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Genetic Engineering Newsletter Special Issue 13 (text)



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Genetic Engineering Newsletter – Special Issue 13
July 2003

supported by
Deutscher Tierschutzbund e.V.

Transgenic livestock

CONTENTS
Preface
Objectives of genetic modifications of farm animals
Improved productivity of livestock	
Altered traits of agricultural products
Improved resistance to diseases
Improved uptake of nutrients
Improved adaptation to specific environmental conditions
Detection of water pollutants
Combating invasive species
State of art in producing transgenic livestock
Risk aspects
Impacts on the environment
Impacts on human health
Impacts on animal health
Further considerations concerning transgenic livestock
Conclusions
Bibliography

Preface
Public awareness of the development of transgenic livestock [Within the scope of this 
newsletter the term livestock will exclusively be used for vertebrates.] is much smaller 
than of transgenic agricultural crops. This might be so due to the fact that products of 
transgenic farm animals did not yet become available to consumers. But the situation 
could be changing soon. In the USA and Cuba applications for the commercial use of 
transgenic fish have already been filed for [In the USA the company „AQUA Bounty 
Farms" is awaiting the approval of their transgenic salmon (AquAdvantage) for 
human consumption. In Cuba applications for the commercial use of African perch 
(Tilapia) was filed for.]. Therefore there is an urgent need for public discussions about 
the risks and benefits of transgenic livestock.
The deficiency of scientific studies and public debates concerning risks caused by 
transgenic farm animals is astonishing, having in mind the abundance of research 
carried out in the field of animal biotechnology. As early as in 1985, the birth of the 
first transgenic farm animals was announced. The first experiments were conducted 
with sheep, pigs and rabbits (Hammer et al. 1985). In the meantime also cattle, 
goats, chicken and 35 different fish species have been subject of genetic 
modifications (Meier et al. 2003).
Below the objectives of genetic modifications of farm animals are described. The 
possible impacts of transgenic livestock on the ecosystems affected, the consumers 
and the farm animals themselves are evaluated in a separate chapter. Possibilities to 
minimize these risks are illustrated.

Objectives for genetic modifications of farm animals
In general the objectives for genetic modifications of farm animals are similar to those 
of traditional breeding of farm animals. Most of them aim at a higher productivity, a 
modification of characteristic traits of agricultural products, an improved resistance to 
diseases, an improved uptake of nutrients or an improved adaptation to specific 
environmental conditions. Furthermore, concerning transgenic fish, some 
experiments with the aim of detecting water pollutants or combating invasive species 
were carried out.
Two different expectations mainly promoted the research on transgenic livestock so 
far: to receive the desired traits faster than by traditional breeding techniques and to 
be able to transmit specific traits of agricultural products beyond the natural 
boundaries of species.
Currently most experiments dealing with the development of GM livestock do not yet 
(or not exclusively) aim at the objectives mentioned above. In fact most research 
projects on GM livestock try to improve existing methods of gene transfer or develop 
new techniques. Problems of transgenic technology that have to be faced are that it 
is still very time consuming, generates very high costs, is characterized by an 
exorbitant inefficiency resulting in a very high lethality of the animals (embryos and 
newborns) and often produces abnormal deformations of several organs of 
transgenic animals. Methods of transgenic technology are further illustrated in the 
chapter "State of art in producing transgenic livestock".
Below the above-mentioned objectives of genetic modifications of livestock will be 
further specified.

