PIGS, goats and cattle have been created to produce sperm - from another father, scientists have revealed writes Mark Waghorn.

The 'Frankenstein farming' technique could one day solve starvation for the world's growing population - or save species from extinction.

Surrogate 'super dads' will dramatically boost the quality of livestock, say the US and British team.

They could help conserve rare breeds of chicken in the UK, for instance - or other birds threatened by climate change.

In experiments, mice have already fathered healthy offspring who carried the genes of donor rodents. The larger animals have not been bred yet.

Project leader Professor Jon Oatley, director of the centre for reproductive biology at Washington State University, said: "With this technology, we can get better dissemination of desirable traits and improve the efficiency of food production.

"This can have a major impact on addressing food insecurity around the world. If we can tackle this genetically, then that means less water, less feed and fewer antibiotics we have to put into the animals."

His researchers included colleagues at Edinburgh University's Roslin Institute, famous for Dolly the Sheep - the world's first cloned mammal.

They used a gene editing (GE) tool called CRISPR-Cas9. It has been described as a pair of 'molecular scissors' - snipping DNA using a harmless virus.

Unlike GM (genetic modification), nothing is added from another species. But there will be ethical concerns.

Consumers have traditionally been reluctant to eat genetically altered animals and crops.

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This poses a significant problem for farmers owning gene-edited animals. The absence of regulation currently prevents their sale anyway.

Critics also say disease resistance will discourage improvements in the way they are kept, leading to poor welfare.

Prof Oatley and colleagues knocked out a male fertility gene called NANOS2 in the embryos of pigs, goats, cattle and mice that would be raised as 'surrogate sires'.

South West Farmer:

Jon Oatley, director of WSU's Center for Reproductive Biology. Picture: Bob Hubner / WSU / SWNS

They grew up sterile, but otherwise healthy. They began producing sperm after stem cells from donor animals were transplanted into their testes.

It held only the genetic material of the selected creatures. The groundbreaking procedure only seeks to bring about changes that could occur naturally - such as infertility.

Prof Oatley's lab is now refining the system before the next step - getting offspring from the pigs, goats and cattle. They will not be their own - but the donor's.

Co-author Prof Bruce Whitelaw, of the Roslin Institute, said: "This shows the world this technology is real. It can be used.

"We now have to go in and work out how best to use it productively to help feed our growing population."

Experts have been searching for a way to create surrogate sires for decades to overcome selective breeding and artificial insemination.

The latter is common in dairy cattle who are often confined. Their reproductive behaviour is relatively easy to control.

It is rarely used with beef cattle who need to roam freely to feed. For pigs, it requires the animals be nearby as their sperm does not survive freezing well. In goats, it sometimes requires surgery.

Surrogates deliver the donor genetic material the natural way - through normal reproduction.

This enables ranchers and herders to let their animals interact normally on the range or field.

Donors and surrogates do not need to be near each other since either frozen sperm or the animal itself can be shipped to different places.

In addition, female NANOS2 knockout animals remain fertile.The gene only affects male fertility. They could be bred to generate sterile males as surrogate sires.

It has great potential to help food supply in places in the developing world. Herders have to rely on selective breeding to improve their stock.

Co-author Prof Irina Polejaeva, of Utah State University, said: "Goats are the number one source of protein in a lot of developing countries.

"This technology could allow faster dissemination of specific traits in goats, whether it's disease resistance, greater heat tolerance or better meat quality."

It also opens the door to genetic conservation of endangered species whose dwindling numbers leave animals isolated - limiting their genetic diversity.

But even once ready for commercialisation, the surrogate sires could not be used in the food chain under current regulations.

This is partly due to the misperception GE is the same as GM, said Prof Oatley. He has joined the National Task Force on Gene Editing in Livestock to address the issue.

It includes researchers, industry representatives, bioethicists and policymakers who are seeking a path forward.

Prof Oatley added: "Even if all science is finished, the speed at which this can be put into action in livestock production anywhere in the world is going to be influenced by societal acceptance and federal policy.

"By working with policymakers and the public, we can help to provide information assuring the public that this science does not carry the risks that other methods do."

The study - the result of six years of collaborative work between the US and Scottish boffins - is published in Proceedings of the National Academy of Sciences.