Page 8 • Dairy Star - Third Section • Saturday, December 12, 2015
Genomic testing tool for evaluating cattle BY RON JOHNSON Staff writer
CALMAR, Iowa – Is genomic testing a good t for your farm? The question was posed during a workshop Dec. 4 at the Northeast Iowa Dairy Foundation in Calmar, Iowa. Titled “Genomics 101: Putting Genomics to Work,” the Midwest Dairy Day session featured Dan Weigel, director of outcomes research for the animal health company Zoetis, and Carla Stetzer, regional program specialist with Accelerated Genetics. Genomic testing is a relatively young science. It looks at an animal’s DNA, identifying a set of genetic markers along each chromosome that an animal received from its parents, Weigel said. These segments of chromosomes are tracked. Then they are matched with the animal’s real-life performance, or with its sons’ or daughters’ performance. Doing so allows scientists to assign a value to each set of markers. Along with that, scientists can tell how closely animals are related, Weigel said. The more DNA they share, the more closely related they are. The main benet of genomic testing is it can be an early and accurate barometer of an animal’s genetic merit, Weigel said. Knowing where an animal ranks in a herd and within a breed can help when making management decisions. These decisions include how much money to invest in the animal, whether or not it will be protable and whether it should be culled. For example, genomically testing
a group of calves can determine which ones have the best genetics and which have the worst. Then, the bottom 15 to 20 percent can be culled. Doing so means less money and time devoted to calves that would not do well as mature animals. Besides the money saved, there’s the time factor to consider. Two years or more of feeding, bedding and treating can be devoted to the better calves. Along with identifying genetically better animals, genomics has other uses, Weigel said. It can identify cattle that carry genetic defects such as mule foot in Holsteins. Other traits can be found in the sire or dam. Is he or she a carrier of the red gene? How about the gene that makes an animal polled? Besides nding these defects, there’s no need to test for individual conditions by using genomics because even the lowest-density test places thousands of genetic markers, or indicators, on a microchip. The information is then analyzed in labs. These genetic markers are called SNPs, shorthand for single nucleotide polymorphisms. Using Holsteins as an example, Weigel said genomics can identify parents who are more likely to produce stillbirths. Holstein heifers average 8 percent for stillbirths, but the percentage can run higher or lower for individual animals. “When calves were $500 apiece, farmers really paid attention to this,” Weigel said. Positive genetic factors can also be found through genomic testing. These
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include milk production, heifer conception rate and productive life, the length of time an animal can be expected to stay in a herd. Another use for genomics is nding who sired a particular animal. Weigel said nationwide approximately 15 percent of registered and grade Holstein sires have been wrongly identied. Genomic testing turned up the mistakes. One way to use the genetic information is when a farm wants to expand its herd. The testing can identify which cows are genetically better. Therefore, labor, time and semen can be devoted to them. But genomic testing is not a cureall for a farm’s breeding problems. “It doesn’t make the calves any better … You’re just buying information,” Weigel said. And there is a lot of information. Stetzer said a high-density test, at a cost of $100 through Accelerated Genetics’ AMP program, delivers 140,000 SNPs. Even a lower-density test provides 26,000 SNPs. Of course, genetics isn’t the only thing that makes a dairy animal fail or helps it succeed. Weigel reminded the approximately 50 people at the workshop that environmental variance can play a large role, and the amount of environmental variance is different for each herd. “Some herds have great environments for their cows. Some don’t,” Weigel said. The less adequate the cattle environment, the less able the animals are to achieve their peak genetic potential. Things like poor feed, overcrowding
and exposure to disease organisms can stie an animal’s genetic potential. At one time, only bulls could be genomically tested. But now, Accelerated Genetics is testing females, too. Genomic testing is changing the articial insemination industry, Stetzer said. Since it’s no longer necessary to raise bulls to maturity and see how their daughters turn out, “dud” bulls can be weeded out earlier, thanks to genomic testing early on, meaning fewer bulls are kept. Less group housing is used, and instead, more sires have individual pens. A genomic test uses a sample of an animal’s tissue or hair. For a hair sample, Stetzer said 35 to 50 strands of hair is needed from the tail. She suggested using needle-nose pliers. Make sure the hair is free of manure, dirt and other material. Tape them together and submit them in a test kit, which is available free by contacting an A.I. representative. Along with the hair sample, other information needs to be submitted. Stetzer said it includes the animal’s permanent identication number and its birth date. Also include the permanent identication numbers of the animal’s sire and dam, if they are available. Note the breed of the animal being tested. As of now, only Holsteins, Jerseys, Brown Swiss and Ayrshires are being tested. Another detail: genomic tests are only accurate on purebred animals of the four breeds mentioned above. To be considered purebreds, they must by at least seven-eighths of the particular breed.