A 2-year comparison study of Crl:CD BR and Hsd:Sprague-Dawley SD rats

In this 2-year study, the suitability of the Hsd:Sprague-Dawley SD (SD) as a replacement for the Crl:CD BR (CD) rat was assessed by comparing survival rates, palpable mass incidence, body weights, food consumption, clinical laboratory parameters, and necropsy and histopathology observations. At week 104, survival rates in the CD and SD males were 29 and 49%, respectively. Corresponding survival rates in females were 44 and 63%. The total numbers of animals with palpable masses and animals with neoplasms were similar in the CD and SD rats; however, the total numbers of palpable masses and neoplasms were higher in the CD rats. The incidence of corneal lesions was higher in the SD rats, whereas the incidence of lenticular opacities was higher in the CD rats. Body weights, food and water consumption, and organ weights were significantly lower in the SD rats. In contrast, food intake per kilogram of body weight was slightly higher in the SD rats. Numerous differences in clinical laboratory parameters between the CD and SD rats were observed. Some of these were consistent with the increased prevalence of kidney disease and secondary sequelae in the SD rats. Taken together, the better survival, smaller size, and lower food consumption of the SD rat may make it a better model for chronic bioassays. However, the increased propensity for spontaneous renal disease may limit the utility of the SD rat for studying nephrotoxic compounds.