Fatal skull trauma in caged layer chickens associated with a moving feed hopper: diagnosis based on autopsy examination, forensic computed tomography and farm visit.

Investigation of unexpected mortality in caged layer chickens led to the discovery of a consistent traumatic injury to the heads of affected hens. Initial post-mortem examination found linear skin lacerations and associated fractures in the dorsal cranium of all birds examined, and 5 to 10 mm deep trauma in the underlying brain tissue. Post-mortem multidetector computed tomography (CT) scanning of two affected birds demonstrated similar obliquely orientated, linear, depressed fractures of the skulls consistent with a single, severe impact force to the head. Both skull fractures had a pattern of rounded, rostral expansion measuring approximately 3 mm in width. On inspection of the cages during a farm visit, this CT pattern corresponded with the size and shape of sheet metal lugs holding feed troughs onto the cages (on which blood stains were subsequently observed). Based on this analysis and hypothesizing that hunger was a triggering factor, a recommendation was made to reverse the shed "lights on" and feed hopper operation times with instant reduction in mortality. This case highlights the value of post-mortem CT imaging in bird death investigation where trauma is a postulated cause.