Genetic modification (GM) of farm animals started in the early 1980s. Most research on GM farm animals (cattle, sheep, pigs, chickens and goats) has been carried out in the United States, Australia, New Zealand and Japan. Some GM animals have been produced to aid food production but there are also other uses. For example, researchers have produced GM farm animals to:
- increase meat production through rapid growth or leaner animals
- improve the amount and quality of wool
- alter the composition of milk to make better cheese, to reduce intolerance to milk or to produce medicines and neutraceuticals
- increase disease resistance
- reduce pollution from pig manure
- produce strong, spider-silk fibres in goat milk for military use.
Animal welfare issues associated with GM animals
- Only 1–3% of experiments to genetically modify animals are successful.
- Cloning is often used with the genetic modification, which increases losses of embryos and offspring at around the time of birth. GM and cloned animals are often oversized, weak and susceptible to disease. In experiments, 50% of calves died before weaning, and mice had greater than normal illness in later life plus abnormalities in future generations.
- Belgian Blue beef cattle have double-muscling genes producing muscles that bodybuilders would envy. This may be good for beef production but not for reproduction. As calves are so big, births are painful and most are by (repeated) caesarian section.
- GM of gut microbes could make fodder more digestible for farm animals. However, the GM microbes could unbalance the gut, cause disease to the animals and contaminate food.
- Developing GM (transgenic) pigs to produce donor organs for humans causes public concern but this is mostly about the ethics of human use, rather than about the welfare of the pigs. Research in GM mice with a gene involved in organ rejection has shown vision impairment and increased susceptibility to blood infections.
The main benefits from GM animals are economic — more product at a lower production cost. Because some people in developing countries can now afford more food, it has been argued that GM is needed to increase production to meet demand for meat, cheese and milk.
The use of GM in farm animals has focused on high-value products, for example medicines in milk. In the future, it is hoped that GM will focus on improving the health and welfare of animals. There has been some success with GM disease resistance and it is now possible to produce cattle without the gene for mad cow disease, giving hope it can be eliminated. In relation to improved welfare, GM research has produced hornless cattle that don’t need to be subjected to painful disbudding or dehorning; cattle better able to withstand hot climates; and the ability to block pubertal development in pigs to avoid the need for castration.
GM may have potential benefits, however, animal welfare should not be compromised in achieving them.