How do chickens have the spare resources to lay a nutrient rich egg EVERY DAY?


It just seems like the math doesn’t add up. Like I eat a healthy diet and I get tired just pooping out the bad stuff, meanwhile a chicken can eat non stop corn and have enough “good” stuff left over to create and throw away an egg the size of their head, every day.

In: 11289

Farm chickens have been bred to eat a lot and make an egg every day. The chickens that laid the most eggs the easiest were actively selected by farmers to reproduce so that they could have better and better chickens and more and more eggs.

You’ve got a big ol’ brain that takes a lot of energy just keeping running even if you just sit on the couch all day.

Meanwhile, while chickens aren’t particularly dumb, they’re not expending anywhere close to the same amount of energy just keeping the lights on.

Plus you know, an egg is only 78 calories. For a 1.5kg hen, it’s around 175 calories just for body maintenance and another 100 for egg production. You can consume 275 calories in a big bite and 4+ times that in a single meal.

Edit: As I’ve gotten a few comments suggesting chickens are dumb, here’s an article and a study addressing that.

Eli5 is they don’t have the spare resources. It takes a *massive* toll on their bodies.

Wild chickens will lay 10-20 eggs a year. The breeds that lay roughly an egg a day have been ~~naturally selected~~ artificially selected to lay around 200 eggs a year. This is indeed impossible to sustain. In studies, the vast majority of laying hens have bone fractures because those resources weren’t spare. Their bodies can’t support this. The best equivalent (not perfect, but as a simple comparison) is if human women were bred until they have their heaviest day of a period every day. You can imagine that wouldn’t be sustainable.

As a result the chickens inevitably burn out and can’t produce at that rate as their bodies deteriorate. And so once they’re not profitable, then they’re sent to the slaughterhouse.

Edit: thanks for the love, all. Edit on the strikethrough for correct term.

It is indeed good to know where your food really comes from and thus if you really want to keep eating eggs or any other animal part. Feel free to PM if you want advice on turning vegan. We’d love to help.

To answer a common point, backyard hens can (and do) live much longer and keep laying eggs. Part of this is being fed much more. They’re supplemented too. Of course better conditions will help, that’s true. The breed is still in pain laying so often. Some rescue places will use birth control so the hens don’t lay as often (this improves other health outcomes too). The main point is it’s also not profitable on a large scale. The price of eggs would maybe triple or more if that was the norm. So I’m of course speaking of how the vast vast majority are made. And again the short answer for OP is it’s not sustainable. Those chickens were artificially created by humans to lay so many and it hurts to do so. It will take its toll on the chicken’s health, bones, and mind.

For those wanting the studies, this isn’t a controversial point in general that laying hens get frequent fractures but this is the [latest systematic review I]( read. There’s a LOT of links there from various countries with estimates.

Egg-laying hens (like all farmed animals) are bred to prioritize production over the long-term health of their own bodies, so they’re not just using “spare resources.” They’re only given those resources in order to produce eggs. My friends who run bird sanctuaries talk about the terrible condition of hens coming even from free-range operations.

TL;DR: All their food consumption goes into laying eggs, they can’t do this for more than a couple years, and are euthanized the moment their laying rate drops.

Layer hens eat a lot. They eat around half their body weight in feed weekly, and they need a lot of protein. They’re kept in appalling, confined conditions where they don’t spend much energy beyond laying eggs, so all their energy and protein goes into eggs.

The reason is breeding. Wild chickens, or breeds not designed for egg production, lay only around an egg a month. Layer hens (not the same breeds as those you eat, which are called broilers) lay an egg a day and this is not great for long-term health.

They also only can maintain this rate for a short period in their lifespan. The average layer hen is allowed to live only about 2 years in a factory, because after that their productivity rate drops off and the cost of feed for them becomes less efficient. They are rarely slaughtered for meat, because layers are not as plump as broilers and do not meet supermarket customer expectations for dinner. Most layer hens are gassed with CO2 and processed for animal feed or fertilizer, or just buried in landfills.


In traditional farms, layer hens may live longer, since they are allowed to forage which reduces feed costs. But they rarely are kept for more than a few years due to declining egg production. Layer hens can live naturally to about 8 years, compared to wild junglefowl who live up to 20.