Abstract
The effect on the growth rateFor convenience the βgroth rateβ is used throuthout this paper to signify βrate of weitht gainβ.
of male weanling rats of progressively raising the level of bread protein in the diet, by adding increasing amounts of gluten, has been investigated. With additions of dried gluten as 10, 20, 30, 40 and 50% of a basic bread diet there was a slow increase in growth rate as the protein content was raised, and the increase was approximately proportional to the quantity of gluten added. All the diets were still deficient in lysine and, owing to this deficiency, the growth rate at even the highest protein level examined, about 44%, was only about 3.3 g./rat/day. This is only about three times the rate obtained on a diet of ordinary bread (12β13% protein) and considerably less than the rate on a diet of ordinary bread supplemented with lysine and threonine (about 4.8 g./rat/ day). When Lβlysine was added to correct the deficiency of this aminoβacid in the glutenβbread diets, the growth rate increased rapidly as the gluten content of the diet was raised, reaching a maximum value when the gluten addition was 10% of the diet (protein content about 20%). Under these conditions the growth rate was high (about 5.0 g./rat/day), equal to that obtained by adding 15% of casein to the basic bread diet, and was not increased by raising the gluten content to higher levels. These results are interpreted in relation to the lysine and threonine contributed by the gluten supplements, and their relevance to the suggested official standards for highβprotein breads is noted.