L-Arginine is a basic amino acid and serves as the most abundant nitrogen carrier in tissue proteins. In mammals, it is considered a conditionally essential amino acid. However, poultry are unable to synthesize arginine on their own, making it an essential amino acid that must be supplied through the diet. The dietary requirement for arginine in broilers varies with the season. During the summer, the requirement increases to support optimal growth under heat stress conditions, so higher levels of arginine should be included in the diet.
Animal Nutrition Technical Manager
CJ BIO China
ARGININE IS AN ESSENTIAL AMINO ACID FOR BROILERS
Uric acid is the vehicle for nitrogen excretion in poultry metabolism. It originates from the purines which derive their nitrogen from amino acids. Therefore, arginine would not be expected to function in nitrogen transfer to the extent that it does in animals with an ornithine cycle (Figure 1). Klose (1938) and Leveille (1959) studied that arginine is essential for the growing chick as well as the adult bird. Arginine could not be replaced by ornithine and citrulline. Tamir and Ratner (1963) found that carbamyl phosphate synthetase has not been detected in any tissue, while ornithine transcarbamylase, argininosuccinate synthetase, and argininosuccinase lyase have been found in the kidney but not in the liver. Small amounts of argininosuccinate lyase activity were also presented in the spleen, pancreas, and intestinal tract. Jones et al. (1961) studied the enzymes of arginine metabolism in rats. Compared to the enzymes in rats, it can be concluded that arginine is essential for broilers because they lack carbamyl phosphate synthetase.
NUTRITIONAL EFFECT OF ARGININE IN BROILERS
The Requirements of Arginine in Broilers
Arginine is an essential amino acid for broilers. The requirement of arginine in broilers is affected by many factors such as breed, environment, etc. Moreover, Corzo (2020) indicated that the ratio of dArg/dLys increased as the birds’ age increased. The optimum dArg/dLys value to optimize BW gain and FCR from 1-14d was 106 for both parameters, however, it was determined to be 129 and 116 from 25 – 42d, respectively. The arginine requirement also increased in broilers fed diets without antibiotics. Ruan et al. (2020) demonstrated that growth performance of Qingyuan partridge chickens, which belong to the yellow-feathered broilers, was improved by increasing dietary Arg from 8.5 to approximately 12.0 g/kg in antibiotic-free diets. The study also showed that ileal secretary IgA levels were increased by Arg supplementation. Secretory IgA is the primary immunologic barrier preventing intraluminal pathogens from colonizing the intestinal mucosa, and this aids in maintaining homeostasis with the commensal microbiota. It may be expected that arginine plays important roles in intestinal health and immunity.
The Arginine Requirement Increases in Heat Stress
From market application experience, the requirement for arginine in broilers is different in different seasons. In the summer, nutritionists might appropriately increase the arginine level of the diets in order to avoid poor growth performance. A trial run by Sirathonpong et al. (2019) studied increasing arginine:lysine (Arg:Lys) requirement at high temperatures. Ross 308 broilers were reared under 27-30℃ and fed 5 different diets with Arg:Lys of 0.85, 0.95, 1.05, 1.16, and 1.26. Trial resulted in consistent improvements in feed conversion without any loss in growth and meat yield (results shown in Figure 2). Under heat stress, the organs such as the small intestine, liver, and spleen are experiencing ischemic and hypoxic conditions. Arginine was shown to have an important role in vasodilation and adversely changing blood flow. That may be why arginine plays a functional role under heat stress.
FUNCTIONAL EFFECT OF ARGININE IN BROILERS
Improve Intestinal Health
Zhang (2018) conducted six experiments to study the effects of L-arginine supplementation on the intestinal mucosal injury induced by the intestinal pathogenic bacteria in broiler chickens and related mechanisms. One experiment demonstrated L-arginine supplementation could inhibit Clostridium perfringens overgrowth and alleviate intestinal mucosal injury by promoting innate responses and maintaining intestinal barrier function. Dietary L-arginine supplementation prevented C. perfringens challenge-induced circulating arginine deficiency and normalized arginine transport and metabolism. L-arginine also plays a role in downregulated the activated JAK-STAT (jejunal Janus kinase, signal transducer and activator of transcription) signaling pathway. In another, L-arginine alleviated the intestinal inflammation and mucosal injury of chicken challenged by Clostridium perfringens. The arginine supplemented diet fed during the whole period exhibited more beneficial effects than that only fed during the infection stage.
Improve Immunity
Tan (2014) studied the effects of dietary L-arginine supplementation on growth performance, immunosuppression, inflammation, and intestinal barrier dysfunction in broiler chickens. The results demonstrated that additional dietary arginine supplementation is required to get the optimal growth performance and immune function for immunosuppressive broilers, and arginine supplementation attenuated IBDV (Infectious Bursal Disease Vaccine) inoculation induced immunosuppression via modulating circulating T cell subpopulations. Dietary arginine supplementation attenuated intestinal mucosal disruption of coccidiosis-challenged chickens probably through suppressing TLR4 and activating mTOR complex 1 pathway, and attenuated the overexpression of pro-inflammatory cytokines probably through the suppression of the TLR4 pathway and CD14+ cells percentage.
CONCLUSION
As an amino acid, arginine in poultry is essential. It plays a nutritional and functional role in broilers. The requirement of arginine is increased in antibiotic-free diets and during heat stress in order to ensure the growth performance of broilers.
About Xiaoli Dong
Getting her Ph.D in animal nutrition from the Chinese Academy of Agricultural Sciences, Xiaoli Dong joined CJ BIO China in 2015 working in the amino acid technology department. Now, she works as a technical director and is responsible for the application and promotion of small variety amino acid in Chinese markets.
