"They (horses on ABS) often have more of a sour disposition and are more aggressive and unpredictable," says Sue McDonnell, MS, PhD, head of the Equine Behavior Program at the University of Pennsylvania's New Bolton Center.

"You might be walking a mare and all of a sudden, unprovoked, she bites your arm," McDonnell says.

Not that stallions won't do the same: Males and females on anabolic steroids seem to have aggression in somewhat unusual patterns and intensity. "They seem to have a short fuse for rage," notes McDonnell. "They overreact to things or react unpredictably. One day it's fine to pick up their feet and the next day they violently object.

"This behavioral inconsistency is pretty common with ABS or exogenous androgen treatment. It always rings true to me when I hear reports on the concerns about erratic behavior in humans on steroids — that's exactly my experience with horses. I'd rather be around a consistently tough stallion on his natural hormones than a mild stallion or a gelding or a mare that's on anabolic steroids. You let your guard down, and you can get hurt," McDonnell cautions.

Will ABS make a filly or colt more aggressive? "Absolutely," says Churchill Downs' Dunlavy. "But, purely subjectively, I can tell you from experience that is not the case for stanozolol. It doesn't seem to produce the personality changes that testosterone or boldenone do. I don't care whether it is a male or female, you'll see a definite male aggressiveness on those, while on stanozolol you really won't. So, for the horse with the aggressive personality, the pharmacological choice would be stanozolol or nandolone. I don't think you see it as much with those two, for whatever reason.

Effects on reproduction

In female horses, large doses of exogenous TES eventually caused total suppression of all reproductive activity and the development of stallion-like behavior and aggression. Most stallions have reduced reproductive capacity. After administration of ABS to geldings and mares, stallion-like behavior was observed, "indicating residual androgenic activity of ABS. Mares with ABS show stallion-like behavior, including mounting, teasing and aggressive behavior toward other horses," McDonnell says.

"Though it depends on what age they are treated, theoretically if they started early enough, with a weanling or yearling ABS could delay puberty," she adds.


With colts/stallions treated with ABS, response is not black and white," says Varner, who examined many stallions at the racetrack in preparation for their first year at stud. "We had evidence of stallions with a history of treatment with anabolic steroids having small testes," Varner says.

Sometimes the testes do not grow even after the horse is removed from a race setting, he explains, while at other times there is a significant increase in testicular size. "It's difficult to say what's attributable to the anabolic steroids, and to other factors associated with their racing career," Varner says.

It appears that boldenone is more likely to be detrimental to semen quality than stanozolol. "It (boldenone) was found to cause a more rapid reduction in testicular size than stanozolol when given to pony stallions," notes Terry Blanchard, DVM, dipl. ACT, a reproductive specialist. However, both caused significant decreases in testicular size, seminiferous tubule diameter, sperm production and size of Leydig cells within the testicular interstitium, compared to non-treated control stallions. This difference was believed related to a longer half-life and different chemical structure (i.e., boldenone more closely resembles the chemical structure of testosterone).

No controlled trials have been conducted with boldenone and stanozolol to see which has the more profound effect, Varner says.

"Long-term use of anabolic steroids with young Standardbred and Thoroughbred colts/stallions will interfere with semen production," says Michelle LeBlanc, DVM at Rood & Riddle. However, most horses leaving the racetrack have fair to good quality semen within six months, she says. "We have had discussions of poor-quality semen in some horses in the first two to four months after racing — whether it's due to anabolic steroids or the stress of living the racetrack life. I don't think that we can blame it all on steroids. Too many horses turn around too quickly after being let down."


With fillies or mares that have already started cycling, ABS often do not actually stop the mare from ovulating but do change behavior so that the filly or mare doesn't show estrus and becomes studlike. "She tends to fight with the stallion even though she may have a follicle on her ovary all ready to ovulate; she becomes very difficult to breed," McDonnell explains. Some need to be off steroids as long as six months before they resume normal estrus and discontinue the male-type behavior.

Even without ABS, if a mare comes right off the racetrack to become a broodmare it may be difficult to get her pregnant in that first season. If she comes off in summer or early fall and has six months or so before breeding, most will return to normal sexual behavior, McDonnell explains.

"It might be a function of body weight, just as women athletes don't cycle when they get too fit and thin. We took mares and treated them with doses of anabolic steroids so that we could follow them and know how much they received, and followed their ovarian activity," says McDonnell. "It was expected that from those doses the mares would stop ovulating. Some continued to ovulate, but they were not as regular as the control mares."

McDonnell and colleagues published a paper of how one could make a "teaser stallion" out of a mare with anabolic steroids, on doses similar to those given on the racetrack. Many of the mares would mount other mares. "You can pretty much turn them into a 'stallion,' " McDonnell says.

Given some time, mares removed from racing will return to normal as medication is removed from their system, and will return to normal estrus behavior, says Brown. "It can be frustrating for breeding managers and owners, though, because it often takes a while for them to settle."

ABS for racehorses?

"It was really our organization that spearheaded the drive to start developing the model rules (to regulate ABS) now being adopted by the various jurisdictions," says Scot Waterman, DVM, executive director of the RMTC.

Evidence was growing that anabolic steroids were being overused and abused in racing. Also instrumental was the threat of congressional intervention, starting with a bill put forward by Rep. Ed Whitfield (R-Ky.).

That bill would prohibit the use of anabolic steroids in any horse that ran in a race subject to simulcast wagering under the Interstate Horseracing Act.

"Most of the people we talked to at the time didn't think the bill had much chance of success, but it was still clearly a shot across the bow. We needed to deal with this as an industry, or Congress was going to do it for us," says Waterman.

"They (ABS) need to be eliminated in racing," Dunlavy argues. "The bottom line is, nobody wants anabolics in football or baseball players and to have horseracing as the only major sport out there allowing them — well, I think it's bad," Dunlavy says. "It creates a poor public impression of the game and the industry."

"I don't think they're necessary," agrees Rick Arthur, DVM, executive director of the California Horse Racing Board (CHRB). "Our position is that there may be times when legitimate use would be warranted (horses rehabbing from an injury, recuperating from debilitating disease, chronic pleuritis, pneumonia).

"But that is quite different from racing on anabolic steroids. ... What we propose is a regulation that would allow some use of anabolic steroids for a limited number of days prior to racing."

"Horses around the world race without anabolic steroids and very successfully," Arthur says. "In terms of the sport, I doubt that many people are aware that we don't regulate anabolic steroids. It's going to be difficult to convince the public that Barry Bonds can't have them, but these animals ... need them. It's something the racing industry is going to have to face and is facing I think quite successfully."

Kane is a Seattle author, researcher and consultant in animal nutrition, physiology and veterinary medicine, with a background in horses, pets and livestock.

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