Benefits of genetic improvement

When examining a specific trait or characteristic in any animal population, the majority of the population will be clustered around the 'average'.

The average represents the flock's genetic merit for a trait. Genetic improvement occurs when the genetic merit is improved through selection.

The improvement in genetic merit refers to the overall improvement in a flock brought about by selection for a number of traits that contribute to the flock's breeding objective, such as high growth rate or carcase yield.

Rate of genetic improvement

Genetic improvement takes time. The amount of time is influenced by three key factors:

1. Heritability of the trait - The degree to which the trait will be passed on. Highly heritable traits are easier to select for. While the heritability of a trait cannot be changed, the degree of heritability of particular traits needs to be considered in the overall breeding program.
2. Generation interval - The time interval between generations, determined by the average age of the parents at each mating. This can be reduced by using young sires and technologies such as JIVET (juvenile in vitro embryo transfer).
3. Selection differential - The difference between the average genetic merit of the parents and the average of the population from which they came. This is a breeder's main tool in driving genetic improvement. Producers who buy ram from seedstock breeders who undertake whole flock recording and have high quality data and, therefore, more accurate Australian Sheep Breeding Values (ASBVs), will be better able to exploit selection differential as a driver of genetic improvement.

While the selection of ewes and wethers can raise the average performance and productivity of animals retained within the flock, the most influential driver of ongoing genetic improvement is ram selection. A ewe may breed one or two lambs per year, however, a ram can sire 40-60 lambs per year.

Benefits of genetic improvement

Genetic improvement benefits individual breeders and the broader sheep industry by increasing productivity and profitability.

Genetic improvement takes time and a long-term view of production and market requirements is required when selecting for genetic improvement.

Genetic improvement has the potential to:

• Assist in meeting market requirements.
• Improve overall productivity and profitability.
• Improve specific traits of a flock including growth rate, carcase yield, fleece weight, fibre diameter and variation in birth weights.

More information

• Module 9: Gain from Genetics from the Making More From Sheep producer's manual
• EDGEnetwork
• Sheep Genetics