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Maine Anjou breeders manage oldest genetic mutation
“PHA looks to be the oldest mutation we have dealt with. It continually pushes down through generations having continual sequential breed downs,” said University of Illinois researcher, Dr. Jon Beever. By Jennifer Bremer
Pulmonary Hypoplasia with Anasarca (PHA) is a lethal recessive disorder which affects Maine Anjou and Maine Anjou influenced cattle. The calves have little, poorly formed lungs, and they have lots of excess retained fluid. The calves are usually born dead and may be aborted early. “At the onset, June 2005, the AMAA had just been introduced to the potential genetic problem,” said John Boddicker, executive vice president of the AMAA. “An immediate research program was set in motion and a notification letter was sent to the entire membership in September 2005.” Indiana veterinarian Dr. Chuck Hannon had discovered some of these PHA calves while he was researching Tibial Hemimelia (TH) in the Shorthorn breed. Some Shorthorn calves thought to have had TH actually were PHA calves.
University of Illinois researcher Dr. Jon Beever had been working with Dr. Hannon with TH testing and then became aware of PHA. Dr. Beever then began the search for the gene causing PHA. PHA was a bit of a challenge since it overlapped some of the same cattle which were carriers of the TH gene. “With PHA we had to rely heavily on breeder reports and samples in order to develop the test,” he said. “Now we know cattle can be carriers for both TH and PHA or perhaps other genetic mutations and that they aren’t linked to each other.” PHA, unlike some of the other genetic defects, will cause early term abortions, which leads to open cows. Dr. Beever said this made many breeders unaware of the PHA problem, often blaming the open cows on other health issues. With PHA, embryo loss at 90 to 180 days can be as high as 30 percent. Calves that do survive and go full term or near full term often times must be delivered via cesarean section. Calves can retain so much fluid that an 80-pound calve can weigh as much as 200 pounds. Often times difficult deliveries can lead to extreme damage to the cow and may lead to problems with future breeding or even survival, according to Beever. Old mutation “PHA looks to be the oldest mutation we have dealt with. It continually pushes down through generations having continual sequential breed downs,” said Dr. Beever. After much research and pedigree search, the mutation was traced to three commonly used AI sires in the American herd. Due to incomplete or inaccurate pedigrees or the inability to obtain samples from older full-blood Maine Anjou cattle, Beever said molecular markers surrounding the gene suggested a bull born in 1970 to be a common source for the mutation. While the Maine Anjou breed is considered the source of PHA in the U.S., with the allowance of registering percentage cattle in some breed registries, PHA has been found in other breeds as well. The genetics PHA, like other recessive defects, can only show up when two carriers are mated to each other. Affected calves are rarely tested for the defect and some are aborted too early to be tested; however, those calves would be considered homozygous for the mutation. A PHA carrier (PHAC) would be heterozygous for the mutation. Using the genetic information known on two animals, a breeder can determine the chances of having an affected calf, according to Dr. Beever. He explained: “If the normal gene is “P” and the defective gene is “p,” mating a carrier bull with the genotype Pp for the PHA gene to a carrier cow also with the genotype Pp for the PHA gene will result in three calves that look normal at birth, but two of the three will be PHA carriers (Pp). The fourth calf will be born with PHA (pp). Thus, mating two carriers gives a breeder a 25 percent chance of having a PHA calf every time this mating is repeated. “Mating a carrier bull or cow to a non-carrier cow or bull will result in 50 percent of the calves being PHA carriers (Pp). A non-carrier or PHA-free (PHAF) animal would have the genotype PP.” Abnormality policy Beginning Feb. 1, 2006, the AMAA required AI sires, donor dams and cloned animals to be tested for genetic defects. Their initial focus was on PHA and TH, with the thought that other defects may be addressed as needed. The AMAA publishes a list of animals which have been tested and their carrier status. While PHA seems to be somewhat under control at the breeder level because of testing which has been available, Boddicker said it is important for breeders to continue to report cattle which are affected by the gene. “Breeders can utilize the commercial test and most importantly use common sense in their breeding schemes. Over time the PHA issue will take care of itself,” said Boddicker. “The key to a quicker resolve in these genetic issues is open communication and a steady stream of documented information.” Genetic problems should be reported to the AMAA or a veterinarian for further research. Jennifer Bremer can be reached by phone at 515-833-2120 or by e-mail at jbremermaj@hotmail.com. GENETIC DEFECT—The Maine Anjou breed and Maine Anjou influenced cattle have been affected by a recessive genetic disorder over the past few years. (Journal photo by Jennifer Bremer.) PHA5 PHA-AFFECTED—This Maine Anjou calf with PHA is full of fluid and weighed about 200 pounds at birth. Delivered via c-section. (Photo provided by Jennifer Bremer.) PHA11 Proper testing procedures get accurate results By Jennifer Bremer With many different genetic defects coming onto the forefront in several different breeds, it is important to know how to properly collect samples for testing animals to determine their status. Dr. Jon Beever at the University of Illinois and AgriGenomics lab performs tests for Arthrogryposis Multiplex (AM), Tibial Hemimelia (TH), Pulmonary Hypoplasia with Anasarca (PHA) and Idiopathic Epilepsy (IE), as well as other non-defect tests. Dr. Beever has developed the tests for these defects, but other labs are performing the tests in some cases. “With TH and PHA, it was more of a niche market and we estimated the number of tests per year to be what we could handle,” he said. “With the IE test, the American Hereford Association has a contract lab. The AM test will likely be performed by several different labs.” Dr. Beever said each lab will have its own set of protocols for sample collection procedures. Currently, three labs are online to do the AM test with more expected. The procedures used at Dr. Beever’s lab are to use either blood or semen samples. When taking blood samples, new needles and syringes should be used for each collection to prevent contamination. The sensitivity of the test can detect very small quantities of contamination potentially producing invalid test results. Blood samples • Collect at least 2 cc of whole blood in an EDTA purple top tube. An anticoagulant is used in the purple top tubes to keep the blood from clotting. • After collecting the blood, the tube must be mixed thoroughly by inverting 5-10 times. Severely clotted blood samples received will not be processed and must be resubmitted. • Blood tubes must be labeled with the animal's permanent ID and/or registration number, making sure to label the tubes correctly. • Samples should arrive at the laboratory within 48 hours of collection for best results. • When temperatures exceed 90 degrees for extended periods, samples should be packed with a cold pack but not frozen. • When temperatures are below 35 degrees, samples should be in an insulated container to prevent freezing. Semen samples If sending a semen sample for testing, producers should: • Send at least one straw of thawed semen. • Semen straws should be protected from breakage during shipment by placing them in a semen cane or goblet and packaged in a padded envelope or small box. • It is important to mail the straw in a protected envelope to prevent crushing during handling. Other instructions It is important to include all the pertinent information with the samples. Individual breeds have submission forms available on their websites. Samples sent to AgriGenomics will not be processed without payment. Written results are provided on all samples tested. Each breed association is handling the results differently. Some require proof of test results prior to registration, while others allow carriers to be registered, but the animal’s genetic status to be known prior to the entry of an animal in an association sponsored sale. For more information on testing, visit individual breed association websites or AgriGenomics website at www.agrigenomicsinc.com. Jennifer Bremer can be reached by phone at 515-833-2120 or by e-mail at jbremermaj@hotmail.com. 12/29/08 Date: 12/22/08 Advertisement
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In 2005, the Maine Anjou breed was affected by a genetic defect that eventually was traced back to a bull born in 1970. 