Effects of environmental complexity on behaviour in fast-growing broiler chickens

Modern broiler chickens spend a great proportion of their time resting, which poses a major threat to their welfare due to the increased risk of contact dermatitis and the incidence and severity of leg problems. Provision of environmental enrichment or manipulation of existing resources in the environment may increase the activity level of broilers and simultaneously improve their welfare. The aim of this study was to investigate the effects of different types of environmental complexity on broiler behaviour. Five types of enrichment (elevated platforms with/without ramps, vertical panels, straw bales, roughage), three types of manipulations of the environment (two groups with differing increased distances between resources and one with reduced stocking density) and one control group were arranged in a randomised block design consisting of six blocks, each with 10 pens. Depending on the treatment, a flock of 422-497 broilers was housed in each pen. Fifty broilers from each pen were randomly marked and acted as focal birds for the investigation of behaviour on days 6, 13, 20, 27 and 34 of age using scan sampling with instantaneous recording. The percentages of broilers performing active behaviour and which active behaviour they were performing, as well as the use of enrichment, were investigated. Activity increased in the first two weeks of age when the distance between feed and water was increased, whereas the performance of specific active behaviour varied between treatments and ages. Compared to the control group, foraging behaviour increased when the broilers had access to maize roughage. In contrast, access to straw bales did not increase foraging, nor was any effect found on locomotion or standing. At days 6 and 27, reduced stocking density positively affected locomotion. Broilers used the platforms more frequently for standing, resting and performing locomotive behaviour, whereas foraging was performed more frequently on the maize roughage compared to any of the other types of enrichment investigated. Provision of elevated platforms also promoted the performance of comfort behaviour, indicating an improvement of welfare. The present study illustrated that the various types of environmental enrichment or manipulations of existing resources in the environment have different effects on the activity and behaviour of broilers. To decide on the applicability of the various types of environmental enrichment and environmental manipulations investigated, the effect on health, welfare and production parameters should be taken into consideration in addition to the results gained in the present study.