Welfare has several definitions, but Donald Broom, a welfare scientists from the University of Cambridge summed it up nicely. It is the state of an animal with regards to its ability to cope with its environment. Coping means sustaining both physical and mental fitness. The environment includes not only the climactic conditions such as, is it too hot, or too cold, but whether or not there is adequate shelter, food and water, and if there are other chickens around, are there predators and so forth. Another definition of animal welfare is a state of harmony between the animal and its environment, whereby the animal is able to maintain or return to a homeostatic state, which means one of balance, of equilibrium, of stability. The concept of farm animal welfare really took off first in the UK in the 1960s, after the publication of a book that was called Animal Machines by Ruth Harrison, in 1964. And this exposed the modern factory farming processes at the time. This led to the formation of the Bramble Committee, which in 1965, reported on farming practices and made recommendations that animals should be, 1) free from pain, injury and disease by prevention or rapid diagnosis of illness or injury. 2) free from fear and distress, by ensuring conditions do not cause mental suffering. 3) free from thermal and physical discomfort by providing suitable shelter and a comfortable resting area. 4) free from hunger and thirst, by providing fresh water and a diet suitable to the animals needs. and 5) freedom to perform most natural behaviors by providing, for example, adequate space, facilities, and substrates, and other chickens in this case. These are known as the Five Freedoms and they have been used as the basis from which to assess the welfare of animals ever since. Meeting these five freedoms is a good guide to ensuring your animal's well-being. However, in recent years there has been development in the concept of welfare for animals, and that we shouldn't just ensure that they are not suffering. In other words, they might have an acceptable quality of life on the scale that I'm going to show below, but in fact, they should have a good life. Here's that scale, on which you might be able to assess how various housing methods for chickens affect their quality of life.