It sounds like a culinary catastrophe but scientists have shown that it may soon be possible to breed beef cattle whose meat is enriched with the healthy properties of fish oil.
The researchers have shown that it is possible to create genetically modified (GM) mammals that secrete the Omega-3 constituent of fish oil in their muscles.
Although the work has so far been carried out only on laboratory mice, the Harvard University scientists believe it is just a matter of time before a similar attempt is made on farm livestock.
Jing Kang, the leader of the research team from Harvard and the Massachusetts General Hospital in Boston, said that mammals cannot normally make their own Omega-3 fatty acid which is found in abundance in fish oil and is known to prevent heart disease and furred-up arteries.
However, when the research team inserted a gene into mouse embryos for an enzyme that can help to synthesise Omega-3, the researchers found abundant amounts of Omega-3 in muscle tissues and relatively low amounts of the less beneficial Omega-6 fatty acid - which the enzyme converts into Omega-3.
The researchers wrote in the journal Nature: "The obvious follow-up would be to create livestock animals and see if their tissues also contain Omega-3s," Dr Kang said.
Some domestic livestock, such as laying hens, are already fed a diet rich in fish oils in the hope of boosting levels of Omega-3 in farm products.
But the scientists believe a that a GM alternative could be more effective. Mr Kang said that meat, milk or eggs from the GM animals will not taste fishy because Omega-3 does not have a taste. "Correction of the usually Omega-3 deficient western diet has become a key step towards reducing the risk of several modern diseases," Dr Kang said. The enzyme gene used in the study was derived from a nematode worm.
The gene, called fat-1, helped to convert Omega-6 fatty acid into Omega-3 and causes no apparent harm to the laboratory mice, the researchers said.
"Another possibility to explore would be gene therapy to introduce fat-1 directly into human tissues," he added. That idea could lead to people being able to manufacture their own Omega-3 internally.
Lord Melchett, policy director of the Soil Association, which certifies organic farmers, dismissed the idea that the research would lead to GM farm livestock that would benefit human health.
"We know that all or nearly all such claims turn out to be rubbish," Lord Melchett said. "There is a widespread view that GM farm animals are going to be even less acceptable to the public than GM crops."
Joyce d'Silva, of Compassion in World Farming, said the idea of creating GM livestock enriched with Omega-3 is an appalling prospect. "Omega-3 is easily obtained from plant sources such as rape oil. GM and cloned farm animals often suffer from a range of defects, such as malformed limbs or organs," Ms D'Silva said.