ASK THE VET

with Sue Hengemuehle, DVM

Dear Doctor Sue,

I read your column in the last issue about corticosteroids and asked my trainer if my mare was getting any of that stuff. He said that the only medication that the vet had given her was a few shots to perk up her appetite. It did work and she's eating a lot better but after reading your column, I'm concerned about side effects of the medication. Are there any? She seems fine to me.

Debbie, Phoenix, AZ

Debbie:

It's not uncommon for horses at the track to become "sour" and go off feed for a short period of time. Sometimes it is because they've had a hard race, are sore somewhere or simply are bored. There are a few different things that can be done to freshen up sour horses. Some people prefer to ship them to the farm for a mini-vacation, but this can't be done with all horses; those at the peak of their form that are high strung have been known to go through fences, especially if they are not used to being turned out. You mentioned that your mare had been given some medication to stimulate her appetite. She probably received either some B vitamins, anabolic steroids or both. Ask the veterinarian that treated her and you'll know what she was given. If she was given B vitamins, she shouldn't have any problems. All of the B vitamins and vitamin C are water soluble/ any that are given in excess of what her system needs will be filtered out by her kidneys and excreted in her urine. Vitamins A,D,E, and K are fat soluble vitamins that take longer to clear from the system and can build up to toxic levels if dosed repeatedly. Low doses of anabolic steroids are commonly used as appetite stimulants. There is a limited amount of research that has been done with these compounds in horses in spite of their widespread use. Most anabolic steroids are synthetic analogs of the naturally occurring male sex hormone, testosterone. Their chemical structure has been altered to maximize the anabolic (tissue building) effects while minimizing the androgenic effects (such as aggressiveness and stallion-line behavior). They have been used therapeutically in debilitated horses, such as those recovering from major surgery, as adjunctive treatment to stimulate healing and increase appetite. They are not a substitute for proper care, conditioning and nutrition. In most cases, only one or two doses are needed for appetite stimulation. Most manufacturers recommend that these compounds not be used in stallions as they can impair fertility and cause the testicles to shrink in size One must also consider that in stallions, you are supplementing something that is already there (testosterone) so are the anabolic agents really needed? In addition, when treated with therapeutic levels recommended by the manufacturer, some animals (both mares and geldings) will still exhibit androgenic behavior which may persist for six to eight weeks after treatment. In 1992, J.W. Miles and associates, published a research paper in the American Journal of Bone and Joint Surgery regarding the effects of anabolic steroids on the biochemical and histological properties of rat tendons. The conclusion of their study was that anabolic steroids appear to produce a stiffer and weaker tendon that fails with less elongation (ie: the tendon loses its elasticity and tears sooner that the tendon of a rat that has not received and anabolic steroids). Is it possible that with excessive use of anabolic agents, we are increasing the probability of bowed tendons and torn ligaments in our horses by injecting them with a substance that increases muscle mass yet weakens the supporting tendons? There are other potential problems with the excessive use of anabolic agents in mares. In prepubescent mares, prolonged anabolic treatment inhibits normal ovarian development and estrous cycles may be erratic or suppressed. Future breeding soundness may be compromised. As an interesting side-note, permanent clitoral enlargement consistently is seen in mares that have received long term anabolic steroid therapy and may be a useful marker to aid in the selection of future broodmares prospects. Anabolic steroid therapy is also contraindicated in animals that have existing heart and kidney problems, as they increase sodium and water retention and may aggravate these conditions. According to Current literature, the United States and Canada are the only thoroughbred racing countries that allow the use of these compounds; in all other countries, the presence of them in a post-race urine sample constitutes use of an illegal substance.

Sue Hengemuehle, DVM

Sue Hengemuehle, DVM is a veterinarian on staff with the Dept. of Animal Science at Michigan State University and has a private equine practice in Okemos, Michigan.

Editor's note: In my observations at the track, many fillies are given anabolic steroids consistently while racing. It does make them look and act more aggressive and masculine. A shy timid filly may run more assertively but are weakened tendons caused by the loss of elasticity the price we want to pay? Is the benefit worth the risk to overall horse soundness? In theory it may be appealing to treat geldings with anabolic steroids, howerver they would also suffer the same side effects. For fillies, colts, and geldings, long term use is contraindicated and could be very harmful.