Improved productivity of livestock
Up to now the most common objective in transgenic technology dealing with livestock 
is an improved productivity. Experiments were carried out with pigs (Pursel et al. 
1989, Ebert et al. 1990, Coleman et al. 1995), cattle (Brem & Müller 1994, Hill et al. 
1992), sheep (Rexroad et al. 1989, 1991, Nottle et al. 1999), rabbits (Koval et al. 
1991, Medvedev et al. 1995, Rosochacki et al. 1992), salmon (Sin 1997), carp 
(Venugopal et al. 1998), trout (Devlin et al. 2001) and African perch (Hernández et al. 
1997, Martínez et al. 1996). In most cases growth hormone genes of the same or a 
different species were transferred. The accelerated growth of animals shall reduce 
the time span until they can be slaughtered.
·	The development of fast growing salmon was successful. The company AQUA 
Bounty Farms is currently awaiting the approval for commercial aquaculture 
[Production in aquaculture has increased during the last years and currently 
constitutes one fourth to the amount of fish traded on the world market.] concerning 
their transgenic salmon.
·	Transgenic fast growing pigs were reported to produce meat with a lower fat 
content (Niemann 1998, Mitchel & Pursel 2001). Another possibility to produce fast 
growing pigs was tested by Wheeler et al. (1999). They designed transgenic sows 
that produced more milk. During the first weeks after birth the shoats lactated by 
those sows showed an increased gain of weight.
·	Different methods to develop transgenic sheep that produce more wool were 
tested. One approach was the transfer of growth hormone genes (Damak et al 
1996b, Bullock et al. 1997, Su et al. 1998). A different approach aimed at the 
improvement of the cystein supply of sheep. Sheep are not able to synthesize this 
amino acid, which is essential for wool production. Therefore genes from bacteria 
were transferred that encode enzymes necessary in the synthesis of cystein (Powell 
et al. 1994). The transgenic sheep could produce a small amount of cystein for a few 
months.

Altered traits of agricultural products
The idea of altering specific traits of meat, milk, eggs or wool by means of transgenic 
technology was already tested in several experiments. Mainly the possibility to alter 
the composition of milk produced by cows, sheep or pigs was discussed (Wall et al. 
1997) and in some cases put into practice. However most of those experiments aim 
at the production of pharmaceutics.
·	The production of cow milk with a lower content of lactose resulting in a better 
compatibility for humans was only accomplished in model experiments with mice. 
The production of low fat milk with a higher content of vitamins, proteins or calcium 
was another aim that was often stated. However no experimental work has been 
done so far. Up to now other characteristic traits of milk connected with the 
processing of cheese, yogurt or ice cream, have rarely been modified. For example 
Brophy et al. (2003) developed transgenic cows that exhibited an increased amount 
of two different caseins [For the production of cheese several proteins, called 
caseins, that are contained in milk play an important role.] in their milk.
·	The production of the iron-binding protein lactoferrin [Lactoferrin protects the 
suckling from gastrointestinal infections. It acts as an anti-oxidant.] contained in 
human milk was the aim of the development of the transgenic bull "Herman" by the 
Canadian company GenPharm. The bull was born in 1990 and bequeathed the 
human genes to its female offspring, enabling them to produce small quantities of 
lactoferrin in their milk. The transgenic cows developed by Berkel et al. (2002) were 
also able to produce lactoferrin. In addition another human protein (a-lactalbumin 
[The protein a-lactalbumin is important for the provision of the amino acid tryptophan 
in mothers' milk.]) was already produced in the milk of transgenic cows (Eyestone 
1999).
·	The Canadian company Nexia Biotechnologies announced the birth of two 
BioSteel®-goats in January 2000. Genes of a spider species encoding fibre proteins 
had been transferred to the goats. The proteins produced in milk of the goats were 
aimed to be processed into "spider silk" later on.
·	Efforts to change the characteristic traits of wool were undertaken by Powel et 
al. (1994). They showed that it is possible to alter the traits of wool by means of 
transgenic technology. However the wool did not show the desired characteristics but 
only abnormal characteristics. A specific alteration of selected traits of wool fibre 
cannot be obtained yet.
·	Experiments to alter characteristics of fish as flesh colour, fat and proteins 
contents and flavour were already conducted (Teufel et al. 2002).

