Triennial Growth Symposium--Effects of dietary 25-hydroxycholecalciferol and cholecalciferol on blood vitamin D and mineral status, bone turnover, milk composition, and reproductive performance of sows.

To evaluate the role of vitamin D3 during gestation and lactation of sows, 2 independent experiments were performed with the aim of investigating sow reproductive performance, milk composition (study 1 only), and changes in blood status of 25-hydroxycholecalciferol (25-OH-D3), 1,25-dihydroxycholecalciferol (1,25-(OH)2-D3; study 2 only), minerals, and bone markers of sows during gestation and lactation. Study 1 comprised 39 primi- and multiparous crossbred sows fed 1 of 3 barley meal-based diets fortified with 200 IU/kg vitamin D3 (NRC, 1998; treatment DL), 2,000 IU/kg vitamin D3 (cholecalciferol; treatment DN), or 50 µg 25-OH-D3 (calcidiol; treatment HD)/kg feed. This study was conducted over a 4-parity period under controlled conditions. Study 2, running over 1 parity only, was performed in a commercial farm with 227 primi- and multiparous sows allocated to 2 dietary treatments: control (CON), receiving 2,000 IU vitamin D3/kg (equivalent to 50 µg/kg) feed (114 sows), and test (HYD), supplemented with 50 µg 25-OH-D3/kg feed (113 sows). Blood samples of sows were collected at 84 and 110d postcoitum and 1, 5, and 33 d postpartum (study 1) and at insemination and 28 and 80 d postinsemination as well as d 5 and 28 postpartum (study 2). Colostrum and milk samples in study 1 were obtained at 1, 9, and 33 d of lactation after oxytocin administration. Plasma 25-OH-D3 concentrations were increased (P < 0.05) in sows receiving 25-OH-D3 (HD and HYD) at any time of sampling whereas circulating plasma concentrations of 1,25-(OH)2-D3, Ca, and P were not affected by treatment. Milk concentrations of Ca and P were similar, but 25-OH-D3 content (except in colostrum) was clearly increased (P< 0.05) when 25-OH-D3 was fed. Most characteristics of sow reproductive performance responded similarly to the 2 sources and levels of vitamin D3, but weight gain of piglets between birth and weaning was decreased (P< 0.05) in offspring of DL and HD sows compared with animals of treatment DN (study 1). In study 2 total litter weight and birth weight per piglet were increased (P< 0.05) with 25-OH-D3 supplementation in comparison with the control (CON). Overall, feeding sows with 25-OH-D3 was considered to improve maternal supply with vitamin D3 and thereby maintain Ca homeostasis during gestation and lactation.

Effect of source and quantity of dietary vitamin D in maternal and creep diets on bone metabolism and growth in piglets.

Piglets are born with reduced plasma concentrations of 25-hydroxycholecalciferol (25-OH-D(3)) and are thus highly predisposed to vitamin D deficiency. Furthermore, sow milk contains little vitamin D, and the slow intestinal vitamin D absorption of sows limits the efficacy of dietary vitamin D supplementation. Hence, the neonate depends, to a large extent, on the vitamin D stores built up in fetal tissues from maternal sources. The current study was undertaken to evaluate whether the source and quantity of dietary vitamin D provided to the gestating and lactating sow, and also directly in the form of creep feed to the piglet, would influence the vitamin D status, growth performance, and skeletal development of piglets. A total of 39 primiparous and multiparous sows were randomly assigned to 1 of 3 dietary treatments (13 in each treatment), supplemented with either 5 or 50 µg of the commonly used cholecalciferol (vitamin D(3)) or 50 µg of 25-OH-D(3) per kilogram of feed. By wk 3 of lactation, piglets were offered a creep diet with vitamin D supplementation according to the treatment of the dam, and they were offered the same creep diets after weaning at d 35 of age until they reached a BW of approximately 20 kg. When dietary 25-OH-D(3) was provided, circulating concentrations of 25-OH-D(3) in piglet serum increased (P < 0.05) as early as d 21 and later at d 33 and 77, indicating greater body stores in those animals. Bone-breaking strength and cortical bone mineral content and density at the tibial midshaft of piglets were reduced (P < 0.05) when vitamin D(3) was supplemented at 5 µg/kg compared with the bone traits of other groups, but no differences (P > 0.05) were observed between the 2 other groups. After weaning, ADFI was greater (P < 0.05) and growth performance tended (P = 0.08) to improve when doses of 50 µg/kg were administered, regardless of the vitamin D source. In conclusion, supplementation of the diet with 50 µg/kg of either source of vitamin D was proved to be adequate in meeting the needs of gestating sows and in permitting the accumulation of vitamin D in fetal tissues, as well as for normal skeletal mineralization and growth in the offspring. Furthermore, the markedly improved vitamin D status of piglets whose mothers received 25-OH-D(3) possibly resulted from greater tissue reserves present at birth and a greater availability of vitamin D when released from those stores.