by Patricia N. Saffran

“Do you see that Thoroughbred in the pasture over there with the splotchy paint colors and white socks above the knees? He has to have Quarter Horse in him, but don’t say I told you so.

I could get in a lot of trouble with the Jockey Club if anyone found out I was saying Thoroughbreds aren’t what they’re supposed to be,” so says an anonymous source on a visit to a New York State Thoroughbred farm. Sure enough, the horse in question had a beautiful Thoroughbred conformation but was quite colorful.

Do Thoroughbreds have Quarter Horse in them and is that responsible for the occasional high colors and socks above the knees? What are the genetics responsible for the high colors in both breeds so that one pattern can resemble the other, or more importantly, what are the latest genetic findings?

The Thoroughbred is often described as a purebred horse but this is not the case according to Franco Varola. He modified a French mathematical theory, Dosage Index, for racehorse performance with a points rating to distinguish short distance sprinters against the stamina needed for long distance runners.

In Typology of the Racehorse, J.A. Allen, 1974, Varola writes, “The Thoroughbred in the present-day meaning of the word is neither a pure nor an impure animal, but much more simply a hybrid, obtained by crossing different strains for racing purposes, and by keeping these strains isolated from the remainder of the species of the genus Equus within a register known as the General Stud Book [UK, first published in 1793].”

Varola finds the influence of the founding fathers of the breed in the 18th century too nebulous and prefers to trace them through more recent descendants, who have been bred to each other in what he calls a kaleidoscope of changing parts that remain the same. Regardless, he still refers to Thoroughbreds as hybrids. The notion of hybrid also applies to Quarter Horses.

Read more: In Hot Pursuit of Thoroughbred and Quarter Horse High Colors

Kathleen Gustafson, PhD and Eleanor M. Kellon, VMD

The ECIR Group has improved the welfare of equines with metabolic disorder by focusing on prevention and treatment of Laminitis. The US alone has almost 10 million horses. The most current estimates are that 10% to 15% of horses will suffer from Laminitis every year, with 80% to 90% of the cases caused by endocrine disease. On average, that is 1 million horses per year in the US alone.

They recommend that Horses who cannot regulate insulin should not be grazing pasture. Owners should concern themselves with the insulin in the horse, not the fructan in the pasture.

This is ECIR Group review of an article which is largely based on the 2006 research dissertation of Dr. Bridgett McIntosh, entitled, “Circadian and Seasonal Variation in Pasture Nonstructural Carbohydrates and the Physiological Response of Grazing Horses”. The entire dissertation is publically available HERE This is an excellent resource.

Read more: Spring Grass Safety - A Review