Question

Contrast breeding value and producing ability. For a repeated trait of your choice, describe how each value might best be used.

Answer 1

Breeding value

Predictions of additive genetic breeding value and future performance are used so frequently in animal breeding that they have been given specific names. The additive genetic value of an animal for a specific trait is referred to as its breeding value (BV) for that trait. The BV estimated from various measures (records) of performance is called estimated breeding value (EBV). The term BV is used to denote additive genetic value because it is mostly the additive values of the individual genes possessed by an animal which are transmitted directly to its offspring. An animal’s additive genetic value, therefore, reflects its value or worth for breeding.

Producing ability

Producing ability is the performance potential of an individual for a repeated trait. A repeated trait is a trait which individuals commonly have more than one performance record. Prediction of future records works in the same way as EBV. Here the breeder is interested in the future performance of an individual in some repeated trait sometimes referred to as true producing ability, of the individual. This gives the best estimate of future performance. The producing ability of an animal is the sum of its total genetic value (G = A+D+I) and any environmental effects which are permanent to all records (PE). Producing ability would therefore indicate exactly the next record, except for the unpredicted temporary environmental effects (TE) which will be associated with that record.

With the understanding that breeding values are needed by animal breeders in order to make accurate selection and culling decisions. Breeders rank animals based on their estimated breeding values, select those with highest estimates as parents of the next generation and cull those with low breeding values. Without the knowledge of breeding value estimates, selection will not be possible. If you are a livestock breeder, you can use this knowledge to improve either one trait at a time (single trait selection) or more than one trait at a time (multiple trait selection) depending on your selection goals.

For a repeated trait ,this is how individual values can be used

Depending on the amount and source of information available, proper weighting may depend on the heritability (h²) and repeatability (r) of the specific trait. The number of repeated records (n), the genetic relationship (a_ij) between a relative and the individual, the number of relatives (m) of a specific type and any environmental correlation (C²) due to extra common environmental factors shared by relatives

Factors considered in weighting performance records to estimate breeding value and producing ability

Observed Performance	Estimated Breeding Value	Estimating Producing Ability
Individual One record n record	h2 h2, r, n	r r, n
Single Relatives One record n records	h2,aij h2, aij, r,n
m Relatives One record each n records each	h2, aij, m, C2 h2, aij, n, r, m, C2