Forensic cases of bruises in pigs.

Bruises in pigs inflicted by blunt trauma are a significant animal welfare problem, and affected skin and underlying muscle are regularly submitted for forensic investigation. Central to the evaluation is an assessment of the age of the bruises. This paper presents cases of bruises in pigs sent for forensic investigation that were collected retrospectively. Data comprised photographs of the gross lesions, slides for histology, and written reports. The time from collecting the animals at the farms and delivery to the slaughterhouse was recorded together with the time of slaughter. Since 2005 there has been an increase in cases, with a peak in 2008 and 2009 of 40 cases for each year. At gross examination, the pattern of bruises often reflected the type of object which caused them. Histologically, haemorrhage and cellular infiltrations were frequently present. Currently, the age of bruises may be estimated to be more or less than four hours based on a porcine bruise model. In bruises more than four hours old, estimations of two-hour intervals are used based on studies of wound healing. The time from collecting the pigs at the farms until slaughter was between one and four hours in 44.1 per cent of cases, during which time the pigs had been handled by several people. In addition, in 22.0 per cent of cases of bruising an inflammatory response was absent, making it impossible to estimate the age of the bruise.