Percent inhibition of serum anti-rabies antibodies prior to vaccination, prior to booster vaccination (8 wk later), and at the end of the study (4 wk after booster) in adult horses (n = 5 per group) receiving supplementary inorganic Se (0.3 ppm DM, as sodium selenite), organic Se (0.3 ppm DM, as Se yeast), or receiving no supplementary Se (< 0.05 ppm DM).