Preventing the spread of mad cow disease through contaminated cattle feed is a major concern of beef and dairy producers, regulators and consumers around the world. Routine testing of cattle feeds for the presence of banned substances is a critical control point in assuring animal health and food safety. We compared the results of two test procedures (a real-time polymerase chain reaction [PCR] assay and a commercially available ruminant antibody detection kit) on five cattle rations spiked with bovine meat-and-bone meal, or with bovine dried blood. The real-time PCR consistently detected these contaminants at lower levels in each of these diverse cattle rations.