This thesis investigates different aspects of rearing broilers organically in floorless pens on pasture. The birds and pens were moved daily to fresh pasture. The interdisciplinary studies comprise the birds' growth performance and carcass quality, health, behaviour, leg condition and the birds’ effect on pasture. In the final study, on-farm diets were tested in a feeding experiment indoors. The data are based on four experiments carried out during 2000 to 2003. In 2000 and 2002, restricted-fed conventional broilers (ROSS 208) were reared in floorless pens on pasture and in control groups outdoors on straw. In 2001, two genotypes, ROSS 208 and the slow-growing ISA 657 were reared on three ground types, pasture, outdoors on straw and indoors on wood shavings with either an ad libitum or restricted feeding level. In 2003, a feeding experiment with slow-growing broilers fed on-farm diets in a choice feeding system was conducted indoors. Most birds were reared to 12 weeks of age, but ad libitum-fed ROSS birds were reared to 6 weeks. The experimental phase was from ca. 3 weeks to slaughter. The experiments indicate that under the given conditions - access to pasture does not offer sufficient protein and metabolizable energy to allow considerable feed savings in the farm enterprise (Paper I) - moving the floorless pens daily provides favourable conditions to prevent infections with Campylobacter and Eimeria in outdoor broilers (Paper II) - access to pasture as such appears to play no major role for the broilers' physical activity (Paper III) or leg condition (Paper IV) - broiler chickens on pasture can sustain white clover in a mixed grass/white clover pasture (Paper V) - with access to high-quality protein during the first three weeks there is a good potential to produce organic broiler meat with feed produced on-farm in northwestern Europe (Paper VI)
