L-ornithine-L-aspartate enhances protein anabolism and growth performance in broilers by modulating the...

Dysregulation of hepatic nitrogen metabolism precipitates ammonia (NH₃) accumulation, severely compromising broiler growth performance and muscle protein homeostasis via the liver-muscle axis. While L-ornithine-L-aspartate (OA) enhances NH₃ clearance and mitigates sarcopenia in human liver disease, its effects and mechanisms on nitrogen metabolism and muscle development in broilers remain limited.

This study investigated the impact and underlying mechanisms of dietary OA supplementation on white-feathered broilers.

Four experiments were conducted using Arbor Acres broilers. Experiments 1 and 2 evaluated dietary OA (0-750 mg/kg) to determine the optimal inclusion rate (400 mg/kg). Experiment 3 established a stable hyperammonemia model via intraperitoneal injection of ammonium acetate. Experiment 4 utilized a 2 × 2 factorial design (0 or 400 mg/kg OA × saline or ammonium acetate challenge) to elucidate OA's protective mechanisms against NH₃-induced toxicity.

OA supplementation (optimally 400 mg/kg) significantly increased body weight and feed conversion efficiency. OA enhanced Gln metabolism by regulating hepatic nitrogen metabolism. Specifically, it promoted Gln synthesis (increased glutamine synthetase activity and Gln levels) and NH₃ detoxification, thereby improving amino acid utilization. Furthermore, OA promoted protein synthesis by activating the hepatic mTOR signaling pathway. At 42 days, 400 mg/kg OA significantly increased breast muscle percentage, improving both growth and slaughter performance. Additionally, OA significantly increased levels of Gln in breast muscle, and effectively reduced NH₃ and myostatin levels, thereby alleviating the suppression of muscle growth. OA also promoted muscle development by increasing protein synthesis and deposition through up-regulating the mTOR signaling pathway and down-regulating NF-κB expression.

OA safely improves broiler growth and slaughter performance by enhancing Gln production and NH₃ detoxification through the liver-muscle axis, and increasing protein synthesis and deposition. With a confirmed 5-fold safety margin, OA serves as a safe and novel feed additive to optimize nitrogen metabolism in poultry production.