In most horse sports, mares are required to compete on a level playing field with geldings and stallions. In some cases, such as racing and steeplechasing, trainers believe mares have a disadvantage. They say mares are generally not as fast or as tough as the males. Other trainers, mostly in different disciplines, believe a mare’s sensitivity and desire can make her the ultimate competition mount.

Mares can, however, become cranky, spooky, tense and aggressive during the estrus phase of their heat cycle. If that time just so happens to be the day of the big race or during the championship show, a mare may not perform at the top of her game. On the other hand, sometimes the heat cycle can give a mare a winning edge.

“Gold Mitten got off the trailer and it was obvious she was in heat, and I thought to myself, ‘Oh great,’ ” said steeplechase trainer Neil Morris, referring to his 2004 National Steeplechase Association filly/mare champion. “But she won her race that day so I decided it wasn’t going to be a problem.”

Gold Mitten, a solid performer, won the Shawan Downs (Md.) filly and mare hurdle race and the Peapack Filly and Mare Grade III hurdle stakes at the Far Hills Races (N.J.) in 2004.

When it does become a problem, owners and trainers and their veterinarians experiment with a variety of remedies in an attempt to even out the ups and downs changing hormonal levels can cause. But each mare is an individual and not every solution works for every mare. While one mare may spook at the flowers in a dressage arena, another may exhibit aggressive or even nymphomaniac behaviors.

It’s The Hormones

One way to deal with a mare that behaves badly when she’s in heat is to suppress that heat. Progestin supplements, or hormonal therapies, do just that.

“Some [mares] can be very difficult to train. You never get anywhere with them,” said Tom Voss, trainer of the 2005 NSA Novice Hurdler Filly/Mare champion, Guelph. “You can give them some Regumate or take them out [of training] to breed them and it changes their attitude.”

Guelph’s impressive performances last season, including five starts, four wins and one third, left her seventh in the NSA money-won standings for all horses, with $87,000 in winnings.

Regumate contains the oral progestin Altrenogest and vegetable oil. Although widely used and proven effective, Regumate has its drawbacks. This product is administered orally and daily, which can become a nuisance. Those dispensing the drug must wear rubber gloves, and it’s suggested that women who are pregnant or suspect they’re pregnant shouldn’t handle the product. Finally, because of the daily dosage and the expense of Regumate, this treatment can be considered costly.

“Regumate remains the most popular drug therapy for cycling mares,” said Bill Ley, DVM, of Rectortown Equine Center in Virginia. “But other methods are used, such as Depo-Provera and other long-acting progesterone agents. Also relatively common are growth hormone implants used in cattle. Even intrauterine devices, otherwise known as the marble technique, are still used today.”

The drawbacks of Regumate may be worth enduring if the desired outcome is achieved. A study done by the College of Veterinary and Biomedical Studies at Colorado State University found the product Synotex-S, one of the cattle implants used in mares <!– /* Font Definitions */ @font-face {font-family:”Times New Roman”; panose-1:0 2 2 6 3 5 4 5 2 3; mso-font-charset:0; mso-generic-font-family:auto; mso-font-pitch:variable; mso-font-signature:50331648 0 0 0 1 0;} /* Style Definitions */ p.MsoNormal, li.MsoNormal, div.MsoNormal {mso-style-parent:””; margin:0in; margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:12.0pt; font-family:”Times New Roman”;} table.MsoNormalTable {mso-style-parent:””; font-size:10.0pt; font-family:”Times New Roman”;} @page Section1 {size:8.5in 11.0in; margin:1.0in 1.25in 1.0in 1.25in; mso-header-margin:.5in; mso-footer-margin:.5in; mso-paper-source:0;} div.Section1 {page:Section1;} –> ineffective—even in high doses—in suppressing behavior related to estrus or ovulation in mares.

On the other hand, according to Jos Mottershead, an equine reproduction specialist, research has confirmed that when a marble is placed in a mare’s uterus, 45 to 70 percent of mares, depending upon which research project is reviewed, will not return to estrus for up to 90 days.

