Behaviour of fast- and slow growing broilers to 12 weeks of age and the physical consequences

Behaviour of broilers up to 6 weeks of age has been studied extensively, but little is known what happens after 6 weeks. Insight in the behavioural abilities after 6 weeks may also yield insight in the period before 6 weeks as the disbalance between motivation and physical abilities is more clearly elucidated with increasing weight. The purpose of this experiment was to investigate behaviour in fast- and slow growing broilers to 12 weeks of age and the physical consequences of the prolonged rearing period. Ninety-six 1-day-old female broiler chicks, 48 of a slow growing and 48 of a fast growing line were allocated to 16 floor pens (1.5 m(2) per pen): eight pens of six birds per line. Each pen contained perches and the floor was covered with wood shavings. One day per week, each bird was observed five times, distributed regularly over the day. Behaviour, posture (sitting or standing) and position (floor or perch) of each individual were recorded. After 12 weeks, the birds were killed and post-mortem examination was done to detect physical abnormalities. Fast- and slow growing broilers performed the same behavioural elements, but time budgets of fast- and slow growing broilers were different. Slow growing broilers perched, walked and scratched more than fast growing broilers. Fast growing broilers performed more sitting on the floor, eating and drinking than slow growing broilers. No differences were found for resting, preening, stretching, ground pecking or dust bathing. Time spent on several behaviours changed with increasing age or the posture during behaviour changed with age. Although several physical abnormalities were found in both lines, no correlation was found between physical abnormalities and behaviour. Physical abnormalities seemed not to be so severe to have hampered behavioural activity. The experimental conditions, such as only females, good quality of bedding, low stocking density, and perches seemed to be crucial to prevent serious physical abnormalities and to keep these birds to 12 weeks of age. This study showed that fast- and slow growing broilers are motivated to perform all kinds of behaviour in an environment where that is possible also after 6 weeks of age, but that the ability of performing some behaviours are more and more hampered with increasing age most probably due to their weight. (C) 2002 Elsevier Science B.V. All rights reserved.