The Importance of Breeding
for Fox Trot Gaits
The Importance Of Breeding For The Fox Trot Gait
In 1948, when the first organization was formed to register Missouri Fox Trotting Horses, people had already been breeding horses for the fox trot gait for over a century. Even after the Missouri Fox Trotting Horse Breed Association was formed, the requirement for registration was the ability to demonstrate the fox trot gait. It was not until 1982 and 1983 that the books were closed, meaning, for horses to be registered both parents must be registered.
This changed the definition of a Missouri Fox Trotting Horse. No longer was a Missouri Fox Trotting Horse, a horse that was bred to perform the fox trot gait, it was now a horse whose parents happened to be registered Missouri Fox Trotting Horses. Relying on parentage alone will not perpetuate the fox trot because of the genetics involved in producing the gait. The gait will only be perpetuated if breeders continue to breed for it specifically, like those who bred for the fox trot gait before there was a registry.
Remember, in high school Biology class, studying about a monk named Mendel who raised peas in his garden? He noticed some of the pea’s shells were smooth and others were crinkled. By crossing different combinations of smooth and crinkled shelled peas, and observing the results, he discovered the existence of genes that control the physical characteristics of all living things. He further determined that some genes acted in a dominant fashion and others in a recessive fashion; crossing combinations of dominant and recessive genes yielded predictable out comes based on the mathematical probabilities of which genes each parent passed on.
Applying this to horses, we have genes that cause a horse to trot and genes that cause a horse to pace. The trot genes, T, are dominant and the pace genes, p, are recessive. So, of the three possible combinations of trot and pace genes, TT, Tp, and pp, TT and Tp both show the trot and pp shows the pace characteristic. When crossing these pairs, each parent passes on one of its genes; which of the genes from the pair that is passed on is determined by random chance. If one parent has the TT combination the offspring will always show the trot characteristic, because of the presence of the dominant trot gene. If both parents have the pp combination, the offspring will always show the pace characteristic. When crossing Tp with pp, half the offspring will show the trot and half will show the pace characteristic. When crossing Tp with Tp three fourths of the offspring will show the trot characteristic and one fourth will show the pace characteristic. Up to this point, for the purposes of explaining basic genetic principles, I have looked only at the trot and pace genes themselves. I wish breeding for the fox trot gait was this straight forward. Unfortunately, at least in my biology class, they didn't tell us the whole story.
Eldon Eadie has done extensive study on the genetics of soft gaits in horses. His research shows soft gaits result from the application of a modifier to trot and pace gene combinations. A modifier is a gene, or combination of genes, that has an affect on the characteristic another gene pair determines. Modifiers are not dominate or recessive, their ability to influence other genes varies. The strength of the modifier is the combined result of the modifier from each parent. In other words, for the modifier to be strong, the modifier of both parents needs to be strong; breeding a strong modifier to a weak modifier results in weakening the modifier in the offspring.
In a weak form this modifier allows non gaited horses to walk. In a stronger form it interferes with the trot of TT and Tp horses, and the pace of pp horses. Although the TT and Tp combinations may make it easier for a horse to perform a fox trot, with training, even a pp combination can be taught the gait if the modifier is strong enough. If the modifier is too weak the horse will be too lateral to fox trot. We can observe the strength of this gait modifier in the horse’s ability to walk fast and gait fast. A horse with a weak modifier will not show a good flat walk and will tend to break into a hard trot, or pace, at a fairly slow speed. A horse with a strong modifier will show a very good flat walk, and will tend to gait right up to the speed of the canter. Of course there are a multitude of variations in between, these examples tending to be at opposite ends of the strength scale.
What does all this mean for today’s breeder? It means we need to continue to place the highest priority on producing the fox trot gait. If we rely on the registration of the parents to perpetuate the gait, concentrating our efforts on developing other characteristics, we will end up with a lot of Missouri Fox Trotting Horses that can’t fox trot. Not only should we cross horses for gene pairs that make a fox trot come out easier, i.e. pacey horses to trotty horses, but it is even more important to breed horses for a strong modifier. After all this is what makes gaited horses gait, and the gait is what the registry was originally based on.
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