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

Many of previous studies on lactating animals with natural litters did not support the negative link betweenlitter size and pup mass; however, artificial manipulation of litters could be an option to support that. Inthis 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 micewere assigned for control group. Mother’s body mass and food intake were daily measured throughout theexperiment. Litter size, litter mass, pup mass, mortality rate of pups in the studied groups were also dailymeasured throughout lactation. The lactating mice in both groups significantly ate more food intake comparedto non –reproducing mice. Mice with enlarged litters had significantly greater food intake compared to themice with reduced litters. Litter masses at weaning of SL mice were significantly higher compared to theSS mice. However, pup mass at weaning was significantly lighter in SL mice compared to the pup mass inthe SS mice. Our present study concludes that the litter size of manipulated litters was negatively associatedwith pup mass at weaning