ABSTRACT
Traditionally, hens have lived alongside human families literally scratching a living from the scraps available. Harvest time provided a bonanza of spilt grain to be gleaned from the fields where it was sustainably gathered using low-tech human energy. Egg production has evolved to supply the demands of an increasingly industrialised, urban and expanding human population. Most of the loose-housing systems are based on the traditional 'deep litter' barn with a single-tier raised slatted area. Increasingly, the economic advantages of keeping more hens per unit area and using the warmth from the metabolic heat of the birds are being realised in multi-tiered indoor housing, including those with access to a range. The welfare disadvantages are that the hens may be exposed to weather extremes and also to predation. The majority of barn systems makes use of the height dimension and may have raised perches or slats so that birds can show roosting behaviour.
