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The aim of the study was to use spatial and multiple correspondence analysis (MCA) to describe and compare the regional proportion and spatial pattern of volumetric bone mineral density (BMDv) values within loaded regions of the plantar metatarsal epiphysis of young horses in race training. A single 2 mm transverse peripheral quantitative computed tomography 'slice', 10 mm proximal from the distal limit of the sagittal ridge of the distal metatarsal epiphysis was obtained from 14 2-year-old Thoroughbred fillies (7 exercised and 7 controls). Six regions of interest were generated and examined for relative BMDv using MCA. The spatial distribution of BMDv was statistically examined at two sites loaded by the proximal sesamoid bones using geographical information software. The BMDv response was focal with distinct regional differences in relation to load. Deposition of new bone within existing high density bone contributed to a greater bone fraction and the distinct profile of clusters of uniformly distributed high density bone as well as a lower proportion of lower density bone in exercised horses. The MCA and spatial analysis provided statistical techniques to quantify and describe non-invasively the exercise induced changes in bone that had previously been described using microradiography of thin slices and by block-face imaging. These statistical techniques may prove useful in quantifying spatial patterns of response to load., (Copyright © 2014 Elsevier Ltd. All rights reserved.)

Objective: To investigate the effect of exercise during yearling sales preparation on the risk of interruptions during training in Thoroughbred racehorses., Animals: 114 Thoroughbred racehorses., Procedures: Information regarding the daily exercise of yearlings during sales preparation was obtained prospectively from a convenience sample of stud farms. Yearlings were followed to entry into race training, and subsequently, daily training information was recorded until the end of the racing season. Competing-risks survival analysis was used to model time from entry into race training to voluntary training interruption (no known condition or disease identified) and time from entry into race training to involuntary training interruption (due to presence of a condition or disease) occurring before the first trial (practice race for education). Total hand walking time and mechanical walker time accumulated during sales preparation were the main exposures of interest., Results: 82 of 114 (71.9%) horses had an interruption before the first trial; 65 (79%) interruptions were voluntary, and 17 (21%) interruptions were involuntary. Increased total hand walking time was significantly associated with decreased risk of voluntary interruptions, whereas longer cumulative distances at a canter were significantly associated with decreased risk of involuntary interruptions., Conclusions and Clinical Relevance: Results identified an association between early exercise during sales preparation and decreased risk of voluntary interruption and increased risk of involuntary interruption during training of 2-year-old Thoroughbred racehorses. Further investigation into the effects of early exercise on racing performance is needed, but results have indicated that there may be an opportunity to modify early exercise programs.

This study recorded the response to training of the diaphysis of the proximal phalangeal bone and the third metacarpal bone (Mc3) and the Mc3 proximal metaphysis. Nineteen 2- and 3-year old horses in training were exposed either to spontaneous exercise at pasture (PASTEX group) or additional imposed exercise (CONDEX group) from a very young age. Quantitative computed tomography scans were analysed for bone mineral content, size, bone mineral density, periosteal and endosteal circumference, cortical thickness and an estimate of bone strength. The bones of the CONDEX horses were bigger and stronger than those of the PASTEX horses at the start of the observation period, and these differences were maintained after adjusting for training workload. Increase in the bone strength index was through size and not density increase. Density increased during training and decreased during paddock rest between the two training campaigns, during which time bone strength continued to increase because of the slow growth that was still occurring. The greatest variance in the response to the training exercise of diaphyseal bone mineral content, bone strength index or cortical thickness was associated with the cumulative workload index at the gallop, although statistically significant unexplained variances remained. There were no differences in bone response to training, with the exception of the endosteal circumference at 55% of the Mc3 length from the carpometacarpal joint space between CONDEX and PASTEX, which indicated that young horses may be able to be exercised slightly more vigorously than currently accepted., (Copyright © 2011 Elsevier Ltd. All rights reserved.)

Exercise or lack of it in early life affects chondro-osseous development. Two groups of horses were used to investigate the effects of age and exercise regimen on bone parameters of diaphyseal, metaphyseal, epiphyseal and cuboidal bones of the distal limb of Thoroughbreds. One group had exercised only spontaneously from an early age at pasture (PASTEX group), while the other group of horses were exposed to a 30% greater workload through additional defined exercise (CONDEX). Longitudinal data from peripheral quantitative computed tomography (pQCT) were obtained from eight scan sites of the left forelimb (proximal phalangeal (P(p); 1 site), third metacarpal (Mc3; six sites) and third carpal (C(3); one site) bones) of 32 Thoroughbred foals scanned five times from ∼3 weeks to 17 months of age. The primary outcome measures were bone mineral content (BMC), bone area (BA), and periosteal circumference (Peri C) in diaphyseal bone, with cortical thickness (CortTh), volumetric bone mineral density (BMD(v)) and a bone strength index (SSI) also being analysed. At the P(p) site within the model there was a significant effect (P=0.00-0.025) of conditioning exercise increasing bone parameters, except endosteal circumference (Endo C) and BMD(v). The BMC, BA, and SSI of P(p) were significantly greater in the CONDEX than PASTEX groups at 12 and 17 months (P=0.015-0.042) and CortTh at 17 months (P=0.033). At the M55 site of Mc3 BMC, BA and SSI (P=0.02-0.04), and at the M33 site, SSI (P=0.05) were higher in the CONDEX than PASTEX group. The adaptive responses, consistent with diaphyseal strengthening, were more marked in the diaphysis of P(p) than Mc3. In the Mc3, metaphysis, trabecular BMD(v) was less in the CONDEX than PASTEX group, associated with greater bone mineral accretion in the outer cortical-sub-cortical bone in the CONDEX group. There were no significant between-group differences in any epiphyseal or cuboidal bone parameter. Although the early imposed exercise regimen was not intensive, it had significant effects on diaphyseal bone strength, through change in size but not bone density., (Copyright © 2010 Elsevier Ltd. All rights reserved.)