United Poultry Concerns  

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

VI. Genetic Engineering and Cloning of Domestic Fowl: Manipulating the Genetic Matieral of Unborn Birds

“As each chick emerges from its shell in the dark cave of feathers underneath its mother, it lies for a time like any newborn creature, exhausted, naked, and extremely vulnerable. And as the mother may be taken as the epitome of motherhood, so the newborn chick may be taken as an archetypal representative of babies of all species, human and animal alike, just brought into the world”
—Page Smith and Charles Daniel, The Chicken Book 1975, p. 321; 2000, p. 317).

“Chickens are suitable for gene manipulation because, unlike other domestic animals, they mature quickly, and a single bird can have thousands of offspring. Foreign genes need only to be inserted into one generation, which passes the genes on. Unfortunately, genetic material cannot be introduced into recently fertilised ova of birds this way.”
—Test-tube chicks pave way for ‘super-animals.’ – Lionel Milgrom, New Scientist February 4, 1988, p. 36.

“They are proliferating lives that endure nothing but misery. It’s the new horror for animals in the 21st century.”
—Karen Davis, President of United Poultry Concerns, quoted in Poultry industry not ready for cloning, by Joe Cacchioli, The Daily Times (Salisbury, Md), January 18, 2002.

Ethical objections to the genetic engineering of birds and other animals have focused primarily on the violation of species integrity (Rifkin), although attention has also been given to the suffering of individual animals and to the definition of animals as patentable “manufactures and compositions of matter” (Davis 1990; Kimbrell). This definition represents a further debasement of nonhuman animals from their traditional low status as human property devoid of value and claims in their own right. Animals used for genetic engineering are not recognized as whole beings but only as technology components. The indifference to the animals who are being used in genetic engineering experiments was expressed by the researcher who told his colleagues at a poultry science meeting in 1992, “We are no longer selling broilers [i.e. baby “ meat-type” chickens], we are selling pieces. A knowledge of how broilers of different strains and sexes grow and become pieces is increasingly important” (Dudley-Cash). 

Chickens are being used in genetic engineering research in pursuit of three primary objectives:

  1. to develop and refine experimental methodologies and technologies;
  2. to produce pharmaceuticals and other proteins in eggs for potential use in human medicine and animal agriculture; and
  3. to identify and exploit profitable biological traits for poultry meat production.

To Develop and Refine Experimental Methodologies and Technologies

“An obstacle to avian transgenesis is the low-efficiency of introducing foreign DNA into the chicken genome. Procedures that have worked for other animals are difficult, if not impossible, due in part to the unique reproductive physiology of the chicken. New methods, including the use of transposable elements, show promise but require additional refinement before their utility is confirmed.”
—Harvey, A.J. et al., Poultry Science, February 2002, p. 202.

Researchers using birds in genetic engineering experiments are trying to overcome the inaccessibility of the birds’ fertilized ova. In mammals, such as mice, the fertilized ova are relatively easy to obtain in large numbers, and they have visible pronuclei for DNA microinjection. However, a hen produces only one fertilized ovum per day. This ovum, the yolk, is large and fragile. Its cytoplasm makes the pronucleus impossible to visualize for DNA microinjection. By the time the egg is laid the embryo has already begun to develop on the yolk and has about 60,000 cells. Another problem is that the viruses that are used to carry the foreign genes into the birds can dangerously replicate: “The major problem associated with the use of retroviral vectors is the generation of infectious virus that can be indefinitely transmitted” (Legras and Verdier 1997 quoted in Turner).

  • In the mid-1980s, a researcher at the Institute of Animal Physiology and Genetics Research in Edinburgh injected foreign DNA into single-cell chicken embryos and then cultured them through hatching in vitro. The embryos was removed from the hen’s oviduct, placed in various vessels containing solutions similar to those in an egg, then placed in artificial eggshells sealed with glue made from albumen and antibiotics, and mechanically incubated through hatching. New Scientist called them “[t]he world’s first test-tube chickens” allowing researchers to create “‘super-chicken’ by inserting foreign DNA into chick embryos” (Milgrom).

  • In 1993, Poultry Science published an article describing a National Institutes of Health (NIH)-supported study of the potential of the avian liver to express (manifest a trait linked to a particular gene) recombinant proteins in vivo. The research was designed to estimate use of the avian liver “to influence growth rates, metabolism, body fat composition, and the effectiveness of various drugs” and be a model for treatment of human genetic diseases. In the experiment, avian leukosis retroviral vectors were used to introduce a recombinant rat neomycin-resistance gene into chicken embryos before and during incubation. Upon hatching, the surviving chicks were killed by cervical dislocation (neck-breaking) and their tissues were frozen in liquid nitrogen for further analysis (Cook et al.).