Improved resistance to diseases
Diseases of livestock can often cause high costs in intense forms of livestock 
husbandry. This applies not only to the epidemics of BSE (mad cow disease), foot-
and-mouth disease, avian influenza or classical swine fever that were often reported 
in press coverage in recent years, but also to other diseases. In theory different 
possibilities exist in order to combat these diseases by means of transgenic 
technology. One is to improve the immune system, another to transfer genes for 
resistances, an immunisation or the deletion of genes that may cause diseases 
(Niemann et al 1996). In fact only few of these ideas have been pursued so far. None 
of these attempts resulted in animal lines that were in fact resistant to any disease.
·	Efforts to transfer immunoglobulin gene constructs were undertaken with pigs 
and sheep (Lo et al. 1991, Weidle et al. 1991). Thereby the animals should receive 
an "inborn" immunisation against specific bacteria but the attempts were 
unsuccessful. Müller et al. (1992) tried to transfer genes into pigs encoding a 
resistance against an influenza virus but the experiment showed no success.
·	In order to combat scrapie, a disease that affects the central nervous system 
of sheep, research on prion resistant strains was conducted (Denning et al. 2001). 
Prions are a group of proteins that are supposed to cause scrapie in sheep and BSE 
in cattle. Another experiment aimed to provoke a resistance to the visna virus 
(Clements et al. 1994).
·	Attempts to produce transgenic cattle that possess a higher resistance to 
mastitis were undertaken. Mastitis is an inflammation of the udder caused by bacteria 
(often Staphylococcus aureus) that is responsible for high economic losses in dairy 
farming. Kerr et al. (2001) could transfer a gene construct into mice that enabled 
them to produce the antibacterial substance lysostaphin. The experiments can be 
seen as preparatory work for the development of corresponding transgenic cows.
·	Experiments to create transgenic chicken bearing a resistance to the leucosis 
virus were conducted by Salter & Crittenden (1989). Leucosis, also called poultry 
cancer, is one of the most common diseases of chicken.
·	Endeavours to produce transgenic salmon that are resistant to the bacteria 
Vibrio anguillarum were undertaken by Jia et al. (2000). Hew & Fletcher (2001a) 
carried out similar experiments aiming at a higher resistance to bacteria.

Improved uptake of nutrients
In pig breeding animal feed mainly consists of cereals, rapeseed and soy. The 
problem is that in those plants the vital nutrient phosphorus is almost inaccessible for 
pigs because they are missing the necessary enzyme [Phosphorus is only available 
in form of phytate in this animal feed which cannot be directly uptaken by the 
organism. The uptake is only possible after the decomposition of phytate with the 
help of the enzyme phytase]. Therefore phosphorus is generally supplemented to 
their feed. Golovan et al. (2001) developed transgenic pigs that could produce the 
enzyme that enables them to a successful uptake of phosphorus. Thereby the 
amount of phosphorus supplemented to animal feed of pigs could be reduced. As a 
side effect of the improved uptake of phosphorus, the amount of phosphorus in the 
excrements of pigs also decreases. This could counteract an over-fertilisation of 
farmland with phosphorus, which is especially problematic for neighbouring aquatic 
ecosystems.
Experiments of a modified uptake of nutrients were also undertaken with fish. Gene 
constructs of the genome of man and rat were transferred into trout (Oncorhynchus 
mykiss) and arctic char (Salvelinus alpinus) that should enable them to an improved 
use of carbohydrates (Pitkänen et al. 1999). This aim could not be achieved in the 
scope of the experiment and was not subject of further investigations so far.

Improved adaptation to specific environmental conditions
Each animal species and variety of farm animal is adapted to specific environmental 
conditions because of evolutionary effects and breeding activity. Therefore specific 
limitations for each species or variety exist regarding the area where farming is 
possible. In Canada efforts were made to improve the frost tolerance of salmon by 
genetic modification (Hew et al 1999, Hew & Fletcher 2001b). In Canada salmon can 
only be produced in aquaculture farms situated at southern coastlines. The climate at 
northern coastlines is too cold for salmon production. By the transfer of genes that 
code for antifreeze proteins that were isolated from the American winter flounder, 
these restrictions could be broken. The antifreeze proteins are produced in the liver 
of the fish and accumulated in the bloodstream where they lower the freezing point 
by reacting with aggregating ice crystals thus preventing their formation. So far the 
researcher only succeeded in developing transgenic salmon that produce a 
preliminary stage of the antifreeze-protein. However this substance shows only a 
very small antifreeze effect.

Detection of water pollutants
In the Netherlands, the USA and Japan several working groups try to develop 
transgenic fish, which can be used for the detection of water pollutants (Amanuma et 
al. 2000, Carvan et al. 2001). The transferred gene constructs provoke that the fish 
produces certain substances if the pollutant is present. In another experiment gene 
constructs were transferred that tend to mutate if the pollutant is present. Afterwards 
these mutations can be measured. The water pollutants in the centre of interest are 
heavy metals, aromatic hydrocarbons, dioxins and other mutagenic substances. At 
the moment these experiments are mainly carried out with zebrafish (Danio rerio).

