Some enzymatic activities in chicks, liver xanthine dehydrogenase (XDH), liver alanine amino transferase (GP-T, EC 2.6.1.2), liver aspartate amino transferase (GO-T, EC 2.6.1.1) and kidney arginase (EC 3.5.3.1) were studied in chicks fed 2 types of protein, soybean or gluten at 4 levels 10, 20, 30 and 40% in the diet.The determinations were conducted on 10 and 17-day-old chicks. The increase of the enzymatic activity as a function of the protein level in the diet gives a typical curve for the tested protein. The better comparison was obtained while the curves for the liver XDH were compared on 10-day-old chicks.