The lighting in the house is kept very low, in an attempt to reduce aggression, and 'day lengths' can be lengthened to extend laying periods. This used to be done to take the hens rapidly into a second season of lay, but is less common now as hens are less likely to be kept for more than one laying year. Now it is mostly used to adjust egg supply, or to improve egg shell quality. Battery hens are usually removed for slaughter as 'spent hens' at around 72 to 76 weeks of age. Kept in natural conditions, healthy hens can live for six years - and some live as long as ten years.
Battery hens can suffer during removal from their cages, handling, transport and slaughter.
It is a sad fact that the way production animals are treated often reflects their value to the producer, and 'spent hens' at the end of their productive lives have an extremely low value. The 'spent hens' are usually slaughtered using electrical stunning followed by neck cutting, after which they enter a scalding tank. They can receive electric shocks from water splashing up from the stun tank before they are fully immersed, causing pain and distress. Also, some birds can be seen to flap their wings and rise above the stun bath, meaning that they have their necks cut unstunned. Some have been seen to avoid both electrical stunning and neck cutting, entering the scalding tank fully conscious.