Biochemical markers of bone metabolism and risk of dorsal metacarpal disease in 2-year-old Thoroughbreds.
BACKGROUND
Dorsal metacarpal disease (DMD) is a common problem in 2-year-old racehorses and results in loss of a significant number of days from training. Biochemical markers of bone cell activity measured early in the training season could have value for identifying 2-year-old Thoroughbred racehorses that develop DMD.


OBJECTIVE
To determine the association between serum concentrations of osteocalcin, the carboxyterminal propeptide of type I collagen (PICP) and the carboxyterminal cross-linked telopeptide of type I collagen (ICTP) measured early in the training season and the risk of DMD.


METHODS
Blood samples were collected from 165 two-year-old Thoroughbreds during late November/early December. Osteocalcin and PICP were measured as markers of bone formation, and ICTP as a marker of bone resorption. Training and veterinary records for each horse were monitored over the following training/racing season (10 months). Cases were defined as an episode where signs of DMD were sufficiently severe for a horse to miss at least 5 consecutive days of training. Classification tree and logistic regression analysis were used to identify the most important factors suitable for prediction of DMD risk.


RESULTS
There were 24 cases of DMD during the season (14.6% cumulative incidence), with an average time to recognition of approximately 6 months (May). The earliest recognised case was in February and the latest in September. Osteocalcin and ICTP concentrations in the early stages of the training season were significantly higher in horses that subsequently developed DMD (P = 0.017 and 0.019, respectively). DMD cases were also significantly older compared to noncases (21.04 vs. 20.44 months, P = 0.023). Using a multivariable logistic regression model, it was possible to postulate a set of diagnostic rules to predict the likelihood of DMD injury during the season. This suggested that horses with ICTP concentrations above 12365 ug/l and older than 20.5 months are 2.6 times more likely to develop DMD.


CONCLUSIONS
The measurement of the bone resorption marker ICTP could be useful for identification of 2-year-olds at increased risk of developing DMD.


CONCLUSIONS
These findings, together with other strategies such as modification of training regimens, e.g. early introduction of short distances of high-speed exercise into the training programme, could help reduce the days lost to training as a result of DMD.
Jackson
B F
BF
Department of Veterinary Basic Sciences, The Royal Veterinary College, Royal College Street, London NW1 OTU, UK.
Lonnell
C
C
Verheyen
K L P
KL
Dyson
P
P
Pfeiffer
D U
DU
Price
J S
JS
D000367:Age Factors; D000818:Animals; D015415:Biomarkers / Q000097:blood / Q000378:metabolism; D001846:Bone Development / Q000502:physiology; D016723:Bone Remodeling / Q000502:physiology; D001862:Bone Resorption / Q000097:blood / Q000662:veterinary; D001842:Bone and Bones / Q000378:metabolism*; D016022:Case-Control Studies; D006734:Horse Diseases / Q000453:epidemiology / Q000209:etiology / Q000378:metabolism*; D006736:Horses; D007794:Lameness, Animal / Q000453:epidemiology / Q000209:etiology* / Q000378:metabolism; D016015:Logistic Models; D015675:Osteocalcin / Q000097:blood*; D010446:Peptide Fragments / Q000097:blood*; D011347:Procollagen / Q000097:blood*; D012307:Risk Factors; D012621:Seasons
D015415:Biomarkers; D010446:Peptide Fragments; D011347:Procollagen; C042813:procollagen type I carboxy terminal peptide; D015675:Osteocalcin