Breeding values are a studbook’s estimation of the ability of a stallion or a mare to produce successful offspring in dressage, showjumping and eventing. They are therefore an important tool in supporting the improvement of sport horse breeding and can offer valuable guidance to breeders.

In order to calculate a breeding value, studbooks can use data about a stallion or mare’s progeny, including national and international performance records and linear profiles. These can be collated to identify the phenotype and performance characteristics that the horse appears to be most likely to pass on.

Based on the performance success of the offspring, and the desirability of the traits they most commonly exhibit, a numerical breeding value can be calculated using a “Best Linear Unbiased Predictor” (BLUP), which is a common method used to create indices for various characteristics for breeding animals within a population. A common index is based on a deviation from 100, which is the population norm so an index of 120 is above the norm, whereas an index of 80 indicates an animal below the norm.

The quantitative analyses use Breeding Value data from specialized evaluation tests, actual performance results, and desired trait scores. As these observable traits and performance outcomes in horses are also subject to a wide range environmental influences, from nutrition of the broodmare all the way to ability of the rider, these values are an estimation.

Since there is large variability among individuals - even closely related individuals - large data sets are required to develop the benchmark index.

Historically, studbooks have been working with their own separate data sets, including their national performance records and their own linear profiles. As many of the most successful and popular stallions are graded with multiple studbooks, and produce offspring all over the world, this has led to some anomalies, with different breeding values generated for the same stallion, depending on country and breeding population.

Working towards International Breeding Values

It is obvious that bringing all the information together from different studbooks, different countries and international sports results, provides a more complete, and reliable picture of a stallions’ heredity than the smaller pockets of data from individual countries or studbooks. This advantage is not purely a function of the larger volume of data available. Calculating breeding values beyond the refines of a single studbook also increases the likelihood of including a wider range of mares, which again allows to paint a more reliable picture of a stallion’s contribution.

At the WBFSH annual meeting 2019 in Saumur, delegates participated in a seminar and workshop about International Breeding Values, organised by the Scientific Advisory Committee’s predecessor, CIGA. The outcome was a clear mandate to continue with the work towards the calculation of international breeding values, with strong interest from studbooks of all sizes and from all over the world.

Since then, the SAC team have been working on a plan for the costs and execution of the IBV project.

To be able to do so they have developed a questionnaire to be filled in by interested studbooks with existing national genetic evaluations. The report recommended to use the IBV project for comparing between different approaches of international genetic evaluation and investigate first whether and how MACE (multi-trait across country evaluation) can be adopted for the sport horse. The team of scientists has suggested some alternative options for this investigation, and we continue to work on a road map for the implementation of this interesting and important project.