Skeletal lesions in the broiler, with special reference to dyschondroplasia (osteochondrosis). Pathology, frequency and clinical significance in two strains of birds on high and low energy feed.

The material consisted of 2,950 broilers of the variety Hybro Compact of two lines. An equal number of birds of both lines were given either a high energy feed (H) or a low energy feed (L), containing all nutrients known to be required by broilers. During the first 3 weeks, H and L starter feeds were given and thereafter H and L finishing feeds. At 21, 35, and 45 days of age, the birds were weighed in groups, and feed conversion calculated. At 21 days of age, the frequency of crooked toes and swollen hocks was registered. Birds were taken from each group for necropsy at regular intervals. Both clinically normal birds and those with locomotor disturbances were selected for necropsy, including radiographic examination. With the exception of 240 birds, which were kept for a long-term study, the birds on the H feed were slaughtered at 42 days of age and the ones on the L feed at 49 days of age. The long-term birds were slaughtered at regular intervals, weighed, and necropsied. The last birds were slaughtered at 134 days of age. A large number of skeletal lesions were found. They were: Twisted legs, slipped tendons, crooked toes, bowing of the proximal tibia, dyschondroplasia at different sites, fracture of the fibula, deformity of the spine, deviated sternum (with breast blisters), arthritis, and osteomyelitis. Leg weakness was found to be almost synonymous with skeletal deformities. Other causes were rare. The normal development and morphology of the skeleton and the morphology of tibial dyschondroplasia were the same as those previously described in the turkey. Dyschondroplasia was found not only in the proximal tibia but also in the distal tibia, proximal tarsometatarsus, proximal and distal femur, and to some extent also in the costochondral junction. Tibial dyschondroplasia was more common in the birds on the H feed than in the birds on the L feed. Hence, tibial dyschondroplasia was correlated with rapid growth. The other skeletal lesions did not differ in incidence in the birds on the H and L feeds. It was postulated that greater difference in growth rate is necessary for a demonstration of a possible correlation between skeletal deformities and growth rate.