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TRANSGENIC FISH STOCKED INTO AU RESEARCH PONDS
AUBURN, Ala.__--Researchers in Auburn University's Alabama Agricultural
Experiment Station advanced genetic development of fish one step further
today by stocking into research ponds common carp that contain growth
hormone genes from rainbow trout. These "transgenic" fish
will be evaluated periodically and compared to nontransgenic carp, which
share their research ponds.
Release into research ponds built with detailed security measures to
prevent escape or removal of the fish was approved by the U.S. Department
of Agriculture. Stocking of the transgenic carp represents the next
step in developing fish that grow more rapidly due to the inclusion
of a single growth hormone-producing gene from another species. The
gene donor is a rainbow trout, a fast growing, cold water fish.
"Putting these fish into an aquacultural environment is critical
to learning what effect the extra gene will have on various production
criteria such as growth rate, body composition and dressout percentage,"
according to Rex Dunham, an associate professor of fisheries and allied
aquacultures at Auburn University. Dunham, who headed the research team
that developed the transgenic carp in research supported with Hatch
funds through USDA's Cooperative State Research Service, noted that
the genetically altered fish grew 20-40 percent faster than nontransgenic
carp in aquariums. The Auburn researcher believes the addition of an
extra growth hormone-producing gene, in addition to the carp's own growth
producing genes, is responsible for the accelerated rate of growth.
Dunham pointed out that testing in an outdoor pond setting is necessary
to evaluate many environmental factors that could not be considered
in an inside aquarium. Without testing in ponds, researchers could not
know whether the more rapid growth of the transgenic carp in the aquarium
environment would be the same as in a pond environment.
In inside aquariums, transgenic fish showed little production difference,
other than growth rate, from nontransgenic common carp. Such characteristics
as survivability, percentage of deformation, color, shape and other
measurable production parameters were virtually the same. The transgenic
fish only grew faster, which was expected since only a single gene for
growth was added to their genetic makeup.
In their new pond home, the transgenic fish will be evaluated monthly
and compared to nontransgenic common carp. The Auburn scientists will
check such parameters as growth inheritance of the gene, survivability,
tolerance to low oxygen levels and susceptibility to disease and predators.
"Putting the transgenic carp into outdoor ponds represents the
fourth step in our research project," Dunham said. The first step
was to get the gene into the fish, which was done by injecting egg masses
with the growth hormone from rainbow trout genes. The second step was
to determine if this extra gene was expressed in the genetic makeup
of the carp, which was done by growth hormone assays by Dunham's collaborators
at the University of Maryland. The third step was to determine if the
extra gene was passed along to progeny of the original transgenic carp,
which also was done by growth hormone assays, Dunham explained.
If the transgenic carp prove to have the same 20-40 percent rate of
growth advantage as shown in inside aquariums and the same lack of other
production differences, the first model for developing transgenic fish
will be completed. Using this model, scientists conceivably could manipulate
the genetic codes of food fish, such as channel catfish. The potential
will exist through genetic manipulation for control of diseases and
parasites, improved feed efficiency, tolerance of varying oxygen levels
and other commercial fish production limitations.
The long term impact of faster growing, not necessarily larger, fish
is dramatic. For example, in the United States the cost of importing
fish is second only to oil products. So, increased production could
help reduce the federal trade deficit. Worldwide the shortage of meat
protein is increasing, which could be offset by the ability of fish
farmers to produce three crops of transgenic fish in the same time it
takes to produce two crops of nontransgenic fish. Not only could fish
production be increased, but so could the production of more nutritious
fish, because growth hormones tend to promote leaner, higher protein
growth.
In the United States, catfish production has increased steadily for
the past 25 years. The ability to produce a uniform crop of catfish
in less time could help insure the continued growth of this industry.
The benefits would be felt by both producers and consumers, because
of the increased supply of fish.
"The potential benefits to man are great, but right now, we just
want to develop the model by which all these potential changes can be
produced. The evaluation in ponds of these carp, which we know possess
one extra growth hormone gene, puts us one step closer to having that
model," Dunham concluded.
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By:
Roy Roberson
5/23/91
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