The effect of tail docking on the welfare of pigs housed under challenging conditions

• A lack of docking had no effect on physiology and behaviour at the weaner phase.
• At fattening, undocked pigs had a higher prevalence of mild tail lesions (18.57%).
• At fattening, a lack of docking decreased the frequency of belly nosing.
• At fattening, a lack of docking had no effect on mortality and blood measures.
• Straw consumption was 5 g/pig/day at the weaner phase and 30 g/pig/day at fattening.

This study was performed to investigate the effect of tail docking in the weaner and finishing phase in 448 heavy pigs (slaughtered at 40 weeks of age and 170 kg) reared under challenging conditions that were previously considered as risk factors for tail biting (e.g., male gender, high stocking density, fully slatted floor and poor health). The finishing unit had a history of mortality higher than 5%, mainly due to Porcine Reproductive and Respiratory Syndrome, Influenza and Actinobacillus pleuropneumoniae circulation. In both units, a rack with straw and a metal chain were constantly available in all pens. A 2×2 factorial design was adopted to test the effects of gender and tail presence on blood measures (cortisol, haptoglobin, and albumin/globulin ratio), behaviour and skin lesions. Tail docking did not have an effect on the physiological measures, conflicts, and ear and tail biting behaviours at the weaner phase or at fattening. However, in the last days of the weaner phase, an outbreak of tail biting triggered by a “biter” was recorded in one pen of barrows. At fattening, tail docking did not produce any significant difference regarding skin lesions on the ears, the front, the middle and the back third of the animals. Nevertheless, undocked animals showed a higher prevalence of mild tail lesions (P<0.01) and a lower frequency of belly nosing behaviour (P=0.04). In undocked animals, the average frequency of severe tail lesions was 3.6%, whereas the average frequency of mild tail lesions was 18.57%. Two peaks were detected at 12 and 32 weeks of age (P=0.01), i.e., at the beginning and in the middle of the fattening period. Overall, the behavioural activities of exploring chain decreased throughout the fattening cycle (P=0.02), whereas the activity of exploring straw in the rack increased according to age (P=0.05). The frequency of ear biting showed a decrease (P=0.02), whereas the frequency of lying behaviour increased (P=0.04). The mortality was approximately 5%: 4.5% in undocked vs. 5.5% in docked pigs; 6.5% in barrows vs. 3.5% in females. The straw consumption was 5 g/pig/day at the weaner phase and 30 g/pig/day at fattening. The results did not demonstrate a generalised welfare endangerment directly related to tail biting in undocked heavy pigs housed under challenging conditions.