A systematic review
Improvements in leg health in broilers have the potential for improving overall broiler welfare markedly. One of the few realistic possibilities for the individual farmer to do this is to add enrichment to the rearing environment. Environmental enrichment is here defined as any physical change in the environment that is expected to lead to an improvement in leg health and welfare. Several enrichment alternatives and their effect on leg health have been investigated through a systematic review by PROHEALTH. Six types of enrichment were assessed in the review: light program, light intensity, stocking density, perches, separation of resources (food/water) and straw bales. The review included 62 studies and a list of different leg health measures was assessed in these studies, with gait score, foot pad- and hock dermatitis and tibial dyschondroplasia being the most frequently assessed measures. The results for these four measures are presented in Table 2.
Light program and stocking density are well-studied areas with 24 studies fit for inclusion each. Light program, i.e. implementing an intermittent light schedule, was especially effective in improving gait scores (Table 2). A lowered stocking density mostly affected foot pad and hock dermatitis, possibly through an increased litter quality at the lower stocking densities. The results for provision of perches (9 included studies) and light intensity (7 included studies) did not show a clear effect of enrichment on leg health. However, an increased intensity of light did reduce foot pad dermatitis in 3 out of 4 studies. For straw bales (1 included study) and separation of resources (5 included studies) the amount of literature was limited. However, the existing literature did suggest an effect of enrichment on gait scores. While some of the enrichment types are clearly costly (e.g. lowering the stocking density), others can probably be introduced with no or a minor cost (e.g. intermittent light schedules). All in all, light program and stocking density are well-studied types of enrichment that can improve gait score and contact dermatitis, respectively. Intensity of light and perches do not appear effective in improving leg health. For straw bales and separation of resources the number of studies is low and caution should therefore be taken with recommending these. However, both types of enrichment show potential for improving leg health and merit further investigation.