Effects of preweaning nutrition on weight gain during pregnancy in mice.

Previous work has shown that preweaning litter size affects the response of adult mice to dietary induced obesity, with animals reared in small litters showing increased hyperphagia and weight gain. The present work addressed whether a similar effect would be seen in the weight changes normally accompanying pregnancy and lactation. B6D2F2 mice were reared in small (4), medium (8) and large (12) litters. Adult females from each of these conditions were mated with males from medium litters and their body weight and food intake measured throughout pregnancy and lactation. Food intake increased during pregnancy and correlated with the dams' litter size, but the amounts consumed by all groups appeared similar. This was also true of maternal weight gain during pregnancy, pup weight and litter size. During lactation, the only differences were that animals which had been reared in large litters ate more food and weaned heavier pups than those in medium litters. These results differ from those previously obtained on dietary induced obesity, supporting different regulatory mechanisms in the two conditions.