With breeding season just around the corner, it's time to start planning your management of empty mares. Nothing drains your enthusiasm and your bank account more than
mares who don't produce foals. Open mares who are
"problems" are those whose fertility has been
declining over time due to irregular cycles, failure to
ovulate, recurrent uterine infection, or repeated
pregnancy loss.
Regardless of the cause, basic management is critical
in handling these mares. You must be able to determine
when the mare is receptive to a stallion and you must be
able to document ovulation. The first requirement is best
accomplished by teasing on a regular schedule, and the
second by having your veterinarian examine the mare. Then
you must keep accurate records.
If you haven't used lighting systems to advance the
season, don't get impatient and breed the mare before she
has established a good cycle with short heat periods and
predictable ovulation. Much damage is done by breeding
mares too often during a given estrus. In temperate
zones, the average first ovulation of the season is in
April!
Prior to breeding the mare, she should be examined,
during estrus, to determine the following: presence of a
pre-ovulatory follicle, lack of fluid in the uterus, no
evidence or signs of uterine inflammation (redness of the
cervix or vagina, discharge from the cervix or vagina,
positive uterine cytology). These determinations require
rectal palpation of the reproductive tract, visual
vaginal examination, a swab to collect a cytology
specimen, and ideally, ultrasound evaluation of the
uterus. If there are signs of inflammation, a culture is
indicated to identify the cause. (Some farms require a
negative culture before they will breed your mare, but
negative cytology is more reliable as an indicator of
uterine health.)
Mares that have positive signs of inflammation may
require treatment before they are bred. The decision to
treat, and with what, must be based on history, the cause
of the inflammation, and the overall assessment of its
significance. You and your veterinarian need to discuss
the situation and agree on a course of action. There is a
growing tendency by some practitioners to avoid infusion
of antibiotics in favor of uterine lavage or other
alternative therapy. This is based on experiences with
resistant bacteria or yeast infections after prolonged
antibiotic use.
It is important to understand the concept of uterine
resistance when managing a mare with a history of
recurrent infection. All mares develop an inflammation
after breeding. If that process is resolved quickly,
pregnancy is possible. If the inflammation drags on for
days, the embryo will not survive. Thus, mares resistant
to infection are those with effective defense mechanisms.
A key factor in uterine resistance is the ability of
the uterus to empty itself after inflammation begins. Dr.
Michelle LeBlanc, at the University of Florida, has
demonstrated this very clearly (MHB, January 1995, pages
16-17). She has shown that treatment to enhance uterine
clearance after breeding is indicated in more than 60% of
mares with recurrent endometritis. Treatment administered
8-12 hours after breeding with oxytocin or oxytocin plus
uterine lavage resulted in significant improvement in
conception.
Mares that may benefit from this treatment are those
that remain actively inflamed several days after
breeding. This can be confirmed by finding fluid in the
uterus (using ultrasound) seven days following breeding.
Another highly suggestive sign is a positive cytologic
exam when the mare returns to heat.
While recurrent infection is a major source of reduced
fertility in mares, there are several other common
problems with which to contend. Most can be resolved by
good husbandry and management practices used in
conjunction with veterinary expertise and advice. When
good managers team up with veterinarians, positive
results are most likely to follow.
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