Size isn’t just important at the sales grounds. Sometimes, I would swear it is everything. The advantage of large horses at the sales is that they tend to generate a larger return for sellers, providing they are strong and correct, walk well, and pass the vet.
The competition at the racetrack is even stiffer than at the yearling sales, and the results at the racetrack leave no doubt that big horses have some advantages over smaller competitors.
Some of these advantages are as obvious as those that attract attention at the sales. A big horse should have a bigger stride, for instance. With longer legs, a longer body, and correspondingly larger muscles and bone, a big power horse is a formidable competitor, and one of John Madden’s maxims comes to mind: “A good big horse will beat a good little one.”
But, as with most maxims, there was a corresponding one from Madden: “Many big turnips are hollow.” There’s more truth in the statement than might appear from the homely wrapping of Madden’s phrase.
Just as they have advantages, the big power horses possess some disadvantages when compared to their slightly smaller, typey, and mechanically well-balanced competition.
The big horse has two chinks in its armor. With increasing size also comes increasing difficulty in preserving soundness and speed.
The soundness issues come from two sources. First, the power horse puts more pressure on its legs by relying on its propulsion power for speed, and second, the longer any bone is, the greater the bending stress it has to survive when put under great pressure.
To compensate for these challenges, a power horse needs more bone, and this adds more weight. To compensate for the increase in added weight and size, the power horse’s engine, which he is relying on for his success, has to increase in greater proportion to what it is pushing forward.
An appropriate analogy would be the difference between the engines of a large sedan and a compact car. While a small car can race very efficiently with an oversized engine, a large car with a little engine cannot go very far or very fast.
Following this analogy, horses who succeed due to specialized traits are more likely to lose class (or success) if they aren’t mated so that they have greater chances of retaining their best traits. In the normal course of breeding, these specialized horses will not find the most suitable mates as often, and as a result, they will be less consistent than the horses of Type I, who can mate with most mares and still retain many of their best traits.