Genomics testing cited as a reliable selection tool

Ray Mueller
Now Media Group


Dairy farmers who want to play odds that are about 85 to 15 in their favor on raising heifers that will express the traits that they have chosen for those animals can do so by relying on genomics testing.

That compares to about a 60 to 40 chance of making similar choices by 'eyeballing' or other selection methods on what dairy heifers to raise or cull, Vita Plus dairy technology specialist Pat Hoffman told attendees at the Raising Quality Heifers seminar sponsored by Extension Service's offices in east central Wisconsin and its dairy team.

Improving those odds by 25 or more percentage points is certainly worth the $45 cost of the test that would preclude the spending of $2,000 or more to raise a dairy heifer before she begins to provide a return on that investment, Hoffman said.

Theory of genomics

As the per-cow milk production has gradually increased over the decades, the variances between individual cows that are due to parental genetics and random factors have been more pronounced and therefore more important to the bottom line for dairy farmers, Hoffman pointed out.

Compared to 20 percent variances (8,000 to 12,000 pounds of milk per lactation) when the average was 10,000 pounds or variances from 16,000 and 24,000 pounds when the average was 20,000 pounds, Hoffman considers that a similar percentage difference which ranges from 24,000 to 36,000 pounds from a 30,000-pound average to be 'a tremendous variation' that could be addressed in an economically efficient manner with genomics testing.

It is legitimate to ask is why not all dairy cattle possess high genetics after 50 to 60 years of artificial insemination breeding with sires selected on their merits. He explained that it is due to the natural variances and also pointed out that environmental and management factors will also have a significant effect on dairy cow production, health and longevity.

Basics of genomics

Obtaining a round bead of tissue from a heifer with an ear punch is a 'great improvement' from the previous practice of taking blood or hair samples in order to conduct the genomics test that can identify up to 50 traits that owners might want to have in their dairy cattle, Hoffman said.

That test is able to isolate those relevant factors from short DNA strands (26,000 of them) through via a chemical test which identifies traits that differ from what's normal, Hoffman explained. An electronic program titled Enlight provides an easy format for reviewing all of those 50 traits.

Because of the concern in the dairy sector today about inbreeding, Hoffman was asked how this is addressed in genomics. Not only is that one of the traits which is identified but so is the one that increases the likelihood of fetus loss that occurs when carriers of that trait are mated, he said.

Human foible factors

Perhaps the greatest downfall in the use of genomics is the human error factor which results from input that isn't correct, Hoffman observed. 'That is where the work is in genomics.' He recommends using DairyComp numbers for accuracy and consistency.

Because the test results are based on a combination of data from the parents and the DNA of the heifer, it is crucial that the correct information be provided, Hoffman emphasized. He indicated that a 7 to 15 percent error rate is typical for such reasons for incorrectly entering the name or number of a parent or having used the wrong straw of semen.

In extreme cases that Hoffman has learned about, the genomic test has shown neither the sire or the dam of the heifer was properly identified. With embryo transfers, there's also the possibility that the recipient female will be incorrectly named as the dam.

Genetic selection proofs

Armed with data from the University of Wisconsin dairy research herds, in which milk production differences of 6,000 pounds per lactation are also normal, Hoffman stated that the predictions made from the genomics results are proving to be true at a high percentage.

On milk production alone, 40 to 50 percent of the variances can be attributed to the genetic traits which are identified by the genomics test, Hoffman pointed out. He noted that environmental factors are responsible for a big share of the remaining difference.

With genomics management being based on the goal of identifying that heifers are likely to place at the top and bottom in milk production and other performance factors, there is little or no doubt that it is proving to be highly reliable, Hoffman indicated. He cited the statistics – the 85 to 15 odds of being right – in the milk production data for the top and bottom 20 percent groups for milk production for the first lactation in the Wisconsin university herds.

Based on those findings and levels of confidence in making the right choices via genomics information, Hoffman advises dairy farmers who aren't faced with a requirement of raising all of their heifers to cull according to the genomics tests, thereby also paying for both the genomics testing and sexed semen for the heifers predicted to be in the top 20 percent group.

Statistical differences

The documented results from the University of Wisconsin-Madison for research groups of 216 to 410 Holstein cows are showing that genomics testing 'doubles the ability to find differences' on such variables as milk production; butterfat and protein percentages; days open before pregnancy; and less so for somatic cell count, Hoffman reported.

While noting that genomics testing does not replace the importance of sire selection, Hoffman is greatly impressed by some of the statistics from the research data in the university herds. Those include 2,366 pounds of milk per lactation attributed to sires alone but an increase of 4,801 pounds due to genomics testing and respective differences of 3 and 21 less open days before pregnancy.

In a very high producing commercial dairy herd of more than 400 head, the results with cows calving after August 2013 have also been impressive, Hoffman stated. Those included 1,465 pounds of milk per 305-day lactation attributed to sires and 5,061 pounds credited to genomics selections; respective reductions of 21 and 31 days open; and smaller but very consistent differences in favor of butterfat and protein content and lower somatic cell count with the cows chosen for their DNA, he noted.

Recommended protocols

The use of genomics testing is not a 'one size fits all' protocol but to achieve genetic progress and to enhance revenue it does require protocols for sire selection, sexed semen, genomic testing itself, herd health status, early culling and other relevant factors, Hoffman explained.

There's no value in having the information on then not acting on it to cull certain heifers, Hoffman stressed. Looked at in another way, it's worth a lot more to spend $45 for the test than to probably waste up to $2,000 raising a heifer that will not prove to be profitable.

Hoffman acknowledged that, as a protocol, the degree of culling must also be governed by any expansion plans, facilities, cash flow, feed costs, genetic levels and other factors that differ from farm to farm. If nothing else, he suggested that genetic information, which should not be viewed as research data, might serve to inspire a rebirth in tracking the genetics of dairy cattle.

Although he didn't delve into the specifics, Hoffman observed that genomics 'has its share of detractors,' just as is true with recombinant bovine somatotropin, brown midrib corn and genetically modified organisms.