Dietary arginine: metabolic, environmental, immunological and physiological interrelationships

Arginine is an essential amino acid for chickens due to the absence of a functional urea cycle in birds. Arginine plays critical roles in metabolic pathways associated with growth and immune-competence. Likewise, as a precursor of nitric oxide synthesis, arginine is important as the key vasodilator that opposes the onset of pulmonary hypertension in broiler (meat-type) chickens. Dietary arginine levels in commercial broiler diets meet NRC recommendations. However, this review shows that NRC recommendations may not be adequate to support maximal growth, support arginine-depleting immune responses, and prevent the onset of pulmonary hypertension in broilers reared under rigorous environmental conditions. Dietary composition is highly important and broiler performance may suffer when insufficient levels of arginine are included in the diet. Fortification of broiler diets with supplemental arginine may be necessary under such circumstances.