Availability of solid feed and growth rates of pre-weaned mice of different litter size.

The effects of litter size and availability of solid feed before weaning on the growth mice were studied. Pups of small litters (n = 3) grew significantly faster than mice of large litters (n = 10), the mean difference at weaning being about 3 g. The difference in body mass persisted after weaning; at the age of 98 d the mean difference was about 5 g. Availability of solid feed to pre-weaned mice significantly stimulated mass gain of litters consisting of 10 but not of 3 pups. Body masses of the dams during the suckling period were markedly influenced by litter size: Mice with 10 pups had increased body masses when compared with mice having 3 young. By the time of weaning, body masses of mothers with larger or small litters had become similar again just as they were immediately after parturition.