Effects of Oral Administration of “Rumen-Bypass” Vitamin D₃ on Vitamin D and Calcium Metabolism in Periparturient Cows

Abstract

Eleven late-pregnant Jersey cows were assigned to two groups; a group (PO-RBVD group) consisting of five cows treated with an oral administration of 10 million I.U. of an encapsulated form of vitamin D₃ (“rumen-bypass” VD₃; RBVD₃) and another group (IMVD group) consisting of the other six treated with an intramuscular injection of 10 million I.U. of vitamin D₃ (VD₃). The cows received the RBVD₃ or VD₃ administration at 7 days before the expected parturition. The changes in the plasma concentrations of vitamin D metabolites, ionized Ca (Ca⁺⁺) and inorganic phosphorus (iP) were evaluated. Of the vitamin D metabolites, the plasma 25-hydroxyvitamin D concentrations in PO-RBVD group increased significantly after the RBVD₃ administration and remained in high levels that were significantly higher than those in IMVD group. This suggested that RBVD₃ was absorbed rapidly and excellently from the post-ruminal digestive tract without the degradation by ruminal microorganisms. The plasma Ca⁺⁺ and iP concentrations in PO-RBVD group tended to be higher after the administration and around parturition than those in IMVD group. From these observations, it was suggested the oral RBVD₃ administration had more potent ability to prevent parturient paresis compared with the VD₃ injection used widely in Japan.