The physical design of pig housing has profound effects on welfare outcomes. Well-designed pens support natural behaviour, minimise competition, allow adequate rest, and reduce injury risk. Poor design creates chronic welfare problems regardless of stockperson skill.
EU minimum space allowances (40–110kg pigs: 0.65–1.0m²/pig depending on weight) are generally considered welfare-inadequate by researchers. Welfare-based recommendations typically exceed legal minimums by 20–50%. Key principles: space affects aggression, access to resources, and lying comfort simultaneously. RSPCA Assured standards require higher space allowances at all weight categories. Research shows that even modest increases above minimum space (0.1m²/pig) significantly reduce aggression, lesion scores, and tail-biting incidence.
Floor surface affects: foot and leg health, cleanliness (affecting respiratory disease risk), lying comfort, and manure management. Fully slatted floors (all slats, no solid lying area) allow manure to fall through but restrict lying comfort and cause higher foot lesion rates than pen designs with partial solid areas. Deep straw bedding provides excellent lying comfort and enrichment opportunities but requires intensive management and is incompatible with slat-based manure handling. Rubber matting over concrete reduces lying discomfort and foot problems while remaining compatible with manure handling systems.
Effective pen layout provides: separate lying, feeding, and dunging areas (pigs naturally separate these functions), adequate feeder and drinker space, environmental complexity that reduces monotony, escape routes for subordinate animals, and appropriate lighting. Long, narrow pens create escape route problems and concentration of aggression. Square pens with feeding along one short wall and dunging at the opposite end approximate natural space use patterns.
Group sizes in commercial production vary from small groups (8–20 animals, typical for family farms) to large groups (50–200+ in some intensive systems). Research on optimal group sizes shows complex results: very large groups can reduce individual competition but make individual monitoring difficult. Key welfare-relevant principles: avoid unnecessary remixing of unfamiliar animals, maintain stable social groups where possible, provide adequate space and resources to buffer competition effects of larger groups, and identify and respond to aggression indicators (lesion scoring) regularly.
Pigs are highly sensitive to temperature — welfare-relevant zones are 15–22°C for growing/finishing pigs, with piglets requiring additional supplementary heat (creep heaters). Draughts at lying level cause cold stress and increase disease susceptibility. Hot conditions above 25°C cause heat stress with reduced feed intake and welfare problems. Pen design must accommodate temperature management through ventilation, insulation, and heating provision.
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