Dietary L-carnosine enhances the growth, muscle hardness and protein deposition in red swamp crayfish (Procambarus clarkii)

Abstract

This study aimed to evaluate the effects of dietary L-carnosine on growth performance and muscle quality in red swamp crayfish (Procambarus clarkii). A total of 324 red swamp crayfish, with an initial body weight of 6.19 ± 0.03 g, were randomly divided into 6 groups of three replicates and 54 crayfish per group (18 crayfish per replicate). Six experimental diets containing graded levels of L-carnosine (3.35, 59.28, 106.84, 222.20, 452.93, and 821.16 mg/kg) were fed for 8 weeks. Regression analysis revealed dose-dependent responses in multiple parameters. Weight gain rate, specific growth rate, protein efficiency ratio, protein deposition rate, muscle percentage, whole-body and muscle crude protein content, muscle textural properties (hardness and chewiness), hydroxyproline levels (alkaline-insoluble and total), myofiber density, small myofiber proportion (<50 μm), and total amino acid content exhibited quadratic trends (P < 0.05), with peak values observed in the 452.93 mg/kg group. Conversely, feed conversion ratio and large myofiber proportion (>70 μm) showed significant quadratic decreases (P < 0.05), reaching their lowest values at 452.93 mg/kg. Transcriptional analysis demonstrated that, compared with the 3.35 mg/kg L-carnosine group, the 452.93 mg/kg L-carnosine group significantly regulated genes involved in several key pathways: mTORC1 signaling (igf-1, pi3k, akt, tor, s6k1, and 4ebp1), eIF2B-eIF2 signaling (eif2a), ubiquitin-proteasome system (ub, psma2, psmc1, and murf1), autophagy-lysosomal system (atg16l1, atg5, beclin1, and atg12), TGFβ /Smads pathway (TGF-β1, smad6, smad3, smad4, and colla1), and myogenic regulators (mef2a, mef2b, and mstn) (P < 0.05). These molecular modulations were consistent with observed phenotypic improvements. Overall, the findings demonstrated that a dietary L-carnosine level of 458.06–500.00 mg/kg, as determined by quadratic regression analysis, significantly enhances growth performance, feed utilization, muscle hardness and chewiness, and nutritive value in red swamp crayfish.