  • A 1994 article in Bio/Technology described a method of producing transgenic chickens based on microinjection of foreign DNA from two different types of bacteria into the birds. First the researchers artificially inseminated hens with semen pooled from young roosters. Then they killed the hens by intravenous injection of an anesthetic overdose of Expiral. Next they opened the dead hens’ abdomens and removed the oviduct section containing the shell-less fertile eggs. They then placed the eggs in surrogate shells and injected the bacterial DNA into the cytoplasm of the germinal discs of the zygotes (the one-cell embryos). Next they filled the shells with a culture medium and sealed them shut. Following this, they analyzed the fate of the plasmid DNA microinjected into the germinal discs of embryos who survived for at least 12 days in culture. Of the 128 original ova, seven chicks survived to sexual maturity. Of these, one rooster transmitted the bacterial DNA to 3.4 of his offspring. Of these offspring, those who survived to sexual maturity were bred to produce transgenic offspring, “demonstrating that stable transmission of foreign DNA can be obtained by our method” (Love et al., p. 60).

  • The aim of a study published in 1995 in Transgenic Research was “to develop a safe retroviral system to obtain transgenic chickens” (Thoraval, p. 374). The problem addressed was the fact that replicating avian retroviruses used in vivo can be pathogenic even after a long time, increasing the risk of disease states associated with chronic viral infection. As the avian spleen necrosis virus (SNV) is closely related to mammalian retroviruses, and it has been found that SNV can infect human cells, the researchers sought a way to produce transgenic chickens using replication defective vectors based on a system (an “ecotropic” system) which is able to infect avian cells only.

    Using vectors derived from ecotropic avian leukosis viruses, the researchers microinjected foreign bacterial genes into the subgerminal cavity of unincubated chicken embryo blastoderms (tiny reproductive cells). DNA was then extracted from these embryos and injected into another group of unincubated chicken embryos who were then incubated. Of the group of 1550 chicken embryos infected with the ecotropic vectors, only 36 hatched. According to the researchers, most died early after injection due mainly to the opening of their eggshells. One surviving rooster managed to transmit vector DNA to his progeny, at a rate of 2.2 percent. The researchers concluded that their data showed “the efficacy of ecotropic avian retroviral vectors to produce transgenic chickens” (p. 375).

  • In a paper published in Poultry Science in 2002, researchers at AviGenics, Inc. and the Department of Genetics at The University of Georgia in Athens sought to “further validate the ALV [avian leukosis virus] retroviral vector system for the production of transgenic chickens,” as well as to develop “procedures that would identify transgenic offspring rapidly with less labor-intensive methods.” They describe “the production of three flocks that harbored stably integrated transgenes that were transmitted through several generations,” along with “methods for high-throughput DNA extraction and transgene detection to facilitate identification of transgenic founders and their progeny” (Harvey, A.J. et al., p. 203).

    Following the description of their “less labor-intensive methods,” the researchers concluded that their data revealed “a low rate of germline transmission, which can be expected for most transgenes inserted into the chicken germline via the NLB system” (the avian leukosis virus retroviral vector system they used). And while less than 5 percent of the “generation zero” males hatched from injected embryos produce transgenic offspring “at an efficiency rate of 1% or less,” the “low rate of germline transmission from founders to fully transgenic offspring using existing methods was partially overcome by the improved screening methods described here” (p. 211).


Global Exploitation of Chickens for Commercial Use of Their Flesh and Eggs: Governments and Private Corporations Work Together

“When the chicken genetic map is completed it should provide a means of selecting production traits for a variety of desires.”
— Hans Cheng, USDA Agricultural Research Service, in The chicken genetic map: a tool for the future, Poultry Digest, June 1994, p. 24.

In 1993, the U.S. Department of Agriculture began funding the National Animal Genome Research Project. Its purpose is to develop genetic maps for agriculturally important species—“cattle, swine, sheep and poultry.” The Project’s headquarters for gene mapping of poultry is the USDA Agricultural Research Service’s Avian Disease and Oncology Laboratory in East Lansing, Michigan. According to researcher Hans Cheng, “The main goal of our laboratory is to decode the genetic information in the chicken genome. . . . Armed with this powerful tool, researchers will be able to identify and isolate regions of the chicken genome that influence production traits such as feed efficiency or disease resistance. This information could, in turn, lead to improved methods for breeding superior chickens. In addition, much of the information and technologies will be readily transferable within poultry since the genomes of other avian species such as turkeys and ducks are similar to the chicken genome” (Cheng).