Combating invasive species
The term "invasive species" is used for species (accidentally or deliberately) 
introduced into new areas mostly by man. They can severely damage the 
ecosystems in which they were introduced and may cause the extinction of native 
species. Farm animals can also be invasive species if they are able to live in the wild 
as different fish, rabbits, cats and dogs are. Ron Thresher of CSIRO, Australia's 
national research organisation plans to develop a transgenic carp that produces 
exclusively male offspring. With the help of this fish, the invasive carp population in 
the Australian river Murray, which already account for more than 90 percentage of all 
fish biomass in that river, shall be brought to collapse. Recently model experiments 
with zebrafish are undertaken (Davis et al 1999, Mcennulty et al. 2001).

State of art in producing transgenic livestock
For the first time the technique of producing transgenic vertebrates was successfully 
applied to mice (Gorden et al. 1980). Since that time mice were the preferred objects 
of research regarding experiments with transgenic animals. That explains why 
technical methods of gene transfer are most sophisticated in mice. However, the 
results obtained with mice cannot directly be applied to the production of transgenic 
farm animals. Each species exhibits a very specific reproduction system. The 
development of transgenic cattle, sheep, pigs, chicken or the respective fish species 
requires the application of a species-specific technique. The development of 
transgenic fish currently poses the smallest amount of complications (Teufel et al 
2002) out of all vertebrates.
Despite the technical differences in the production of transgenic animals, the same 
underlying approach exists for almost all species. So far the most common method is 
the transfer of gene constructs via "microinjection" (Brem & Müller 1994, Amoah & 
Gelaye 1997). DNA that is produced in vitro is thereby injected into a fertilized egg 
cell. The exact position where the injected gene construct is integrated into the genes 
of the egg cell cannot be predicted (Gibson & Colman 1997). The transformed egg 
cells are kept in cell culture until they are transferred into foster mother animals as 
embryos. The rate of success is generally extremely low. Between 85 and 99 percent 
of the embryos die before they are born. Only 0,5 to 4 percent of the embryos 
transferred to foster mother animals are born alive and are in fact transgenic 
(Ammann & Vogel 2000, Meier et al. 2003). The rate of success varies depending on 
the experiment and the animal species chosen. The majority of transgenic animals 
that are born alive do not reach the expected average life-span of the respective 
species. Malformations of the viscera are often the cause for a reduced life span (see 
chapter „Risk aspects - Impacts on animal health"). Altogether both the loss of animal 
life and the amount of time and money spent are extremely high in the production of 
transgenic animals.
Furthermore in some cases the transferred genes are not bequeathed to the next 
generation, because the gene construct was not stably incorporated into the genes of 
the animal. Even if the gene construct was successfully incorporated into the genes, 
the subsequent breeding may raise problems. The random split-up of maternal and 
paternal genes in the course of sexual reproduction may cause that specific 
characteristics are lost and others appear. Therefore it is often stated that cloning 
should be applied as supplementary technique in the development of transgenic 
animals. However the rate of success in this technique is also very low so far. In the 
case of the so-called nuclear transfer [The technique of nuclear transfer consists of 
transferring the nucleus of a cell into an unfertilised egg cell whose nucleus had been 
eliminated. This technique was applied for example in the production of "Dolly".] 
technique the rate is approximately 2 percent for sheep, goats and cattle. Another 
technique of cloning is the so-called "embryo-splitting". Generally embryos of few 
days age are split into two [Out of ten embryos twenty halves may be produced and 
transferred into recipient cows. On the basis of an approximate rate of success of 50 
percent ten calves would be born. Out of ten undivided embryos only six calves 
would be born on the basis of a rate of gestation of 60 percent (Nickel 1998).]. A 
disadvantage of this method is the limited number of identical clones that can be 
produced (Revermann & Hennen 2000). However, embryo-splitting is often used in 
practice (Niemann & Wrenzycki 1998).

Risk aspects
Research projects dealing with the development of transgenic livestock have been 
granted much subsidy from both industry and state. In the beginning there was an 
euphoria about the new technical possibilities. Research concerning the risks of 
genetic modifications for human health, the environment or the transgenic animals 
themselves was therefore not undertaken. This lack of research is understandable 
during the first years of the application of transgenic technology because research 
mainly aimed at the obtainment of new scientific knowledge and took place in very 
few laboratories. Since the development of transgenic animals that promise to show 
suitable characters for livestock production the situation was completely different and 
accompanying research on possible risk should have been carried out. However this 
has not been so and therefore there is a great deficiency concerning the knowledge 
of possible risks now.
The few existing hints and data on risks caused by transgenic livestock are compiled 
and evaluated below. Furthermore comments on the needs of research are given.

