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. Harlan Laboratories' outbred stocks are easily
identified by their nomenclature; we follow standardized
nomenclature rules. All our stocks are designated with the holder
code, for example “Hsd,” followed by the stock abbreviation.
Outbred colonies such as Hsd:Sprague Dawley®TM
(SD®TM) rats are maintained as closed colonies of
genetically variable composition. Harlan outbred stocks have a
minimum of 200 female breeders to safeguard the outbred integrity.
Although individuals of such colonies will tend to be similar,
their genotype at a given locus is usually unknown unless the
animal is individually typed.