I am a strong believer in the power of genetics. Obviously. Otherwise it would be kind of dumb for me to breed or be so obsessively interested in pedigrees and bloodlines. While we haven’t gotten particularly far along in equine genetics, we do know that certain traits are heritable, or at least seem to be more heritable than others. Here are a few studies if you’re interested in nerd things:
If you really want to lose a couple days, there are studies out there covering the heritability of everything from facial hair patterns to OCD to cribbing to speed. Go to town.
Obviously many breeders and breed associations are obsessed with this. The goal is to make superior horses, generation over generation, and data can certainly be essential to that. Most registries track the offspring closely, assign breeding values to stallions, and even make handy dandy charts to show how a stallion’s offspring tend to trend as far as size, gaits, foot shape, back length, hock angle, etc. While nothing is heritable all the time, I do believe that a lot of things are highly heritable, and some stallions (and mares) are more prepotent for certain traits. A lot of people base a lot of breeding decisions based off of that theory, me included. Looking at the trends among the offspring is much more valuable to a breeder than looking at the stallion himself – you want to know how he produces, what traits seem most heritable. That’s the important part.
Of course, we also know that getting all the necessary traits for success into one package is a tough thing to do. The horse can have all the speed in the world, but if it doesn’t want to run, it won’t be a successful race horse. It could have gaits like Totilas, but if it doesn’t have the brain to withstand the pressures of the job, it probably won’t be winning any medals. Or if it doesn’t stay sound, or if it’s ridiculously hard to ride, etc etc. There’s also the flip side, where the horse might not be particularly talented, but it loves to work and is easy to ride and wants to do a job. Many horses live somewhere in that area. But the truly tip top horses… they tend to have a lot of those qualities combined into one horse.
The recipe for success certainly isn’t as easy as breeding a tip top horse to another tip top horse. Zenyatta’s foals are good examples of that. These traits, while definitely carrying a heritable tendency, just don’t come through all the time, or even most of the time. And to make things even more complicated, there are certain individuals that seem to either seriously out-produce their own quality or seriously under-produce their own quality. It isn’t at all uncommon for a relatively mediocre performance mare to become an absolute tip top producer. Breeding is hard, and relatively unpredictable, at least from our current understanding of genetics.
Like I said earlier though, I do believe that heritability, or at least some genetic tendency, is generally a relatively reliable thing. I become even more convinced of that when I watch JB and Presto at play. JB, the yearling, is very well bred for dressage. He doesn’t quite have the big flashy movement yet, but his natural balance is quite impressive. I have watched him do more textbook perfect canter pirouettes than I can even recall at this point. He’s naturally much stronger behind and across his topline, and has much more natural “sit” ability than Presto does. Which makes sense. Presto is bred to do this:
It’s really interesting to watch them, because they both love to run and buck and roughhouse and all the things that babies do, but their natural predispositions – their purposely bred genetic tendencies – definitely come out. JB’s balance. Presto’s boldness. They’ll be galloping together and then all the sudden Presto will veer down and zip past the edge of the pond, or jump down the bank, or leap over the ditch. He likes the more fun “offroad” path and aims for it on purpose. JB tends to always decline those options, instead choosing to redirect himself to a less risky path, probably throwing in a lovely lead change in the process. I can watch them forever and be endlessly fascinated by it, theorizing on why and how they’re wired to react the way they do. Most of it makes a lot of sense.
I chose Presto’s sire specifically because of the rideability and seemingly natural cross country prowess of all the offspring I’ve seen. He appeared to have a relatively high tendency to produce whatever qualities combine to contribute to success in that phase, particularly with amateur and junior riders. Of course, I do believe that the mare is a, probably the, crucial part of the equation, so I went with a mare that had similar qualities too. Watching Presto now, as he shows me some natural predisposition to his future job, I become even more sold on just how heritable all of these things can be. Certainly, a lot of it is “nurture”, but you can’t discount the basic influence of what we breed into their nature.
I can’t wait to see what scientists keep learning about all of this as we move along and our understanding and technology increases. I’m relatively convinced that there’s a genetic factor to almost everything, maybe even the things that seem anomalistic to us now.