午夜福利1000集合

Gene editing could make horn-free cattle in the near future (Image: Remsberg Inc/plainpicture)

TO THE casual eye, they look no different to other dairy cows. But where most dairy cows have scars from where their horns have been removed, these have none. Thanks to a tiny tweak to their DNA, they will never grow horns.

Created by a Minnesota-based company called Recombinetics, the hornless cattle are the first of a new wave of farmed animals developed using techniques that, unlike conventional genetic engineering, involve no 鈥渇oreign鈥� DNA (see 鈥�How to tweak a genome鈥�).

鈥淲e already have numerous cattle in more than one location,鈥� the founder and head of Recombinetics, Scott Fahrenkrug, told New Scientist. And while he would not discuss the details, Fahrenkrug hinted that the company will this year begin selling semen from bulls with the hornless trait for breeding.

Recombinetics has used gene editing to make existing breeds hornless without affecting any of their other traits. This approach could eliminate the common practice of dehorning, Fahrenkrug says 鈥� and farmers would be very happy if it did.

The hornless animals were created specifically to improve the welfare of cattle. Next up could be ways of ensuring that dairy cows produce only female calves and chickens lay eggs that can be sexed long before they hatch, so ending the mass slaughter of male calves and chicks.

Genetic techniques are also making farm animals resistant to infectious diseases, which will benefit people and wildlife. Researchers are already working on TB-resistant cattle, potentially ending the culling of wild animals blamed for spreading the disease, such as badgers. Flu-resistant chickens and pigs, also in development, would help prevent the emergence of new viral strains capable of causing a human flu pandemic.

鈥淚f an animal is resistant to a virus, that is good news,鈥� says of the Roslin Institute in Edinburgh, UK. In June, his team announced the birth of pigs gene-edited to be resistant to African swine fever, a highly contagious and deadly virus. 鈥淚t鈥檚 good news to the producer, it鈥檚 good news to the person who pays the money to buy the food in the supermarket, it鈥檚 good news to the animal.鈥�

There is still opposition to genetically modified food, even in countries like the US where it has long been grown and eaten. But Whitelaw thinks the potential benefits of gene editing are so great that it will win over some critics. 鈥淕enome-edited livestock is the biggest thing that鈥檚 ever hit genetically engineered livestock, and I do think it鈥檚 big enough to trigger [a change in] public opinion.鈥�

In the case of the hornless cattle, there is no doubt the gene edit will improve welfare. To prevent injuries to farm workers and other animals, cattle routinely have their horns sawn off, or else a hot iron or caustic paste is used to destroy the 鈥渂uds鈥� on a calf鈥檚 head that develop into horns. The process is painful and is usually done without anaesthetic.

It is possible to create hornless cattle by crossing a horned breed with a hornless one, and indeed this is being done. But the offspring lose some of their desirable traits too, so many further crosses are required to get them back. Gene editing massively speeds up the process, achieving in a couple of years what would take a century with conventional breeding, Fahrenkrug says.

What鈥檚 more, gene editing can improve welfare in ways simply not possible with conventional breeding.

For instance, it is standard practice in many countries to castrate pigs to prevent 鈥渂oar taint鈥�, an unpleasant odour that develops in meat from some sexually mature males. Recombinetics has instead disabled a gene essential for testicular development, so there is no need for castration.

Climate-ready cattle

Fahrenkrug says that the pigs appear to grow faster than ordinary pigs during puberty.Once again, the will sell semen with this disabled gene to farmers for use in artificial insemination.

Another major welfare issue in farming is the routine slaughter of unwanted animals. Dairy cattle have to be female, for instance, whereas more muscly males are preferred for beef. 鈥淚f we鈥檙e having to kill thousands of the wrong-sex animal, that鈥檚 a welfare issue,鈥� says Whitelaw. Several groups around the world, including Fahrenkrug鈥檚, are working on ways of producing only offspring of the desired sex.

Recombinetics has also identified the mutations responsible for several traits that make cattle more comfortable in warm climates, such as having shorter hair, more active sweat glands and a paler coat colour. Adding these traits would allow some breeds to thrive in places that are now too hot for them, and also help maintain production as global warming continues.

Obviously, gene editing could also be used to make changes that will worsen animal welfare. But conventional breeding is no different. It has already produced many breeds that suffer, from chickens whose muscles grow so fast they develop deformities, to bulldogs that struggle to breathe because of their deformed faces.

鈥淕ene editing could end the routine slaughter of animals simply because they are the wrong sex鈥�

There鈥檚 still some way to go before we create cows that walk up to tables in restaurants and beg to be eaten, like the one in Douglas Adams鈥檚 The Restaurant at the End of the Universe. But we do now have the genetic know-how to make major improvements in livestock welfare over the coming decades 鈥� should we choose to allow its use.

Although genetically modified crops are now grown and eaten in most of the world, genetically modified animals have yet to be officially approved for food production in any country. This is partly because creating GM animals was very difficult and expensive until recently, and partly because of concerns over the safety of taking whole genes from one species and putting them into another.

Because gene editing is different, there is no reason to think there will be any safety issues with milk or beef produced by gene-edited hornless cattle, for instance. The tiny change in one gene that results in hornlessness is identical to one already found in a few breeds of beef cattle. 鈥淲e already eat them,鈥� Fahrenkrug says.

The US Department of Agriculture has said that crop plants produced by gene editing will not require special regulation. It regards deliberately making plants with a desirable mutation as no different to selecting plants that just happen to have desirable mutations 鈥� something farmers have been doing for at least 10,000 years.

The US Food and Drug Administration has yet to make it clear whether it will adopt a similar position on gene-edited animals, or require approval in advance as it does with transgenic animals. 鈥淚f any of these projects come good, then the regulatory system has to address it,鈥� says Whitelaw. 鈥淎nd I suppose society has to say, do we want this?鈥�

This article appeared in print under the headline 鈥淒awn of edited animals鈥