"Previous research determined that maintaining young animals in stalls is detrimental to their bone health, while the addition of 50 to 82-m sprints 5 d/wk aids in counteracting the reduction to bone health. This research aimed to determine if 1 or 3 d/wk of sprinting would yield the same benefits to bone as 5 d/wk of sprinting compared to confined animals. Twenty-four Holstein bull calves were obtained from the MSU Dairy Cattle Teaching and Research Center. At 9 weeks of age, calves were randomly assigned to treatments of 0, 1, 3, or 5 d/wk of sprint exercise. Individual sprinting bouts included a single sprint down a 71-m concrete aisle. For the duration of the 6-wk study, calves were housed in individual stalls at the MSU Beef Cattle Teaching and Research Center. Serum was collected weekly via jugular venipuncture to obtain concentrations of osteocalcin (OC) and C-telopeptide crosslaps of type I collagen (CTX-1)---markers of bone formation and degradation. On d 42, calves were humanely euthanized and both front limbs were harvested. Computed tomography scans and mechanical testing were performed on the left fused third and fourth metacarpal bones. Serum OC concentration was highest for calves sprinted 5 d/wk (P < 0.001). All exercise treatments experienced greater dorsal cortical widths compared to control animals (P < 0.01). Through mechanical testing, fracture forces of all sprinting treatments were determined to be greater than the control treatment (P < 0.02). Results from this study support that sprinting 1, 3, or 5 d/wk during growth can improve bone health and cause favorable alterations in bone markers. This study demonstrates the remarkably few strides at speed needed to enhance bone strength and emphasizes the danger to skeletal strength if sprinting opportunities are not afforded."--Page ii.
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