| dc.description.abstract | 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. | en |
