Factors influencing bone mineral content, density, breaking strength, and ash as response criteria in assessing bone quality in chickens

Two experiments were conducted to determine the influence of the method of removing the tibiae and the physical state of the tibiae (wet versus dry) on various bone quality properties in chickens. In Experiment 1, 40 Leghorn hens in each of two trials were killed at oviposition and tibiae were removed either by direct excision (Method 1) or by skinning the drumstick, removing the bone, and boiling it for 10 min (Method 2). In Experiment 2, broilers were fed a control or a cholecalciferol-deficient diet for 28 days, after which the birds were killed and both tibiae were removed by direct excision. Two trials were conducted using 100 broilers in each trial. Tibiae obtained in each experiment were analyzed for bone mineral content, bone density, bone strength, and bone ash either as wet (fresh) or air-dried at room temperature for 3 or 7 days. In Experiment 1, results showed that the method of removing the tibiae did not affect mineral content, density, and strength; whereas values for ash varied with the physical state of tibia and method of removal. It took .67 h to obtain 40 clean tibiae by Method 1 whereas it took 2.7 h by Method 2. Values for mineral content, density, and strength differed for fresh (wet) and air-dried tibiae. When tibiae were dried for 3 or 7 days, mineral content and density were reduced by 25 to 28% (Experiment 2). Bone strength of cholecalciferol-deficient birds increased more than twofold when dried for 3 or 7 days. Bone ash was not affected by physical state of bone. Results indicate that the bone properties, mineral content, density, and strength commonly used to assess bone quality, are influenced by physical state of bone (wet or dry), which should be considered when making decisions about the effect of nutrients on bone status or bone mineralization.