Genomics – What now for Terminal Sires?

In 2022 AHDB launched the UK’s first genomic breeding values for sheep, as part of Signet’s hill sheep breeding program. This was pioneering work, which has ultimately been ground breaking in the way it helps us to select performance recorded hill rams – particularly for maternal traits.

Shortly after their release we were approached by several Breed Societies looking to share genomic information with AHDB for sheep bred in pedigree flocks if we could work with them to add value to these genotypes. Initial research from this work will be released at stakeholder meetings in the coming month.

Why genomics?

Genomic information (data that directly reflects genetic variation in an animal’s DNA) has a wide variety of potential uses.

• Sire / dam verification – the primary use for Breed Societies
• Reporting major genes, such as Scrapie, Myostatin and major fertility genes
• Increasing the accuracy of breeding values. Genomic data adds massively to our knowledge of traits that are only expressed in one sex (like milk), expressed later in life (like longevity) and hard/expensive to measure (like methane or meat eating quality)
• Increasing the robustness of comparisons between flocks.

Genomic data increases the accuracy of breeding values

In Table 1, data from our hill sheep breeding programme clearly shows two of the benefits that arise from genomics. Firstly, we see a lift in accuracy arising from genotyping animals that have been measured, helping to find elite breeding lines amongst the better animals.

Secondly, in this scenario and only because lots of related animals have been measured, we can see that those sheep with a genotype (but were never measured) have a breeding value of similar accuracy to those that were measured, but never genotyped.

The take home message here is not that we don’t need to measure sheep, but that we may be able to be more selective in our measurements and by doing a good job at measuring sheep in one closely related population we may be able to make robust predictions of genetic merit in another. This is clearly useful when the trait concerned is hard or expensive to measure.

Table 1. Data for Welsh Mountain Ram Lambs (born 2023)

What are the next steps?

SRUC/AHDB are currently looking at the relatedness of Terminal Sire breeds at a genomic level to see if the genotypes provided for recorded and unrecorded sheep are representative of the wider population. Initial work indicates this is the case and breeding values have already been produced for Charollais, Hampshire Down and Suffolk sheep that incorporate their genotypes.

 

These initial results show tremendous promise, augmenting the accuracy of the breeding values that we produce for well recorded terminal sires, while introducing new information for previously unrecorded sheep that provide them with a fairer and more robust starting point when entering a genetic evaluation.

Chart 1. Genomic Spread in Terminal Sire Breeds

An analysis of genomic variation clearly shows the differences that we may logically expect between three of our terminal sire breeds. Interestingly within the Suffolk there is greater variation reflecting the introduction of New Zealand genetics (and other breeds) into some Suffolk flocks, as well as the degree to which recorded sheep now differ from more traditional unrecorded types.

 

Take home messages

Genetic evaluations that take into account genomic data are coming, with plans to launch genomic breeding values for the large terminal sire breeds mentioned in this work in 2025.

As progressive breeders, take any opportunity you can to get important stock sires genotyped, this will help to increase the accuracy of the breeding values produced for them and their lambs, support you in making better breeding decisions.