Breeding Efficiency Analysis Useful for Breeders

Breeding Efficiency Analysis Useful for Breeders

The difference between foaling rate and pregnancy rate is pregnancy loss, another important statistic; pregnancy losses greater than 10% indicate a problem requiring immediate attention, Freeman says.

Photo: Anne M. Eberhardt/The Horse

If a horse farm experiences consistently low conception or foaling rates, it is likely that a step in breeding management is the cause rather than the breeding efficiency of the mare, according to Dave Freeman, PhD, Oklahoma State University Cooperative Extension equine specialist.

"To promote good conception and foaling rates, the horse breeder first must identify the farm's efficiency status and compare it to a realistic optimum," said Freeman

The first item to review is the farm's pregnancy rates. To find a pregnancy rate, take the number of mares in-foal and divide by the number of mares bred, then multiply by 100. Pregnancy rates can be affected by many factors including the reproductive status of mares, the age of mares, and the time of breeding in relation to the estrous season.

"Early season pregnancy rates may be lower because of transitional estrus irregularities in some mares," Freeman said. "In addition, the number of mares handled and bred on a farm can affect pregnancy rate if stallion semen production, time, or labor constraints result in poor management."

On an average population of mares, pregnancy rates should be at least 80% with goals of 90% or more.

Another useful breeding efficiency tool is to look at heat cycles per conception. A breeding manager's goal is to approach one cycle per conception for the breeding season. In other words, have each mare bred on one heat cycle.

"Goals between 1.3 cycles and 1.7 cycles per conception would yield an average of 1.5 cycles per conception," Freeman said. "This would indicate that half the mares were settled on one heat cycle while the remaining mares were settled on the subsequent estrus. As a practical management tool, that's fairly efficient."

Finally, it's important to examine the farm's foaling rate (the number of mares foaling divided by the number of mares bred, then multiplied by 100). The difference between foaling rate and pregnancy rate is pregnancy loss, another important statistic.

"The ultimate goal is to get a live foal on the ground," Freeman said. "Pregnancy losses greater than 10 percent indicate a problem requiring immediate attention."

Pregnancy loss may be affected by early embryonic loss or misdiagnosis of pregnancy. Late gestation losses may be caused by rhinopneumonitis or ingestion of endophyte-infected fescue.

While pregnancy rate, cycles per conception, and foaling rate cannot identify the cause of a farm's poor reproductive performance, they do assist in identifying a farm's strengths and weaknesses in the different areas of a breeding program.

"If any of the three indices are not satisfactory, then the breeding manager should review all management practices during or following the breeding season," Freeman said. "After review and consultation, new procedures can be implemented."

In turn, the effectiveness of new procedures can be measured by comparing them with rates from past breeding seasons.

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