Nearly everyone who has an interest in breeding better meat goats has heard of heritability. It tells us to what extent the differences observed in animal performance are due to inheritance. But, what does that really mean? What causes some traits to be more heritable than others? Does the heritability level influence our priorities in traits for which to select?

Heritability has been defined in various ways, but for our purpose we will consider it to be a measure of the strength or consistency of the relationship between performance or phenotypic values and breeding values for a trait in a population. Recall that breeding values are an indication of how much genetic value is passed along to the next generation. Our definition of heritability is a reflection of the degree to which offspring performance is a reflection of the performance of their parents.

From a practical standpoint, when a trait is highly heritable the performance of animals reveals a lot about their breeding values. In contrast, when a trait has a low heritability, a breeding goat’s own performance is not likely to be a good indicator of its breeding value. Under those circumstances, the offspring of high performing parents will probably not perform much differently than the offspring of low performing parents.

Mathematically, heritability values are always positive and theoretically ranging from zero to one on percentage terms, e.g. 12% or 35%. In livestock species, heritability values above .7 (70%) are extremely rare. Typically heritability estimates below:

• .2 (20%) are considered lowly heritable,
• traits with heritabilities between .2 (20%) and .4 (40%) are considered moderately heritable,
• and traits with heritabilities above .4 (40%) are considered highly heritable.

Appendix E contains more useful basic information on heritability and a related notion known as Repeatability.

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