Proximal femoral degeneration in growing broiler fowl

The pathologies in proximal femora of broilers with lameness attributed to disorders of the proximal femur, including so-called 'femoral head necrosis', are described. Samples were collected from a variety of flocks, farms and production systems. Ten 'normal' broilers were also examined. Birds were identified by a characteristic lameness whereby they used a wing for support during locomotion and hip flexion (i.e. whilst sitting down). The appearance of the proximal femora at post mortem was used to place 67 proximal femora in three categories: (a) gross disintegration of the epiphysis, physis and/or metaphysis (43 samples); (b) epiphysiolysis-separation of the cartilaginous epiphysis from the underlying femoral metaphysis (growth plate) (17 samples) and (c) apparently normal (seven samples). Samples from each category were collected for mycoplasmology, virology and bacteriology. All the samples were negative for Mycoplasma, and there was no correlation between pathology and the presence or absence of viruses, but bacteria were cultured from about half the proximal femora and most of these femora showed histological evidence of bacterial infection. Although bacterial culture was negative, evidence of bacterial infections was seen in tissue sections from a further 15 proximal femora. Serial sections were required to find the foci on bacterial lesions. 'Femoral head necrosis' was not considered appropriate to describe the pathologies seen and the term proximal femoral degeneration (PFD) was adopted. Histological examination showed that PFD was most frequently due to a bacterial chondritis and osteomyelitis, with frequent involvement of surrounding tissues. Non-lame controls all had non-bacterial pathologies in the proximal femur which were also seen in many of the lame birds and may have provided a foci for the establishment of bacterial infections. The non-bacterial pathologies when severe were considered the cause of non-infectious PFD which would cause lameness in some cases. Epiphysiolysis was either a post or peri-mortem artefact, traumatic in origin, or could be attributed to underlying growth plate (physeal) pathology which in some cases was due to bacterial infection.