Farming - egg production systems

Around 30 million commercial egg-laying hens are kept in the UK.

After hatching, the chicks are transferred to a pullet-rearing farm where they stay until they are about 16 weeks of age. ‘Pullet’ is the term for a young hen before it starts laying eggs. Pullets destined for non-cage systems will typically be reared in large barns, sometimes with access to an outdoor range, while many pullets destined for cages will be kept in cages from one day old.

Just before they are ready to start laying eggs the birds are then moved to a laying unit where there are facilities for egg collection. Three different types of systems can be used to house hens on a laying unit - battery cages, barn or free-range (which may also be organic).
 

Free-range
The majority of free-range hens on commercial farms live in buildings similar to the barn system, but with the addition of access to the outside through openings called ‘popholes’. EU laws require that free-range hens must always have access to an outside area with adequate vegetation during the daytime  and the stocking density must not exceed 2,500 birds per hectare at any one time.

The RSPCA welfare standards recommend that there should be no more than 2,000 birds per hectare over the life of the flock, in order to allow resting of various areas at different times and active management of the range area to encourage ranging, maintain vegetation quality, provide shade and shelter and minimise risk of disease.
  

Barn systems
In barn systems hens are not kept in cages, and have the freedom and space to move around, stretch and exercise within a building. Perches are also provided for the hens to roost on, as well as material to dustbathe and forage in, and nest boxes where they can perform their nesting behaviours and quietly lay their eggs. Some barn systems are ‘multi-tier’, providing additional levels above the ground, which the birds can use to move up and down.

Battery cages
‘Conventional’ battery cages are made of thin wire mesh and typically measure about 50 x 55 centimetres. Each cage may house about five hens, with current EU laws requiring a minimum space allowance of 550 square centimetres per bird, which is less than the size of an A4 piece of paper. There may be as many as 9 rows of cages stacked on top of each other in one building, with walkways for the stock-keepers in between and often hundreds of cages in each row. 

So-called ‘enriched’ cages are similar to conventional battery cages, but they also provide limited facilities for nesting, perching and scratching. There are various designs of enriched cages, and they may house 20 to 120 birds each. Enriched cages offer very little extra space that the hens can actually use when compared with conventional cages - only 50 square centimetres extra per bird, which is less than the size of one beer mat! Even in enriched cages, hens will still spend a significant amount of their time standing on wire floors with little room to move around.

In 2008 the proportion of eggs produced in these different systems in the UK was:

• 58 per cent of eggs produced in battery cages
   
• 4 per cent in barn systems
   
• 38 per cent in free-range systems (of which 6 per cent were organic systems). 

In the EU as a whole there are approximately 300 million egg-laying hens, around 80 percent of which are still housed in battery cages.

More and more people are choosing to buy eggs from hens kept in free-range or barn systems when they buy boxes of eggs. 10 years ago only 25 per cent of eggs in the UK were produced by hens kept in these systems, but this has now risen to 42 per cent.

However, although consumers are buying more free range and barn eggs when we buy boxes of eggs, about 85 per cent of eggs used as ingredients in products like mayonnaise, cakes and sandwiches are still from hens kept in cages.

Hens are typically kept until they are 72 weeks of age, when egg production and quality declines.