Fillet texture, physicochemical indexes, muscle cellularity and molecular expression in muscle of Yellow River carp (Cyprinus carpio haematopterus) in response to dietary hydroxyproline supplementation

The 8-week rearing trial was conducted to estimate the effect of dietary hydroxyproline (Hyp) supplementation on growth performance, amino acid profiles, fatty acid profiles, and collagen concentration in muscle samples, liquid holding capacity (LHC), pH, cooking loss and antioxidant activities in flesh of post-mortem, histo-morphology, ultrastructure and molecular expression of muscle samples, and raw-and cooked-fillet texture characteristics of Yellow River carp (Cyprinus carpio haematopterus). Six isoproteic and isolipidic practical diets were formulated to contain graded levels of Hyp (1.36, 3.93, 7.14, 8.86, 11.45 and 13.69 g/kg of dry matter). A total of 840 carps with an average initial weight of 17.90 & PLUSMN; 0.28 g were randomly allocated to 24 polypropylene tanks with funnel-shaped bottom (400 L capacity filled to 300 L and 35 fish per tank). The results showed that no significant differences were found in growth performance and morphology parameter among all treatments (P > 0.05). With the increase of dietary Hyp levels, the glycine (Gly) content, and the proportion of 22:6n-3, n-3 PUFA and collagen concentration in carp fillet showed a significant ascending tendency, while arginine and proline were in downtrend (P < 0.05). Liquid loss, lipid loss and cooking loss were significantly decreased with the increasing dietary Hyp levels (P < 0.05), and the pH values in muscle samples of carp fed with dietary Hyp (> 3.93 g/kg) were significantly higher than that in control group (P < 0.05). Dietary Hyp supplementation improved the antioxidant properties of hepatopancreas and muscle with the increasing dietary Hyp levels (P < 0.05). Overall, we posed that appropriate dietary Hyp supplementation can promote myogenesis and collagen synthesis in muscle of carp, ultimately improved the raw-and cooked-fillet texture characteristics. The current research will be contributed to find an efficient way to ensure predictable and firmer texture of farmed Yellow River carp.