Rising temperatures are causing hens across India to lay fewer eggs with thinner, more breakable shells, as heat stress disrupts the biological process of eggshell formation. (Photo: Unsplash)

Eggs on your plate are getting smaller and the hens blame climate change

The egg you cracked into your pan this morning may look the same as always. But the hen that laid it was having a very bad summer. Climate change is making eggs smaller, shells thinner, and production lower.

by · India Today

In Short

  • Heat stress causes hens to lay smaller eggs with thinner shells.
  • Climate change is disrupting poultry feed crops like maize and soya.
  • India's poultry sector contributes 11 per cent of total livestock GDP.

The egg you cracked into your pan this morning may look the same as it always did. But something about it has quietly changed. The shell is thinner. The white is looser.

And the hen that laid it was, in all likelihood, having a very bad summer.

India's poultry sector is the fastest-growing segment of its livestock industry, contributing approximately one per cent to national GDP, and it is among the most exposed to the consequences of a warming climate. (Photo: Unsplash)

This is the latest story in Climate on My Plate, India Today Science’s series on how the climate crisis is reshaping the everyday things we eat, drink, buy and own.

This week, it is the egg on your plate and the chicken on your thali.

WHAT HEAT DOES TO A HEN

A hen is, physiologically speaking, a creature built for a narrow temperature window. According to a 2025 study published in Veterinary World, the optimal environmental temperature for pullets (hens preparing to lay eggs) ranges between 19 and 22 degrees Celsius.

Go beyond that, and the bird enters a state called heat stress, which is simply what happens when an animal’s body generates more heat than it can release.

Unlike humans, hens cannot sweat. They release excess body heat almost entirely by panting, the way a dog does on a hot afternoon.

When the temperature climbs too high for panting to keep up, the bird’s internal chemistry begins to shift.

Hens in a poultry farm during summer. Unlike humans, hens cannot sweat and release excess body heat almost entirely by panting. When temperatures exceed the optimal range, the bird’s internal chemistry shifts, reducing egg production and quality. (Photo: Unsplash)

According to a review published in ScienceDirect, the adverse effects of high environmental temperature on poultry include a decrease in growth rate, body weight, egg production, egg weight, and egg quality, causing vast financial losses to the poultry industry.

In practical terms, this means fewer eggs, smaller eggs, and eggs with thinner, more breakable shells.

Research compiled by The Poultry Site confirms that heat stress reduces productivity, impacts fertility, increases susceptibility to disease, and reduces both the size of eggs and the thickness of eggshells.

WHY YOUR EGG IS CHANGING

The eggshell is made almost entirely of calcium carbonate, which is the same compound found in chalk and limestone.

A hen deposits this calcium while the egg is forming inside her body, a process that takes roughly 20 hours.

When a hen is heat-stressed, she pants more rapidly, which causes her to exhale more carbon dioxide than usual.

Carbon dioxide is a gas that the body produces naturally, and losing too much of it disrupts the blood's chemical balance.

An omlette. Heat stress causes hens to exhale excess carbon dioxide, disrupting the blood's chemical balance and interfering with their ability to deposit calcium onto forming eggshells. (Photo: Unsplash)

This disruption, called respiratory alkalosis, which means a shift in the blood towards being too alkaline or non-acidic, directly interferes with the hen's ability to deposit calcium onto the forming eggshell. The shell comes out thinner.

A 2025 systematic review published in ScienceDirect on climate change and food security in India found that research in Odisha and Uttar Pradesh has confirmed that heat stress affects the shape of eggs, while studies in Punjab have shown that heat stress delays egg production altogether by pushing back the age at which hens begin to lay.

THE FEED PROBLEM NOBODY TALKS ABOUT

The impact of climate change on poultry does not stop at the hen. It reaches all the way back to her food.

Poultry feed is made primarily from maize and soya, two crops that are acutely sensitive to heat and erratic rainfall.

According to a 2024 review published in Discover Sustainability by Springer Nature, approximately one third of the world's cereal harvest is used to feed animals, including poultry.

As climate change disrupts these crops, feed becomes more expensive and less nutritious. A hen eating lower-quality feed produces lower-quality eggs.

Climate change is affecting the chicken on your thali. (Photo: Unsplash)

The climate crisis, in other words, is hitting the egg from two directions at once, through the hen's body and through her food.

India's poultry sector is the fastest-growing segment of its livestock industry.

According to The Poultry Punch, the sector contributes approximately 1 per cent to national GDP and 11 per cent of total livestock GDP, and it is among the most exposed to the consequences of a warming planet.

The egg on your plate has not been swapped for something else. It is still an egg. But the planet that produced it is a degree warmer than it was a generation ago, and the hen that laid it felt every bit of that difference.

#ClimateOnMyPlate

- Ends