The relationship of various tibia bone measurements in hens

Tibias from 50 Single Comb White Leghorn hens were used to study the relationships among various bone measurements. The bone ash (BA), length, wet bone volume (V), fat-free dry matter (FFDM), fat-free bone density (BD; mass per unit bone volume), and bone breaking force (BF) were measured, and the BA concentration (BA/V) and BA as a percentage of FFDM (BA/FFDM) were calculated. Bone ash was highly correlated with FFDM (r = 0.975). The BD was poorly correlated with any of the parameters measured in the present study. The BF was highly correlated with BA (r = 0.922) and FFDM (r = 0.918), but less well correlated with BA/FFDM (r = 0.496) and BA/V (r = 0.694). However, the inclusion of volume2 significantly improved the BF predicting models when BA/V was used as predictor (R2 = 0.855), indicating that BF is not only a function of BA density but also of bone size. The BF adjusted for V may better reflect treatment effect upon bone status than BF alone. The coefficient of variation of BA/FFDM and BD was smaller (0.007) than the CV with BA/V (0.026), which may indicate the BA/V is potentially a better indicator of bone status than BA/FFDM and BD. Bone length was poorly correlated with BA, FFDM, and BF, but highly correlated with V (r = 0.844). The volume of the same bone measured by the water weight change method gave the most consistent measurement. The data showed that BA/V may be a better measurement to reflect the bone status changes of hens than other measurements tested. When BA, FFDM, or BF are used in laying hen's bone status studies, the data analysis needs to be adjusted for V, an V is closely correlated with these variables.