Foal Heat Breeding

Mares are individuals and each pregnancy has its own unique problems and outcome. This means there is not one right answer for every mare. To help better determine the proper response for your mare, let's look at the basis for the controversy.

Fear of an early abortion from a foal heat breeding is the primary argument used for skipping foal heat. The theory goes that, by skipping foal heat, the uterus of the mare has more time to involute (shrink back down in size). It is suggested that this extra time gives the mare a greater opportunity to prepare an ideal environment for the next newly fertilized egg. The better the conditions, the less chance of abortion.

Research data tends to lend some support to these proponents. A survey done in the early 1960's on Quarter Horses reported that only 50% of the mares conceiving from a foal heat breeding carried to term; in Thoroughbred mares this figure may drop as low as 20%. In reproductively sound mares, the conception rate for all other estrus cycles varies from between 70% to 80%. Comparing these statistics it is obvious to see why it is generally accepted that the other estrus cycles are more fertile than foal heat breedings.

But reduced fertility is not the biggest disadvantage of foal heat breeding. There are three possible outcomes for any breeding: (1) the mare will conceive and carry to term (2) the mare will not conceive (3) the mare will conceive yet will not carry to term. It is mares that abort that are the cause for concern for it is this group that has the most detrimental effect on next year's foal crop. The longer the mare carries before aborting, the greater the chance that she will not produce a foal the following year. Time works against her. The closer to the end of breeding season that she aborts the less time is available to get her back in foal. Also there is a relationship between the length of an aborted pregnancy and the length of time before a mare returns to estrus. The longer the pregnancy the great the interval between the abortion and the first estrus cycle.

With all these negative comments about foal heat breeding, it's hard to imagine how anyone could favor the practice. But there are some advantages that might outweigh the disadvantages.

Foal heat is one of the most predictable estrus periods. Mares normally come into estrus nine days after foaling and stay in standing-heat two to five days, ovulating or leasing an egg 24 48 hours before going out of heat. This makes the number of stallion covers minimal even for the most naive stud manager.

Foal heat breeding is also the most advantageous way to move back a mare's foaling date. For example, a mare foaling on May 25 should be in foal heat around June 3rd. Conception during this cycle will bring the resulting foal to term about the middle of May of the following year. By continuing to practice foal heat breeding, it is, theoretically, possible to get a mare's foals on the ground earlier each year.

For today's horse business, this is a very viable reason to practice foal heat breeding. Financial success, however, is hinged on your ability to also make it a wise management decision. Over the last thirty years in the business of breeding horses, we have developed a set of guidelines to determine when foal heat breeding is a good risk. By religiously applying these standards, foaling rates of 70% 90% from foal heat breeding can be produced. This means that a mare must pass all of these requirements to be bred on foal heat. Failure to qualify on any one of the criteria determines that the mare is no longer a candidate for foal heat breeding.

1. A mare must have a normal presentation at birth. The delivery must not be excessively difficult. This helps insure that there are no hematomas, lacerations or excessive bacterial infections.

2. The placenta or afterbirth must not weigh over 14 lbs after the embryonic fluids are drained from it unless the foal weighs over 120 lbs. A heavier placenta would indicate a thickened wall perhaps due to a endometritis during pregnancy.

3. The mare must expel the afterbirth voluntarily within three hours after foaling. Failure to eliminate the afterbirth within this time period provides a larger window of opportunity for a larger-than-normal bacterial infection of the reproductive tract.

4. By the time the mare reaches her nine day heat there should be no discolored (purulent) discharge coming from the vulva to indicate puss cells from infection.

5. It is essential that the mare had a normal, strong, healthy foal that nursed vigorously for the first nine days. Nursing foals stimulate the release of the hormone, oxytocin. Oxytocin triggers milk let-down and uterine contractions. Uterine contractions cause the mare's uterus to involute and clean up quickly, preparing the uterus for another subsequent pregnancy.

Nature designed this fertile foal heat period for the horse. Evolutionarily it must have served as an advantage to the species. Although 5000 years of domestication has created some problems with the system, proper management can turn nature's design into a blessing rather than a curse.