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Physiological role of Arginine in growth performance, gut health and immune response in broilers: a review

SUMMARY Arginine (Arg) is one of the metabolically versatile essential amino acids. Dietary supplementation with Arg has been shown to stimulate the secretion of insulin-like growth factor while improving growth performance and feed efficiency in broilers. In addition to its role in protein synthesis, Arg is also a precursor of nitric oxide, creatine, and polyamines. It also modulates lipid metabolism by reducing total body fat accumulation to improve meat quality and antioxidant defence. Moreover, it is considered as an essential amino acid for chicks due to the absence of a functional urea cycle in birds at an early age. Arginine plays a crucial role in metabolic pathways associated with immune-competence and growth. Dietary supplementation of Arg at 12 to 15 g/kg of diet resulted in linear increase in body weight gain from 7.5 to 17% in broilers fed soybean meal-based diets. Arg acts as a key vasodilator that opposes the onset of pulmonary hypertension in broilers and is particularly beneficial under high altitude and hypoxia conditions. Dietary Arg supplementation reduces ascites-related mortality under low ambient temperatures and attenuates adverse effects of heat stress and high stock density. Moreover, in ovo feeding of Arg increased levels of secretory immunoglobulin A revealing its potential to modulate immune barrier function leading to enhanced overall immunity and intestinal health of birds. The NRC recommended levels of Arg are 1.25%, 1.10%, and 1.00% (of the broiler diet from 1–3, 4–6 and 7–8 weeks, respectively). However, other studies have reported 101, 103 and 107% of NRC recommendation of Arg for maximum feed efficiency, growth performance, and optimal immune function, from 1–3, 4–6 and 7–8 weeks, respectively, under thermoneutral conditions. This review provides insights into the optimal supplementation of Arg above NRC recommendations to improve growth performance, meat quality, and immunity of broilers.