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Newly diagnosed disorder revealed in beef genetics
By SARAH B. AUBREY
Indiana Correspondent

URBANA, Ill. — A University of Illinois (UI) researcher has successfully diagnosed a second fatal beef cattle disease.

“The likelihood of two separate genetic problems in similar pedigrees occurring at roughly the same time is basically - infinity,” said Dr. John Beever, an assistant professor of animal science at University of Illinois, Urbana-Champaign.

Since early 2005, Illinois researchers have worked on diagnosing a fatal disorder in beef cattle. Beever has been involved in genetic disorder research in sheep and cattle since 1996, and he led the way to uncovering a genetic defect called Tibial Hememelia (TH) in Shorthorn cattle earlier this year.

Now, as the first commercially available test for TH hits the market, researchers and field veterinarians are solving a second fatal problem affecting unborn calves.

The disorder, known as Pulmonary Hypoplasia with Anasarca (PHA), appears to affect calves with both Maine Anjou and Shorthorn pedigrees.

Congenital disease diagnostics specialist Dr. David Steffen, director of the Veterinary Diagnostic Lab at University of Nebraska, Lincoln, coined the term PHA as it clinically describes the calf’s symptoms. PHA calves are normal size in the womb, but have lung and heart defects causing these organs to grow abnormally.

“My suspicion is that the calves have pulmonary hypertension, and the heart does not pump the blood properly; thus the blood backs up in the heart and causes severe edema (or fluid retention), and this excess fluid seeps out into the calf’s skin and causes intense swelling,” described Steffen.

PHA calves are often born early; and yet, can weigh as much as 250 pounds - putting the cow at grave risk. Dr. Chuck Hannon, a veterinarian from Rensselaer, Ind., said it is possible for PHA calves to be born alive. In cases seen so far; however, the condition has proven to be immediately fatal. Hannon said PHA calves will likely have underdeveloped respiratory systems.

“The calf’s body fills up with fluid causing a variety of appearances including a severely bloated head and body cavity,” he said.

Hannon is a major proponent of on-farm data collection, and he works with producers and other vets to submit samples to genetic researchers. Due to his involvement with TH sample collection, he was among those that brought the PHA issue to the forefront.

“In investigating TH cases, we discovered that a few of what we are now calling PHA were actually being called TH by producers,” said Beever. “There exists a real need to clarify that the problems are different.”

Hannon added, “It is possible that both, separate, defects could be found in the same calf.”

Beever pointed out that the group may have seen at least one calf so far affected with both disorders.

“But we have to start distinguishing between the two so that the newly developed test for TH is not devalued,” he explained.

Hannon noted that TH calves are not usually bloated or overtly large in size such as PHA calves. And, unlike PHA calves, TH calves exhibit a lack of pelvic bone development, a condition that leads to malformed legs. Even though physical conditions may seem obvious, Steffen cautioned against jumping to immediate conclusions when a producer has a deformed calf.

While severe fluid retention may give the calf a “bulldog” (or large head) look characteristic of PHA, there are a few other external factors besides potential defects that could cause the problem, he said.

“The cause of PHA is not clearly established yet,” said Steffen who was aware of PHA in early 2005. “But we have a strong suspicion that this is an inherited trait.”

Due to this uncertainty, researchers are avidly seeking calf samples to study the DNA.

“The goal of research is to create a test for the disorder,” Steffen said. “With all of the information we now have on the bovine genome, there is good reason to believe that these markers could be done within two years.”

Beever and his team are awaiting enough samples from producers to begin genetic researching.

“We need 60-65 individual animals in a certain lineage before we can start looking for a gene marker. We’re about halfway there on (supplied) samples,” Beever said. “Right now we are starting to follow a couple of lineages in both Shorthorn and Maine breeds.”

Geneticists and field veterinarians tend to agree that this problem is not isolated to cattle with Shorthorn and Maine-Anjou influence, as many breeds have open herd registries that allow for percentage cattle to be registered. Due to the potential prevalence of the situation, Beever hopes a test for PHA can be developed soon.

“Every breed can have its problems; but with what we now know, these things can be managed by breeders,” he said to encourage producers to submit samples if they have a deformed calf with PHA symptoms.

A potential PHA calf

Both geneticists and breed association representatives urge producers to submit samples if they see or hear of a potential PHA calf.

The protocol is first to contact a veterinarian to help verify the physical symptoms and collect samples including lungs, heart and kidneys. Steffen, at the University of Nebraska, will review the samples and diagnose if the calf in question has PHA. Hair and or tissue samples (such as a 2-inch-by-2-inch section of the calf’s ear) are helpful and will be used to determine the calf’s parentage for pedigree verification.

“Pedigree material is necessary for us to find a segment of the disease and help us follow through with markers we already have,” said Beever.

Photos should also be taken, if possible. A call to the breed association is a good idea to help them build their database of potentially affected pedigrees and to clarify any questions a breeder has about collecting samples.

“Once we establish this information, we want to use it to help breeders,” said Beever. “Genetic defect information puts something in the hands of the breeder to help them make an informed decision.”

Published in the August 31, 2005 issue of Farm World.

10/26/2005