Diets of cooked maize meal and dried skim milk were fed to newly weaned mice for 2 weeks, and to lactating females for 3 weeks. The diets ranged from 16% to 100% maize, with complementary amounts of from 84% to 0% milk and a 5% supplement of yeast.

Live-weight gains from 3 to 5 weeks of age were greatest when an intermediate diet containing 76% maize was fed. Average gains on 16%, 76% and 100% maize were 8·0 g, 17·7 g and 5·5 g respectively. The full sib phenotypic correlation was 0·45 but gains were independent of weaning weight. No carry-over effect was detected from maize-milk diets that had been fed to the dams; the dams' own gains at the same age had little influence on their offspring.

Weight of food consumed per mouse varied little between diets despite marked differences in gain. Food and energy intakes relative to gain showed no trend between 16% and 88% maize but doubled between 88% and 100% maize. Protein was used most economically for gains on 88% maize.

There were health problems. When high milk diets were first used many mice suffered from diarrhoea. A few mice on 95% maize, whose dams had been given the same diet during lactation, died without prior symptoms. Mice on 100% maize were thirsty, but not glycosuric.

Females nursing litters on high milk or high maize diets drew on reserves in the carcass, liver, pancreas, spleen and fat. In addition, high milk diets caused hypertrophy of kidneys and caecum, and diarrhoea.