Curly Calf Syndrome

A Lethal Genetic Defect

Arthrogryposis Multiplex (AM) is commonly referred to as Curly Calf Syndrome

Curly Calf is a syndrome that effects Angus or Angus-cross cattle. Calves are born dead, or die shortly after birth, due to the inability to start breathing. The spine and legs are twisted. Calves are very small due to lack of muscle development while in the womb. The joints of the legs are often stiff and contracted.

Examples of Curly Calf Syndrome in Newborn Calves


In 2007 the American Angus Association(AAA) first recieved reports of stillborn calves with twisted spines and stiff extended legs. In 2008 the AAA and researchers started sampling calves that fit the description of Curly Calf Syndrome and within 2 months they had pedigrees of the calves and identified the mutation. They then determined the status of over 700 A.I. Angus bulls.
They researched the pedigree date and were able to trace all the calves to the sire Rito 9J9 of B1567T26. They now know that this sire is where the mutation originated.

GAR Precision 1680

GAR Precision 1680 was a very popular bull in the Angus world. He had traits in carcass, calving ease and early growth rate that made his offspring well-rounded and high preforming in most environments. Through A.I. technology his semen was used to produce thousands of offspring. GAR Precision 1680's dam's( 9J9 GAR 856) sire (Rito 9J9 of B1567T26) was determined to be the common link in AM calves that were tested in 2008. GAR Precision 1680 genetics were found on both maternal and paternal sides of effected calves. Due to some degree of inbreeding the outcome was a homozygous recessive genotype. GAR Precision 1680 was the first bull to produce offspring that had the AM phenotype.

Genetic Transmission

Curly Calf is cause by a autosomal recessive mutation on a single chromosome. Only those that are homozygous recessive will show signs of this syndrome. Carriers of this disease do not show any symptoms, but if bred to another carrier there is a 25% chance of having offspring with the syndrome, 50% chance the calf will be a carrier, and 25% chance that the calf will be homozygous dominant and not carry the mutated gene.

The Mutation

The mutation that causes Curly Calf is the deletion of 3 genes, one of which involves the development of nerves and muscles. Homozygous recessive calves are missing about 23,000 base pairs. Without these base pairs the 3 genes do not function at all.

While in the Uterus

While in the uterus the calves do not move. A protein that allow the nerves and muscle tissue to communicate is missing and that is why there is minimal muscle development. The legs are contracted and twisted because of the lack of movement. This can cause birthing difficulties.

Scientific Description of Physical Appearence

  • Kyphoscoliosis: Curving, hunching and twisting of thoracic spine (this is what causes the ribs and sternum to appear atypical)
  • Distal arthrogryposis of the carpal and tarsal joints
  • Cleft hard and soft palate or palatoschisis

DNA Testing

There is a test available to see if your cattle are AM carriers. You can do the test using DNA samples from hair, blood, tissue or semen.

DNA Results

  • Non-carriers can be used in a breeding program and have no risk of producing AM calve
  • Carriers can be used in a breeding program is they are bred to non-carriers. Breeders need to test all offspring to see if they are carriers
  • If the carriers are bred only to non-carriers there will never be a AM calf
  • Carrier cows can be used as embryo transplant (ET) recipients because her genetics will not have an effect on the calf

American Angus Association Registration Policy

  • Heifers: Must be tested. Can be registered even if a carrier.
  • Bulls: Must be tested. Can only be registered if AM free.
  • Embryo Transplant Calves: Depends on sex and if the calf was sired by a confirmed carrier A.I. Bull
  • Steers: No testing required.
  • Confirmed Carrier A.I. Bulls: Calves that are conceived 60 days after the date the bull was confirmed as a carrier cannot be registered.

Arthrogryposis Multiplex Occurs in Different Species

  • Sheep: in multiple births (twins, triplets, etc.) there may be only one affected lamb
  • Humans: Associated with neurogenic bladder, cleft lips & palates. There are many subgroups of AMC in humans. Affects about 1 out of every 2,000-3,000 births. Does not always result in death.

Discussion Question

Is the testing required by the American Angus Association enough? Should carriers of the Curly Calf mutation be allowed to breed at all? What about in commercial situations where heifers & bulls will not be registered?


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Steffen, David. "Reporting Abnormal Calves Is an Opportunity for Proactive Breeders." Angus Journal (2008): 33. <>.

Tejedor, M.T., L.M. Ferrer, L.V. Monteagudo, J.J. Ramos, D. Lacasta, and S. Climent. "Ovine Heritable Arthrogryposis Multiplex Congenita with Probable Lethal Autosomal Recessive Mutation." Journal of Comparative Pathology 143.1 (2010): 14-19. Web. 29 Apr. 2013. <>.

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