I
n hundreds of grocery stores here, shop-
pers can pay a few extra cents for eggs
stamped with a heart and the word
respeggt—to show that they were laid by
hens that did not hatch alongside male
chicks destined for slaughter. This week,
the eggs will be available for the first time
in stores outside of Berlin. By the end of the
year, they will appear all across Germany—a
sign that scientists are getting closer to solv-
ing a tricky chick-and-egg problem.
Modern laying hens have been bred to pro-
duce huge numbers of eggs, but their broth-
ers are useless. They don’t put on weight fast
enough to be raised for meat. So hatchery
workers—specialized “sexers”—sort day-old
chicks by hand, squeezing open their anal
vents for a sign of their sex. Females are sold
to farms. Males—roughly 7 billion per year
worldwide, according to industry estimates—
are fed into a shredder or gassed.
Sorting males from females before chicks
hatch at 21 days wouldn’t just avoid the mas-
sacre. Hatcheries would no longer need to
employ sexers, they wouldn’t waste space
and energy incubating male eggs, and they
could sell those eggs as a raw material for
animal feed producers, the cosmetics indus-Rewe and HatchTech, a Dutch hatchery
equipment supplier, founded Seleggt, a spin-
off based in Cologne, Germany, to market the
technique. The company built a robot that
fires a laser to open a hole in the shell much
smaller than a pinhead. It sucks out a minus-
cule drop of the fluid and adds it to a solution
that turns blue in the presence of the female
hormone. Female eggs go to the incubator
and male eggs are sent off to be frozen and
processed into powder for animal feed.
Ludger Breloh, Seleggt’s managing direc-
tor, says that the system is sorting up to 3000
eggs an hour in a Dutch hatchery. As those
hens reach laying age, Seleggt will be able
to supply eggs to more than 5000 grocery
stores across Germany. But large hatcher-
ies process as many as 50,000 eggs an hour,
which would overwhelm the current system.
Some animal welfare advocates raise a more
fundamental problem, claiming that a 9-day
embryo might feel pain. And hatcheries
must pay for 9 days of incubation costs.
Gerald Steiner, an expert in medical imag-
ing at the Technical University of Dresden
in Germany, helped find a test that works
at day 4. His team shines a laser through
a thumbnail-size hole in the eggshell and
measures fluorescent signals from the blood
cells. The signals are different for male and
female embryos, likely because males de-
velop slightly faster and form certain blood
cells sooner. In female eggs, the hole is sealed
with medical tape, and the egg is returned to
incubation. The group is working with Agri
Advanced Technologies (AAT), a German
subsidiary of one of Europe’s largest chicken
breeders, to develop a prototype system. So
far, says Jörg Hurlin, managing director at
AAT in Visbek, sorting accuracy is high,SCIENCE sciencemag.org 16 AUGUST 2019 • VOL 365 ISSUE 6454 627PHOTO: EGGXYT LTD.
By Gretchen Vogel, in BerlinAGRICULTURAL TECHNOLOGY‘Ethical’ eggs could save day-
old chicks from slaughter
Scientists find ways to count male chicks before they hatch
Chickens have been
genetically engineered
to produce male eggs
that are fluorescent.IN DEPTH
try, or vaccine manufacturers. The United
Egg Producers, a U.S. cooperative, says it
wants to be cull-free by 2020, and the Ger-
man government has said it will outlaw the
practice. “Everyone wants the same thing,
and the right piece of technology could solve
this right now,” says Timothy Kurt, scientific
program director at the U.S. Department of
Agriculture’s Foundation for Food and Agri-
culture Research (FFAR) in Washington, D.C.
One contender is the technology behind
the respeggt eggs, which sorts them based
on sex hormones. Funding from govern-
ments and industry has prompted an
abundance of other ideas—from laser spec-
troscopy to MRI scans to genetic engineer-
ing. And next month, FFAR will announce
seed funding for six finalists—selected from
21 entries from 10 countries—for an Egg-
Tech Prize competing for up to $6 million
for a workable method.
Almuth Einspanier, a veterinary endo-
crinologist at Leipzig University in Germany,
and her colleagues laid the groundwork for
the respeggt brand. They found that by day
9 of development, female embryos produce
a hormone called estrone sulfate that can
be detected reliably in fluid that builds up
in the egg—“essentially the embryo’s pee,”
Einspanier says. The German grocery chain