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Historical Link Between Agricultural Experiments and Biomedical
Experiments on Birds
“In many cases, it isn’t easy to categorize a particular project
as biomedical or agricultural. The distinction becomes less and
less clear as biochemists, physiologists, and biomedical engineers
become more and more prevalent within our agricultural universities."
—Philip Tillman, Integrating Agricultural and Biomedical Research
Policies, ILAR News Spring 1994.
The tie between the agricultural use of domestic
fowl and their use in biomedical research is close and longstanding.
Domestic fowl—“farm” birds-- have been, and continue to be, major
research animals because they are cheap and readily available, bred,
and managed. A single rooster and hen can produce many offspring,
especially through the use of artificial insemination, and their
pedigrees can be easily maintained. However, the most prized feature
of the fowl, according to researchers, is that the developing embryo
can be conveniently studied (vivisected and otherwise manipulated)
outside the mother. A 2002 report on animals slated for gene sequencing
research explains that chickens are being targeted because they
are already “widely used as a non-mammalian vertebrate system for
investigating several important biomedical research problems, including
the development of the embryo (particularly the nervous system)
and the causes of birth defects.” Since agribusiness is eager to
identify and exploit the genes responsible for “food production
traits” in birds, private investors count on government assistance.
Thus, the U.S. Department of Agriculture “has expressed interest
in helping to support the project” (Bees, Chickens, p. 24).
Going Further Back
"Turkeys have arterial blood pressure higher than that of other
domestic birds. They also have a number of arterial and cardiac
diseases. However, because of their size and difficulties in maintenance,
they are not used as much as the small avian species or the most
popular chicken models.”
(Ediger 1990, p. 2)
Chickens have been used extensively in experimental
research for more than a century. The science of embryology, which
can be traced as far back as Aristotle’s time, is largely based
on the use of avian embryos and birds’ eggs, in which viruses could
be cultivated long before in vitro methods were available
(McArdle 1999, p. 8). In the 19th century, the anatomist Theodore
Schwann investigated embryo respiration in hens’ eggs, showing that
oxygen is necessary to the avian embryo’s vital processes. While
studying chicken cholera on behalf of the French poultry industry
in 1880, Louis Pasteur learned by accident that exposure to an attenuated
disease microbe can produce immunity in the host. While a drop of
fresh cholera microbe would kill a chicken, hens given three-week-old
culture resisted it as well as subsequent inoculations of the attenuated
virus. In 1885, Pasteur proposed the chick to the French Academy
as the most suitable subject for studying germ-free hosts. His idea
became rooted in biology, because the incubation of chicken embryos
is easier than the surgical removal of mammalian fetuses (Coates).
A particular finding came in 1908 from Rous’s
investigation of chicken tumors which showed that a virus can cause
cancer (Ediger). What became known as the Rous sarcoma virus is
part of a complex of immunosuppressive leukosis viruses of domestic
fowl, which made the chicken a prototype model system for AIDS and
other immunodeficiency diseases (Gardner and Luciw).
Chickens are also used to study diseases in which
the immune system, instead of being deficient as in AIDS, reacts
destructively by attacking the host’s own tissues. An example is
rheumatoid arthritis, in which the immune system attacks membranes
in the joints. This and other autoimmune diseases (AID) are experimentally
induced in chickens, who are then bred to “model” the disease. Another
example is Hashimoto thyroiditis, a human condition in which an
autoimmune attack is mounted on the thyroid gland (Hala).
Still another AID model is artificially obtained
by crossing chickens and quails to produce autoimmune disorders
that are said to resemble human multiple sclerosis (MS). White leghorn
chick embryos given Japanese quail nervous system tissue mount a
prolonged rejection of the graft leading to paralysis that starts
in the bird’s wings, spreads to his or her legs, and can include
the bird’s spinal cord. While noting that no real animal model of
MS exists and that MS is thought to derive primarily from an undetermined
viral infection, the researchers claim that this cross-species model,
called a chimera, shows pathological signs “very similar to those
of the active plaques of multiple sclerosis and of the lesions of
experimental allergic encephalomyelitis and neuritis.” (Kinutani
et al., p. 307), and may be “a model for MS” (Barnes, p. 931).
Birds as Animal Models
Countless numbers of domestic fowl are thus used
as experimental animal models in basic and biomedical research and
toxicity testing, in which conditions and responses in nonhuman
animals are considered or induced to resemble those occurring in
humans. Like other animal models, birds can be roughly classified
as genetically-based and spontaneously-manifested models arising
through selective breeding and inbreeding, or experimentally-produced
and artificially-manifested models obtained through surgery, drugs,
or genetic engineering. The typical “poultry” model comprises hereditary
and experimentally-induced traits. However, even the so-called hereditary
and spontaneous traits have been manipulatively produced through
experimental breeding on farms and in laboratories, often through
decades of tinkering, and are thus a distortion of natural evolutionary
patterns of expression in fowl. Bizarre pathological symptoms and
conditions that necessarily arise over time in highly inbred experimental
flocks will often then be “selected for” by the researchers, who
will claim to have created a “model” which “may resemble” or “mimic”
some human disease pattern or other. In all cases, “more research”
is always “needed.”
Chickens and other domestic fowl have therefore
not only the tragedy of being considered food; they are fair game
for all sorts of cruel, wasteful, and invalid research—everything
from being forced to “model” the effects of cigarette smoke inhalation
and high-cholesterol diets to having their faces disfigured in experiments
designed to make them grow teeth or sprout extra beaks. Poultry
production colonies on university campuses provide biomedical researchers
with a virtually endless supply of cheap birds and hatching eggs
to do whatever they want with (Tillman, p. 29). Following are some
examples of the kinds of experiments that are done on birds in the
name of biomedical research and toxicity testing followed by some
examples of the kinds of experiments that are performed on birds
on behalf of the food industry.
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