National Anti-vivisection Society


National Antivisection Society

Genetically Modified Animals

Posted: 15 November 2016. Updated: 15 November 2016


In the UK, more than half of all research now uses genetically modified (GM) animals. Animals are created to replicate diseases and disorders which occur in humans by changing the animal’s biology with the modification or removal of genes (short sections of DNA).

Scientists use GM animals for research into drug development and human disease. Abnormalities studied on animals include Alzheimer’s, Parkinson’s, deafness, diabetes, cancer and psychosis. Experiments have also explored transplants between animals such as pigs and primates.

Animals involved in genetic research often undergo invasive procedures and suffer from harmful effects of the modification.

In 2015, a total of 4.14 million procedures were carried out on animals in the UK. The use of GM animals in experiments and animals used to create GM animals accounted for 2.8 million procedures – 67% of all procedures on animals.

The use of GM mice accounts for 49% of experimental procedures. Other frequently used species include fish, rats and birds. 61,247 experimental procedures on GM animals were classed as ‘severe’, which means animals will have suffered long-term disease, a major decline in health or a significant loss of normal behaviour.

Causing mutations in animals

The creating of GM animals, most often mice, typically begins with the injection of hormones into a female. This causes her to release a huge number of eggs during ovulation – also known as superovulation. She is then mated with a male to fertilise her eggs.

The pregnant female is killed and her fertilised eggs removed; animals are often killed by having their neck broken. DNA in the fertilised egg is modified to implant the defect or cause a mutation in the developing foetus.

A second surrogate female is then mated with a vasectomised or genetically sterile male to induce a fake pregnancy. Symptoms of pregnancy such as weight and uterus changes and the development of mammary glands occur before the female undergoes surgery to have the modified eggs transferred into her uterus.

The tiny babies will be born or the surrogate mum killed and the tiny babies removed. Some may be displaying retarded growth or other abnormalities, even at this early stage of life. Babies have parts of their tails or ears cut off for DNA analysis in order to establish which of them have been born with the defect.

Poor science

The use of animals in research is fundamentally flawed due to ‘species differences’. These differences make animal experiments unreliable in predicting effects in humans, can lead to disastrous consequences and, in some cases of drug development, the result has been fatal.

Mice are predominately used in GM research and yet not all mice DNA have a direct equivalent in humans and many genes in mice are expressed differently in humans. Attempts to “humanize” mice by inserting human genes into animals would never produce a similar result to drug metabolism in a person, because the genes are in a non-human. Hopes of using humanized mice to predict the breakdown of drugs in the human body have even been called “wishful thinking”.

65 million years of evolution separate mice and humans, creating considerable differences between the two species. The life span, anatomy and living environment of mice is significantly dissimilar to that of humans, making direct comparisons problematic. Even those advocating the use of GM animals have warned that “there are significant limitations of genetically modified mouse models”.

Suffering in GM animals

The number of animals used in research has significantly increased since the introduction of genetic modification, because of the large numbers used in breeding, to create just a small proportion of animals with the “desired” genetic defect. Animals used for the creation of GM animals are killed once their function in the process has been performed, resulting in the death of millions of animals every year.

In 2015 in the UK, 2.06 million procedures on animals were specifically for breeding and creating GM animals. Those used to produce GM offspring undergo numerous surgical procedures such as hormone injections, egg collection, embryo transfer and vasectomies.

Many animals die before they are born and only 1-3% of those that survive actually have the characteristic or defect, therefore huge numbers are killed and discarded.

GM animals experience prolonged pain and suffering from both undergoing repeated surgical procedures, from the genetic defect itself and from undergoing experiments. Genetic defects can cause severe health problems, mutations and premature death.

Living conditions for laboratory animals are sterile, confined and often un-stimulating. GM rodent rooms often contain racks with row upon row of plastic cages containing hundreds or thousands of animals.

An undercover investigation by NAVS at Medical Research Council (MRC) Mammalian Genetics Unit in Harwell, Oxfordshire, discovered the reality of these experimental facilities. Issues included over breeding and an inability to manage breeding groups, as well as animals with a whole host of deformities and illnesses, caused either by the intended mutation or as a side effect.

Please support research without animal suffering »

© National Anti-Vivisection Society