The purpose of this experiment was to investigate the behaviour of fast-and slow growing chickens, when the birds had access to the outdoors. Fifty of both 1-day-old male chicks of a laying hybrid ISA BROWN (IB) and broilers ROSS 308 (RS) were kept in two pens in the same building. In each group ten birds were marked with a colored spray. From three weeks of age the birds had access to the outdoors. From the age of one to seven weeks old, one day a week the marked birds were observed from 8:00

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... o 18:00 every ten minutes and the activity was noted. At 49 and 90 days old twenty birds were slaughtered and the strength of bones was measured. The behaviour was expressed as percentage of the time spent in activity. The average time that the birds spent eating during the 7 week period was almost the same in IB and RS. On average, IB birds spent significantly higher (P<0.05) an amount of time moving around, but until the fifth week of age there was no significant difference between these genotypes. In IB, movement was the more frequent activity. The resting sitting down was the most frequent activity in RS and since three weeks of age they spent significantly more (P<0.05) time with this activity than IB. On average, the IB birds spent significantly more (P<0.05) time scratching than did the RS. No aggression or pecking was observed in the IB males during the whole test period. The strength of the femur was significantly higher in RS in comparison with IB in both ages (49d -P<0.001, 90d -P<0.05). Although the rules for organic farming dictate that the chickens have to have enough outdoor area to move around in, the fast growing broilers do not use it.