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Table 5 Risk analysis regarding main disease categories between laying hen flocks in cages1 and litter-based systems2.

From: Causes of mortality in laying hens in different housing systems in 2001 to 2004

Disease category Observed no. of flocks from litter-based systems Expected no. of flocks if same risk as in cages Excess no. of flocks in litter-based systems compared to cages
Bacterial diseases 94 9 85***
Viral diseases 15 4 11***
Parasitic diseases 23 1 22***
Cannibalism 24 1 23***
Total 129 14 115***
  1. 1Includes conventional battery cages and enriched cages.
  2. 2Includes single-tiered floor systems and multi-tiered aviary systems.
  3. Level of significance is denoted by *** P < 0.001.