(OR08-06-24) Calcium Intake Influences Feed Intake, Bone Mineral Density, and Growth Independent of Vitamin A Status

Objectives: Hypervitaminosis A impacts bone formation. The interaction of vitamin A (VA) and calcium (Ca) intakes and statuses on bone formation and growth has not been determined. The objective of this study was to investigate the interaction between VA and Ca in bone formation and growth in a swine model.

Methods: Pigs were weaned on d 17 and randomized by sex, weight, and litter to 5 treatments (n=12/group) containing low VA, adequate Ca (-VA=Ca); adequate VA, adequate Ca (=VA=Ca); high VA, low Ca (+VA-Ca); high VA, adequate Ca (+VA=Ca); and high VA, high Ca (+VA+Ca) for 5 wk. Adequate VA was based on the National Research Council 2012 Nutrient Requirements of Swine.  Feed intake and pig weight were measured weekly. Serum, liver, and extrahepatic tissues were collected and analyzed for VA concentrations using UPLC. Bone mineral density (BMD) was assessed by DXA. Outcomes were compared among treatment groups and time using linear effects mixed models in RStudio.

Results: The highest and lowest daily feed intakes were recorded in +VA+Ca (0.69 kg/d) and +VA-Ca (0.54 kg/d) and were significantly different (P = 0.04). Similarly, weight gain demonstrated treatment effects (P < 0.05) with the highest daily weight gain in -A=Ca (0.44 ± 0.018 kg/d) and the lowest in +VA-Ca (0.34 ± 0.018 kg/d). The mean liver VA concentrations were 3.31 ± 0.65, 3.25 ± 0.42, and 3.07 ± 0.59 µmol/g for +VA-Ca, +VA=Ca, and +VA+CA treatments, respectively, indicating toxicity in the +VA groups. The –VA and =VA groups were deficient (0.007 ± 0.003, 0.033 ± 0.008 µmol/g, respectively). All pigs in +VA-Ca and +VA+Ca, and 91.7% of pigs in +A=Ca had retinyl esters above 5% of the total serum retinol, indicating toxicity. The highest mean BMD value was from the +A+Ca treatment (0.639 ± 0.048 g/cm²) and was significantly different from the other treatments (P < 0.0001), with the lowest recorded value in the +A-Ca treatment (0.354 ± 0.035 g/cm²), indicating the importance of Ca in promoting bone mineralization. The other three groups (+VA=Ca, =VA=Ca, and -Va=Ca;) did not differ (P > 0.05).

Conclusions: Ca supported bone development and weight gain. At the levels fed in this study, VA intake had no effects on BMD and growth for the 5-week trial. Further investigations are required to determine the VA dietary requirements of swine.

Funding Sources: This research was supported by the U.S. Department of Agriculture Hatch WI1022808.