Outbred stocks are most often used in research projects requiring vigorous, economically priced animals, but in which considerations of specific genotype are of lesser importance. Outbred stocks are often used in biological assays or in preliminary studies in which techniques are being perfected prior to more detailed studies using inbred strains. These animals are also useful in studies where large bodyweight or good breeding performance is of greater importance than a defined genotype, or in any study where previous experience has shown that they are suitable.

ORIGIN: Originated in 1925 by Robert W. Dawley from a hybrid hooded male and a female Wistar rat. To Charles River in 1950 from Sprague Dawley, Inc. In 1991, 8 colonies were selected to form the IGS Foundation Colony. Rederived into an isolator foundation colony in 1997. IGS refers to animals bred using the Charles River International Genetic Standardization system.To BioLASCO Taiwan in 2004 from Charles River.
COAT COLOR: White (albino)
RESEARCH APPLICATION: general multipurpose model, safety and efficacy testing, aging, nutrition, diet-induced obesity, oncology

 Wistars rats, Nomenclature Crl :WI

Institute. To Charles River in 1975 from CRUK. This particular colony was selected because of a low incidence of hydronephrosis.To BioLASCO Taiwan in 2004 from Charles River.
COAT COLOR: White (albino)
RESEARCH APPLICATION: general multipurpose model, infectious disease research, safety and efficacy testing, aging