From: Causes of mortality in laying hens in different housing systems in 2001 to 2004
Disease category | Observed no. of flocks from free range housing | Expected no. of flocks if same risk as in cages | Excess no. of flocks in free range housing compared to cages |
---|---|---|---|
Bacterial diseases | 17 | 1 | 16*** |
Viral diseases | 1 | 1 | 0 |
Parasitic diseases | 5 | 0 | 5*** |
Cannibalism | 6 | 0 | 6*** |
Total | 23 | 2 | 21*** |