Bone breaking strength in mature dairy cows
2005
Keene, B.E. | Knowlton, K.F. | Wilson, J.H. | McGilliard, M.L. | Holtaway, C.
This study was conducted to evaluate the effects of parity, stage of lactation, and measurement site (fused 3rd and 4th metacarpal bone vs. caudal vertebrae 14 and 15) on breaking strength of bone in dairy cattle, and to assess the relationship between breaking strength and bone mineral content. The caudal vertebrae and right front metacarpal (sample pairs) were excised from 107 Holstein cull cows following slaughter. Parity, age, and days in milk (DIM) of the donor animal were obtained for 43 pairs of samples. Samples were grouped by parity (1, 2, 3, and greater than or equal to 4) and stage of lactation (stage 1: <90 DIM; stage 2: 90 to 150 DIM; stage 3: 150 to 250 DIM; stage 4: >250 DIM). Samples were analyzed for breaking strength with mechanical methods, and mineral content was analyzed chemically. In the caudal vertebrae, stage of lactation affected breaking strength, with the highest values observed in early lactation and in animals between 151 and 250 DIM and the lowest values observed in late lactation. No effect of stage of lactation on breaking strength was observed in the load-bearing metacarpal. Parity did not affect breaking strength of the metacarpal or caudal vertebrae. The relationship between mineral content and breaking strength of bones was weak, likely due to the relative maturity of animals in the sample set, and lack of variation in mineral content.
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