The Sprague Dawley rat is an outbred multipurpose breed of albino rat used extensively in medical research. Its main advantage is its calmness and ease of handling. This breed of rat was first produced by the Sprague Dawley farms (later to become the Sprague Dawley Animal Company) in Madison, Wisconsin. The breeding facilities were purchased first by Gibco and then by Harlan (now Harlan Sprague Dawley) in January 1980.
The average litter size of the Sprague Dawley rat is 10.5. The adult body weight is 250–300g for females, and 450–520g for males. The typical life span is 2.5–3.5 years. These rats typically have increased tail to body length ratio compared with Wistar rats.