ABSTRACT
Genetic improvement in horses involves the same basic principles as genetic improvement in beef cattle, sheep, hogs, and dogs. Genetic improvement in horses is attained through the use of mating systems and the selection of superior individuals in a given generation to be the progenitors of the succeeding generation. Quantitative traits are difficult to recognize because the phenotype is controlled by many pairs of genes. The degree to which traits are genetically controlled is the heritability estimate for that trait. Horse breeders should be discreet in their breeding programs and attempt to select for as few traits as possible in a given generation. Money earned or average-earnings index values take into account both speed and soundness and enable breeders to make considerable genetic progress. Genetic improvement in horse breeding is slow at best and the responsibility for breed improvement rests upon the shoulders of the few tried-and-true breeders that have bred for specific goals over a period of generations.
