Musculo-skeletal lesions in adult male broiler breeder fowls and their relationships with body weight and fertility at 60 weeks of age.

1. Males from three broiler breeder experiments were examined to determine the incidence of musculo-skeletal lesions (destructive cartilage loss, dyschondroplasia and its sequelae, ruptured tendons and ligaments) in birds culled for low fertility and in males surviving to the end of the breeding period. Relationships with body weight and fertility were studied. 2. The incidence of musculo-skeletal lesions in males culled for low fertility was high. 3. In two experiments, high body weights at termination of the breeding period were associated with a raised incidence of musculo-skeletal lesions and lowered fertility. 4. The results support the hypothesis that lack of control of male body weight gain per se is an important cause of declining fertility with age in broiler breeder flocks. There was no evidence that males were obese.