Heritability is the percentage of observed variation that is explained by genetics. For example, a heritability of 0.3 means that 30% of the variation observed in the trait is due to genetics and the remaining 70% is due to environmental factors.
The genetic variation for most production traits (e.g. growth, fertility, carcase) is controlled by many hundreds or thousands of genes.
Most production traits are moderately heritable, with the heritability of BREEDPLAN traits typically ranging from 0.05 to 0.65.
A low heritability (e.g. heritability of 0.1) indicates that genetics has only a small influence on the observed variation for a trait, while environmental factors have a large influence. On the other hand, a high heritability (e.g. heritability of 0.6) indicates that genetics has a large influence on the observed variation for a trait, and the impact of environmental factors is smaller.
While it is easier to make genetic progress for traits that are moderately to highly heritable (compared to lowly heritable traits), it is important to note that improvements in genetics can happen for all traits that can be passed down from one generation to the next, even those with low heritability. Take “Days to Calving,” a trait related to fertility, which usually has low heritability. Despite this, we can still make noteworthy genetic advancements because there is observable genetic diversity within this particular trait.
Key messages
Heritability is the percentage of observed variation that is explained by genetics.
Genetic progress can be made even in lowly heritable traits as genetic variation still exists.