Effect of dietary calcium and vitamin D supplements on plasma bone turnover biomarkers, bone mineralization, bone strength, and lameness score in gilts.

This study investigated the impact of calcium (Ca) and vitamin D supplements on bone metabolism, bone measurement, lameness, and selection rate in gilts fed 5 dietary treatments. Two Ca levels (6.85/6.42 [adequate; ACa] or 8.99/8.56 [high; HCa] g/kg) were combined with either 856 IU/kg vitamin D3 (Danish feeding standards; adequate; AD3) or 50 μg/kg 25-hydroxyvitamin D3 (high; HHyD) to create ACaAD3, HCaAD3, ACaHHyD, and HCaHHyD diets. The values 6.85/6.42 and 8.99/8.56 g/kg correspond to adequate and high Ca supply for gilts weighing 32 to 100 and 100 to 180 kg body weight (BW), respectively. The fifth diet was a combination of HCa and 2,000 IU/kg vitamin D3 (high; HD3) to create HCaHD3. Two hundred gilts were phase fed the dietary treatments from 32 to 100 and 100 to 180 kg BW until they were slaughtered, either at 100 or 180 kg BW. The gilts were weighed fortnightly, and plasma and urine samples were collected at 100 and 180 kg BW. At slaughter, the 2nd and 3rd metacarpal bones were collected for bone parameters measurements. Lameness and selection rate were assessed within the last 7 d at 100 and 180 kg BW. Dietary treatments did not affect gilts' growth performance and plasma concentration of Ca, but the urinary concentration of Ca was greater in HCa-supplemented gilts at both 100 (P = 0.003) and 180 (P = 0.05) kg BW. Plasma concentration of vitamin D3 (P < 0.001) and 25-hydroxyvitamin D3 (P < 0.001) showed dose-dependent responses at both 100 and 180 kg BW. Bone-specific alkaline phosphatase was greater (P = 0.02) in the plasma sample collected at 180 kg BW in gilts fed the HCaHD3 diet and tended to be greater in gilts fed the ACaAD3 diet (P = 0.06). The bone ash content (P = 0.02) was greater in gilts fed the HCaAD3 diet and slaughtered at 100 kg BW compared with gilts fed the ACaAD3 and ACaHHyD diets. However, bone weight, length, thickness, dry matter, and mineral content did not differ among the dietary treatments at both 100 and 180 kg BW (P > 0.05). Neither lameness nor selection rate was affected by the dietary treatments. The average daily gain of gilts weighing 32 to 100 and 100 to 180 kg BW showed a positive correlation with bone strength (r = 0.37; P < 0.001) and bone ash content (r = 0.24; P = 0.02), respectively. In conclusion, higher Ca and vitamin D3 supplementation slightly increased bone ash content but had no effect on the lameness or selection rate of the gilts compared to those fed according to the Danish nutrient standards.