from the Vet Corner Archives

Part of Horse Previews Magazine website. Posted on 08/2000; 2:00:00PM.


Veterinary Corner 08/00: Considerations of a Large Breeding Operation

by Sylvia Miller, DVM
Edgecliff Equine Hospital
S. 1322 Park Road, Spokane, WA 99212 * 509/924-6069


Howdy! It's great to be back in Washington after some lethal 108[ring] days in central California. In an attempt to further my education (aside from continuing education courses and the usual conventions) and indulge in my passion of horses, I spent several months on a large (700 horses) Thoroughbred breeding farm in the central valley this spring. The farm stands 11 stallions and in addition to the broodmares, also has a training division for 2 and 3 year olds with a track.

Mares are arranged by pregnancy status (last breeding date or open), whether resident or nonresident mares, and foal age. Nonresident mares live in large individual comfortable pens that are freestanding and separated from other pens by at least 10 feet. The foaling barn and close up pasture are adjacent to the many rows of pens.

A 24 hour foaling crew observes all mares close to their foaling dates and attends each parturition (birth). Each foal is administered oxygen if needed and closely observed. The appearance of the foal, time to stand, time to nurse, umbilical dips, and passage of meconium are recorded as well as the weight and appearance of the placenta. A thorough physical exam, including CBC and zinc sulfate precipitate test (for failure of passive transfer of immunoglobulins from colostrum), are performed within 12 hours of birth by the veterinarian. Flexural deformities are noted and treated if needed, along with other anatomical anomalies. At the same time, the mare is inspected via speculum for the presence of lacerations, hematomas, urine pooling, and discharge.

Due to the numbers of foaling mares, a large colostrum bank can be maintained for those foals anticipated to have such problems as neonatal isoerythrolysis.

Each foal's temperature, attitude, frequency and duration of nursing, and activity level is noted for the first 5 days of life. A foal may be normal one minute, then break with diarrhea and become prostrate within hours. Any foal "not acting right" is examined and a CBC/panel run immediately. Luckily, the farm has in-house laboratory machines available, enabling us to have results within 30 minutes and to adjust the IV fluids or treatment regimen accordingly.

The differences in breeding operations is considerable. The absence of teasers on the small (less than 10 mares) or backyard operations is significant. Large farms (greater than 100 mares) use teasers every day or every other day and keep detailed records of the mare's response to teasing, heat cycles, palpation and ultrasound findings, hormone therapies, parturition dates, foal weights, and any problems noted.

This documentation is used to interpret the current palpation/ultrasound picture of her reproductive tract. With this information, you can answer such questions as: Does she have a dominant follicle? Will there be a double ovulation (and possibly twins)? Is she still transitional? Is there uterine edema and/or fluid-and what is the character of the fluid? What is the cervical tone in conjunction with follicular development/ovulation? Does she have a CL (corpus luteum) or has the follicle regressed without ovulating? Does she have uterine cysts that would complicate pregnancy findings or a pregnancy?

Each mare is followed closely. Once she is bred, she is evaluated for ovulation, pregnancy at about 16 days, embryo size and development at 26-28 days, and again before being shipped home or to pasture. The size of the embryo and presence of a heartbeat are recorded. Unless previous pregnancy problems exist, mares are turned out on pasture after the final preg check at 45 days.

The most common factors that sabotage fertility in the mare are uterine infectious agents and pathological problems. Such diagnostic tools as uterine cultures and sensitivities, biopsies, endocrine and hormone assays may be employed to determine the exact culprit. Any mare that has been bred twice and does not become pregnant should be further evaluated if the stallion's sperm has good forward motility and morphology. It may even be prudent to culture the stallion's semen.

Someone once said, "It's easy to get high pregnancy numbers, but how many actually foal determines the success of your breeding program." Thus, good nutrition and regular "tune ups" are key to maintaining the mare's health, along with extra care and diagnostics for those with placental insufficiencies suspected from previous pregnancies. A large breeding operation has to have some method of herd health program-vaccinations, deworming, regular farrier care, and dental evaluations/work, not only for the mare, but for the foal as well.

As we approach the end of the breeding season, it is a good time to evaluate those mares that are barren and won't conceive this year, to laser the cysts, treat the mares with severe uterine infections and afford them "sexual rest," and to make plans for the next breeding season.

If you need additional information, there are many references available, from web sites for "The Horse" to reproduction books and, of course, your veterinarian. We at Edgecliff are happy to answer your questions.

May all your broodmares be pregnant and a prosperous season follow!

Sylvia Miller, DVM


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