Effects of supplemental vitamin D3 on serum 25-hydroxycholecalciferol and growth of preweaning and nursery pigs

Four experiments were conducted to investigate the effects of varying concentrations of supplemental vitamin D-3 on pig growth, feed preference, serum 25-hydroxycholecalciferol [25(OH)D-3], and bone mineralization of nursing and weanling pigs. In Exp. 1, 270 pigs (1.71 +/- 0.01 kg BW) were administered 1 of 3 oral vitamin D-3 dosages (none, 40,000, or 80,000 IU vitamin D-3) on d 1 or 2 of age. Increasing oral vitamin D-3 increased serum 25(OH)D-3 on d 10 and 20 (quadratic, P < 0.01) and d 30 (linear, P < 0.01). No differences were observed in ADG before weaning or for nursery ADG, ADFI, or G: F. Vitamin D-3 concentration had no effect on bone ash concentration or bone histological traits evaluated on d 19 or 35. In Exp. 2, 398 barrows (initially 7 d of age) were used in a 2 x 2 split plot design to determine the influence of vitamin D-3 before (none or 40,000 IU vitamin D-3 in an oral dose) or after weaning (1,378 or 13,780 IU vitamin D-3/kg in nursery diets from d 21 to 31 of age) in a 45-d trial. Before weaning (7 to 21 d of age), oral vitamin D-3 dose did not influence growth but increased (P < 0.01) serum 25(OH)D-3 at weaning (d 21) and tended (P = 0.08) to increase 25(OH)D-3 on d 31. Increasing dietary vitamin D-3 concentration from d 21 to 31 increased (P < 0.01) serum 25(OH)D-3 on d 31. Neither the oral vitamin D-3 dose nor nursery vitamin D-3 supplements influenced nursery ADG, ADFI, or G:F. In Exp. 3, 864 pigs (initially 21 d of age) were allotted to 1 of 2 water solubilized vitamin D-3 treatments (none or 16,516 IU/L vitamin D-3 provided in the drinking water from d 0 to 10) in a 30-d study. Providing vitamin D-3 increased serum 25(OH)D-3 concentrations on d 10, 20, and 30; however, vitamin D-3 supplementation did not affect overall (d 0 to 30) ADG, ADFI, or G: F. In Exp. 4, 72 pigs were used in a feed preference study consisting of 2 feed preference comparisons. Pigs did not differentiate diets containing either 1,378 or 13,780 IU vitamin D-3/kg but consumed less (P < 0.01) of a diet containing 44,100 IU vitamin D-3/kg compared with the diet containing 1,378 IU vitamin D-3/kg. Overall, these studies demonstrate that supplementing vitamin D-3 above basal concentrations used in these studies is effective at increasing circulating 25(OH)D-3, but the supplement did not influence growth or bone mineralization. Also, concentrations of vitamin D-3 of 44,100 IU/kg of the diet may negatively affect feed preference of nursery pigs.