The USDA poultry genome research project laboratory is working with other laboratories around the world, in England, Scotland, The Netherlands, and Israel. The effort to identify economically important genes in poultry is coordinated by an International Poultry Genome Workshop. Due to large investments and expected profits, the United States also has “secrecy and confidentiality agreements which accompany an intense competitive relationship between laboratories and between countries” (Witter).

“Chicken functional genomics is in its infancy. This technology has many other applications to chicken biology. Some obvious applications are to improve disease resistance, hasten immune competence, and manipulate growth regulation. It is essential to couple technology development with potential applications in order to most efficiently exploit chicken genomics.”
—Robin Morgan, PhD, University of Delaware, in a presentation given by Hans Cheng at the National Breeders Roundtable, May 2-3, 2002.

AviGenics is a U.S. biotechnology company established in 1996. Located in Athens, Georgia, home of both the USDA Agricultural Research Service’s Southeast Poultry Research Laboratory and The University of Georgia, the company shows how it and other biotech companies around the world are coupling genetic engineering experiments on chickens with potential business applications (www.avigenics.com). AviGenics is in the business of creating and commercializing recombinant biopharmaceuticals using transgenic chickens as “oviduct bioreactors” and developing lines of “meat” birds with economically favorable “agronomic traits” through cloning and genetic modification. The company’s Windowing Technology, now patented, allows researchers to put DNA into chicken embryos through a hole or “window” in their shells. AviGenics has announced its intention to control proliferation of the company’s proprietary genetic lines, like its “FibrGroTM Advantage broiler lines” which will be rented to poultry breeding companies, four of which companies own 92 percent of the world’s market (Aho, p. 36). 3

To Produce Pharmaceuticals and Other Proteins in Eggs for Potential Use in Human Medicine and Animal Agriculture

A major venture in this area is the mass production of egg yolks with antibodies to be used as artificial growth promoters in chickens and other farmed animals now that the use of growth-promoting antibiotics is being reduced or eliminated in meat-animal production as a result of having contributed to the worldwide growth of antibiotic-resistant bacteria (Howie).

For this and many other uses, hens and their eggs are being genetically engineered to be protein and antibody “factories.” They are being used:

  • To make vaccines.(Michael)
  • To produce antibodies in eggs that are added to pig feeds to fight off bacterial infections such as E. coli. (Cochrane)
  • To produce growth-promoting antibodies in egg yolks to be fed to farmed animals to increase their growth rates by disrupting their normal peptide and gut processes, thus, for example, tricking animals who are already full to continue eating. (Recombinant Proteins)
  • To produce recombinant lactoferrin and lysozyme as alternatives or supplements to growth-promoting antibiotics and/or antibodies in poultry diets. (Recombinant Proteins)
  • To produce antibodies to fight cancer in humans. (Coghlan)
  • To secrete human growth hormone to help dwarfs grow taller. (Clark)
  • To produce eggs with lower cholesterol for human consumption. (Michael)
  • To produce soy isoflavons in eggs sold for human consumption. For example, poultry researchers at the University of Maryland and the University of Arkansas are experimenting with Japanese quails to see if soy isoflavons can be transferred and accumulated in their eggs. The University of Maryland’s Office of Technology Commercialization has filed a patent application for the research “hoping to license the technology to a commercial egg producer” (Michael).
  • To produce yolk antibodies--specifically, avian immunoglobulins, or IgY--for a range of diagnostic systems as a substitute for the use of laboratory mammals (Schade et al.)
  • As fertile “egg-type” hens’ eggs carrying “meat-type” chicken cells in order to mass-produce cloned “meat” (broiler) chickens, and thus do away with the expensive maintenance of broiler breeder flocks. In this program, “certain individuals from the pedigree flocks would be cloned and the genetic material placed into fertile eggs. Cloning companies would culture cells and then place them into the embryo of a fertilized recipient egg forming a chick called a chimera. . . . The recipient fertile eggs could come from flocks like leghorns that produce a large number of inexpensive eggs. When those eggs are hatched, they are broilers”  (Aho, p. 38).  

To identify and exploit profitable biological traits for poultry meat production

Manipulation of Growth Characteristics in Poultry

  • “Growth promotion will be the primary target for application of recombinant DNA techniques directly to chickens.” —The Chicken Industry: New Products Promise Change, Genetic Technology News, August 1988.

  • “Remember, the whole idea of meat production is to get the time from chick to market weight down from 42 days to as brief a time as technically feasible.” —Tom Abate, Origen Far From Chickenhearted About Bioengineering; Program may yield birds that grow faster, bigger, San Francisco Chronicle, July 10, 2000.

