Abstract #M158

# M158
Effects of dietary vitamin D3 or 25-hydroxyvitamin D3 on mineral metabolism in growing calves.
R. Zimpel*1, M. B. Poindexter1, A. Vieira-Neto1, A. Husnain1, S. Buoniconti1, P. Celi2, C. Cortinhas2, C. D. Nelson2, J. E. P. Santos1, 1University of Florida, Gainesville, FL, 2DSM Nutritional Products, Columbia, MD.

Objectives were to determine the effects of dose and source of vitamin D (vitamin D3 or 25-hydroxyvitamin D3 [25OHD3]) on mineral metabolism and bone mineral density (BMD) in calves. The hypothesis was that dietary 25OHD3 would enhance Ca accretion and BMD. Forty-five Holstein male calves were enrolled within the first week of age in a randomized complete block design. Calves were assigned to 1 of 5 treatments: T1 (0.25 mg of vitamin D3/kg BW), T2 (0.25 mg of vitamin D3 + 1.5 mg of 25OHD3/kg BW), T3 (0.25 mg of vitamin D3 + 3.0 mg of 25OHD3/kg BW), T4 (1.75 mg of vitamin D3/kg BW) and T5 (3.25 mg of vitamin D3/kg BW). Treatment were supplied from birth to 131 ± 9 d of age when calves were euthanized and tissues collected. Calves were fed milk replacer until 49 d of age and had ad libitum access to starter grain and water. Blood was sampled on d −15, −14, −13, −12, −11, −9, −7, −5, −3 and −1 relative to slaughter. Intake of DM was evaluated in the last 15 d before slaughter. Total fecal collection and spot urine was sampled on d −4 to −2 relative to slaughter. The BMD was determined in the right metacarpus. Data were analyzed by ANOVA with mixed models using the MIXED procedure of SAS. Contrasts evaluated included the effects of supplementing vitamin D (Sup: T1 vs. T2+T3+T4+T5), source of vitamin D (Source: T2+T3 vs. T4+T5), dose of vitamin D (Dose: T2+T4 vs. T3+T5), or the interaction between Source and Dose (Int: T2 + T5 vs. T3 + T4) (Table 1). Intake of DM or Ca did not differ among treatments. Supplementing vitamin D reduced blood Ca; however, supplemental 25OHD3 increased blood Ca compared with vitamin D3. Treatment did not affect digestibility or retention of Ca, but calves fed 25OHD3 tended to have increased BMD. Table 1 (Abstr. M158).
 DM, kg/d4.
 Ca, g/d61.955.158.656.762.24.0
 BW gain, kg/d1.321.
 tCa, mM*,†2.8682.8582.8402.7882.8080.024
 iCa, mM *1.4731.4541.4371.4461.4290.014
 Calcitriol, pg/mL51.453.855.253.457.03.2
BMD, g/cm2 †,‡0.9861.0331.0540.9671.0380.024
Ca digestibility, %50.553.251.652.152.92.5
Ca retention, g/d31.129.030.329.433.12.9
*Sup (P < 0.09); †Source (P < 0.10); ‡Dose (P < 0.07).

Key Words: bone density, calcium, vitamin D