Articles: Horse Tips
Mathematics Can Assist Evaluation Of Horse Breeding Activity
By Donald Stotts
STILLWATER - Mathematics is often associated more with feats of engineering
or abstract thought than with raising horses, but mathematics can play a
vital role in meeting breeding objectives.
The goal of breeding farm activities is to produce live foals, said Dave
Freeman, Oklahoma Cooperative Extension Service equine specialist.
"Review of past breeding and foal histories allows for more accurate
assessment of procedures that aid in obtaining a live foal," Freeman said.
"Annual breeding season records can be summarized to aid in the evaluation
of breeding procedures used on the farm."
Several ratios can be calculated from breeding records to determine how well
the goal of producing live foals was reached.
Freeman said the most routinely conducted evaluation is pregnancy rate.
Pregnancy rate is the number of mares pregnant on a specific day divided by
the number of mares bred.
"Pregnancy rate can be determined on the basis of one ovulatory period or on
the total breeding season," Freeman said. For example, an early pregnancy
check of 20 mares reveals that 17 have embryos and three remain unbred.
The pregnancy rate is 17 divided by 20 times 100, a figure of 85
Number of cycles per pregnancy further defines breeding efficiency. The
smaller the average number of cycles per pregnancy, the greater the
efficiency, Freeman said.
Given the operation in example one, a review of records indicates that 10
mares were settled on one heat cycle, five mares were settled on two heat
cycles and two mares were settled on three cycles. The number of cycles per
pregnancy would be [(10x1)+(5x2)+(2x3)] divided by 17, the number of mares
that got pregnant. Thus, the average number of cycles per pregnancy would
be 1.5 cycles. Freeman said foaling rate is another useful tool. It
indicates the percent of matings that produced a live foal. Foaling rate is
determined by dividing the number of foals by the number of mares mated then
multiplying by 100. If 15 of 20 mares bred produced live foals, the foaling
rate would be 75 percent (15/20 x 100).
"The foaling rate provides the overall ratio of efficiency, but more
specific ratios such as pregnancy loss rate, embryo loss rate, fetal loss
rate and stillbirth fetal loss rate are needed to identify important
differences at specific times of gestation," Freeman said.
Pregnancy loss rate is the number of mares not foaling divided by the number
pregnant on the first pregnancy check, usually around day 20.
Embryo loss rate is the number not pregnant at the end of the embryo stage
(day 40) divided by the number pregnant on a specific day, such as the day
of the first pregnancy check. Fetal loss rate is the number not foaling
divided by the number pregnant on a specific day.
"Records provide the basis for making decisions on breeding individual
mares, allow evaluation of operational success in producing foals and
provide evidence of the need for changes in breeding management activities,"
Freeman said records need to be designed to provide accurate information
that is understandable and readily accessible; records should allow cross
referencing from one record to another, and should minimize time spent
recording without jeopardizing accuracy and detail.
"It's generally best for one person to be responsible for record keeping
throughout the breeding season because this method tends to promote clarity
and consistency," he said.
Freeman said horse owners breeding small numbers of mares may find written
information to be adequate for record keeping, but managers of larger
operations should make use of one of many record keeping computer programs
This article has been graciously provided by OSU Animal Science