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11 July 2006

The Importance of Culling Mares

by Tom Reed

Morningside Stud's mission is to breed and produce world-class competition horses for the three Olympic disciplines of showjumping, eventing, and dressage by crossing world-class warmblood sires with mares that possess world-class performance bloodlines and outstanding athleticism.
Morningside Stud's Mission Statement

The goal we have set for ourselves of breeding and producing world-class athletes is a tough one. If we are to achieve this goal on a systematic basis we must use world-class stallions and mares in our breeding program and make informed, creative, and bold choices about which particular genetic endowments to combine each year to produce a foal. That's the fun part: analyzing bloodlines, genotypes, phenotypes, and the actual production of mares and stallions to decide which stallions and mares are paired each year.

The not-so-fun part is deciding which mares (and stallions) to remove from our breeding program.

Each year we cull a minimum of 10% of our female herd (in practice we have been culling 10 - 15% each year). How do we decide which mares and fillies to cull?

If a mare produces a foal that is in the bottom 10% (10th percentile) of its cohort in terms of athleticism, type, movement, and conformation the mare is put on a "watch list".

The following year if she produces a foal that is in the bottom 10% of its cohort the mare is culled. If she produces a foal that is between the 11th and 25th percentile of its cohort the mare is maintained on the "watch list" for another year.

The next year if the produces another foal that is below the 25th percentile she is culled.

If the foal she subsequently produces is an extraordinary filly -- and apparently superior to its dam in terms of athleticism, type, movement, and conformation -- we cull the mare from the breeding program and keep the filly foal.

What do we do with our culled mares?

If the mare produces correct foals but they are simply not good enough for Morningside Stud's breeding and competition program we give the mare to a good friend whose breeding aspirations are not as high as ours.

If the mare produces incorrect foals she is removed from the breeding population through euthanasia.

We never sell culled mares to other breeders.