The systematic eradication of male chicks is a common practice in the poultry industry, which says it is the only viable option for birds that have no economic value.
But the cullings, which were upheld by a German court on Thursday, have long been denounced as inhumane and ethically unacceptable by animal rights activists. Egg production requires the hatching of millions of chicks every year, with the females sold to be raised and exploited by either individual farmers or commercial poultry farms. Adult roosters, however, produce no eggs and develop far less meat than the so-called "broilers" bred especially for eating.
As a result, producers say the male chicks aren't worth the cost of raising to adults.
But currently a chick's sex cannot be determined while still in the egg without invasive testing that is both time-consuming and often results in damage or death to the embryo.
After hatching, male chicks are separated from the females, and then mechanically shredded or crushed, or else suffocated by carbon dioxide.
Often their remains are used as animal feed.
An EU directive from 2009, for example, authorises shredding as long as it causes "immediate" death for chicks less than 72 hours old.
It is not the only agriculture industry that culls by sex: Female ducklings produced on farms making foie gras pate, for example, are usually killed because only bigger males are fattened for slaughter.
The two main alternatives to industrial culling are to raise the male chicks as usual, or try to determine the sex of chicks while still in the egg, so they can be killed before hatching.
But poultry farmers are loath to start using chicken breeds suitable for both egg-laying and meat production.
"They would reduce egg production and therefore increase costs, something that consumers won't accept," according to the French poultry farmers' union (SNA).
France's ITAVI technical institute for poultry farming says researchers in several countries are actively trying to develop in-the-shell alternatives for sex identification.
"These methods will need to be reliable and not interfere with hatching rates before they can be introduced on an industrial scale," it said.
Gerald Steiner, an analytical chemist from Dresden University in Germany, has developed a spectroscopic method that analyses an embryo's blood vessels to determine the sex of chicks.
And in the Netherlands, a start-up analyses hormones in the egg white to identify the chick's sex.
But both methods involve making a tiny hole in the shell, which then has to be plastered up to ensure the chick's survival.
American researchers are also looking for solutions, with the United Egg Producers trade group saying in 2016 it hoped to eliminate the culling of male chicks "by 2020 or as soon as it is commercially and economically feasible".
In France, the government partnered with electronics firm Tronico in 2017 to develop a way of identifying chicks' sex by analysing the transparency of the egg.
But the agriculture ministry has said the method is "still experimental" and "not 100% reliable", while vowing "firm measures" later this year on ensuring animal welfare, including the shredding of male chicks.
"The day a company brings out a viable, large-scale method, obviously the hatching firms will want it," the SNA said.