Longevity and reproductive comparisons for male ACI and Sprague-Dawley rat aging colonies

ACI male rats had a life span approximately one-half year greater than that of Sprague-Dawley male rats. For ACI male rats, median survival was 31.5 months for virgins and 30 months for breeders; for Sprague-Dawley male rats, median survival was 24.5 months for virgins and 25 months for breeders. There was increased fertility of aged ACI males relative to Sprague-Dawley males. ACI males, approximately 2 years old, sired an average of 3.8 litters during a 6-month breeding period, while Sprague-Dawley males of similar age sired an average of 0.9 litters within an equivalent period.