On The Other Side of Nicking: Female Families

Some stallions seem to have an affinity for specific female families

Nicking is a well-known pedigree concept best explained as the affinity of stallions from a certain sire line with mares from another sire line. It's a very useful tool in pedigree analysis, and programs like eNicks and TrueNicks make them easy to measure and track. However, they are just a piece of puzzle that is pedigree, and by nature overlook an incredibly important aspect - the family of the mare.

Unlike with stallions, there is a guarantee with a mare that part of her DNA - her mitochondrial DNA - is being passed on to all of her offspring. This mitochondrial DNA remains unchanged through generations (except in the case of mutations, which are estimated to be 10 to 20 times more frequent than in nuclear DNA but still exceptionally rare), and thus we can assume that a mare has the same mitochondrial DNA as all of her tail-female ancestors.

While historical stud book errors do muddy the waters of some Bruce Lowe families, others seem to be remarkably well-preserved based on genetic testing, and I consider these family numbers to be a convenient way of grouping and analyzing female families for this purpose. I find the idea of stallions having an affinity for certain female families or mitochondrial haplotypes to be a fascinating concept, and have spent a lot of time doing what research I can with the tools at my disposal to determine if there's any merit to the idea. Today, I’d like to talk about three stallions who it appears may have an affinity for being crossed with specific female families, but I’ll likely return to talk about other stallions in the future.

Of course, there's the major issues of sample size and confounding variables in most pedigree research, but I figure that if TrueNicks can give the Curlin/More Than Ready cross an "A++" based on five starters, we can at least explore the possibility of stallion affinity with certain female families. Below, I'll discuss a few stallions who might have a pattern of success with specific female lines. I've looked at both how these stallions fare with a direct female family (and thus a shared mitochondrial line), as well as with mares by stallions from this female family, to see if perhaps there are certain nuclear DNA traits more commonly found in certain female families that work well together (in a similar fashion to the assumed genetic mechanism behind nicking).