| dc.description.abstract | Two animal models, growing pigs (n = 26) and yearling horses (n = 20), were used
to test the hypothesis that whole body vibration (WBV) would improve bone density and
composition. Digital radiographs with an aluminum step wedge were used to determine
bone density in terms of radiographic bone aluminum equivalency (RBAE). Serum
biomarkers of bone formation (osteocalcin, OC) and bone resorption (carboxy-terminal
collagen crosslinks, CTX-I) were determined as measures of bone cell actibvity. The effect
of dietary calcium (Ca) and phosphorus (P) on bone was also tested in the pig study.
The maximum RBAE values for the medial or lateral cortices of the left third
metacarpal bone were not affected by WBV in either the pig or horse models. Although
there was not a statistically significant difference between vibrated pigs and horses and
their respective controls, horses that were vibrated tended to have increased (P = 0.062)
maximum RBAE values for the lateral cortices compared to controls. Pigs fed a diet with
adequate concentrations of Ca and P tended to have increased RBAE max values for the
medial and lateral cortices compared to those fed a diet with deficient concentrations of Ca
and P. Mean RBAE max values for medial cortices increased (linear, P = 0.028) in pigs
from d 0 to 60. Mean RBAE max values for the lateral cortices had a marginally
significant increase (quadratic, P = 0.084). from d 0 to 60.
Horses and pigs receiving vibration treatment had decreased CTX-1 concentrations
(P = 0.003 and P = 0.044, respectively) compared to the non-vibrated control group. The
decreased CTX-I concentrations observed may be the result of an adaptive response of
modeling bone to whole body vibration.
Mean serum concentrations for CTX-1 and OC increased (quadratic, P = 0.0002
and linear, P = 0.001, respectively) in horses from d 0 to 120 indicative of a measured
bone turnover response. Increased CTX-I was likely the result of housing in individual
stalls which could have contributed to increased bone resorption, as characterized by
osteopenia during immobilization. Pigs fed a diet with adequate Ca and P had decreased
concentration of OC from d 0 to 30, and then increased concentrations from d 30 to 60.
Whole body vibration treatment did elicit a response in the trabecular bone
parameters trabecular number (TbN.) and trabecular separation (Tb.Sp) in pigs. Those that
were vibrated had lower Tb.N values and higher Tb.Sp values, suggestive of bone
resorption, and WBV did not significantly change any cortical bone parameters.
Normal physiological responses of bone to a low Ca, P diet were observed in this
study. Although WBV did not elicit an osteogenic response, indications of an early local
adaptive response were observed. The frequency and amplitude of WBV applied in this
study was likely sufficient to elicit a bone remodeling response, but the duration of the
study may not have captured the full cycle. | en |
