United Poultry Concerns  

The Experimental Use of Chickens and Other Birds in Biomedical and Agricultural Research

II. History and Definition of Birds as Animal Models

 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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