Body weight and composition in the Sprague Dawley rat: comparison of three outbred sources

Body weight with age and final composition for water, fat, and protein, were measured in three outbred stocks derived from the Sprague Dawley rat. Three groups of 10 individually housed male rats from three outbred colonies (Crl:CD[SD]BR, Hsd:SD[SD], and Tac:N[SD]fBR) provided with standard rodent chow and water ad libitum were weighed weekly for 56 consecutive weeks. Rats in each group were born on the same day, and each group was born within a 4-day period. Significant group effects were found for upper weight limit, carcass weight, water, and fat content (P < 0.05). The Hsd:SD(SD) and Tac:N(SD) rats grew, in proportion to their upper weight limits, at a faster rate (P < 0.01) and contained a greater percentage of body protein (P < 0.05) than did heavier, reportedly shorter-lived Crl:CD(SD)BR rats.