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Polygenic Score in Horses: Lessons from Racehorse Fractures
Can a polygenic score alter a horse's genetic makeup? Short answer: no. A polygenic score doesn't change a horse's DNA. It adds up the tiny effects of hundreds to thousands of genetic variants into a single number that estimates predisposition – a risk, not a diagnosis. Nowadays, scientists know that some of the complex conditions in horses are due to the combined effect of a number of variants rather than the result of a single faulty gene mutation, and one of the most interesting examples currently available is that of Thoroughbred racehorses.
Genetic Regulation of Body Size in Horses - From Shetlands to Shires
There is considerable variation in height within the horse population. There are tiny ponies, which can be even smaller than some dog breeds, as well as large draught horses, whose height at the withers is often close to 2 metres. While height is to some extent affected by environmental factors, it’s also strongly influenced by genetics. There is not a single gene that determines how tall a horse will eventually become. Rather, the final height of a horse is a result of effects of multiple genes and other factors. Let’s take a look at some of them!
Polygenic Score in Horses: When a Single Mutation is not Enough
Many people associate the term genetics with a simple and direct cause-and-effect relationship: one gene, one mutation, one trait. However, the genetic outcomes for many traits, such as performance, behavior, athleticism, disease susceptibility, and temperament, cannot be simplified in this way, as these traits are not defined by a single mutation but by hundreds to thousands of minor factors, each with its own tiny effect on the outcome. Individually, many of these variants have only a small effect, but when we look at them as a whole, they become more meaningful.
White Markings and their Genetic Background
Across the animal kingdom, white markings are thought to be associated with domestication. They are typical for domesticated animals such as dogs, cats, pigs, cows, and horses, in contrast to their wild counterparts. White markings are caused by the absence of melanocytes (pigment-producing cells) in certain body areas, resulting in white hair.
Genetics of Ambling
The three basic horse gaits are walk, trot, and canter. Gallop, sometimes considered to be the fourth basic gait, is practically a variant of canter. The main difference between these two gaits is that a canter is a three-beat gait, while a gallop is a faster four-beat gait that covers more ground.
Horses and Heat Stress
If you’ve ever been around horses during the summer when the temperatures are high, you might have noticed a few things, such as changes in behaviour, seeking shade, drinking more water, sweating, more visible veins under the skin, or a higher respiratory rate. All of these changes are the horses’ way of adapting to the heat.
Equine Blood Types
Horses, just like humans and other animal species, have blood types. Blood types are determined by antigen structures on red blood cells and are based on genetic information inherited from one’s parents. You’ve almost certainly heard about the ABO blood group system in humans, which divides our population into four groups – A, B, AB, and O. However, in some animal species, the blood group systems are not as straightforward, and horses are not an exception.