Processing , Products , and Food Safety : Processing , Products and Food Safety

The humerus is often used to assess skeletal health in laying hens. It usually contains an airsac in the central cavity, but studies have demonstrated that the humeri of some hens do contain medullary bone. This study used radiographs to compare the incidence of increased radiodensity in the central cavity of humeri between lines of highproducing non-commercial laying hens. Hens of six lines (n=71 to 78, 451 total) were euthanized at two ages: 1) 65 wk [Barred Rock (BR), Columbian Rock (CR), Rhode Island Red (RIR), and White Leghorn-Burgundy (WL-BUR)], and 2) 47 wk [WL-Black (WL-BLK), WL-Blue (WL-BLU)]. Hens were euthanized using Euthanyl Forte, stored at -20 C, and thawed prior to being x-rayed. The radiographs were examined for increased radiodensity in the central cavity of the humeri of each hen, the extent of which ranged from a small section at the distal end of the bone to the entire length. Each humerus was recorded as having or not having increased internal radiodensity. Contingency chi-square analysis was used to compare lines within age groups. Among the older hens, the incidence of birds with at least one humerus with increased radiodensity was highest in the BR and RIR (61.0 and 66.7%, respectively). The incidence in CR (17.8%) and WL-BUR (18.3%) was signifi cantly lower. The incidence in the younger birds did not differ signifi cantly (16.0 and 15.1% for WL-BLK and WL-BLU, respectively). These results demonstrate substantial variation in the occurrence of increased central cavity radiodensity between lines, which can likely be attributed to medullary bone development. This variability, along with the variable amount of the humerus affected, could impact results of humerus bone assessment using methodologies dealing with the whole bone (ash, density, strength) and those such as quantitative computed tomography that use only a small portion of the bone. Caution should be used when using the laying hen humerus to assess skeletal health.