About this time every year, as mares foal, mare owners begin
to consider rebreeding on foal heat (estrous), rather than waiting for the
30-day estrous. Wanting to move the
birth-date of next year’s foal up a couple of weeks is an option that horsemen
have considered for decades. When weanling and yearling halter futurities were
popular, early foals were highly desired.
Thoroughbred breeders, especially those breeding for the sales ring,
seek early foals as well while racing soundness and success, is less affected
by an early birthdate. If you are
considering breeding your mare on foal heat, ask yourself two questions: 1. What do you actually gain by moving the
breeding date and resulting foaling date up approximately 3- weeks? 2. Is
there anything to be gained by waiting until the 30-day foal heat?
Let’s look at the first question, what do you actually gain
by moving the breeding date and resulting foaling date up approximately 3
weeks? The first answer to this question
is actually found in the question itself, by breeding your mare on the foal
heat, the foal is born approximately 3 weeks earlier the next year, than it
would have been had you waited to breed the mare during the 30-day heat. Of course, this assumes the mare conceives on
either of those heat cycles.
The second advantage to breeding mares on foal heat is that
the mare is less likely to return to anestrus (period of reproductive
inactivity) following the foal heat. If
the mare does return to anestrus post foaling, it may be 2-3 months before she
is physiologically ready to be bred. So,
these are the primary advantages of breeding on foal heat, what are the
disadvantages?
First, comparing mares bred for the first-time, postpartum,
on either foal heat or on a 30-day or later heat, mares bred on foal heat have
a lower pregnancy rate. Second,
postpartum mares bred on foal heat, lose a greater number of the resulting
pregnancies than mares bred on or after the 30-day heat. This information alone, suggests that waiting
to breed mares on the 30-day postpartum estrous, may result in greater
reproductive efficiency (pregnancy and then carrying the foal to term).
In the week or two after parturition (foaling) occurs, the
reproductive tract goes through a period of cleansing and recovery. The length of time required for post-foaling
recovery may be determined by the ease of the foaling process, the level of
trauma to the uterus during foaling, and the timely passage of the placenta,
among other things. Therefore, not every
mare is a good candidate to be bred on foal heat and even if the mare becomes
pregnant off of that breeding, chances of carrying the foal to term are generally
less than if the mare were bred on the 30-day or later heat.
If the mare undergoes a normal foaling, the placenta is
passed in a timely manner, the mare carries good body weight, and a breeding
exam by a veterinarian indicates the reproductive tract has recovered
sufficiently, then breeding on foal heat may be a reasonable option. If the breeding soundness exam indicates the
mare could use a week or two of further recovery before breeding, you have
little to lose by waiting. In this
situation, if you breed the mare on foal heat and she later loses the
pregnancy, you may lose the entire year, only to start over the following
breeding season.
