Whey derived from ordinary milk includes a bottom fraction including lactose and minerals, a middle fraction including lower molecular weight proteins, and a top fraction including higher molecular weight proteins. The top whey fraction includes a measurable but low level concentration of immunologically active immunoglobulin plus other pathogen specific antibodies. The whey is ultrafiltered through one or more different process steps to yield a filtered product having a concentration of immunologically active immunoglobulin of at least about seven percent of total solids. The filtered product is periodically tested to verify its activity to a specified microbe. The filtered product is orally administered in a therapeutically effective dose to an animal to treat a disease.