Effects of dietary 25-hydroxyvitamin D3 on the lactation performance, blood metabolites, antioxidant and immune function in dairy cows

Abstract

The objective of this study was to evaluate the effects of 25-hydroxyvitamin D3 on the lactation performance, blood metabolites, and antioxidant and immune function in dairy cows. Thirty-six mid-lactation Holstein dairy cows were blocked according to day in milk, milk yield and somatic cell counts (SCC) and were randomly assigned to 3 treatments. Treatments were a basal diet plus 0 mg, 1 mg or 3 mg 25-hydroxyvitamin D3 per cow per day throughout a 9-week trial period. Cows were milked three times daily, and dry matter intake and milk yield were measured daily. Milk components were sampled at days 0, 21, 42 and 63 for milk fat, protein, lactose and SCC analysis. Blood was sampled for blood metabolites, parameters of antioxidant and immune function at days 0, 21, 42 and 63. Dairy cows fed 25-hydroxyvitamin D3 showed linear increases (P < 0.05) in milk yield, energy-corrected milk, milk protein and lactose yield and a decrease in somatic cell counts in milk (P < 0.01). Feeding dietary 25-hydroxyvitamin D3 linearly increased serum total Ca, P, 25-hydroxyvitamin D3 and 1,25-dihydroxyvitamin D3 and had no negative effect on blood biochemical parameters and markers of fat mobilization. Additionally, dietary 25-hydroxyvitamin D3 linearly increased (P < 0.05) total antioxidant capacity, total superoxide dismutase, glutathione peroxidase, immunoglobulin A and immunoglobulin G and linearly decreased (P < 0.05) malondialdehyde and tumor necrosis factor-α. In summary, dietary supplementation with 25-hydroxyvitamin D3 increased milk yield and decreased SCC, improved serum minerals, 25-hydroxyvitamin D3 levels, and antioxidant and immune function of dairy cows.