Each year, the global egg industry kills billions of male baby chicks because only female hens lay eggs — but CSIRO scientists say they have now come up with a solution to this major ethical issue.

Scientists at the CSIRO's Animal Health Laboratory say they can use biotechnology to ensure the males are never born, let alone culled.

The culling of male chicks

Chicks are bred by hatchery companies who sell the day-old animals to farmers — but before the producers receive the fluffy little chicks, they are sorted by sex.

The global egg industry kills billions of male baby chicks every year. ( Reuters: China Photo ASW/BM )

Female chickens will grow to become hens and lay eggs until they are about 80 weeks old.

But Pete Bedwell, the editor of industry magazine Poultry Digest, said the useless males were destroyed shortly after they hatched.

"They can be killed — either just macerated or they can be can be gassed with carbon dioxide, go to sleep," Mr Bedwell said.

"A day-old chick is extraordinarily cute and unfortunately that is a factor, it's killing Bambi."

The males cannot be grown out for chicken meat because they are bred to be small in frame, not round and muscular like meat chickens.

The science that could offer a solution

Tim Doran and Mark Tizard work at the Australian Animal Health Laboratory in Geelong.

The pair were studying poultry disease when, almost accidentally, they made a breakthrough with biotechnology.

Dr Tizard said an embryo could be micro-injected and a green fluorescent protein gene placed on the male chromosome.

The technique has the support of the industry body the Australian Egg Corporation. ( ABC News: Caitlyn Gribbin )

"Sex is determined by chromosomes in chickens — and in humans — and you have a chromosome that tells you whether to be female or male," Dr Tizard said.

"We're marking the chromosome that says become male. When you get to breeding to produce the birds that will go on to lay eggs, the mark follows the males and not the females."

Once the egg is marked with a new gene, a chick will hatch, which will be used to generate a breeding flock.

When the females from that flock are included in a breeding program for layer hens, their male offspring will easily be identified by a laser by their fluoro mark.

The eggs containing males will be removed and the animal will never hatch.

Dr Doran said that could be an ethical and welfare win — and that the eggs would not be wasted.

"Our concept is that once you remove the male embryos from the incubation process they can go off and be used for vaccine production, which is obviously a very high-value application that can have huge benefits for the community," he said.

Is this genetic modification?

The short answer is yes — and that has already upset anti-genetic modification groups like the Safe Food Foundation.

Anti-genetic modification groups have expressed concern at the technique. ( ABC News: Caitlyn Gribbin )

Director Scott Kinnear has been vocal in Australia about genetically modified crops.

"I wouldn't be satisfied that any genetic modification is safe unless it's been through an exhaustive method of testing by independent bodies," Mr Kinnear said.

Dr Tizard said international experts agreed genetic modification was not an issue in this case.

"The process we use to mark the males does involve a genetic modification, an introduction of the marking gene, the green fluorescent protein gene," he said.

"That gene segregates and if it's male it will carry the gene and if it's female it won't. It's an on-off situation; you can't partly carry the gene."

Who wins?

The research has been presented to international breeding companies and it is now up to them to decide whether they will use it.

The technique has the support of industry body the Australian Egg Corporation and some farmers.

Tamworth egg producer Bede Burke said the industry needed get on the front foot.

"Ethically, I think if we can move toward getting this right it will be a wonderful outcome, a win-win," Mr Burke said.

"At last we've got something that is tangible and can deliver real outcomes."

Egg producer Bede Burke says the research could lead to "win-win" outcome. ( ABC News: Caitlyn Gribbin )

For years, the RSPCA has urged the egg industry to invest in alternatives that allow sex to be determined in the early egg incubation phase.

Scientific officer Melina Tensen has welcomed the breakthrough.

"We're really encouraged by this research because in-ovo sex determination has the real potential to end the culling of male chicks in the egg industry each year," Ms Tensen said.

"We're certainly hopeful the research will progress to implementation and commercialisation phases."

This story will air on ABC Landline on Sunday at midday on ABC TV.