Effects of selection on growth, body composition and food intake in mice: II. Correlated responses in reproduction

Abstract

SummaryFemale reproductive performance is reported in mice selected for ten generations for one of three criteria: either appetite (A), fat percentage (F) or total lean mass (P). For each criterion lines were selected for high (H) or low (L) performance, with contemporary unselected controls (C). In theAandPlines, litter size changed in the direction of the selected criterion, the changes being larger and more rapidly established in theAthan in thePlines. At generation 10, the differences in litter size between high and low lines were 2·6 live young born in theAlines, and 1·0 live young born in thePlines. The differences in 6-week weight between the high and low lines were 3·5 g in theAlines, 6·5 g in thePlines. Changes in ovulation rate were the primary reason for changes in litter size, the differences between the high and low lines being 3·8 corpora lutea for theAlines, and 3·1 corpora lutea for thePlines. Fitting body weight at mating as a covariate within lines in the analysis of ovulation rate and live foetus number removed the differences between the high and low selectedPlines, but not those in theAlines. The high and low selectedAandPlines did not differ in prenatal survival. There were no consistent differences in litter size, ovulation rate or pre-natal survival in theFlines.