Remember that the objective is to evaluate the possibility of replacing soybean meal with the novel ingredient, the latter presumably has about 15% crude protein while the former is assumed to contain 40% crude protein. Hypothetically the control diet contained about 20 g of soybean meal for every 100 g of the complete diet. Replacement of 15% of the soybean meal (i.e. 3 g inclusion of the novel diet per 100 g of the complete diet), 30 % (total inclusion of 6 g per 100 g diet) and 45% (total inclusion of 9 g novel ingredient per 100 g diet). thus, the absolute inclusion were small enough that protein content varied little. Mathematically, if one considered the small absolute replacement of 3, 6, and 9 g per 100 g diet, total protein should vary very little. Do you think that the experimenter should try (1) to maintain the proportion of all ingredients except those of soybean and the novel ingredient (replacing one for the other) or (2) the experimenter should try to maintain the total protein of the diet (i.e. making the diet isonitrogenous) even if it meant varying other dietary components such as starch to make the diets isonitrogenous?