Dairy genomic indexes stand the test of time
Our major new study of Holstein dairy sires has confirmed that genomic indexes are a highly reliable predictor of actual daughter performance.
This provides reassurance to the thousands of UK dairy producers who select service sires on the strength of an index based on their DNA.
The study included every genomic sire marketed in the UK in August 2014 and compared its genomic index at that time with its daughter-proven index in August 2018.
Genomic indexes remain marginally less reliable than daughter-proven indexes which means their likelihood of change is greater. However, this study has indicated the indexes used over the past four years have been extremely accurate.
Ultimately, farmers have to take their breeding decisions based on their attitude to risk. Usage should continue to be based on the existing advice, which is to limit the use of any single young sire to 12.5 per cent of the herd, which – if all inseminations are to genomic sires – means using a minimum of eight young sires each year. Current young sire usage runs at about 70 per cent of dairy inseminations in the UK.
Some 7,745 bulls were included in the analysis which showed there was little difference between their average genomic index in 2014 and their proven index four years later.
We introduced genomic indexes for bulls marketed in the UK in 2012. At that time, the technology to calculate the indexes was still in its early stages, and producers were made aware they were more likely to change over time than indexes for proven sires, which already had many daughters milking.
However, the attraction of using these young sires was their generally superior genetics, which would help producers breed better replacement dairy heifers. Thousands of producers took this opportunity and some now breed 100 per cent of their replacements from genomic sires. Across the UK, around 70 per cent of dairy replacements are now bred from these young bulls.
We were confident in the system when we launched genomic indexes in the UK in 2012, and this analysis confirms the reliability of the techniques we used.
This study should give complete reassurance that UK genomic indexes are among the most stable and reliable in the world. Provided they chose their service sires wisely, the many producers who put their faith in genomic indexes should have made substantial genetic gains in their herds.
Marco Winters – Head of Animal Genetics, AHDB Dairy.
