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.