Effect of Litter Size Manipulation on the Reproductive Performance of BALB/C Mice

Abstract

Many of previous studies on lactating animals with natural litters did not support the negative link between
litter size and pup mass; however, artificial manipulation of litters could be an option to support that. In
this study, we manipulated the litters of lactating BALB/C mice with having two groups. Enlarged litter SL
(LS=8; N=5) and reduced litters SS (LS=2; N=6) were used in this experiment and also 7 virgin female mice
were assigned for control group. Mother’s body mass and food intake were daily measured throughout the
experiment. Litter size, litter mass, pup mass, mortality rate of pups in the studied groups were also daily
measured throughout lactation. The lactating mice in both groups significantly ate more food intake compared
to non –reproducing mice. Mice with enlarged litters had significantly greater food intake compared to the
mice with reduced litters. Litter masses at weaning of SL mice were significantly higher compared to the
SS mice. However, pup mass at weaning was significantly lighter in SL mice compared to the pup mass in
the SS mice. Our present study concludes that the litter size of manipulated litters was negatively associated
with pup mass at weaning