  • “The days needed to raise a 35-pound tom today is 38 percent less than it took in 1966, and today’s hens require about 33 percent fewer days to reach a 16-pound market weight. The yearly average body weight of 18-week-old toms continued to rise from 1966 to 2001. . . . Projecting this trend to the year 2010, commercial toms should easily achieve a live weight of over 35 pounds by 18 weeks of age.” —Peter Ferket, Growing Bigger, Faster, WATT PoultryUSA, February 2002.

  •  Under the heading of The Chicken Industry: New Products Promise Change, Genetic Technology News predicted in 1988 that recombinant products that could improve growth offered the biggest potential market for genetically engineered poultry products (p. 8). In this forecast the marketing of such products was on the horizon, as the research was already underway. For example, the global conglomerate pharmaceutical company Merck, which now under the name of Merial owns one of the largest shares of poultry breeding stock in the world, was experimenting on chickens using growth hormones from cattle. In the early 1990s, Merck filed for a European patent on a “Macro Chicken,” described on the patent application as a “transgenic fowl expressing bovine growth hormone” (Mather, p. 1D).

  • Meanwhile geneticists were searching for a fat-reducing gene to insert into broiler chickens because selection for fast rapid growth has increased the number of fat cells in these birds (Gyles). With these and other projects in mind, genetic engineers were eager to manipulate the chicken’s DNA to make the birds grow larger, leaner, and faster, and to change the shape and composition of their bodies to fit the “value-added,” deboned chicken parts market overtaking the traditional sale of whole birds.

Misery of Modern “Meat” Birds

Genetically manipulating a bird who would normally weigh little more than a pound at six weeks old into a bird weighing four and a half or five pounds at this age (growing at a rate of three and a half times faster than normal) has created major metabolic and skeletal disorders in “meat-type” chickens. Their mortality rate is 7 times that of laying hens of the same age, and 2 percent or more of these birds die of heart failure in their infancy (Turner, pp. 11-12). At least a quarter of all broiler chickens are lame, and studies show that they are in pain. When given a choice between food with painkillers and regular food, the birds quickly identify the food with the painkillers and eat only that (Danbury et al.).

Given the multitude of problems caused by forced rapid growth using 20th-century selective breeding methods, the poultry industry is considering cloning and other genetic modification procedures to multiply chickens for the world market in years to come (Leach 1996). According to agribusiness economist Paul Aho, “In the 21st century, the breeder industry may or may not be headed in the direction of cloning. What is certain is that breeder companies will become increasingly interested in traits other than growth rate” (Aho, p. 38). Notwithstanding, biotech companies boast of plans not only to increase the numbers of chickens raised for slaughter but to shrink the time that it takes these birds to grow to existing, or even larger, body weights.

Cloning: Biotech Companies Seek to Bridge the Gap Between Egg Laying and Meat Production in Chickens

“[T]raditional breeding techniques are starting to hit some limits. For instance, when breeders select birds that grow fatter faster, these birds tend to be duds at laying eggs. . . . But what if there was a way to have the best of both worlds, to create a breed that reached market weight in record time, but also had a high egg-laying potential, so breeders could quickly supply farmers with billions of these new super-birds?”
—Tom Abate, Origen Far from Chickenhearted About Bioengineering, San Francisco Chronicle, July 10, 2000.

Unlike transgenic birds, who have had genes from other species inserted into their embryos, cloned birds have had embryonic stem cells from members of their own species microinjected into their eggs to replicate virtually identical birds. In September 2000, the United States Department of Commerce gave AviGenics, based in Athens, Georgia, a $2 million grant “for the creation of the world’s first cloned bird” (Adams 2000). The following year two companies, Origen Therapeutics in Burlingame, California and Embrex, Inc. of North Carolina, received $4.7 million from the U.S. National Institute of Science and Technology to fund chicken cloning experiments for the poultry industry (Chicken Cloning). The idea, according to biotechnology writer Paul Elias of the Associated Press, is “to create identical copies of eggs with desirable traits that can roll off assembly lines by the billions” (Elias). The “desirable traits” is in the hands of Origen experimenters. The “assembly-line billions” of identical chicks is in the hands of Embrex, which already injects vaccines into billions of embryos each year in commercial hatcheries (Graves).

The San Francisco Chronicle provides a glimpse of the chicken cloning process: “Imagine peering through the shell, past the egg white to the tiny embryo, about the size of a match head, that floats on the yellow yolk. In laboratory experiments, Robert Etches, Origen’s chief scientist, has removed embryonic cells from one breed of chicken and injected them into the embryo of a different breed. The process is akin to cloning. When the experiment works—which Origen says is about one out of 10 tries—the result is a chicken that gets many of its traits from the injected embryo. So far, the company has focused on showing visible traits, such as feather color. It is trying to boost its success rate, especially in assuring that the desired trait—fast weight gain—ends up being dominant” (Abate).

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