United Poultry Concerns  

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

III. Birds Used in Biomedical Research

 Sclerosis and Fibrosis Experiments

  • Young white leghorn chickens inbred at the University of California-Davis develop an inherited fibrotic disease in their combs that spreads through their systems. Researchers see this as having a resemblance to human progressive sclerosis, a connective tissue disease of unknown cause characterized by fibrosis of the skin and internal organs (Water and Gershwin).

  • Broiler chickens (6 week-old baby birds slaughtered for meat) fed an essential fatty acid deficient diet (EFAD) were evaluated as a model for cystic fibrosis. According to researchers, the results showed that essential fatty acids are necessary to maintain proper lung function, thus making the chicken a model, in this respect, for studying the relationship between EFAD and pulmonary disease in cystic fibrosis patients (Craig-Schmidt).

Diet and Nutrition Experiments

  • Pigeons fed cholesterol in their diet show an increase in serum lipids and arterial lesions causing heart attacks, resulting in the frequent use of these birds in atherosclerotic and other metabolic studies considered applicable to humans (Ediger).

  • Because of their extreme susceptibility to vitamin deficiencies, young chicks are used to check the validity of chemical and microbial methods of measuring vitamins in foods. Experiments with chicks and chick embryos deprived of vitamin B12, for example, have been used to predict the likely effects of vitamin B12 analogues. In addition, the specialized requirements of birds for vitamin D have made the chick a preferred model in studies of the physiological forms and function of vitamin D (Coates).

  • Researchers at the University of Wisconsin in Madison have found that laboratory chickens and mice infected with a human virus, adenovirus-36, put on much more fat than do uninfected chickens and mice, making this virus “the first human virus that has been shown to cause obesity in animals.” They caution that “far more research is needed before any practical benefits can be reaped from this research” like whether it may be possible to develop a vaccine against human obesity (Crenson).

Muscular Dystrophy and Muscular Performance Experiments

  • Specially-bred chicks and ducks are considered with mce as possible models for studying the basic pathogenic mechanisms of muscular dystrophy. This “spontaneous” disease of inbred stocks of white Pekin ducks and chickens is said by researchers to show features resembling those of the human body (Gopalakrishnakone)

  • Interested to find out whether static muscular contractions in birds act the same as those in humans and other animals, two University of California-Davis researchers funded by the American Heart Association experimented on thirteen white leghorn male chickens, three to four weeks old (Solomon and Adamson). The researchers recommended the use of chickens because “[f]irst, they are far less expensive” than other birds, and second because they are easy to obtain in large quantities (p. R764). After anesthetizing them with chloralose, the researchers stuck tubes in the birds’ ulnar (wing) vein, left carotid artery, and cervical trachea. They ruptured the clavicular air sac (part of the chicken’s respiratory system) and pumped oxygen, carbon dioxide, and nitrogen into the birds’ lungs. They inserted a thermistor probe into their colons. They pinned the birds down to cut their muscles and attach other machinery to them. They exposed the sciatic nerve in the birds’ hips, induced paralysis, and electrically stimulated the exposed sciatic nerve of the hip. They measured blood pressure and heart rate responses to static contraction of the gastrocnemius (leg) muscle. Fifteen minutes later they repeated the experiment. The results showed that static muscular contractions increase arterial blood pressure and heart rate in chickens the same as in humans and other animals: “We have provided good evidence for the existence of an exercise pressor reflex in chloralose-anesthetized chickens” (Solomon and Adamson, p. R759).

  • To “solve the puzzle” of how muscles and tendons work together when humans and other animals run, Princeton University researchers implant tiny strain gauges and electrical flow sensors into the legs of wild turkeys and make them run on treadmills. They claim that turkey treadmill experiments have “important consequences” for physical, occupational and rehabilitative therapy as well as for the design of prostheses, selecting appropriate animal models for experiments involving the musculoskeletal system, and for rehabilitating injured people or training elite athletes  (Taylor; Roberts et al.). Emus and many other animals are used in treadmill studies (Solomon and Adamson, R759).

Visual Impairment Experiments

The superb visual organization of birds has targeted them as models for experimental investigations of eye abnormalities in humans. For example, severe myopia (nearsightedness) is artificially produced in chicks with techniques and devices that blur their vision including altering the amount of light and fitting their eyes with lenses (Dayton; Seachrist). Concerning one of these studies, an article in Science News noted that while the eyes of chicks “wearing spectacle lenses to simulate nearsightedness” grew to compensate for blurred vision, the fact that chick eyes “develop very differently from human eyes” required the use of tree shrews to indicate that the “eyes of higher [sic] animals also grow in response to blurred vision” (Seachrist, p. 318).

Another technique for turning birds into models of human eye abnormalities in humans is eye suture, which may also include eye implants. Eye suture is performed by excising the upper and lower lid margins of a bird’s eye, often involving far more extensive operations (Seachrist, pp. 318-319).

Surgical Experiments

White domestic geese have served as models for intraocular (eye) surgery, and broiler chickens have been used to test the effects of surgical drilling and curettege (the scraping of body cavities and tracts) in acute hematogenous staphylococcal osteomyelitis, a human bacterial bone disease that is experimentally induced in the birds by inoculation (Emslie and Nade).

