The author is an extension dairy scientist in genetics and management at Virginia Tech, Blacksburg.
The dairy breeding industry has had a boisterous 2010. Genomic predictions needed a course correction, and one was applied this past April. "Boisterous" is not the adjective that everyone involved would use to describe events that occurred in April. But now that the dust has settled a bit, it is time to truly understand what happened and why and put energy back towards genetic improvement. Ultimately, everyone who makes a living with dairy cows benefits from more accurate, and publically available, genetic evaluations.
Over 2,000 imputed
The second change in the April 2010 proofs was that genome scan results were "imputed" for cows that had not been genomically tested themselves but had four or more genome scans of their offspring. The imputing process is applied only if the cow herself has not been genomically tested. AIPL website information shows that 1,955 Holstein and 150 Jersey females had new, imputed genome scan results in the April 2010 proofs.
Imputing reveals the nucleic acid base pairs an untested cow possesses at the 50,000 SNP sites (tested by the current SNP chip). It is based on genomic test results in her tested progeny which were sired by genomically tested sires. SNPs in those progeny had to come from parents, and since the sequences in the sire were known, the cow's contribution could be "imputed" by difference. Four tested progeny reveal over 90 percent of SNP sites in an untested dam, while five progeny increase that number to over 95 percent.
Read more in the July 2010 issue on page 482.