Comparison of behaviour and health of two broiler hybrids with different growth rates

Abstract: Until recently fast growing broiler hybrids have been used exclusively in both conventional and organic broiler production in Sweden. This study aimed to quantify differences in behaviour and health between a fast growing hybrid (Ross 308) and a slower growing hybrid (Rowan Ranger). The chickens were reared for 10 weeks in a semi-organic production environment with organic feed and space allowances, but without outdoor access. In the study, 218 Ross 308 and 211 Rowan Ranger day old chicks were split into 20 groups with 10 replicates of each hybrid. Registrations of behaviour and health were done at 2, 6 and 9 weeks of age and mortality was recorded continuously from start to slaughter. Behaviours were recorded through scan sampling and continuous observations. The day after the behavioural observations, a welfare assessment was performed according to the Welfare Quality® Assessment Protocol for Poultry. The results showed that Rowan Ranger chickens were more active than Ross as they were standing more, furthermore, Rowan Ranger were perching more than Ross. Ross chickens had more leg and feet problems than Rowan Ranger chickens, i.e. worse gait score (decreased moving ability), foot pad dermatitis score and hook burn score (inflammation and lesions on the skin). As a result of more severe leg problems, a higher proportion of the Ross compared to the Rowan Ranger birds were culled. Both Ross and Rowan Ranger showed health problems at older ages, likely due to increased body weight in both hybrids. However, results imply that fast growing Ross 308 chickens are poorly suited for a long rearing period (>10 weeks), whereas the slower growing Rowan Ranger chickens seem better suited for the rearing period of 81 days stated by the organic regulations.