The nursery phase — covering pigs from weaning at three to four weeks until about ten weeks of age — is one of the most welfare-challenging periods in commercial pig production, with multiple stressors occurring simultaneously.
Weaning represents a convergence of acute stressors: maternal separation, social disruption, dietary transition from milk to solid feed, environmental change, and immune challenge. Piglets experiencing this transition show elevated cortisol, reduced play behaviour, increased stereotypies, and social aggression. Post-weaning diarrhoea, caused by enterotoxigenic E. coli proliferating in the disrupted gut environment, causes significant suffering and mortality. The historic response — prophylactic antibiotics — is increasingly restricted due to antimicrobial resistance concerns, leaving producers to rely on management improvements. Research consistently shows that later weaning ages, smaller group sizes, familiar pen environments, and good nutrition substantially reduce the welfare burden of this phase.