Growth and reproduction upon simplified food supply

Abstract

Rats were fed rations consisting of white bread (made without milk or butter) either alone or with only one other article of food. Later, ground whole wheat was substituted for white bread in several cases.

In preliminary experiments with animals placed upon the experimental rations at the time of weaning, bread alone resulted in cessation of growth at once and death after about six weeks. With bread and meat there was some growth at first, but the survival period was only slightly longer than with bread alone; with bread and apple there was no growth, but the survival period was considerably longer; with bread and turnip there was continuous slow growth; with bread and milk there was continuous growth at a normal rate. In this case the bread and milk ration consisted of equal weights of fresh bread and market milk, making a food mixture in which the white bread furnished four fifths and the milk one fifth of the total calories. On this ration young rats of both sexes (taken at weaning time from mothers which were receiving mixed food) made normal growth and the males were capable of normal reproduction but the females usually failed to breed and none of them raised any young.

On a ration containing the same proportion of milk (about one fifth of the total calories) but with whole wheat instead of white read or patent flour, young were successfully suckled (though at the cost of considerable loss of weight on the part of the mother) and are growing at somewhat less than the average rate.

When about two fifths of the total calories were supplied by milk and the rest by whole wheat, the mother has suckled the young without undue loss of weight and the young have made a fully normal rate of growth.