although this figure is lower in other European countries (Edwards, 1994). The popularity of outdoor production is a consequence of financial considerations linked to the low establishment and overhead cost of such systems (Edwards, 1996), as well as encouragement from retailers with a market for more extensively produced meat. These conventional outdoor production systems typically have highly selected genotypes, high stocking rates, and total reliance upon manufactured compound feed. However, they are seldom truly outdoor systems for the meat animals; they typically confine the progeny after weaning, sometimes in hit and- run outdoor systems and more often in fully enclosed buildings. Finishing pigs are almost always housed, either in deep litter systems or in conventional controlled environment housing, with b0.5% of UK pigs being finished outdoors (Sheppard, 1996; Edwards, 1999b).