Effects of Dietary Protein and Lipid Levels on Growth, Body Composition, Blood Biochemistry, Antioxidant Capacity and Ammonia Excretion of European Grayling (Thymallus thymallus)

Abstract

This study evaluated growth, body composition, antioxidant capacity, innate immunity and ammonia excretion of European grayling (Thymallus thymallus) fed diets containing different protein and lipid contents. Six diets were produced to contain 30, 40, or 50% protein and 10 or 20% lipid. Juvenile fish averaging 25.2 ± 0.28 g were stocked into eighteen 450-L circular tanks in a recirculating aquaculture system (RAS) and fed the test diets to satiation twice daily for 12 weeks. Fish weight gain (WG) was enhanced (P < 0.05) as dietary protein increased from 30% (229% WG) to 40% (262% WG) and plateaued thereafter. Enhancing protein and lipid content of diet led to reduced feed intake. Also, feed efficiency was improved by increasing dietary protein (by 40.8%) and lipid (by 16.5%) levels. An interaction of protein and lipid was found on whole-body lipid, and muscle lipid content increased as dietary lipid level increased. Muscle arachidonic acid (ARA), eicosapentaenoic acid (EPA, 20:5n-3) and total n-6 long-chain polyunsaturated fatty acids (LC-PUFA) contents enhanced by increasing dietary protein level. Moreover, increasing fat content of diet led to enhanced muscle linoleic acid, linolenic acid, total monounsaturated fatty acids (MUFA), total n-6, ratio of docosahexaenoic acid (DHA, 22:6n-3) to EPA and n-6/n-3. However, EPA, DHA, total n-6 LC-PUFA, total n-3, total n-3 LC-PUFA, and EPA/ARA ratio decreased at higher dietary lipid level. Serum triglyceride (TG) level and lactate dehydrogenase (LDH) activity decreased as dietary protein level increased. Increasing fat content of diet led to enhanced serum TG, cholesterol and glucose concentrations and reduced alanine aminotransferase, aspartate amino transferase and LDH activities. Serum malondialdehyde concentration was enhanced by increasing both dietary protein and lipid. Furthermore, serum myeloperoxidase activity was enhanced at higher dietary lipid level. Water ammonium nitrogen (NH4+-N) concentration was measured after 5 and 24 h of last feeding, and the results indicated the reduction of ammonia excretion as dietary lipid content increased. These findings suggest that 40% dietary protein can support optimal growth of juvenile European grayling reared in RAS and increasing lipid content from 10 to 20% can improve feed utilization and reduce ammonia excretion to the rearing water.

Ameliorative Effect of Quercetin against Abamectin-Induced Hemato-Biochemical Alterations and Hepatorenal Oxidative Damage in Nile Tilapia, Oreochromis niloticus

“…Liver function enzymes are involved in several metabolic processes inside hepatocytes [ 83 , 84 ]. Their blood elevations reflect abnormal hepatic function and/or necrosis [ 85 ].…”

Effects of different protein and lipid levels on the growth performance and intestinal microflora of loach (Paramisgurnus dabryanus)

“…Meanwhile, dietary lipid, as a non-protein energy source, can provide essential fatty acids, phospholipids, sterols and fat-soluble vitamins for maintaining normal function in various physiological, developmental and reproductive processes of fish ( Ai et al., 2004 ; Chaitanawisuti et al., 2011 ; Ghanawi et al., 2011 ; Meng et al., 2019 ). Dietary lipid has a protein-retaining effect, which increases efficient utilization of dietary protein for maximum nitrogen retention and growth performance ( Welengane et al., 2019 ; Liu et al., 2021 ; Rahimnejad et al., 2021 ). Therefore, carnivorous fish fed with sufficient lipids can obtain better growth performance ( Meng et al., 2019 ; Ma et al., 2020 ).…”

Fine ultrastructural features of germ cells and spermatozoa during spermatogenesis in the European grayling, Thymallus thymallus (Teleostei, Salmoniformes, Salmonidae)

“…This species is considered an ecologically valuable bioindicator of water contamination, local habitat, and food supply ( 18 , 19 ). The European grayling is very popular for sport fishing, and its population has been supported by a long sustainable stocking program, including broodstock management ( 20 ) and reproduction ( 21 ), and larval and juvenile culture under controlled conditions ( 22 , 23 ). In this regard, understanding the spermatogenic process and spermatozoa development in the European grayling are important for increasing the knowledge about the reproduction and reproducibility of this species.…”