Charles River Laboratories International counts its chickens before they're hatched. Among other research products and services for pharmaceutical and biotech companies, Charles River Laboratories develops pathogen-free, fertilized chicken eggs used in poultry vaccines. Its Research Models and Services (RMS) unit also produces research models (lab rats and other animals) bred specifically for use in medical testing. The company provides contract research services for drug discovery and development through its Preclinical Services and Clinical Services segments. The company added the Clinical Services business, which manages drug trials on human subjects, when it acquired research firm Inveresk in 2004.