There are important differences between the two kinds of harness horses, besides the obvious one of their racing gaits. The pace has distinct physical requirements, and the two gaits are different enough that an astute observer can tell whether a horse is a trotter or pacer merely by watching him graze in the field.

Trotting Horse Characteristics

Although less than 20 percent of today’s harness races in North America feature trotters, some of the most prestigious ones do, including the Hambletonian, the Dexter Cup, and the Kentucky Futurity. There are also plenty of lower-level trotting races, particularly for young horses.

Here are some of the physical characteristics to look for in your trotting candidate:

• Among trotters, there may be no great advantage to height, but body length does matter. The nature of the gait makes interference between front legs and hind legs possible as the horse reaches for more speed. While there are plenty of exceptions, most good trotters are at least as many inches long in the body as they are in height at the withers.
• A fast trot is best performed by a horse with large hindquarters since the gait is based on rear propulsion. You’ll often see good trotters whose hindquarters are higher than their withers as viewed from the side. This horse is referred to as being built downhill. For a trotter, going downhill doesn’t mean he’s no longer the horse he used to be. It’s a description of good trotter shape.
• People used to think that trotters needed a lot of bend in their rear legs to be fast, but this was probably because the great Hambletonian transmitted the characteristic to his offspring. They most likely won in spite of their rear leg conformation, not because of it. Some horses trot well with straight hind legs, some with dramatic bend. Don’t worry about it.

Do worry, though, if you’re eyeing a trotter whose hind legs bow inward at the hocks as viewed from behind. These cow hocks (so named because every cow you meet, fast or slow, has them) cause a horse’s rear hooves to rotate inward at a fast trot, often striking the opposite front foot. This interference makes a smooth, fast trot almost impossible for the horse to maintain.

Pacing Horse Characteristics

No matter what day you go to the harness races in North America, even Hambletonian Day at the Meadowlands, you’ll see more races for pacers than trotters. So put most of your effort into identifying good pacing body type.

Unlike trotters, pacers don’t need body length to assure that forelegs and hind legs on the same side don’t interfere with each other. Instead, they need adequate body width. So good pacers tend to be blockier than trotters, with comparatively short bodies and wide chests. Narrow-chested pacers can move as fast as others, but they often crossfire, causing injury to themselves or causing them to be slowed by the equipment that prevents the injury.

The pace is powered almost as much from the shoulders as the hindquarters, so you’ll see good pacers with narrower hindquarters and more pronounced shoulders than trotters. Pacers with withers higher than their hindquarters are said to be built uphill, and that doesn’t mean that they have more work ahead of them when they race. For a pacer, it can be an advantage.

Cow hocks present few problems to pacers, unless they’re so severe that the horse can’t keep his balance. It’s not true that a pacer is better off with cow hocks. He’s just not at as much of a disadvantage as other horses.