Acute phase proteins and heterophil:lymphocyte ratio in laying hens in different housing systems

IN most developed countries, approximately 90 per cent of laying hens are kept in cages ([Tauson 1998][1]). From 2012, European Council Directive 1999/74/EC will prohibit the use of conventional cages within the EU, but will permit the use of modified ‘enriched’ cages and non-cage systems.