For anyone interested in this:
http://ard.unl.edu/rn/0900/calf.html
When a local Shorthorn breeder brought a calf with severely malformed hind quarters to the Veterinary Diagnostic Center last summer, warning signals went off in Veterinary Pathologist Dave Steffen's mind. A calf with similar deformities had been described to him by a Canadian veterinarian just weeks before.
As head of the University of Nebraska's Cattle Congenital Disease Program, Steffen knew the calves might be suffering from a genetic disease. He began the genetic detective work that he uses on as many as 80 cases annually: discovering similar cases, collecting data on symptoms, gathering blood samples for DNA testing and analyzing pedigrees.
Steffen uncovered four cases with similar symptoms, two in the United States and two in Canada. After characterizing the calves' symptoms and laboriously analyzing their pedigrees, he diagnosed the condition as tibial hemimelia, a genetic disease caused by an abnormal recessive gene.
"We were able to trace all the calves back within six generations to the same sire, a very popular sire used by a lot of breeders," Steffen said.
Tibial hemimelia is a lethal condition. Affected calves are missing part of their rear legs, have large umbilical hernias and a skull deformity. They cannot stand to nurse and must be destroyed. Although these calves are a loss for owners, the larger problem for breeders is identifying which cattle carry and pass on the recessive gene.
"What happens is that a mutation occurs and it might get carried silently along for generations," Steffen said. "But when a sire and a dam both carry the abnormal recessive genes, one quarter of their calves will be affected or deformed."
When this happens, he advises breeders to cull confirmed carriers. That's an expensive step: average good bulls run about $3,000 and an outstanding sire can be worth tens of thousands.
Expensive, but necessary, Steffen said.
"Just by identifying, reporting and removing confirmed carriers you can keep these diseases beaten back and under control," he said.
Tibial hemimelia is an emerging problem for Shorthorn producers, but all breeds suffer from genetic diseases. Steffen recently researched cases of mule foot disease in Simmentals and Holsteins, alopecia in polled Herefords and a collagen defect in Angus.
"Proving that a problem is not genetic is often the most important thing in these cases," Steffen said. Almost 60 percent of Steffen's cases have non-genetic causes, usually environmental factors. Toxic plants such as poison hemlock, which causes skeletal abnormalities, are a common culprit. When environmental causes can't be pinpointed, thoroughly searching the calf's pedigree often rules out the chance that the trait is inherited, Steffen said.
This Institute of Agriculture and Natural Resources program is the only one of its kind in the nation and gets heavy use by breeders and breeding associations, who refer most of Steffen's cases.
'The breeder associations are really interested in keeping this program going because it is so important to catch genetic problems early," Steffen said. "They learned that lesson in the 1950s when dwarfism became a huge problem in the Hereford and Angus breeds."
The National Association of Animal Breeders, the Angus Association and the Simmental Association help fund this research.