“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:
- to develop and refine experimental methodologies
and technologies;
- to produce pharmaceuticals and other proteins
in eggs for potential use in human medicine and animal agriculture;
and
- 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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