The welfare of early-weaned pigs in different housing systems and the long-term effects of weaner accommodation
The welfare of young pigs was compared in different housing systems using a range of indicators. Groups of twenty pigs were weaned at 6.4 kg into each of four pens built within environmentally-controlled rooms: a) deep-straw; b) Straw-Flow(R) (1 kg straw daily); c) large expanded metal-floored flatdeck; d) small flatdeck. Kennelled lying areas were provided in a and b. Stocking densities were 0.229 m2/pig for a,b and c, and 0.173 m2/pig for d. After 4-5 weeks (19.6 kg liveweight), sixteen pigs from each pen were moved into Straw-Flow grower pens (0.675 m2/pig) and observed until slaughter at 90.6 kg. The remaining pigs were grouped together to examine the effects of mixing. Housing type did not affect growth and feed intake. Food conversion ratio was poorer in large flatdeck than in small flatdeck or Straw-Flow. Behavioural differences between Straw-Flow and deep-straw related to differences in available straw; there were few differences between flatdecks. Access to straw affected pig-directed, pen-directed and straw-directed behaviours. Foot injuries recovered rapidly on deep-straw and increased in flatdecks immediately after weaning (Straw-Flow intermediate); injuries were more persistent in small flatdeck. Deep-straw prevented adventitious bursitis of the hock. Antibody response was examined by challenge with keyhole limpet haemocyanin (KLH). Immunoglobulin (Ig) M response was greater in straw pens. Dust concentration was higher in kennelled lying areas than flatdecks. With removal of kennels, straw pens showed less dust than flatdecks. Thus, welfare of early-weaned pigs in deep-straw was very good, flatdecks poor with Straw-Flow closer to deep-straw than to flatdecks. Early experience had limited effects. Pigs from flatdecks performed increased rooting relative to deep-straw two weeks after moving (Straw-Flow intermediate). These differences did not persist. Pigs mixed at 20 kg showed increased aggression (not significant) and decreased Ig m response to KLH, indicating reduced welfare.