Effect of Protein Level of Diet on Nitrogen Excretion in Fowls

Abstract

Nitrogen metabolism in the fowl was investigated using White Leghorn cockerels with artificial anuses. When fed protein-free diets the excretion of uric acid and ammonia increased with an increase in nitrogen intake. The excretion of urea and total creatinine was relatively constant. Total nitrogen excretion in the urine of birds fed a protein-free diet was higher than that estimated from the regression equation calculated with the data of varying levels of protein. This high nitrogen excretion is due to the ammonia, urea and creatinine excretion. Since a protein-free diet lowers the pH of urine, the excess of excreted ammonia with this diet is considered to be a regulator of the disturbed acid-base balance. There is a highly significant correlation not only between total urinary nitrogen and the sum of uric acid and ammonia nitrogen, but also between total urinary nitrogen and uric acid nitrogen alone. This suggests that the total urinary nitrogen can be estimated by determining the uric acid nitrogen of the fowl's droppings. Birds receiving diets containing more than 3% of casein gained body weight, whereas birds receiving a protein-free diet lost body weight. When birds, weighing 1.5 to 2.0 kg, were supplied with 2.8 g of casein and 51.5 g of starch-oil mixture (calculated metabolizable energy: 280 kcal), they maintained their body weight, but birds receiving 33 g or less of starch-oil mixture lost body weight.