Biochemical markers of bone modeling and remodeling in juvenile racehorses at varying mineral intakes
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Blood-borne biochemical markers were used to track comparative rates of bone turnover in horses fed differing amounts of Ca, P and Mg. Bone turnover was tracked by serum osteocalcin, bone resorption by the carboxyterminal telopeptide of type I collagen (ICTP), and bone formation by the carboxyterminal propeptide of type I procollagen (PICP). Twenty-four long-yearling Quarter Horses were blocked by gender and age, randomly assigned to one of four diets and subjected to 128 d of race training. Horses entered the study at approximately 20 months of age. The study was conducted in 32-d periods, each consisting of 28 d of race training followed by a 4-d fecal and urine collection, or a 4-d rest period. Blood samples were taken weekly during the training period. Serum and plasma samples were analyzed for concentrations of osteocalcin, the carboxyterminal telopeptide of type I collagen (ICTP) and the carboxyterminal propeptide of type I procollagen (PICP). Urine was collected for analysis of deoxypyridinoline (DPD) and creatinine. Onset of training resulted in elevated concentrations of ICTP, PICP and osteocalcin. Horses consuming the highest levels of Ca, P and Mg exhibited higher concentrations of PICP and lower concentrations of ICTP indicating greater bone formation coupled with lesser amounts of bone resorption. Further, ICTP, PICP and osteocalcin concentrations decreased dramatically following 4-d of confinement and relative inactivity. Therefore it appears that feeding minerals at levels greater than current NRC recommendations provided a protective effect on the developing skeleton of the young racehorse. Additionally, the biochemical markers used in this study were sensitive enough to track daily changes in bone activity resulting from daily changes in stress to the skeleton.
Eller, Elena Maria (2003). Biochemical markers of bone modeling and remodeling in juvenile racehorses at varying mineral intakes. Master's thesis, Texas A&M University. Texas A&M University. Available electronically from