Sex-Change Experiments

Researchers interested in how genes interact with hormones to determine sex, inject hormone-altering enzymes into chickens inside the egg. Of the hundreds of enzyme-treated eggs containing genetically female embryos, the majority look like males after hatching. Half of the females in a study reported in Science in 1992 “grew up to look and behave like roosters, even developing testes and producing sperm” (B.R.).

Organ Development and Deformity Experiments

Claiming their research could “one day help to repair damaged organs or even generate new ones in the laboratory,” including new teeth, a team of Harvard researchers reported inserting a substance involved in the development of mouse teeth, called BMP4, into the jaws of chick embryos to show that tooth buds can be made to develop in birds (Wade 2000). This research (which is said to be going on elsewhere as well) is linked to other experiments in which the gene for mouse teeth is “knocked out” (deleted), creating mice with few or no teeth, a field in which researchers claim to be making “brisk progress.” The “hen’s teeth” experiment, which was reported in The New York Times on August 22, 2000, appeared in that day’s issue of the Proceedings of the National Academy of Sciences (Wade).

In an experiment at the University of British Columbia, a research team headed by Dr. Joy Richman, a pediatric dentist at UBC, blocked the activity of a protein that stimulates bone growth in chickens and added a vitamin A-derived acid. Richman made a hole in an eggshell and put microscopic protein-soaked beads on the embryo’s face. Two weeks later, the fetal chick had two beaks. The next step is “to have genes send different signals to grow other parts” of chickens’ faces. This hit-and-miss scramble of facial features in chickens “could help scientists understand normal facial development and what causes facial deformities” (Lee).

Trans-Species Brain Transplants

A story in Sciencemag.org says that University of Illinois neurobiologist Thomas Park claims to have transplanted an inborn behavior from one species to another by putting brain tissue from quails into young chickens, causing the chickens to prefer the sounds made by mother quails over those made by mother chickens. Park called this outcome “a real breakthrough in the study of perceptions, which are very elusive brain functions to study” (Withgott).

Aging Experiments

Entitled “Birds as animal models for the comparative biology of aging: a prospectus,” published in the Journal of Gerontology (1995; Vol. 50a [Biological Sciences]: B59-66), the authors, Donna J. Holmes and Steve N. Austand from the Department of Biological Sciences at the University of Idaho, call for the use of birds as research models for human aging. They suggest that “a number of commercially available bird species would lend themselves to laboratory studies of aging. Because they consist mostly of psittacines (parrots and their relatives) and finches bred and raised by professional pet bird breeders, their husbandry is well understood. The smaller species are inexpensive and easy to maintain; several are easily bred in captivity, including budgerigars, zebra and society finches, and canaries. Finches and canaries are already extensively used in neurophysiology and behavioral biology. Some wild passerines are also easily trapped and adapt readily to captivity, and have been used very successfully in studies of avian endocrinology and nutrition. Small passerines, particularly finches, should be no more costly to maintain than laboratory mice.” They conclude that “There seem to us to be few intrinsic barriers to the development of several avian ‘mice’ -- extensively characterized species exhibiting exceptionally long life and retarded aging.”

Pain Experiments

“The close similarity between birds and mammals in their physiological and behavioural response to painful stimuli argues for a common sensory and emotional experience. It is therefore essential that the ethical considerations normally granted to mammals be extended to birds.”
—Michael J. Gentle 1991

“Comparing pain in birds with mammals, it is clear that, with regard to the anatomical, physiological and behavioural parameters measured, there are no major differences and therefore the ethical considerations normally afforded to mammals should be extended in birds.”
— Michael J. Gentle 1992

“Previously reported methods for measuring nociception [pain] in domestic fowl differed in various ways but in each instance some form of restraint accompanied the assessment procedure. . . . Our purpose of the present research was to examine the ontogeny of nociception in domestic fowl with a procedure that involves confinement but not restraints. Preliminary research indicated that the ‘hot plate’ technique, often used to index nociception in mice and rats, might be used similarly for research on nociception in domestic fowl.”

This “noxious thermal stimulus” research (“the first to examine nociception systematically in domestic fowl within a developmental context") was conducted by Richard A Hughes and Kenneth J. Sufka in the Department of Psychology at Iowa State University in 1989. It consisted of three experiments in which approximately 300 white leghorn male chicks from one day old to two weeks old were confined to hot plates of 59, 61, or 63 degrees C to see whether the chicks jumped faster as the grids grew hotter, whether baby chicks jumped faster or slower than older chicks, and whether socially-raised chicks jumped faster or slower in response to the hot plates than chicks raised in isolation (Hughes and Sufka 1990).

This same Richard A. Hughes, cited above, published another study in 1990 in which chicks were administered codeine or morphine, and then put on hot plates. He showed that chicks on morphine jumped sooner than chicks on codeine (Hughes 1990). Other Hughes research listed in his References section includes the use of other drug combinations or electric shock to show pain and behavioral responses in chicks, and studies in which drugs and electric shocks were administered simultaneously to test their effect on tonic immobility (in which birds “freeze” in response to predators and fear) in chickens.

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