A fourteen-year –old friend of mine became vegetarian and gave up eggs. Nothing unusual in that you might say. No, except that her father owned one of the biggest battery-egg plants in Europe. Her Saturday morning job was to go around all the cages and take out the dead birds! She knew firsthand what egg production is all about.

Forget all those pictures of clucking hens sitting contentedly on their eggs or being followed by a trail of tweeting little chicks. The birds that produce 90 per cent of eggs in Britain (and the rest of the EU, the USA and other industrialised nations) have been turned into laying machines. They never see a cockerel (male bird) so the eggs they lay every year are not fertile and could never hatch even if they were given a chance to sit on them, which they’re not.

Let me take you through the life of a battery hen. A day after being hatched in big, industrial sheds, the chicks are divided by sex; males on the left-hand conveyor, females on the right. The conveyor carries the male chicks away to a bin in which they are dumped.

These chickens have been specially bred to produce eggs and to survive on the smallest possible amount of food, so they’re very scrawny. Because of this, male chicks are no good for meat, no good for laying eggs, in fact they’re good for nothing, so the factory gasses them – 40 million every year. Or sometimes they are crushed to death – it just depends on the fancy of the particular factory.

The females are taken to cages, where they stay until they’re about four months old and able to lay eggs. It’s then that they are put into wire battery cages, five chickens together in a space about 45 centimetres by 50 centimetres, not much bigger that a microwave oven.

Now for a quick bit of maths. If the cage is 50 centimetres wide and a chicken’s wings are 76 centimetres wide when they’re spread out, what does it mean? It means that not even one chicken has enough space to spread her wings properly, so with five to a cage they have absolutely no chance.

In a single shed there can be thousands of cages holding tens of thousands of birds – row upon row stacked four or five deep with nothing between them but wire mesh. (In battery farming 20,000 hens per shed is considered quite a small number.) The droppings from the birds in the top tier of cages fall on to the birds in the cages below, before finishing up on the ground. If you’re ever unlucky enough to go into a battery shed, be prepared for the stink, because they’re usually not cleaned out for between 18 months and two years – the length of the birds’ life. After this time the ‘chickens’ egg-laying begins to slow down so they are killed to make way for new birds, even though they might live naturally for another five years or more. They finish up as stock cubes or in pies or baby food – or even in school meals!

Hens make such good mothers that the word used to describe them – broody – is used to describe human mothers. When the hen’s chicks hatch, she watches over them with an eagle eye. Wherever she goes her chicks follow and at the first sign of danger she gives a special ‘cluck’ and they all dive for safety beneath her wings. When the day is hot and the mother hen rests, her chicks will sometimes climb all over her and doze off on her broad, feathered back. The perfect sun bed!

These are the same creatures that we cram into tiny cages where they can do none of these things. Everything about their lives is automated – the feed, the water and the egg collection. Battery-hen cages all have sloping floors so that the eggs they lay immediately roll down on to a conveyor belt and away from the hen.

Watching a hen lay an egg in this cage is a very sad sight. It can take up to an hour and she will pathetically try to hide from the other chickens, scrambling beneath them in an attempt to disappear from view. Farmers will tell you that because the hens lay eggs it shows they’re happy. This is like saying that everyone who goes to the loo is happy; they are both bodily functions which we can’t control.

It’s not really surprising, then, that battery chickens get frustrated, bored and angry, and that this can make them aggressive. They will often take it out on their cage mates by pecking them; so their beaks are sliced off when they’re chicks in order to stop what producers call their ‘vice’. People used to think that beaks were like fingernails: bits of dead material with no feeling. But research by scientists at the Institute of Animal Physiology in Edinburgh has shown that they are extremely sensitive and contain lots of nerve endings. When their beak is cut off, some chicks die from shock, and some from bleeding, and it’s possible they feel the amputation throughout their lives. But battery hens are subjected to other hardships as well.

A combination of little fresh air and no daylight, overcrowded conditions and selective breeding has led to a whole host of diseases in the battery sheds. Things like egg peritonitis, Gumboro disease, prolapses, leukaemia, and infectious bronchitis, all end up meaning the same thing – distress, suffering and death for two million chickens every year.

One of the most common ailments amongst battery hens is brittle bone disease which results in their bones snapping like dry twigs. Chickens evolved from jungle fowl, which in the wild lay only about 12 eggs a year. Battery hens lay about 300 a year and the calcium which should build their bones is used to make eggshells. The result is weak and brittle bones that break easily. According to the British government’s own research council, a third of all battery hens have broken bones. What must it be like to spend your life like that, especially in a crowded cage being pushed and shoved all the time?

That, then, is the life of a battery hen. The University of Edinburgh looked at all the scientific studies and concluded that ‘battery hens suffer’ and that the cages should be outlawed. Anyone who says they’re wrong should be locked in a telephone box for a month with four other people, and then asked again!

Today most eggs come from battery hens. Don’t be conned by the words ‘country fresh’, ‘farm fresh’ or ‘fresh from the countryside’ either. Unless it says @Free range’ on the box, the eggs you’re buying are from battery hens. Unfortunately, free-range eggs aren’t always all they’re cracked up to be, either. The rules on free range allow producers to keep 1,000 birds per hectare of land, but if they are to move about as they choose, to stretch their wings and legs, run, peck, scratch, find bugs, beetles and seeds, and do all the things that hens like to do, 250 would be much better. Some of the big producers cram thousands of hens into a shed, stick a few openings in it and call it free range. Many of the chickens never even go outside because they’re afraid of crossing other birds’ territory or because they don’t feel safe surrounded by so many other hens.

For most free-range hens, life isn’t any better than for the turkeys which are kept for meat in the pole barns. The majority of sheds are just like there, overcrowded, smelly and dirty. Whatever the system, all the male chicks are still killed at only a day old.