Repeatability in sheep breeding

Repeatability is a measure of the tendency of animals to maintain their ranking over time. It describes the accuracy with which early records of an animal's performance in a particular trait can predict its lifetime performance. It's used to assess which sheep to cull and which to keep, rather than which are the most suitable for breeding.

Repeatable traits

In adult sheep, some characteristics are highly repeatable, such as:

  • greasy and clean fleece weight
  • yield
  • fibre diameter
  • staple length
  • body weight.

Traits with a high heritability also have a high repeatability.

It's almost as efficient to select sheep for production based on the earliest adult records as on the average of 2 records. The slight loss in efficiency as sheep get older is compensated by a higher gain each year because of early selection and the early disposal of surplus sheep.

Repeatability of fertility

Repeatability of fertility, either as number of lambs born or weaned, is low. This means that culling ewes based on their first ewe performance will produce little lifetime gain.

A weaning record is a good predictor of lifetime performance for traits other than reproduction traits.

Also consider...