Also, a less invasive and increasingly popular method for altering a mare’s behavior is herbal supplements. Though little is known about their long-term effects, products such as chasteberry are said to help level out a mare’s hormones and may assist in suppressing excessive behaviors during heat.

Horsemen must use caution when using these or any products to suppress estrus as they may or may not be in compliance with the drugs and medication rules of the sport’s governing body. If you have specific questions, contact your veterinarian, who can guide you in the right direction.

An Eye On The Future

So you’ve found the right therapy to keep your mare’s focus on her work. Everything’s great, right? Well, maybe. Whenever you tinker with nature, you must consider there may be consequences. And altering a mare’s cycle can cause problems later on if the mare is destined for the breeding shed.

“Overpowering the heat phase of the cycle also suppresses the intrauterine immune response, which is important for clearing possible uterine pathogenic contamination on a regular basis. If a pathogen is present in the uterus when the therapy is started and the uterus is then not able to clean itself, a uterine infection may result that could end in infertility,” said Mottershead.

“I highly recommend owners have a uterine swab taken with a culture and a cytology smear performed showing acceptable results before initiating progestin therapy,” Mottershead added. “The cytology will show the presence or absence of inflammatory cells and the culture will hopefully identify that causative pathogen if inflammation is present so that suitable treatment can be initiated.”

Factors other than hormone therapies are sometimes more detrimental to a mare’s future breeding soundness. Spaying a mare is obviously the extreme to this situation, but sometimes this procedure is the only way of dealing with a mare that exhibits extreme behavior.

Age and a mare’s fitness level are also factors to consider if a sport horse mare is also to be a future broodmare.

“It can be difficult to settle a mare who is at a high level of fitness, say a maiden mare straight off racing,” said Ley. “I usually suggest eight to nine months off exercise before she’s to be bred, but it can be as little as three to four months.”

In some circumstances, the best way to deal with a mare’s behavioral issues is to remove her ovaries, called an ovariectomy. For example, a mare with an ovarian tumor typically exhibits an ill-temper, and may squeal, bite, kick and present stallion-like behavior. Once a mare’s ovaries are removed, she no longer has an estrous cycle, so she doesn’t exhibit these behaviors.

In choosing this option, careful consideration must be taken as to the intended use of the mare for the future. Removing the mare’s ovaries is permanent. Studies are currently underway, however, in which the removed ovaries are preserved for future fertilization.

Training And Competition

In steeplechasing, far fewer mares and fillies compete than geldings and stallions. Most trainers agree that, generally speaking, mares are just not quite as tough and not as fast racing over fences and believe they’re at a disadvantage when pitted against their male counterparts.

“Life’s Illusion was built like a stud horse and could easily run and jump with boys,” said Doug Fout, who rode the only filly to ever win the NSA Horse of the Year title and racing’s Eclipse Award in 1975.

“Everyone’s an individual on a given day,” said Voss. “Life’s Illusion could beat the boys. Guelph is not very big; she’s small and petite, but she’s a top class jumper and she can run.”

Fout added, “The good ones have to be tougher than normal.”

Out of the 33 horses in Fout’s barn, only four of them are fillies. Fout, believes that special treatment, rather than drug therapies, works for him with his mares.

“I make sure they’re happy and give them extra turn-out time. They get turned out before and brought in way later than the boys. I keep them on a regular regimen,” Fout noted.

“You can’t run a filly and then put her in again in two weeks. Usually, they can’t take it physically or mentally,” said Voss who, like Fout, believes fillies need to be tough. “The dominant alpha mares are the tough ones. They are the over-achievers. But overall, I think you need to pamper them.”

The NSA awards weight allowances for mares and fillies of up to eight pounds when competing against males. And, in 2003, the NSA added a segregated division just for mares and fillies. “You will see more mares and fillies because now it’s less risky [to run them against the colts] and the money is in it,” noted Fout.