Feeding supplemental 25-hydroxyvitamin D-3 increases serum mineral concentrations and alters mammary immunity of lactating dairy cows

Abstract

Objectives were to determine the effects of feeding supplemental 25-hydroxyvitamin D3 [25(OH)D3] on concentrations of vitamin D metabolites and minerals in serum, mammary immune status, and responses to intramammary bacterial infection in dairy cows. Sixty multiparous, pregnant lactating Holstein cows with somatic cell count <200,000/mL were blocked by days in milk and milk yield and randomly assigned to receive a daily top-dressed dietary supplement containing 1 or 3 mg of vitamin D3 (1mgD or 3mgD), or 1 or 3 mg 25(OH)D3 (1mg25D or 3mg25D) for 28 d (n = 15/treatment). Cows were kept in a freestall barn and fed a total mixed ration in individual feeding gates. Individual dry matter intake (D..