UK genetic evaluations of sheep have traditionally been undertaken within purebred populations. However, much of the UK sheep industry is a stratified system with approximately 56% of ewes in the national flock being crossbred and increasingly breeders are incorporating crossbred sheep into genetic improvement systems. Requests for across-breed Estimated Breeding Values (EBVs) from these cross-breeding flocks are increasing.
Breeders producing purebred and crossbred terminal sires could be serviced by more effectively by moving the evaluation of terminal sire breeds to a “Combined Breed Analysis” in a similar manner to the UK dairy evaluation.
Combined Breed Analysis for Terminal Sires
Combined-breed genetic evaluation allows multiple breeds of sheep to be evaluated simultaneously and where good genetic linkage exists, animals from different breeds can be compared via the resulting EBVs.
The benefits of combined-breed evaluations are that they can accelerate genetic improvement as they increase the accuracy of EBVs (more data is included in the analysis) and allow more intense selection (as the gene-pool to select the next generation can be substantially widened).
Rates of genetic improvement can also be increased indirectly through the provision of a more efficient service.
Combined-breed sheep genetic evaluations are currently available in several countries including Ireland, New Zealand and Australia. However, the existing UK sheep genetic evaluations have been developed for purebred sheep and are not suitable for evaluation of cross-bred sheep.
To expand the UK sheep genetic evaluation system to include multiple breeds and cross-bred data, the existing UK system needs to be modified to allow the methodology to be adapted such that it is applicable to a combined breed scenario.
The concept of a Combined Breed Analysis was discussed at the Sheepbreeder’s Roundtable, November 2013 and over 95% of attendees voted in favour of such an approach for the UK sheep industry.
In January 2014, EBLEX agreed to fund SRUC to develop a Combined Breed Analysis for terminal sire breeds – with a view to delivering this service to sheep clients in 2016.
The new approach will:-
- Enable crossbred animals to be analysed accurately
- Take into account hybrid vigour in breeding value estimates
- Re-base the population to a common and more recent/relevant population of animals
- Enable a review of the genetic parameters and breeding indexes used
- Provide a mechanism for breed comparison in the future
- Improve rates of genetic improvement by potentially providing more accurate EBVs and a wider gene-pool for selection
- Enable a more efficient and frequent service to be delivered to industry
The new breeding information will be:
- easier to interpret
- more accurate (particularly for crossbreds)
- enable breed comparison in the future
- enable a more frequent and efficient genetic evaluation service to be delivered
Each of these issues is expected to lead to a greater uptake of existing breeding technologies by both ram breeders and commercial ram buyers.