Linking Animal Welfare and Antibiotic Use in Pig Farming-A Review

Simple Summary Minimising stress in intensive pig farms is paramount to raising immunocompetent pigs. This entails providing the pigs with living conditions (from birth to the point of slaughter) free of pain, stress, and suffering and simultaneously providing conditions that generate positive affective states. Our review aims to study the relationship between chronic stress, illnesses, their impact on antibiotic use (AMU), and potential housing and management improvements to tackle stress and AMU. According to the literature, pigs kept in crowded, barren conditions, with poor microclimatic conditions, and subject to painful and stressful weaning practices present redirected behaviours, poor immune-competence, and weaker bodies. In turn, pigs are more vulnerable to circulating pathogens and severe secondary infections, which is conducive to high AMU for the sake of the animals' health. Simultaneously, we compiled a list of possible solutions for the current poor environment and practices, including a call for the pig industry to broaden its concept of animal welfare beyond the current biological/productivist scope. We propose that advocating for an industry with enhanced animal welfare is a crucial response to the international call to combat antimicrobial resistance and the social demand for ethically sustainable animal production. Preventative measures, such as biosecurity and vaccinations, are essential but not sufficient to ensure high standards of health in pig production systems. Restrictive, barren housing and many widely used management practices that cause pain and stress predispose high-performance pigs reared in intensive systems to disease. In this context, antibiotics are used as part of the infrastructure that sustains health and high levels of production in pig farms. Antimicrobial resistance (AMR) is a global emergency affecting human and animal health, and the use of antibiotics (AMU) in intensive livestock farming is considered an important risk factor for the emergence and spread of resistant bacteria from animals to humans. Tackling the issue of AMR demands profound changes in AMU, e.g., reducing their use for prophylaxis and ending it for growth promotion. In support of such recommendations, we revise the link between animal welfare and AMU and argue that it is crucial to sustainably reduce AMU while ensuring that pigs can live happy lives. In support of such recommendations, we aimed to revise the link between animal welfare and AMU in pigs by analysing stress factors related to housing and management and their impact on pig welfare. In particular, we reviewed critical management practices that increase stress and, therefore, pigs' susceptibility to disease and reduce the quality of life of pigs. We also reviewed some alternatives that can be adopted in pig farms to improve animal welfare and that go beyond the reduction in stress. By minimising environmental and management stressors, pigs can become more immunocompetent and prepared to overcome pathogenic challenges. This outcome can contribute to reducing AMU and the risk of AMR while simultaneously improving the quality of life of pigs and, ultimately, maintaining the pig industry's social license