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Tail biting has been recognised as an emerging problem in pig production. In Europe, tail docking is performed on swine farms to decrease the prevalence of tail damage. However, this procedure should be applied only as a last resource measure, as it is imperative to consider its negative impact on animal welfare. During meat inspection, tail damage assessment can be challenging and lead to an underestimation of the real tail biting prevalence. This study aimed to evaluate tail biting occurrence in slaughtered pigs, analyse the association of tail damage with the production system and tail length, explore the relationship between postmortem findings, carcass condemnations and tail damage and assess the importance of developing a more detailed tail classification score that includes scarred tissue.
Information on 9189 pigs from 73 batches with different tail lengths (undocked, docked mid-length and fully docked) and distinct production systems (conventional, conventional without the administration of antimicrobials and organic) were collected at a Spanish abattoir. Total and local carcass condemnations were registered. Due to the speed of the slaughter line, it was only viable to classify a subset of 3636 animals, who had their tail classified by two scores: the lesion score (relating to recent tail lesions) and the scarring score (which assesses the presence of scar tissue from healed tail lesions).
The probability of observing tail lesions varied with tail length with undocked pigs having higher odds of showing severe lesions when compared with the other lengths. Batches with higher lesion scores presented a greater chance of total condemnation and showed an even stronger association with scarring scores. The major cause for total condemnation was pyaemia. Pyaemia was influenced by tail lesions and presented an even stronger relationship with scarring scores. The within-batches probability of local condemnations and of local condemnation due to abscesses increased significantly with higher scarring scores. Regarding husbandry systems, organic farms showed a higher probability of total condemnation when compared to the other two production systems.
This research concludes that the scarred tissue presented a close relationship with postmortem findings and total/local condemnations, presenting a more relevant role when compared to recent lesions, which proves that it should be included in the tail surveillance program. There is a need to upgrade the current lesion scoring method for tail damage to help pinpoint carcasses at risk for condemnations, also working as a potential welfare indicator.
