Spatial distribution of cannibalism mortalities in commercial laying hens.

The distribution of cannibalism cases in a flock of 19,776 Babcock White Leghorns was monitored from 21 to 54 wk of age. The hens were kept in a single-floor house consisting of four banks of two-deck stair-step cages. Each of the 4,944 cages held four hens at a density of 152 cm(2) (60 inches(2)) per hen. Each cage was assigned a number from 1 to 4,944, and each dead bird was tagged according to its cage of origin. Dead birds were collected daily, kept in a freezer, and necropsied weekly. Farm personnel routinely transferred a live hen from an end cage to a cage where a mortality had occurred. The cause of death, age, cage number, and cage location were recorded for each dead hen. Of the 1,173 hens that died during the study period, 253 (21.6%) died from egg peritonitis, 184 (15.7%) from hypocalcemia, 167 (14.1%) from cannibalism, 164 (14%) from neoplastic disease, and the rest from various other causes. Cannibalism cases were analyzed statistically for clustering. Cannibalism was defined as death from tissue trauma and hemorrhage inflicted by cage mates. A spatial analysis showed that cannibalism is not a random event but one that occurs in clusters. The incidence of cannibalism was also found to be significantly higher on the top rows of cages as compared with the bottom rows.