Monitoring leg problems in broilers: a survey of commercial broiler production in Denmark

The purpose of this study was to examine the prevalence and the extent of l eg problems in broiler chicks reared in conventional production systems in Denmark. The survey, which was designed as a cross-sectional study, include d 28 broiler flocks (8% of the total number of flocks in Denmark); 2800 chi cks in total (100 chicks per flock) were investigated for the occurrence of leg disorders in relation to animal welfare. The leg disorders included im paired walking ability, tibial dyschondroplasia (TD), varus/valgus deformat ions, crooked toes, foot pad burns, and asymmetrical development of the tar sometatarsus. The mean prevalence of impaired walking ability (gait score > 0), tibial dyschondroplasia (TD score > 0), varus/valgus deformations, cro oked toes and foot pad burns was 75.0%, 57.1%, 37.0%, 32.6% and 42.0%, resp ectively. The risks of the occurrence of these leg problems were significan tly influenced by body weight and sex of the chicks. For birds with impaire d walking ability (corresponding to gait scores > 0 and > 2), significant i nteractions were found between body weight and sex. Positive correlations ( r > 0.20) were found between gait score and TD score, gait score and varus/ valgus deformations, TD score and varus/valgus deformations, varus/valgus d eformations and body weight, crooked toes and body weight, and between varu s/valgus deformations and body weight. Only weak correlations were found be tween the relative asymmetry in the length, thickness and diameter of the t arsometatarsus and the other leg problems measured. It was concluded that t he prevalence of leg problems in broilers in conventional production system s is very high and compromises the welfare of the birds. One of the main fa ctors responsible is their high growth rate.