Page 34 - NMHBA Spring 2022

A MOMENT IN TIME
From Racemare to
Broodmare-Transitions
BY HEATHER SMITH THOMAS • Previously published in the Jan./Feb. 2005 New Mexico Horse Breeder
Ideal age to breed a mare for the first time is when she is 4 to 7 years old, though maiden mares can often be successfully bred later, retiring to the broodmare band after a long athletic career. That career can be quite short, however,
if the filly is retired after an injury or for other reasons. No filly should be bred until she is mature. Some mature early and can be bred at 3 to foal at 4, but most are better off to wait until age 4 to be bred.
A breeding soundness exam should be done ahead of time, whether a mare is 3 or 13. Just because a mare has never been bred does not mean she won’t have an infection or physical problem that might interfere with conception or carrying a foal. When examining a mare for breeding soundness, the veterinarian will check her
uterus and ovaries by rectal palpation and ultrasound. If the ovaries are hard, fibrous, or excessively large, the mare may have a fertility problem. Occasionally a mare may have a cyst or tumor. If one ovary is enlarged (as with a granulosa cell tumor) the opposite ovary may be small and atrophied due to steroid hormones secreted by the tumorous one. A granulosa cell tumor is not uncommon in mares
3 to 5 years old. Some of these mares will show abnormal sexual behavior, due to hormone abnormalities created by the tumor. It must be removed before they can be fertile.
Normal ovaries fluctuate in size, depending on the stage of the mare’s reproductive cycle and follicular activity, so it is important to differentiate between a normal large ovary which is developing several follicles, and a cystic or tumorous one. While checking the ovaries, the veterinarian should also check the fallopian tubes for adhesions that might interfere with passage of eggs. The vagina, uterus and cervix should be checked for any signs of infection, adhesions, scarring or abnormal discharge.
On rare occasion, a mare is found to have an improperly developed genital tract or an inherited or congenital defect that would prevent reproduction. More common is a maiden mare
with an imperforate hymen or an obstructing membrane partition. These problems can be corrected by the veterinarian at the time
of the examination. The membranes generally don’t interfere with breeding because they will be torn at that time, but tearing can lead to infection. It is better to eliminate these obstructions using sterile techniques, allowing the mare 2 to 3 weeks to heal before being bred, so there will be no soreness.
MANAGING FILLIES OFF THE TRACK - If a filly or mare is retiring from an athletic career, she should be given time to “let
down” and adjust to her new status before being bred. Trying to breed her too soon after coming off the track, for instance, may not be successful. She may not be ready physically or psychologically
to make a quick adjustment. If she received medication (such as steroids for treating an athletic injury, or to smooth out erratic behavior) this may interfere with her heat cycles. If she was given hormone treatments to keep her out of heat while racing, this may also interfere with success as a broodmare, until enough time has elapsed to clear all these from her system. Knowing her medical history can be a big help.
Jim Ward, DVM (in equine reproductive practice in East Texas) deals with many fillies coming off the track. “It’s always important to not change their management abruptly when they retire to
the broodmare band. They are accustomed to being treated as individuals. Often when a mare comes off the track, she is thrown out with a bunch of mares and is not accustomed to herd life. In my experience, these young mares are sometimes difficult to breed, perhaps because of nervousness and stress, and sometimes they lose weight from the stress,” he says.
“I always try to keep them in a stall, introduce them to one mare they can be buddies with, and try to minimize the stress. If you can handle them that way, you can often get them bred immediately, coming off the track. By contrast, if you put them out in the herd, they don’t do as well. They’ve been used to a lot of care, and if you suddenly and totally change their environment, this is a stress. Even though you are putting them into a more natural environment (herd life) they are just not ready for it.”
Ward says he continues to keep them in a stall, or at least where they can be kept individually. “I’ve had mares in small groups that would not cycle, and as soon as I put them back into an individual situation, within a week to 10 days they started cycling,” he says.
“Other than that, most of them are generally very fertile, except for mares that have been on hormones to keep them out of heat while racing. If they’ve been on Regumate, it’s usually not long lasting, but it might take a few months for some of these mares to make the transition back to normal heats,” he says.
“Many times, fillies coming off the track are nervous, and a lot of them are not carrying enough body flesh to cycle properly. They are in very fit athletic condition, with no extra weight. If you can get these fillies in the fall, before the breeding season, this gives you time to get them more ready. All too often, however, they have an abrupt change. Something happens, like an injury, so the owner immediately decides to breed the mare, and this can complicate things,” explains Ward.
“Once you get over these little hurdles, however, these mares are usually fine, though there’s a tendency for some of them to lose a pregnancy – and this may be due to stress. So, you have to handle them with care. You can get them bred and pregnant, but you must be careful about introducing them to the herd. If you create too
32 New Mexico Horse Breeder