Impacts on the environment
Impacts on the environment caused by transgenic animals can vary between different 
groups of transgenic species. This has to be kept in mind considering the 
environmental risks of transgenic livestock production. Therefore transgenic 
mammals and chicken will be evaluated separate from transgenic fish.
Mammals and chicken
As a matter of principle, the risk that transgenes from transgenic farm animals are 
incorporated into wild populations by pairing exists for all transgenic livestock. 
Furthermore the outcrossing into other herds of livestock is also possible. However 
the risk has to be assessed depending on the species, the region in which it is kept 
and the form of animal husbandry.
For example in Europe there is no risk of outcrossing for transgenic cattle, because 
the archetype of cattle, the aurochs (Bos primigenius) was already exterminated in 
the 17th century. A small risk exists in Asia and Africa, because wild water buffalos 
(Bubalus arnee), yaks (Bos mutus) und gaurs (Bos gaurus) are living there as 
potential partners for pairing. The situation is similar for sheep and goats. Partners for 
pairing as the argali (Ovis ammon) or the bezoar goat (Capra aegagrus) are currently 
only living in very few regions of the world. Wild boars (Sus scrofa) must be 
considered as potential pairing partners for pigs. The risk of outcrossing into wild 
populations is very high for rabbits compared to other mammals. Rabbits can escape 
relatively easy from enclosures and possess a very high reproduction potential [In 
Australia wild rabbit that had developed a resistance to myxomatosis could 
explosively propagate at the end of the eighties of the last century. The 
consequences for the affected ecosystems were very severe.]. For chicken an 
outcrossing into wild chicken must be considered. For all animals mentioned above 
the risk of outcrossing can be minimised if husbandry is exclusively carried out in 
closed stables. In no case transgenic livestock should be kept in open herds, as it is 
common for cattle in the Alps or in Argentina for example. Transgenic rabbits should 
be kept in escape-proof hutches, even if aspects of animal health are contradictory 
and this form of husbandry is not appropriate to the species. The experience shows 
that it cannot be prevented that rabbits, sometimes in great number, can escape if 
they are kept in open enclosures.
Fish
In contrast to most other transgenic livestock, fish is farmed in the direct surroundings 
of its wild conspecifics. Reports of escapes from aquaculture systems where fish is 
kept in cages are quite common. The reasons are mostly defect or damaged material 
or human failure. During the last years, millions of farmed salmon could escape from 
aquacultures in Canada, Iceland, Ireland, Norway, Scotland, the USA and the Faroer 
Islands [Farmed salmons from aquaculture endanger the declining populations of 
wild Atlantic salmon by spreading of parasites and diseases. Additionally populations 
of Atlantic salmon that are well adapted to their habitat are endangered by a 
„contamination" of their gene pool with genes of farmed salmon. This means that 
genes that are unfavourable for the survival of the species may enter into wild 
populations of Atlantic salmon.].
Escaped transgenic fish may endanger both their wild conspecifics and populations 
of other species. Wild populations of the same species are mainly endangered by the 
ingression of so-called "Trojan genes" into their gene pool (Muir & Howard 1999, 
2001, 2002). Trojan genes are genes or groups of genes that have a positive effect 
on the pairing success, but a negative effect on the survival of the offspring and 
therefore the whole population. According to several mathematical models, Trojan 
genes can lead to the extinction of a whole population. Populations of other fish 
species are endangered by an advantage in selection of the modified competitors or 
predators. A new characteristic such as the increased food uptake of fast growing 
transgenic fish can lead to the replacement of native fish species which may cause 
extinction in an extreme example.
In order to keep the risks arising from transgenic fish low for the surrounding 
ecosystems, transgenic fish production should not take place in aquaculture in the 
open sea [This was also stated in the „Declaration of Bergen", a declaration of the 
ministers of environment of the abutter countries of the North Sea, which was 
adopted in the scope of the Fifth International Conference on the Protec-tion of the 
North Sea]. The probability that fish escapes from those cages is too high. Closed 
land-based facilities are an existing alternative in order to prevent these risks (Potthof 
& Teufel 2003).
Recently research is carried out in order to develop transgenic sterile fish lines. The 
expectation is that the ecological risks of aquaculture in the open sea could be 
diminished by raising sterile fish lines. The transferred gene constructs suppresses 
the release of specific sex hormones. However the obtained sterility was not hundred 
per cent in any experiment so far (Breton & Uzbekova 2000, MacLean & Laight 
2000). Furthermore it cannot be guaranteed that the suppression of sex hormone 
genes persists during the whole life-time of the fish. Therefore the risk that single 
individuals lose their sterility during their lifetime and are able to reproduce cannot be 
excluded. Another form of creating sterile population exists in the so-called 
polyploidisation [The presence of more than two haploid sets of chromosomes is 
called polyploidisation. In contrast to plants, polyploidisation of the whole organism is 
very uncommon for animals and often has a negative effect on their ability to 
reproduce] of the genome. However this method can also not provide sufficient 
security (Teufel et al. 2002).

