USDA Class B dealers provide what?

• A. Random source animals
• B. Specific pathogen-free animals
• C. Purpose-bred animals
• D. Gnotobiotic animals

Answer: (A)

In this topic, the key idea is how USDA classifies vendors of laboratory animals. Class B dealers are defined by providing random-source animals to researchers. “Random-source” means the animals come from a mix of sources with unknown or not fully documented origins, rather than being bred for a specific research purpose or kept in controlled, pathogen-free colonies.

This is different from other options: specific pathogen-free animals are produced and maintained in specialized barrier facilities to ensure they’re free of particular pathogens, a status not guaranteed by typical Class B sources. Purpose-bred animals come from Class A dealers, who breed animals specifically for research needs with documented lineage. Gnotobiotic animals are raised in highly controlled sterile environments with known microbiota, also produced in specialized facilities, not typical Class B suppliers.

So USDA Class B dealers provide random-source animals, which have varied backgrounds and provenance, suitable for certain types of studies where random genetic and health backgrounds are acceptable or desired.