Анотация: An industrial experiment with ISA-Brown commercial layers was carried out during the laying period (from 18 to 76 weeks of age) in 2009/2010 at the poultry complex `Eggs and Chickens - Zora` JSC - Donchevo. The layers were reared under three poultry management systems: in conventional cages type BKN-3 - 66 300 layers distributed equally in five poultry houses; in enriched cages type Eurovent 1500-EU-60 - 123 430 layers distributed equally in two poultry houses; and in barn with slat flooring with manure pit and deep litter - 30 000 layers distributed equally in four poultry houses