CVM Threatens Holstein Herds
Veterinarians are urged to report, submit
abnormal Holstein calves to research centers.
Reprinted with permission from Veterinary Practice News. August 2001, page 36.
By David Steffen, DVM, Ph.D., Dipl. ACVP
Complex Vertebral Malformation (CVM) was first described by Danish
veterinarians in an agricultural research bulletin released in October
2000. The bulletin and press release described a typical case, but data
supporting the mode of inheritance has not been released. Following the
press release, information was distributed to veterinarians with the
American Association of Bovine Practitioners and the American Association
of Veterinary Laboratory Diagnosticians. Within one week, several cases
were confirmed in the United States.
CVM in the Herd
Reported calves with CVM in Denmark and those observed in the United States
are delivered from 250 to 283 days gestation. Most are one to three weeks
premature and nonviable. The appearance of a short neck may identify a calf
as a CVM suspect, but this feature can be subtle. Careful palpation of the
vertebral column may demonstrate kyphosis or scoliosis in the cervical
and/or thoracic region. Arthrogryposis affects all four limbs, which are
flexed at the fetlock by rigidity in the tendonous structures and digits
are medially rotated (Figure 1). Alert your clients to this condition and
instruct them to carefully examine each aborted or stillborn calf.
|
|
Figure 1: Calf With CVM
|
When a Suspect Calf Is Found
All abnormal Holstein claves, particularly CVM suspects, should be
reported to Holstein USA (Irma Robertson, executive director of quality
assurance; 802-254-4551) and the Nebraska bovine congenital disease
investigation program (David Steffen, DVM, dsteffen1@unl.edu; (402) 472-1434).
Contact should be made prior to necropsy whenever possible. Affected calves
can be frozen while necropsy is being arranged. The National Association of
Animal Breeders has provided funding to the University of Nebraska for
necropsy to characterize this disorder, and research is underway to study
the genotype of affected calves and their parents. The bull stud providing
semen may also be of assistance. Holstein USA will assist in arranging
parentage verification and sampling for genotype studies. Calves should
be submitted to the Nebraska Diagnostic Center whenever possible so research
regarding this disease can continue.
Distinguishing Features Seen at Necropsy
Careful necropsy in the field or at State and regional diagnostic labs can
be arranged but should be coordinated by Holstein USA. Thorough recording
of vertebral involvement and cardiac structure anatomy is needed to continue
research and to differentiate CVM-affected calves from calves with Arthrogryposis
or vertebral anomalies caused by environmental factors. The most consistent
necropsy finding is severe malformation of multiple vertebrae near the
cervical thoracic junction. Lumbar and coccygeal vertebrae are also affected
in a few calves. Vertebral body fusion, hemivertebrae, wedge vertebrae and
fused or missing ribs are common; fusion of dorsal spinous processes and
vertebral arches are also seen. Approximately half of the affected calves
exhibit cardiac abnormalities including, high ventricular septal defect
dextroposition of the aorta and right ventricular hypertrophy. Vertebral
changes can be seen without cardiac changes; it’s unknown whether the
reverse is possible.
CVM Genetics
Danish scientists believe CVM is a recessive trait based on proprietary
findings. Data released has identified U.S. sire 7H543 Carlin-M Ivanhoe
Bell as a common ancestor maternally and paternally in the pedigree of
all affected calves.
The Carlin-M Ivanhoe Bell sire line is widely used in the United States.
Despite this fact, very few affected calves have been identified to date,
which raises concern that inheritance may be complex rather than a simple
recessive. Danish segregation studies have found lower-than-expected
numbers of affected calves in sire-daughter matings by retrospective
analysis of field data. To date, no published peer-reviewed reports of
this disorder exist and no data regarding the genotypic studies have
been released.
When CVM Is Diagnosed
The U.S. breeding industry continues to monitor CVM very closely. With
no data publicly available to verify the Danish conclusions regarding
the inheritance of this disorder, it is impossible to make informed decisions
regarding disease control. I recommend removing sires and dams that have
produced affected calves from breeding programs. Productive cows that
produce an affected calf could be used in milk production, but should be
bred to bulls not associated with the disease. Fifty percent of offspring
might be carriers if the Danish hypothesis is proven.
Testing Sires, Dams for Carrier Status
The Danish research group markets a marker test within their lab
(DnaLab@AgrSci.DK) that has been licensed to a lab in Holland. Data that
might validate the accuracy of this test or the inheritance of this trait
has not been made available for peer review. Results of preliminary
screening of a modest group of U.S. Holsteins suggests that putative carrier
status of many animals cannot be established by the test currently marketed.
The test appears to be inefficient, indicating that if valid markers exist,
the ones currently selected must be distant from the putative CVM locus.
It will take at least one year before data characterizing disease inheritance
is available and the validity of the testing procedure is determined.
Participation in the research, by reporting all suspect cases to Holstein USA
and following up by submitting requested samples, is the best way to assist
the dairy industry. The National Association of Animal Breeders and Holstein
USA are aggressively collecting data on this condition and are currently
arranging research aimed at studying the inheritance and genotypic markers
in affected calves and their parents.
Dr. Steffen is a pathologist and director of the Veterinary Diagnostic Center
at the university of Nebraska in Lincoln. His research is associated with
providing bovine congenital abnormality diagnostic support to breed associations
and organizations nationally.
To order product contact:
Select Sires Inc., 11740 U.S. 42 North, Plain City, Ohio 43064 / Phone: (614) 873-4683 Fax: (614) 873-5751
|
