Milk production in mice

Abstract

1. Lactation was studied quantitatively in a heterogeneous stock of laboratory mice, in order to find out whether the milk production of mice could be satisfactorily evaluated from measurements of the growth of the young; and, if individual differences were proved to be readily detectable, to find out to what extent these differences were heritable.2. The total weight of the litter suckled, at 12 days of age, was found to provide a convenient measure of milk production.3. Since the amount of milk given by a mouse is greatly influenced by the number of young suckled, allowance for differences of litter size was made by means of an index of performance which expressed the amount of milk given by a mouse at a particular lactation as a percentage of the average amount given to litters of that size. The index of performance thus evaluated the response of the mouse to a standard stimulus and gave no indication of the maximum productivity of the mouse.