Effect of selenium supplementation on dairy cattle.

The adequacy of current supplemental dietary selenium allowances for dairy cattle has been reviewed from the literature and by monitoring responses of dairy herds in a veterinary practice specializing in nutritional consultation. Both information sources tend to agree that a reference range of 70 to 100 ng of Se/mL of serum is an acceptable target concentration. This range can be attained most often by providing > 6 mg of supplemental Se.animal-1.d-1, but several factors affect the serum Se responses of different cows to specific Se intakes. These factors may include forage types and sources, ruminal environment, supplemental fat, dietary calcium, trace metals, and genetics. The major benefits, observed experimentally, of maintaining optimal Se intakes include minimizing the incidence of mastitis and preventing calf losses associated with myopathy and(or) respiratory disease.