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The Holstein Association USA’s Board of Directors recently
declared Complex Vertebral Malformation, or CVM, as an undesirable recessive.
Animals determined to be carriers will be identified with the code “CV”
and those determined not to be carriers will be identified with the code “TV”.
 The
disorder causes a multitude of possible abnormalities. Most of the affected
calves will be reabsorbed as embryos or aborted as fetuses prior to the 260th
day of gestation. The remaining pregnancies result in a stillborn calf, typically
1-2 weeks prior to the expected calving date. The most noticeable characteristics
of CVM-affected calves are malformed legs with flexed and rigid pasterns, a
shortened neck and an abnormal curvature to the spine. A definitive diagnosis
of CVM requires a veterinary diagnosis or a DNA test.
The Holstein Association will maintain a record of pathological examinations
of malformed fetuses and calves. The primary pathologist for the examination
and diagnosis is Dr. David Steffen, Director, Veterinary Diagnostic Center,
University of Nebraska-Lincoln. (Telephone number 402-472-1434 or [email protected].
) Dairy producers are urged to report the birth or abortion of a malformed fetus
or calf to Dr. Steffen, the Holstein Association or to their AI representative.
The gene responsible for CVM has been identified and a DNA test is available.
Forms and instructions for accomplishing the test can be requested from the
Holstein Association. Hair or semen samples are preferred for this test. The
results are available in about three weeks.
CVM is inherited through a single recessive gene. CVM-affected calves can only
result when a carrier cow is mated to a carrier bull. When two carrier animals
are mated, 75% of the calves will be normal, and 25% will be affected with CVM.
Calves that have one defective gene will appear physically normal, and their
performance will be unaffected, but they will be CVM carriers.
Many of the bulls that are carriers of CVM will also carry numerous other genes
that are desirable for production and type. Absolute avoidance of CV bulls is
not necessary but serious thought should be given when using them. Breeders
should avoid mating CV bulls to cows whose sire and/or maternal grandsire are
CVM carriers. |
