Effect of litter size on weight gain in rats

Male rats, placed in litters of 2, 4, 8, 12 and 16 on the first postnatal day, were weighed at 3-day intervals and killed at days 21 or 58. The carcasses were assayed for total protein, DNA and lipid. Animals raised in litters of 16 were significantly smaller than any of the others at all times examined, and their carcasses contained significantly less protein, DNA and lipid. In contrast, animals raised in very small litters exhibited no persistent significant differences in body weight or composition from animals raised in standard-sized litters of 8 or 12.