Rate of growth, mature weight and life-span

Abstract

Rats which were suckled in large numbers to retard their early growth continued to grow slowly even when they were supplied with unlimited food after weaning, and they became small adults. They lived on the average for about the same length of time as much larger rats which had originally been suckled in small numbers to ensure their unrestricted growth. There was a higher mortality among the slow-growing rats in the first year of life but the effect of this was compensated in the slow-growing females by an increase in life-span among those which survived the first year. No such increase was observed in the surviving slow-growing males, and the slow-growing males as a whole had an appreciably shorter expectation of life than the fast-growing ones. The incidence of lung infections was higher in the slow-growing animals; of kidney disease and of tumours in the fast-growing ones. Kidney disease was more common in males and tumours in females. These findings do not support the view that nutritionally retarded growth necessarily promotes longevity, or that it might increase the life-span of a community.