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Ongoing genetic improvement
Genetic improvement is cumulative and occurs over each generation. The genetic improvement in a flock builds over time with selection resulting in ongoing genetic improvement.
Well-considered breeding objectives are essential given the time required to achieve significant genetic improvement for most traits affecting production.
Breeding objectives
A breeding objective defines the 'ideal' animal a producer aims to produce and is used to guide ongoing genetic improvement.
All sheep breeding enterprises should establish breeding objectives or goals and implement a selection process to meet those objectives as part of the overall business planning process.
Reproduction and fertility
The ability to make ongoing genetic improvement is directly influenced by reproductive performance and fertility of the rams and ewes. The more fertile the sheep, the more progeny will be produced and the higher the selective pressure that can be applied.
Culling
Just as it is important to ensure the right genetics are imported into the flock via selection, it is equally important to export genetics which contradict the breeding objective.
This is done through culling. Once breeding objectives have been established, producers should actively work towards culling those sheep that obstruct these objectives. Certain negative traits are clearly visible and can be selected against through visual assessment eg poor conformation.
Other less obvious traits may be selected against through breeding values or through objective measurement.
Breeding values
There are two breeding values for sheep:
- Australian sheep breeding values (ASBVs) - allow producers to evaluate an animal's genetic potential for a range of traits. These are directly comparable across flocks within a breed and across breeds in the terminal sire group of breeds.
- Flock breeding values (FBVs) - Within flock breeding values that enable genetic comparisons of sheep only within a flock.
LAMBPLAN and MERINOSELECT are the programs that deliver breeding values and can assist producers in their pursuit of ongoing genetic improvement.
