Why is genetic variation necessary for animal breeding to make progress?

Genetic variation is essential to animal breeding because it provides the raw material necessary for populations to undergo genetic change across successive generations. Without this variation, selective breeding cannot alter the phenotype of a population, as there would be no differences in traits for breeders to act upon.12

In practice, breeders rely on heritability—the proportion of total variation attributable to additive genetic effects—to determine the potential for progress. Additive variation is particularly valuable because its effects are permanent and cumulative, allowing for consistent improvements from one generation to the next. While environmental factors also influence performance, these variations are not transmitted to offspring, making the identification of true genetic differences critical for effective selection. Ultimately, understanding and utilizing these genetic differences allows breeders to enhance specific traits, such as production or quality, within a population.12