The current study aimed to determine the dietary L‐arginine requirements of Coho salmon by evaluating key performance indicators, including growth rate, feed efficiency, nitrogen retention, and body composition. A total of 1800 juvenile coho salmon ( Oncorhynchus kisutch ) (initial weight: 0.32 ± 0.01 g) were randomly assigned to six isonitrogenous and isoenergetic dietary treatments containing different L‐arginine levels, with three replicates per group (100 fish per 240 L tank) by following a completely randomized design. The L‐arginine supplementation levels were 0% (D‐1), 0.50% (D‐2), 1% (D‐3), 1.50% (D‐4), 2% (D‐5), and 2.50% (D‐6) of the feed, resulting in cumulative dietary arginine concentrations of 2.18%, 2.60%, 2.97%, 3.41%, 3.79%, and 4.16% in the feed, respectively. Following a 14‐day acclimatization period, the feeding trial was conducted for 84 days. The survival rates were similar across the groups ( p > 0.05). However, growth performance parameters, including body weight gain and specific growth rates (SGRs), were increased with dietary arginine levels ( p 0.05). The quadratic regression analysis revealed that the estimated cumulative total dietary L‐arginine requirement for optimal FCR, SGR, BPD, and protein efficiency ratio of coho salmon was 3.29%, 3.19%, 3.33%, and 3.26%, respectively. Based on the findings, dietary supplementation with L‐arginine at an optimal level of ~1% significantly enhances growth performance, feed conversion efficiency, protein utilization, and the deposition of essential amino acids, particularly arginine, lysine, and valine, in juvenile salmon. However, supplementation beyond this level yields diminishing benefits, likely due to metabolic saturation or feedback regulation mechanisms.
Yu et al. (Thu,) studied this question.