Impacts on human health
Potential risks on human health caused by transgenic livestock has to be assessed 
depending on the transferred genes. Beside the risks arising from the consumption of 
products of transgenic livestock the risks of diseases that could be transferred from 
animal to man during husbandry also has to be considered.
A Cuban study may illustrate the recent state of art and significance of research in 
the field of risks caused by transgenic livestock (Guillén et al. 1999): In order to 
assess the risks on human health arising from the consumption of transgenic tilapia, 
it was eaten by eleven test persons within a period of five days [The experiment was 
carried out with voluntaries of the staff members of the Cuban centre for genetic 
engineering and biotechnology (CIGB).]. As a result the researcher stated that none 
of the measured biochemical parameters of the blood had been altered by the 
consumption of the transgenic fish. The scope of the study regarding the period of 
time and the amount of persons examined is in no way appropriate for a scientific 
survey concerning the harmlessness of food.
Further investigations regarding the impacts on human health caused by the 
consumption of products that derive from transgenic livestock do not exist.
In principle the risk of an allergic reaction caused by transgenic animal products must 
be considered. In addition transgenic livestock could unexpectedly produce toxins or 
show an altered composition [Transgenic fish lines showed an altered composition of 
their body in different experiment. Among other things a higher amount of water, an 
altered composition of amino acids, a decreased content of fat and an increased 
content of proteins could be observed. The effects of this alteration on the human 
nutrition have not yet been examined.] of its meat or milk that can be unfavourable for 
human health. Future research regarding the risks of products of transgenic livestock 
should therefore focus on these problems. For the evaluation of health risks it has to 
be considered that the effect of genetic modifications may differ between species 
(Devlin et al. 2001). Moreover data from one transgenic line cannot directly be 
adopted to another line because the position where the transgene is incorporated 
into the genome of the animal is variable and may therefore cause varying effects.

Impacts on animal health
Even without an explicit risk assessment numerous cases of very grave adverse 
effects on animal health were observed in the scope of many experiments with 
transgenic livestock.
In general genetically modified embryos that are transferred to foster mother animals 
show a very low rate of survival for all farm animals species (see chapter „State of art 
in producing transgenic livestock"). Many transgenic animals that are born alive die at 
an early stage of live. The transfer of gene constructs that encode growth hormones 
may cause malformations in all animal species.
·	Brem & Müller (1994) reported malformations of the stomach, heart and lung, 
skin diseases and a reduced fertility in transgenic pigs.
·	An increased production of growth hormones in rabbits caused symptoms that 
are common to human with abnormal growth [Abnormal growth of man is called 
acromegaly and is caused by the production of growth hormones after ado-lescence. 
Symptoms are a disproportionate growth of the nose, ears, chin, hands, feet, 
zygomatic bone, vertebra and chondral parts of the thorax as well as different 
abnormalities of the tissue.] (Costa et al. 1998). In sheep the transfer of genes 
encoding growth hormones caused severe health problems. Among other things the 
higher concentration of growth hormones caused diabetes (Rexroad et al. 1991, 
Rexroad et al. 1990) and affected the functioning of liver, kidneys and heart 
(Nancarrow et al. 1991).
·	Numerous studies show that genetic modifications in fish cause partly severe 
side-effects (so called pleiotropic effects). Most pleiotropic effects were observed in 
connection with an increased production of growth hormones because most research 
was done in that field of genetic modification. Studies with the explicit aim to evaluate 
the impact of genetic modification on fish health were also undertaken with fast 
growing transgenic fish. Among other things fast growth of fish may cause an 
extreme malformation of the head and other parts of the body. Furthermore tumours, 
an altered colouration, an altered form of fins and vertebrae, abnormal growth of the 
gills, absence of specific body segments and an alteration of the form of the neck and 
caudal fin could be observed (Devlin 1998, Dunham 1999, Hew & Fletcher 1997, 
Pandian et al. 1999). By the transfer of growth hormone genes the whole balance of 
growth hormones is altered (Dunham 1999). Even morphological alterations that do 
not appear to be very severe at first sight may have far reaching consequences. 
Stevens & Sutterlin (1999) observed an increase surface of the gills in transgenic 
salmon. The increase of the gill surface resulted in an increased uptake of oxygen. 
This phenomenon has to be taken into account regarding the calculation of earning 
power of aquaculture because the increased uptake of oxygen requires a raised 
pump activity. Effects on the physiology and biology of behaviour were also 
observed. Farrell et al. (1997) described a severe decrease of swimming ability 
concerning transgenic salmon. Different authors proved an altered feeding behaviour 
in transgenic fish. Jönsson et al. (1996) proved that transgenic trout rises faster in the 
upper regions of rivers and generally ingests more food.

