 In this study, researchers found that oral supplementation of 25 hydrox of vitamin D3, 25, OH, D3, was more effective than oral supplementation of vitamin D3, D3, in raising serum levels of 25, OH, D3 in dogs. This suggests that oral supplementation of 25, OH, D3 may be a better option for raising serum 25, OH, D3 levels in dogs than oral supplementation of D3. This article was authored by Lauren Ayung and Robert C. Bacchus.