Complex Vertebral Malformation (CVM)
Feb. 2 Select Sires Memo
MEMORANDUM
TO: Board of Directors, Member Managers, Member Marketing Directors,
Member Communication Coordinators and Select Sires Staff
FROM: Dave Thorbahn, general manager, Select Sires, Inc.
SUBJECT: Update About Complex Vertebral Malformation (CVM)
DATE: Feb. 2, 2001
Since October, when I first wrote you about Complex Vertebral Malformation
(CVM) in Holstein calves, little more is known about the science of the
condition itself or the genetic mechanism by which it is transferred.
The industry still anxiously awaits the chance to review details of the
initial research about CVM - ideally through a peer-reviewed scientific
article. In the meanwhile, we continue to work through the National
Association of Animal Breeders, Holstein Association USA and leading
U.S. scientists to research this condition, and improve worldwide
understanding about CVM.
During this time, the Scandinavian countries have established import
barriers, allowing only the import of semen produced by sires declared
to be "not a carrier of CVM" by the Danish laboratory. Recognizing this,
in October Select submitted tissue samples for seven sires whose semen
is marketed in these countries. As of last week, we finally have received
feedback on laboratory tests for these sires.
The laboratory was unable to determine a status for four of the seven sires
(7HO5375 MARSHALL, 9HO2224 ELMO, 7HO5244 BLAZE*RC and 9HO1868 BESTOW),
declared two sires as "not a carrier of CVM" (9HO1729 PATRON and 7HO5435 GENO),
and declared one sire as a "carrier of CVM" (7HO5408 CURTIS). The results
also contained this note: "When interpreting our result, you should be aware
that the test is based upon linked markers and that the possibility of
double-crossovers reduces the reliability of the test results. We estimate
that our testing is more than 98% reliable."
So, what do these results mean?
- It's interesting that both sires labeled as "not a carrier of CVM"
have Carlin-M Ivanhoe Bell in their pedigrees. These test results enable
us to continue marketing their semen in Scandinavia.
- Semen from CURTIS no longer will be available to breeders in Scandinavia.
(NOTE: To date we have received no reports of CVM-affected calves sired by CURTIS)
- The current test does not seem to be able to definitively provide results
for the majority of samples submitted. In addition, the turnaround time
for sample processing has significantly exceeded the spirit of the original
estimate of "at least one week."
A recent action that may improve testing turnaround is that a laboratory
in The Netherlands recently was granted a license to perform the diagnostic
test. Even with this additional testing capacity, however, the industry still
is faced with the question of how to properly interpret test results without
access to the original research about CVM to use for background understanding.
Select Sires continues to work closely with the National Association of
Animal Breeders (NAAB) and the Holstein Association to learn more about
CVM, its diagnosis and genetic relationships. Recent communications from
NAAB have pointed out the following:
- Dr. David Steffen, veterinary pathologist at the University of
Nebraska-Lincoln, has reviewed the Danish manuscript about CVM. He found
that not only was Carlin-M Ivanhoe Bell present top and bottom in the
pedigree of every affected calf, but so was Pawnee Farm Arlinda Chief.
Steffen has asked Dr. Agerholm in Denmark to clarify this aspect of the research.
- We accept that CVM is some type of genetic defect, but we can't make
intelligent decisions until we are confident about the mode of inheritance
and the test. Our primary concern is that the mode of inheritance has
not yet been scientifically demonstrated.
- Information about CVM has been widely publicized to U.S. veterinarians
and diagnostic laboratories, yet only four deformed calved reported have
been positively identified as having CVM. If this defect truly is a simple
recessive, with the high level of Bell genes in the U.S. Holstein population,
we are at a loss to explain definitively why more calves exhibiting the
CVM characteristics have not been identified.
- We are supporting research, conducted by Steffen and Virginia Tech, to
produce embryos using a female and male that both have produced a calf
affected with CVM. The embryos will be examined morphologically at the
earliest appropriate time to determine whether the expected number of
CVM-affected calves are produced.
- Although some may criticize the cautious U.S. approach to labeling animals
with a CVM status, our industry's history of handling genetic recessives
like BLAD clearly demonstrates that we will take aggressive actions
once all of the facts are known.
What else can Select Sires do? While we have not begun extensive testing
of sires, we proactively will communicate the test results of any Select
sire that is declared a "carrier of CVM" by a licensed laboratory. We also
will provide test results on other Select sires upon request, but do not
intend to openly promote sires as being "not a carrier of CVM" until the
science clearly supports such a claim.
Unfortunately I feel the need to close this memo in the same way as I did
in October - by saying that there is still great deal about CVM that remains
unknown. While we are waiting for peer-reviewed research to provide concrete
answers, it is likely that dairy producers may come to you with questions
about CVM. Please feel free to share this memo with members who have questions.
If a member wants to discuss the topic in more depth, you can direct
him/her to Chuck Sattler, Dr. Don Monke or me.
Select Sires Inc., 11740 U.S. 42 North, Plain City, Ohio 43064 / Phone: (614) 873-4683 Fax: (614) 873-5751
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