Calves, as a model for juvenile horses, need only one sprint per week to experience increased bone strength

Abstract

Previous research has determined that maintaining young animals in stalls is detrimental to their bone health, while the addition of 50 to 82-m sprints 5 d/week aids in counteracting the reduction of bone strength from confinement. The current research aims to determine if 1 or 3 d/week of sprinting affords the same benefits to bone as 5 d/week of sprinting compared to animals confined with no sprinting. Twenty-four Holstein bull calves were obtained from the Michigan State University Dairy Cattle Teaching and Research Center. At 9 wk of age, calves were randomly assigned to treatments of 1, 3, or 5 d/week of sprint exercise, or to the confined control group sprinted 0 d/week. Each treatment had 6 calves. Individual sprinting bouts included a single sprint down a 71-m concrete aisle. For the duration of the 6-wk study, calves were housed at the MSU Beef Cattle Teaching and Research Center in stalls which afforded calves room to stand, lay down, and turn around. 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, respectively. Sprints were videotaped weekly to determine stride frequency and sprint velocity. On day 42, calves were humanely euthanized at the Michigan State University Meat Lab and both front limbs were immediately harvested. Computed tomography scans and mechanical testing were performed on the left fused third and fourth metacarpal bones. Serum OC concentration was greatest for calves sprinted 5 d/week (P < 0.001). Calves sprinted 5 d/week had both greater stride frequency (P < 0.05) and lower sprint velocity (P < 0.05). 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/week during growth can increase bone health and cause favorable alterations in bone markers. While all exercise treatments had over a 20% increase to fracture force, calves sprinted 1 d/week sprinted only 426 m over the 6-wk study and still experienced over a 20% increase in bone strength compared to confined calves. 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.

Bone Morphology and Strength in the Mid-Diaphysis of the Humerus and Metacarpus in Dairy Calves Prior to Weaning

“…In comparison, calves, which are not a cursorial species, do not have the same predisposition to run at high speed and are therefore unlikely to subject the distal limb to the high strain rates observed in galloping horses. Even when calves were run on a concrete path, this failed to induce sufficient high strain rates to increase bone density, with the primary response being an alteration in bone circumference and focal response in morphology to the strain (deposition of bone on the dorsal surface) [8]. The results from the current study agree with those of Hiney, et al [16] that calves on a pasture-based system will not reach the critical loading threshold to induce an increase in cortical density and no differences in cortical density between calves on restricted and unrestricted exercise would be expected.…”

“…There is limited published literature describing the effect of sex and other factors on bone growth and development in livestock, with much of the published literature focusing on horses [6,7]. There are limited data on bone growth and development in cattle; however, the majority of these have been collected using DEXA, preventing description of changes in bone geometry and microarchitecture [8]. Therefore, the aim of this study was to describe the relationship of pQCT-derived measures of bone strength and morphology within two different bones, in the proximal and distal limb, with gross measurements of size and growth.…”

Training Young Horses: The Science behind the Benefits

“…For this reason, while horses are growing, their skeletal strength is highly influenced by the strains their bones undergo through daily use and exercise [ 19 ]. Short-term dynamic exercise as an adolescent can lead to beneficial changes in bone morphology, increased fracture force, and reduced fracture risk at maturity [ 20 , 21 , 22 , 23 ]. Factors in the strain environment of a bone that elicit remodeling responses include magnitude of strain, rate of change in strain, as well as spread of dynamic strain [ 24 , 25 , 26 ].…”

“…Walking has been shown to lead to deconditioning of bone in previously conditioned horses, as it does not provide a dynamic strain at a threshold to maintain bone content [ 28 ]. However, exercise which elicits bone formation, such as sprinting, during early training could negate the loss of bone due to confinement [ 20 , 21 , 23 ].…”

“…Relatively few cycles of dynamic loading are needed to illicit beneficial changes to bone. Logan and colleagues [ 23 ] recently determined that 71 m sprints performed at least 1 d/wk lead to a 23% increase in the force required to fracture the fused third and fourth metacarpal of young Holstein calves compared to their confined counterparts which endured no sprints.…”