Abstract
In this report a summary is given of the results of studies on growth, nitrogen storage, metabolism and composition of gains of rats on diets containing 8% and 12% lactalbumin and casein.
Growth Experiments. A total of 2 series of animals was used consisting of 3 groups. The rats of the same group were litter mates and of the same sex and weight, and all rats were confined in individual cages. One series of 9 animals was fed a diet containing 8% protein and another series was fed 12% protein. The animals were weighed every other day and accurate food consumption records were kept. The experimental period lasted 70 days. The average results of these growth experiments showed that the gain in body weight per gram of protein intake was 1.65 gm. for 3 animals fed a diet containing 8% casein, and 2.14 gm. for 6 animals on an 8% lactalbumin diet.
On a 12% level of protein these figures were 1.60 and 1.86 for casein and lactalbumin, respectively. Nitrogen storage was determined in the rats of the growth experiments described above. In each group a fourth rat, litter mate of the same sex and weight, was sacrificed at the beginning of the experiment and the carcass was analyzed for nitrogen. These rats served as controls. After the feeding period of 70 days all animals were sacrificed. The percentage of total food nitrogen stored on each ration was computed by subtracting the amount of nitrogen found in the controls killed at the beginning of the experiment from the amount of nitrogen found in the animals that had been on the ration for 70 days. The biological value of the protein was defined as the ratio (expressed in percentage) between the nitrogen stored in the body to the nitrogen intake during the feeding period.
Get full access to this article
View all access options for this article.