MATERNAL EFFECTS ON LITTER SIZE IN MICE

Abstract

An extensive set of data from a selection experiment for 12-day litter weight in mice was analyzed to determine whether standardizing litter size to a constant number at 5 days of age removed the negative environmental maternal effect (acting through adult body weight of the daughter) on litter size. The regression of daughters' litter size on dams' litter size was 0.070 ± 0.013 (d.f. = 851), which was partitioned into a relatively large direct additive genetic effect (0.067) and a negligible environmental maternal effect (0.003). Evidence is also presented that a positive genetic maternal effect influences litter size, which is probably mediated through adult body weight.