AGB 121: Principles of Animal Genetics and Population Genetics (2+1)

Breeding value (BV) and Progeny difference (PD)

BREEDING VALUE AND PROGENY DIFFERENCE

Breeding value

The value of an individual judged by the mean value of its progeny is called breeding value of the individual.

• All of genotypic value is not heritable. Breeding value is the part of an individual’s genotypic value that is due to independent gene effects that can be transmitted from parents to offspring.
• If an individual is mated to a number of individuals taken at random from the population, then its breeding value is twice the mean deviation of the progeny from the population mean.

Estimated breeding value (EBV)

• Prediction of breeding value using performance data is known as estimated breeding value or EBV.

Progeny Difference (PD) or Transmitting ability (TA)

• A parent passes on a sample half of its genes and therefore a sample half of the independent effects of those genes to its offspring. Because breeding value is the sum of the independent effects of all of an individual’s genes affecting a trait, a parent passes on, on average, half its breeding value to its offspring. Half the parent’s breeding value for a trait is our expectation of what is inherited from the parent and is called progeny difference or transmitting ability.

PD = ½ BV

• Like breeding values, progeny differences are not directly measurable, but can be predicted from performance data. Such predictions are called expected progeny difference (EPDs), predicted difference (PDs), or estimated transmitting abilities (ETAs) and are commonly used to make genetic comparisons among animals during selection.