DIETARY ARGININE ON GROWTH AND MUSCLE QUALITY OF SONGPU MIRROR CARP (CYPRINUS CARPIO SONGPU) IN MID-GROWTH STAGE

The study assessed the impact of dietary arginine supplementation on the growth performance, feed efficiency, muscle attributes, and antioxidant potential of Songpu mirror carp (Cyprinus carpio Songpu) during the mid-growth stage. Six semi-refined diets containing 28.11% crude protein were formulated with dietary arginine levels of 0.71%, 1.06%, 1.41%, 1.76%, 2.11%, and 2.46%. Each diet was fed to three replicate groups of carp with an initial body weight of (298.89±15.30) g for 56d. Results indicated that the weight gain rate (WGR), specific growth rate (SGR), and protein efficiency ratio (PER) exhibited an initial increase followed by a decrease as arginine levels in the feed rose, with the most pronounced enhancement occurring at 1.41% arginine. Conversely, the feed conversion ratio (FCR) demonstrated an opposite trend, showing significantly lower FCR (P<0.05) in the 1.41% group compared to the other groups except the 1.76% group. In the 1.41% arginine group, value in hardness, elasticity, chewiness, and shear force metrics were superior to the other groups. Furthermore, water loss rates for centrifugation and cooking in the 1.41% arginine group were the minimal and centrifugation water loss was significantly lower than those in the 0.71% and 2.46% groups (P<0.05). However, cooking loss rates did not vary significantly amongst groups (P>0.05). Myofibre diameter was notably reduced (P<0.05) in the 1.41% arginine group compared to those with 0.71%, 2.11%, and 2.46%, whereas myofibre density was significantly augmented (P<0.05) in other groups except for the 1.76% group. For muscle color, L^* value in the 1.76% group and b^* value in the 1.41% group were significantly lower than those in other groups (P<0.05). The a^* values exhibited an increasing trend, and highest value occurred in the 1.41% group (P>0.05). The activities of superoxide dismutase (SOD) and peroxidase (POD), catalase (CAT) and contents of glutathione (GSH), and total antioxidant capacity (T-AOC) were significantly elevated (P<0.05) in the 1.41% cohort in contrast to the other groups, whereas malondialdehyde (MDA) content in the muscle reached the lowest level in the 1.41% group, showing no significant differences (P>0.05). The expression of rapamycin target protein (tor), protein kinase B (akt), S6 protein kinase 1 (s6k1), 4E-binding protein 1 (4ebp1), and forkhead box O1 (foxo1) was substantially upregulated in muscle in the 1.41% arginine group (P<0.05). Based on WGR, SGR and FCR as evaluation indexes, binomial regression model analysis showed that dietary arginine requirements for Songpu mirror carp in growth mid-stage were 1.41% to 1.58% of feed dry matter.