Ask The Vet: Preparing Your Mare for Breeding Season

Answered by, Madison Seamans, DVM, MS, Cornerstone Equine Medical Service, Wilder, Idaho
Courtesy of AAEP

Question: I have a mare that has had one foal. She is having a difficult time getting bred and I have been told her issue is retained fluids. Suggestions?

Answer: Some mares have difficulty conducting a normal pregnancy to term, but retaining fluids post breeding is just one in a long list of problems. There are several factors involved here. Mares over the age of about 13 years have reached their reproductive peak and we can expect some challenges with this group.  The fact that your mare has had a foal increases our odds for a fertile breeding, but age will become a factor. Careful management of difficult mares can markedly increase their conception rate.

We should start as early as possible during the breeding season. Even if we don’t care about getting early foals for the competitive advantage this can have for young horses, the problem mare may take more time to conceive. By placing these mares under artificial lighting on December 1, (8 hours of darkness, 16 of light) most will have a fertile cycle about February 1. This gives us an average of two extra cycles per year–more than in natural lighting–and hopefully, we won’t see October with an empty mare and a large vet bill.

Careful management includes knowing the time of ovulation. The use of hormonal therapies to stimulate ovulation allows us to breed only one time per cycle.  Fertility is a matter of timing rather than frequency– sperm cells present in the uterus at the time of ovulation present our best chance for establishing a pregnancy. In problem mares, multiple covers increases the chance of infection which impairs fertility.

Accurately assessing the time of ovulation allows us to implement several treatment options. There is a five or six day window between conception and the arrival of the fertilized ovum in the uterus. This gives us time to remove excessive fluid, institute treatment for infection and address luteal insufficiency with synthetic progestagins (i.e. Regumate) in mares that need it.  It is not a good idea to “shotgun” problem mares with synthetic progestagins.

Our management plan for problem mares should include, but not be limited to:

1).  Placing the mare under lights December 1 for a period of 16 hours of light and 8 hours of dark.

2).  Vet exam with ultrasound to assess the lining of the uterus

3).  Daily teasing with the stallion. Uterine culture and cytology during the first two days of standing heat.

4).  Hormonal stimulation of ovulation, breed once, follow up exams daily to assess the time of ovulation.

5).  Treatment plan dictated by ultrasound assessment and the results of the culture. (If timed right, this can happen during the same cycle).

6).  Blood tested for progesterone level five days after ovulation to determine luteal function. Consider starting on supplemental progestagins on day five. This hormonal treatment can be stopped if the test comes back normal, but it is better to have this compound on board by day five.

The average conception rate is about 60% per cycle.  So keep trying.  With careful management and a little luck, you’ll have another mouth to feed next year.