Genomic Inbreeding Value

Another valuable area where ancestry testing comes into play is with inbreeding. It’s widely understood that inbreeding (the practice of breeding from closely related animals, especially over many generations) is not ideal, but it was somewhat unavoidable back when there were considerably fewer horses to breed. Now, however, we can be much more selective in our breeding practices to maximize genetic diversity and performance. One recent study of Thoroughbreds found that a 10% increase in inbreeding is associated with a 7% lower probability of ever racing. Put simply, this means that as inbreeding goes up, performance goes down.

Our ancestry testing provides you with a “Genomic Inbreeding Value.” That is a measure of your horse’s inbreeding derived from their actual genetic diversity as opposed to the more commonly used inbreeding coefficient which is a calculated estimate based on a horse’s reported pedigree. Two full siblings from the same parents will show the same inbreeding coefficient using the traditional pedigree estimate when, in reality, they can be very different.

For example, you could have two broodmares that are full sisters, therefore they share identical pedigrees, but differ in their genomic inbreeding value. Armed with that information, you may choose to breed the mare with a lower inbreeding value over the mare with a higher inbreeding value to optimize your future foal’s genetic makeup for greater diversity.

References

Hill, E. W., Stoffel, M. A., McGivney, B. A., MacHugh, D. E., & Pemberton, J. M. (2022). Inbreeding depression and the probability of racing in the Thoroughbred horse. Proceedings of the Royal Society B: Biological Sciences, 289(1977). https://doi.org/10.1098/rspb.2022.0487.