Horse welfare at slaughter: A novel approach to analyse bruised carcasses based on severity, damage patterns and their association with pre-slaughter risk factors

The study presents a novel veterinary forensic approach to analyse the bruising of horse carcasses, based on the nature of the bruises and how they are grouped in certain anatomical areas. Data on pre-slaughter logistics was obtained for 113 journeys with horses that travelled from Mexico and the USA to a Mexican abattoir. We found that carcass bruising was a highly prevalent problem (79% of carcasses had bruising) and was especially problematic in journeys lasting longer than 12 h, independently of the animal's country of origin, sex, age, lairage time or vehicle type. Multivariable logistic regression showed that the most severe bruises were not dispersed randomly on the carcass and that their distribution was associated with the presence of medium-sized bruises on the abdominal wall, front and rear limb. Cluster analysis suggested four damage patterns based on bruise location: severe and concentrated bruising, as well as non-severe bruises on the rear limb, thoracic-wall or more dispersed throughout the carcass.