Effects of L‐carnitine supplementation on growth performance, histomorphology, antioxidant and immune function of Rhynchocypris lagowskii fed dietary fish oil replaced with corn oil

Abstract

The effects of L‐carnitine (LC) and dietary lipid on the growth and health of farmed fish are still conflicting. This study aimed to explore the effects of LC supplementation and dietary fish oil replacement by corn oil on growth performance, antioxidant, immune function and histomorphology of Rhynchocypris Lagowskii. Six diets were evaluated as follows: dietary fish oil as 50% and 100% replacement by corn oil, and differing in LC supplementation (0 and 400 mg/kg), were tested in R. Lagowskii for 8 weeks. The highest weight gain rate, specific growth rate and feed efficiency were observed in mix oil diets with LC. The diet with LC significantly increased the total antioxidant capacity level, total superoxide dismutase, alkaline phosphatase, lysozyme activities and immunoglobulin M, complement levels in liver and intestine compared with corn oil diet (p < 0.05). Moreover, the diet with LC significantly up‐regulated the nuclear factor E2‐related factor 2 (p < 0.05), and significantly down‐regulated the interleukin‐1‐beta and tumour necrosis factor‐alpha expression in liver and intestine compared with corn oil diet (p < 0.05). In conclusion, LC supplementation improved the weakening of growth performance, antioxidant capacity, immune function and tissue health caused by R. lagowskii intake of corn oil diets.

Evaluation of dietary fish oil: soybean oil ratios on growth performance feed utilization, haematological indices and body fatty acid composition of Keeled mullet, Liza carinata fingerlings

“…In contrast, some studies have shown results in poor growth in marine and freshwater fishes that primary dietary inclusion levels of SO (Chen et al, 2020;Jin, Mu et al, 2018). Similarly, Wang et al, (2022) showed no significant effects between the FO diet and VO diet on WG, SGR, and PER for Rhynchocypris lagowskii. Similar results are reported that no negative effects on growth performance were observed because of the substitute of dietary FO with VO of some fish species blunt snout bream, (Megalobrama amblycephala), red hybrid tilapia (Oreochromis sp), rainbow trout (Oncorhynchus mikyss) and marine fish European sea bass (Dicentrarchus labrax) , Japanese Seabass (Lateolabrax japonicus) (Roy et al, 2020;Torrecillas et al, 2017).…”

“…At high dietary SO including, the body lipid accumulation more compared to other fish gropus. Similarly the replacement of SO for FO increased tissue fat content in grass carp Ctenopharyngodon Idella (Liu et al, 2022); large yellow croaker (Du et al, 2017) and seabream (Izquierdo et al, 2015) .…”

“…These results combined imply that SO supplementation may affect lipid retention in the various fish species differently. Additionally, n-3 PUFAs may prevent the synthesis of fatty acids and lessen the buildup of tissue fat (Liu et al, 2022;Qin et al, 2022).…”

“…Hence the research interest in alternative fat sources is increasing to ensure the reduction of the amount of FO in aqua-feeds and to achieve long-term development of the aqua-feed industry. (Watson et al, 2020;Katsik et al,2021;Liu et al, 2022).…”

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the nutritional strategies developed to bridge the gap between supply and demand for animal protein from seafood, but this development must be sustainable (Aboseif et al, 2022 a,b; Flefil et al, 2021). Fats are important in the aquaculture feed industry, as they are the main source of essential FA and provide energy for fish (Wang et al, 2022; Zorlu et al, 2022). Fish oil (FO) is the primary ideal lipid source in aquatic feeds which is high in n-3 long-chain polyunsaturated fatty acids (n-3LC-PUFA) such as eicosapentaenoic acid (EPA, 20:5n-3) and docosahexaenoic acid DHA, 22:6n-3 (Fukada et al, 2020;He et

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