Genomics

Genomics uses a young animal’s DNA to estimate its genetic potential, giving dairy farmers confidence to make informed breeding decisions with their youngstock. Genomic testing is currently available in the UK for the following breeds:

  • Holstein
  • Friesian
  • Jersey
  • Guernsey
  • Ayrshire and reds

Key benefits

  • Providing young bulls with higher-reliability proofs compared with pedigree index proofs
  • Higher-reliability genomic proof compared with the traditional pedigree index calculation for female youngstock
  • Giving you greater confidence in selecting youngstock from which to breed your next batch of replacement heifers
  • Allowing you to serve the genetically superior animals with sexed semen and put the rest to beef to increase your calf value (or, in the case of excess replacement heifers, to sell the less-superior genetics)
  • Measuring biologically relevant levels of inbreeding rather than estimating them from pedigree

Genomically testing youngstock has an advantage over pedigree index calculations as it evaluates the mixture of genes that have been passed down from both parents. In traditional pedigree index calculations, non-identical twins or full siblings would have the same proof. However, genomics can identify which is superior or help you spot a poor trait that you would not want to breed into your herd.

Genomic inbreeding Recessive haplotypes Genomics fees Crossbreeding Reliability

The first step in the genomic testing process is to build up a reference population for the breed, containing the DNA information of bulls with a high-reliability daughter-based proof.

Any animal with a high-reliability proof can be used, whether they have poor or excellent genetics. This wide spectrum allows geneticists to identify markers (SNPs) in the DNA that are related to poor or favourable traits shown in the animal’s genetic proof.

These are used to create a ‘SNP-key’, which is used to evaluate young animals without daughter or production information, based only on the DNA present in a tissue or hair sample.

To achieve a large enough reference population, genotype sharing agreements may need to be created between countries with similar genetics for breeds with a small population size. Holstein, Guernsey, Jersey, and Ayrshire genotypes are shared between the UK, Canada, USA and Italy.

Step-by-step process

  1. A sample of the animal’s hair or tissue goes to the laboratory
  2. Lab scientists extract the DNA
  3. The DNA is put onto a ‘SNP-chip’ and the sequence of bases that make up the DNA is read at various locations along its length
  4. A computer file showing this sequence is sent to geneticists working at SRUC's Edinburgh Genetic Evaluation Services (EGENES) on behalf of AHDB Dairy
  5. Geneticists develop a ‘SNP-key’, which unlocks or translates the sequences to turn them into a genomic index that can be understood by farmers and cattle breeders
  6. In the UK, the genomic index will be expressed as a Predicted Transmitting Ability (PTA). All official PTAs carry the AHDB Dairy logo