Depletion of bone calcium during the laying cycle results in weakened bones at end-of-lay. The danger of bone breakage in the cage or during handling at disposal is a welfare problem. In this study two strains of hens, one brown (Shaver 579) and one white-egg (Shaver 2000), were studied at the end of lay. The white-egg strain had produced more eggs during the cycle than the brown-egg strain, but the brown-egg strain produced larger eggs with more shell material. The brown-egg strain was slightly heavier at the end-of-lay as well. Bone density of the femur did not differ between strains, but all measures for the humerus and all remaining measures for the femur indicated that the bones of the brown-egg strain were stronger at the end-of-lay. Bone breaking strengths were approximately 20% greater for the brown-egg line. Of the two lines tested, the brown-egg line had better bone quality at the end-of-lay and would be less susceptible to breakage and poor welfare. However, it should be recognized that only one line of each egg type was studied and it cannot be determined if these differences are due to egg-type or unique to the strains studied.
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