Predictive Height in Horses (LCORL)

Predictive Height in horses

Height in horses is multifactorial, depending on the interaction between genetics and the environment; however, studies have estimated that ~84% of height in horses is regulated by variants in just four genes.

A variant in the LCORL gene has a very large influence in height, effectively “releasing” a limit on growth. Interestingly, most draft breeds (both small and tall) are homozygous for the variant; in their case, the variant seems to be more involved with the heavy body type than height. Most horses of normal height  (usually under ~160 cm) such as Quarter Horses, Arabians, gaited breeds, etc., are homozygous for the normal variant (T/T).

In Warmbloods, Thoroughbreds, and Iberian breeds the relationship between the LCORL variants and adult height at the withers is quite predictable. This means that testing can allow breeders to predict the genotypes of offspring of a potential breeding pair, or a foal can be tested to predict its final adult height.

Mode of Inheritance and Predictive Ability

The increase in height influenced by this variant has an autosomal incomplete dominant mode of inheritance, and  the accuracy is estimated to be ~70%, with a deviation of 5 cm in either direction.

This means that compared to a normal (T/T) horse of the candidate breeds, which may be 159 cm (+/- 5 cm), a heterozygous (C/T) horse will usually attain ~164 cm (+/- 5 cm), while a horse homozygous for the variant (C/C) will usually attain 169 cm (+/- 5 cm). Some breeds are less predictable – for example, Trakehners with two copies of the variant are often taller than 169 cm.

Relevant tests

• P326