Mixing pigs from different social groups causes intense aggression that is a major and largely preventable welfare problem across the industry. Science-based pen design and management practices can substantially reduce this suffering.
Mixing aggression represents predictable, preventable suffering inflicted on millions of pigs as a routine management practice. The violence of mixing is severe - wounds requiring veterinary treatment are common, and stress levels during mixing can cause immunosuppression, reduced growth rates, and increased disease susceptibility. Despite this, mixing remains standard practice because production systems are designed around throughput rather than social stability. Adopting stable group management, improved pen design, and evidence-based mixing protocols would significantly reduce suffering without requiring major capital investment. The welfare cost of current practices falls entirely on animals who have no choice in the matter.