[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
fruits of the poisoned tree
The article below shows that there is a great deal of pressure to
commercialized the meat of cloned animals. This strange commercial
pressure seems to be exerted even though it is clear that cloning leads
to extensive abnormal transcription activity in the cloned animals.
Presently the vast majority of clones do not survive so the meat from
cloned animals may be a special case of "road kill". Seriously , the off
springs of cloned animals should be considered "fruits of the poisoned
tree" and treated with considerable care and scrutiny. The proponents
seem to press for "substantial equivalence" concept as providing
adequate safeguards but further work is needed to insure that the off
springs of cloned sires do not bear many subtle genetic or epigenetic
instabilities leading to dangerous products.
http://www.isb.vt.edu/news/2002/news02.nov.html#nov0201
WILL FOOD PRODUCTS FROM CLONED ANIMALS BE COMMERCIALIZED SOON?
Eric M. Hallerman
The development of somatic cell nuclear transfer (SCNT) cloning offers
significant benefits for genetic improvement of production herds, but
poses concerns regarding food safety and animal welfare.1 The US Food
and Drug Administration (FDA) contacted companies developing SCNT clones
for agricultural use and requested that food products from cloned
animals or their progeny not be entered into the human or animal food
supply until evaluation of these issues is completed.2 Against this
background, the FDA and the Pew Initiative on Food and Biotechnology
hosted a public workshop, "Animal Cloning and the Production of Food
Products: Perspectives from the Food Chain,"3 in Dallas, Texas on
September 26, 2002. The workshop was a forum for 150 participants from
industry, academia, non-governmental organizations, and the public to
hear presentations on key issues and to provide input to FDA as it
develops its policy on foods from cloned animals.
SCNT cloning. Somatic cell nuclear cloning involves transferring the
nucleus from a differentiated cell of a donor animal, frequently an
adult, into an enucleated egg. The introduced nucleus is reprogrammed by
the cytoplasm of the egg and directs the development of a new embryo,
which is transferred to a recipient female to develop to term. The
offspring formed will be identical to the donor in terms of nuclear DNA,
but will differ in initial patterns of methylation of nuclear genes and
in mitochondrial genes. Spatial and temporal patterns of gene expression
in cloned embryos differ from those in non-cloned embryos.4 After
cloning of sheep was reported in 1997, SCNT was applied to many species,
including cattle, goats, pigs, mice, and, more recently, rabbits and
cats. At present, production of SCNT clones is inefficient, with less
than one percent of the nuclear transfers resulting in a live, cloned
offspring. Even with low efficiency, there are many potential
applications for reproducing highly desired genotypes, including rare or
endangered species, pets, elite sires or dams, breeds with desirable
production traits but low fertility, or transgenic animals that have
high value, for which rapid propagation is desirable. The success rate
is increasing with refinement of SCNT protocols.
Highlights of the workshop. One key technical issue is whether the
composition of food products from cloned animals is the same as that
from non-cloned animals. Erik Forsberg of Infigen (Deforest, WI)
presented results of a study comparing the composition of milk from 10
cloned and six control cows with values published in the scientific
literature. Milk composition was quantified at laboratories at the
University of Wisconsin and Utah State University where researchers did
not know which samples pertained to clones. Concentrations of solids,
fat, protein, lactose, caseins, lactalbumin, and most minerals, and
somatic cell counts did not differ significantly between cloned and
non-cloned groups. Significant differences in certain fatty acids and
minerals were attributed to differences in feeds consumed by the two
groups. The results are reported in detail in a manuscript submitted to
a peer-reviewed journal.
Ron Gillespie (Cyagra, Worcester, MA) and Don Coover (SEK Genetics,
Galesburg, KS) placed cloning of animals within an agricultural
perspective. At a price of $19,000, commercial producers are not the
ones who are buying cloned calves—rather the consumers of this
technology are selective breeding programs that are marketing
genetically improved germplasm. Producers of selectively bred cattle are
interested in better utilizing the genetics of high performance females;
cloning of selected females will allow more matings with high
performance sires, providing more opportunities to produce fine
candidate sires to improve future production. Should the price decline
dramatically, dairy producers may become interested in cloning in order
to produce only female cattle. For beef cattle, it takes so much time to
identify an outstanding sire that his productive life is limited;
cloning offers the possibility of extending the availability of his
genes. Producers of selectively bred pigs are interested in cloning
because porcine semen does not cryopreserve well, and supplies of semen
from boars in high demand are limited. Gillespie concluded that cloning
will benefit producers and consumers when the price is right. Coover
mentioned that small producers are concerned that they will prove less
able to benefit from cloning than large producers.
A number of workshop speakers presented data showing high rates of
perinatal mortality or clinical signs of distress in neonatal cloned
animals. It is difficult to determine whether such problems are due to
cloning by nuclear transfer, to embryo culture or transfer, or to some
combination of cloning, culture, and transfer methods. Workshop
attendees representing the Humane Society of America, Animal Welfare
Institute, and United Poultry Concerns expressed concern that impacts of
cloning would exacerbate animal welfare problems imposed by conventional
production of animals in confinement facilities.
Carol Tucker Foreman (Food Policy Institute, Consumer Federation of
America, Washington, DC) said that a hasty decision to approve clones as
food carries "incendiary potential for public debate."5 Poor public
acceptance of cloned animals may limit commercial application of the
technology.
Regulatory prospects. John Matheson (FDA) discussed FDA actions
anticipated over the next year. A detailed assessment of food safety
data on SCNT clones and offspring will be prepared. An assessment will
consider animal safety issues for clones and progeny, as well as genetic
diversity impacts of cloning on populations of cattle and hogs. Release
of both white papers is targeted for January 1, 2003. A proposed policy
and guidance document considering risk management, legal, and
enforcement issues will be published during spring 2003. At that time,
comments on the proposed policies will be invited. Depending on the
level of interest and the nature of comments, a public meeting may be
held in spring or summer 2003, possibly before the Veterinary Medicine
Advisory Committee. A "final" guidance policy will be published,
accompanied by monitoring for compliance. The guidance policy will be
revised as needed.
Combining numbers presented by the various speakers, on the order of
100-200 SCNT cloned animals have been produced and transferred to farms
in the United States. Any role they might play in agricultural
production will be determined within the next year.
Sources
1. National Research Council. 2002. Animal biotechnology: Science-based
concerns. http://www.nap.edu/books/0309084393/html.
2. Center For Veterinary Medicine, US Food and Drug Administration.
2001. Update on livestock cloning. CVM Update, July 13, 2001.
http://www.fda.gov/cvm/index/updates/clones.html.
3. Pew Initiative on Food and Biotechnology. 2002. Animal Cloning and
the Production of Food Products - Perspectives from the Food Chain.
http://pewagbiotech.org/events/0924/sept26.php.
4. Humpherys DK, et al. 2002. Abnormal gene expression in cloned mice
derived from embryonic stem cell and cumulus cell nuclei. Proceedings of
the National Academy of Sciences USA 99: 12889-12894.
http://www.pnas.org/cgi/reprint/192433399v1.pdf.
5. Gillis J. 2002. Cloned cows' milk normal, data show: Finding could
speed commercial use. Washington Post, Friday, September 27, 2002, page
E3. http://www.washingtonpost.com (go to archives).
Eric M. Hallerman
Department of Fisheries and Wildlife Sciences
Virginia Tech
ehallerm@vt.edu
.