Histopathology and serum clinical chemistry evaluation of broilers with femoral head separation disorder

Femoral head separation (FHS) and necrosis is a sporadic leg problem of unknown etiology in broiler breeders. To determine the underlying physiology of FHS, the blood chemistry and histopathology of the femoral growth plates of the affected chickens were compared with their age-matched controls and with birds having tibial dyschondroplasia. Femoral problems were categorized on the basis of 1) femoral head separating from articular cartilage without any visible damage to the growth plate (FHS) and 2) FHS with significant tearing and lesions in the growth plate (FHSL). Tibial dyschondroplasia was identified by a widening of the growth plate with an unresorbed plug of cartilage at the proximal end of the tibia. Control birds were without any femoral or tibial problems. The histopathology of FHSL growth plates revealed occasional chondrocyte death, hypocellularity, dysplasia in the prehypertrophic zones, and the absence of inflammatory infiltrates in the lesion areas. Hematoxylin and eosin staining showed brown chromogenic deposits in the metaphyseal bone marrow areas. Blood chemistry of chickens with FHSL showed a modest but significant elevation of cholesterol, triglycerides, and low-density lipoproteins. Only cholesterol and low-density lipoproteins were moderately elevated in FHS-affected chickens. Other blood parameters, such as protein, magnesium, and iron levels, showed differential changes in birds with leg problems, but there were no specific trends. Neither blood ovotransferrin, a marker of chronic inflammation, nor corticosterone, a marker of stress, showed any significant differences from the controls. These results indicate that FHS may be a metabolic problem in poultry, one that is related to fat metabolism disorders, possibly contributing to an unbalanced growth in the articular-epiphyseal complex that leads to its separation under sheer stress.