Influence of low calcium, high calcium and energy-rich diets on bone markers in ovariectomized Beagle dogs

The collagen metabolites hydroxyproline (HYP), deoxypyridinoline (DPD), pyr idinoline (PYD), and the carboxyterminal telopeptide of type I collagen (IC TP) are suitable markers for bone resorption and osteocalcin (OC) and alkal ine phosphatase (AP) for bone formation in several animal species. The purp ose of the present study was to investigate the effect of different diets o n the activity of bone turnover in healthy ovariectomized Beagle dogs. In a 4 x 4 Latin square design with 14-days trial periods, the dogs were fed fo ur different diets [low calcium (LCa), high calcium (HCa) energy-rich (E) a nd control (N)]. Blood and urine samples were collected on day 0 (= before starting with the diets), days 1, 3, 7, 9, 11 and 14. The above-mentioned b one markers and calcium, magnesium acid phosphorus were measured. Mean Ca c oncentrations were significantly lower in the low Ca group compared with th e control group and mean AP activities were significantly lower in the low calcium group compared with all other groups. Mean OC concentrations were s ignificantly lower in the LCa group compared with N group on day 11 and 14. The results showed that only the low calcium diet influenced bone formatio n. Mean ICTP concentrations tended to be lower in LCa. In conclusion, the c omposition of the diet induced a significant effect on the Ca concentration s in serum and the bone formation was significantly decreased. Mean ICTP co ncentrations were also influenced, but only showed a nonsignificant decreas e at days 11 and 14. Thus, bone formation and resorption were only slightly influenced and indicated a decreased turnover in the LCa group. The potent ial effect of the diets on bone was perhaps not evident, because the feedin g trial was too short to show a significant influence on bone resorption.