Abstract
The relationships between litter size, offspring weight, and behavioral development were investigated in 924 offspring from 74 litters of CD-1 control mice. The litters were measured for litter size and offspring weight on postnatal days (PND) 0, 4, 7, 14, and 21 during the lactation period. The offspring were examined for behavioral development including surface righting, negative geotaxis, cliff avoidance, swimming behavior, and olfactory orientation. Offspring weight decreased as litter size increased at PNDs 4, 7, 14, and 21 in both sexes, and the coefficients of determination (r2) of the regression analysis were more than 0.5 and significant (P < 0.01) for each sex. The relationships between litter size and behavioral development were assessed using regression analyses, and litter size incurred few significant effects on the behavioral developmental variables (r2 < 0.5 in each case). The relationships between offspring weight and behavioral development were also assessed using regression analyses, and similarly offspring weight showed few significant effects on the behavioral developmental variables (r2 < 0.5 in each case).
