Strain-specific differences in lactation performance of mice

The QSi5 inbred strain of mice was established from an outbred Quackenbush-Swiss strain by full-sib inbreeding and selection on the basis of increased litter size and shortened inter-litter interval in the Department of Veterinary Physiology (later REPROGEN) , University of Sydney (Holt et al., 2004). The strain has an average litter size of more than 13 pups, and females commonly nurse up to 18 pups with greater than 90% survival to weaning. Along with an increased body weight (BW), these traits are clearly indicative of enhanced lactation performance (Knight et al., 1986). Indeed lactation performance, assessed by a weigh-suckle-weigh method, was 3-fold greater in QSi5 mice than the CBA strain (Riley et al., 2006). In this study, we utilize the divergent phenotypes of QSi5 and CBA/CaH mice to identify genes associated with enhanced mammary gland capacity. Keywords: Strain differences Five replicates from each of the two strains CBA and QSi5 were used for gene expression profiling. Mice were force weaned after 9 days of first lactation and the fourth inguinal mammary glands were collected.