Five different brands of dry milk and freeze dried milk were used in rat feeding trials to study their nutritive value and to assess the effect of the drying process on their nutritive value by using growth response, weight gain, food efficiency and relative nutritive value (RNV). Brand I milk gave better growth response, weight gain and food efficiency than any other dry milk studied, while brand V gave the least values. Freeze dried milk gave better growth response, weight gain and food efficiency than brand I milk. Using Slope-ratio assay, freeze dried milk gave the best RNV compared to all dry milks tested on the basis of the two response parameters used, weight gain and moisture gain.

Five different brands of instant dry whole milk that are most commonly used, and freeze dried milk were analyzed for nitrogen, fat, ash and 4 inorganic constituents and compared with human milk. The composition of the milks differed considerably. The protein content varied widely, ranging from 11.6 to 24.5%. Fat content did not differ widely, ranging from 24.9 to 29.5%. Freeze dried milk had the highest fat content (42.6%). Three out of the five brands of dry milk studied were spray dried and the remaining two were roller dried. All milks tested contained considerably more sodium, potassium, calcium and phosphorus solid than human milk, some of them the four fold amount of calcium and phosphorus.