Genomic testing goes mainstream to dairy herds
Advances in genomic testing create new opportunities for commercial dairy producers to have more control over their herds' profit potential. With an abundance of available replacement heifers, producers have the ability to replace less profitable cows with genetically superior heifers, shortening the generation interval and accelerating the genetic progress.
Genomic testing offers a powerful screening tool to predict what heifer will be a top performer and which will be below average. The payoff can be big, as investing money toward feeding and housing heifers that are not going to contribute to the bottom line only narrows profit margins.
Technology advancements make testing affordable
Once a tool only affordable for dairy producers owning elite dairy herds to identify the best bull mothers, genomic testing is now cost effective on a large-scale basis. Costs have fallen dramatically since genomic testing first hit the market in 2008, and it is now possible to test for as low as $28 per head or approximately 1 percent of the cost to raise a heifer.
Managing genomic information to find genetically inferior calves is quite simple. Dairy producers select a key indicator, such as the predicted transmitting ability (PTA) of net merit dollars (NM$), which estimates the expected lifetime profit of a cow compared to the breed base of an average cow born and raised in the same environment. NM$ include traits that capture an economic impact, such as milk yield, health, longevity, fertility and calving ease. If a heifer does not meet the minimum requirements for NM$, she could be sold prior to breeding.
Another option is to breed the bottom-end replacements to a beef sire and sell the resulting crossbred calves as higher-dollar beef animals. Depending on market conditions, it may be possible to pay for testing costs for all of the replacements just from the increased value of the crossbred calves.
Conversely, a heifer that ranks high in NM$ might be a candidate for sexed semen. Keeping the calves with the best genetics and applying sexed semen, while selling calves with the poorest genetics, can deliver substantial cost savings. Ultimately, producers realize value by collecting the NM$ information at an early age, allowing them to gain an understanding of how profitable the animal will be as a lactating cow.
How it works
Genomics got its start in 2004 with the sequencing of the bovine genome, which is made up of approximately 25,000 useful genes. Sequencing allowed basic information about genetic coding to be used to improve how genetic values of cattle are estimated.
For genomic selection, researchers look for markers or single nucleotide polymorphisms (SNPs). A SNP is a place in a chromosome where the DNA sequence can differ among individuals. SNPs are most useful when they occur close to a gene that contributes to an important trait. Most traits are controlled by many genes, making this a very complex process. Significant progress was made when a genotyping computer chip was developed that could identify more than 50,000 SNPs (50K test) on the genome.
Genomics has rapidly advanced in the past decade. Today most laboratories use custom chips that are able to use fewer SNPs through the use of imputation. Imputation is a method that uses knowledge of the parental genome in calculations to predict the genotype of the calf.
The Council on Dairy Cattle Breeding (CDCB) maintains the genomic database and produces a genomic evaluation report on a weekly basis containing data on every animal. Producers can take a tissue sample from a calf and submit it to a laboratory, which then sends the genotype to the CDCB. The CDCB then calculates PTAs that are equal to progeny tests on many daughters of sires.
While the reports contain extensive data, most dairy producers prefer to use simple rankings, such as Net Merit, Cheese Merit or Fluid Merit. For those who like more details, reports can be run to work with custom-made indexes.
Testing for commercial operations
Neogen Corp. recently introduced Igenity-Essential in response to requests by commercial dairymen for a more convenient and cost-effective genomic assessment of their animals that can be done during times of low milk prices.
An alternative to traditional USDA-CDCB evaluations, Igenity-Essential can be performed soon after a calf is born, and test results are received within two to three weeks after tissue submission. Ideal for simple heifer sorting, Igenity-Essential is powered by a low-density 7K chip with custom content to examine 15 traits essential for improved milk production and reproduction. For the commercial dairy producer looking for a simple but effective sorting tool, this is an excellent option. It is available for Holsteins and Jerseys and contains the key content needed for an accurate genomic evaluation to make management decisions.
Find out more information at www.neogen.com, or contact your local Merck Animal Health representative.
By Todd Bilby, Ph.D., dairy technical services manager, Merck Animal Health.