Further considerations concerning transgenic livestock
Many question arise from the development of transgenic livestock. Some of the 
aspects that are not subject of the risks evaluated in this newsletter shall be 
mentioned below.
·	Is it ethically justifiable to develop transgenic livestock for economic reasons? 
Which amount of dead animals and sufferance of farm animals shall be accepted? 
How important is animal welfare?
·	Which amount of investment is adequate in this field of genetic engineering? 
Will products of transgenic livestock ever cover the enormous costs for the 
development of transgenic livestock? What role may the lack of acceptance of 
products of transgenic livestock on the part of the consumer play in that context?
·	What negative effects regarding the economy and society may occur even in 
the case of a successful development of transgenic livestock? Who would ultimately 
profit from the development of transgenic livestock, which part of the society or which 
occupational group may be the "loser"? Which kind of structural changes could occur 
in agriculture?
·	Can the possibility be excluded that new risks arise in form of misuse from a 
further development and simplification of the application of genetic engineering 
methods?
·	What is the impact on the self-image of man and his view of nature? Which 
could be further consequences?

Conclusions
Experiments with transgenic livestock are undertaken since several decades. The 
aims of the development of transgenic livestock are manifold and mostly similar to 
those of traditional breeding. A strong deficiency of studies and public debates exists 
concerning the risks that transgenic livestock may cause. An appropriate evaluation 
of those risks is therefore not yet possible.
·	Unpredictable and unstudied are the impacts on the ecosystems concerned. 
Therefore precaution should be applied, as it is common for all newly introduced 
species. Transgenic mammals and chicken should be kept in closed stables in order 
to keep the ecological risks low. Transgenic fish should only be kept in closed land-
based facilities for the same reason. However this form of aquaculture generates 
more costs and can barely be realised appropriate to the species. A calculation of 
earning power would also be necessary.
·	Possible impacts on human health caused by the consumption of products 
that derive from transgenic livestock are nearly unsought. Results of long-term 
studies on the consumption of those products are not available so far. All products 
would have to be tested concerning the potential to bear toxins that may be produced 
as a result of the genetic modification or substances that may cause allergic 
reactions. Furthermore it is important to check whether the composition of products 
from transgenic livestock is altered or not. Products could result in being "less 
healthy" for human. Malnutrition could be the consequence that would result in an 
increased susceptibility for diseases. For example it would have to be tested if "low-
fat" transgenic fish contains less omega-3-fatty acids than its conventional bred 
conspecifics.
·	The impacts on animal health are not yet sufficiently studied. All experiments 
that were undertaken so far lead to the conclusion that transgenic animals do very 
often suffer from malformation of different organs and various diseases. If cloning 
would be applied in the process of producing transgenic livestock another problem 
would be that those animals are aging faster, as it was in the case of the Dolly, the 
cloned sheep. Furthermore during the process of the development of transgenic 
livestock the death of an immense number of animals is still inevitable. It should be 
verified in how far this aspect is conform to the aims of animal welfare that is part of 
the German constitution.
The debate about risks arising from products of transgenic livestock has also a 
political dimension. Agricultural products are traded on the world market and 
transgenic fish that escape from aquaculture may enter into the sovereign territory of 
other countries. Therefore it is of particular importance to discuss the subject of 
possible impacts of transgenic livestock on the environment, human health and 
animal health both on national and international level.

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