Early fish domestication affects methylation of key genes involved in the rapid onset of the farmed phenotype.

Animal domestication is a process of environmental modulation and artificial selection leading to permanent phenotypic modifications. Recent studies showed that phenotypic changes occur very early in domestication, i.e., within the first generation in captivity, which raises the hypothesis that epigenetic mechanisms may play a critical role on the early onset of the domestic phenotype. In this context, we applied reduced representation bisulphite sequencing to compare methylation profiles between wild Nile tilapia females and their offspring reared under farmed conditions. Approximately 700 differentially methylated CpG sites were found, many of them associated not only with genes involved in muscle growth, immunity, autophagy and diet response but also related to epigenetic mechanisms, such as RNA methylation and histone modifications. This bottom-up approach showed that the phenotypic traits often related to domestic animals (e.g., higher growth rate and different immune status) may be regulated epigenetically and prior to artificial selection on gene sequences. Moreover, it revealed the importance of diet in this process, as reflected by differential methylation patterns in genes critical to fat metabolism. Finally, our study highlighted that the TGF-ß1 signalling pathway may regulate and be regulated by several differentially methylated CpG-associated genes. This could be an important and multifunctional component in promoting adaptation of fish to a domestic environment while modulating growth and immunity-related traits.

Improvement of growth, intestinal short-chain fatty acids, non-specific immunity and ammonia resistance in Pacific white shrimp (Litopenaeus vannamei) fed dietary water-soluble chitosan and mixed probiotics.

This study was to explore the impacts of water-soluble chitosan and mixed probiotics on growth performance, intestinal short-chain fatty acids (SCFAs) and immunity and ammonia resistance in Litopenaeus vannamei. Shrimp were fed one of four experimental diets including basal diet (CON), 0.10% water-soluble chitosan diet (WSC), 0.30% mixed probiotics (MP) and 0.10% water-soluble chitosan +0.30% mixed probiotics (SYN) for 8 weeks. Results showed shrimp fed with dietary MP and SYN diets could significantly improve growth performance and feed utilization in comparison with those of shrimp fed with CON diet (P < 0.05). Acetic acid content was significantly higher in shrimp fed with all supplemented diets compared to that in shrimp fed with CON diet (P < 0.05). Compared to shrimp fed with CON diet, dietary WSC and MP significantly influenced the contents and/or activities of aspartate aminotransferase (AST), total protein (TP), superoxide dismutase (SOD), lysozyme (LZM) in serum, SOD, malondialdehyde (MDA), acid phosphatase (ACP) in hepatopancreas and SOD and MDA in intestine. In addition, the gene expression levels of prophenoloxidase (proPO), penaiedin 3a (Pen-3a), crustin (Crustin), serine proteinase (SP), GPX and SOD in hepatopancreas, were significantly upregulated compared to those in CON diet at some time points (P < 0.05). Significantly higher survival rate in all supplemented diets were observed after ammonia challenge (P < 0.05). Therefore, the above results indicated dietary WSC and MP or SYN could enhance intestinal SCFAs content, stimulated antioxidant capacity and immune response, and increase the ammonia resistance of Litopenaeus vannamei. Besides, the growth performance was also improved by dietary MP and SYN.

Dietary inclusion of plant ingredients induces epigenetic changes in the intestine of zebrafish.

Epigenetic modifications, such as DNA methylation, can be regulated by nutrition and dietary factors. There has been a large increase in the use of sustainable plant-based protein sources in fish feed due to limitations of fishmeal resources, which are needed to sustain a rapidly growing aquaculture industry. With this major transition from marine ingredients to plant-based diets, fish are abruptly introduced to changes in dietary composition and exposed to a variety of phytochemicals, some of which known to cause epigenetic changes in mammals. However, the effect of plant ingredients on the epigenome of fish is barely understood. In the present study, the nutriepigenomic effects of the addition of pea, soy, and wheat gluten protein concentrate to aquafeeds were investigated using zebrafish as a model. A genome-wide analysis of DNA methylation patterns was performed by reduced representation bisulphite sequencing to examine global epigenetic alterations in the mid intestine after a 42-day feeding trial. We found that inclusion of 30% of wheat gluten, pea and soy protein concentrate in the diet induced epigenetic changes in the mid intestine of zebrafish. A large number of genes and intergenic regions were differentially methylated with plant-based diets. The genes concerned were related to immunity, NF-κB system, ubiquitin-proteasome pathway, MAPK pathway, and the antioxidant defence system. Epigenetic regulation of several biological processes, including neurogenesis, cell adhesion, response to stress and immunity was also observed. Ultimately, the observed epigenetic changes may enable zebrafish to rapidly regulate inflammation and maintain intestinal homoeostasis when fed plant protein-based diets.

Modulation of growth performance, non-specific immunity, intestinal morphology, the response to hypoxia stress and resistance to Aeromonas hydrophila of grass carp (Ctenopharyngodon idella) by dietary supplementation of a multi-strain probiotic.

The present study was conducted to evaluate a multi-strain probiotic (MP) on growth performance, immune and antioxidant function, response to hypoxia stress and resistance to Aeromonas hydrophila of grass carp (Ctenopharyngodon idella). Based on the viable cell counts of aerobic Bacillus spp., six experimental diets with MP supplemented at 0, 0.34, 1.68, 3.36, 6.72, 10.1 g kg-1 were formulated and 900 juveniles (7.30 ± 0.01 g) were equally distributed into 30 aquaria with respective diet for 60 days. Results showed that fish with 0.34-1.68 g kg-1 MP had better growth and feed utilization. Further, plasma total protein, albumin and high-density lipoprotein were remarkably increased with dietary MP at >1.68 g kg-1. Dietary MP supplementation at 6.72-10.1 g kg-1 strikingly elevated plasma myeloperoxidase activity and complement C3 content. For fish with MP at 1.68 and 6.72-10.1 g kg-1, their liver malondialdehyde and glutathione peroxidase were remarkably declined and promoted. After hypoxia stress, fish with 3.36-6.72 g kg-1 MP showed significantly higher respiratory burst activity. Challenge test by A. hydrophila confirmed the protection effects of MP through the decreased cumulative mortality rates. For intestinal histomorphology and enzymatic analyses, fish with 1.68 g kg-1 MP displayed significantly higher intestinal villi height, goblet cells and alkaline phosphatase activity. In conclusion, dietary MP supplementation at 1.68 g kg-1 could promote growth, intestinal morphology and antioxidant capacity, while enhancing host immunity requires higher dosages of MP. Broken-line analysis of weight gain revealed that 1.34 g kg-1 is the optimum dosage for the growth of grass carp.

Effects of dietary hydrolyzed yeast (Rhodotorula mucilaginosa) on growth performance, immune response, antioxidant capacity and histomorphology of juvenile Nile tilapia (Oreochromis niloticus).

An 8 weeks feeding experiment was conducted to evaluate the effects of dietary supplementation with hydrolyzed yeast (HY) (Rhodotorula mucilaginosa) on growth performance, hematological parameters, immune response and antioxidant ability of juvenile Nile tilapia. Five isonitrogenous and isolipidic diets (32% protein and 4% lipid) with different levels (0%, 0.125%, 0.25%, 0.5%, 1%) of HY were formulated. Each diet was randomly assigned to quadruplicate groups of fish (initial body weight 19.1 ±â€¯0.01 g). Results indicated that significantly higher specific growth rate (SGR) and lower feed conversion rate (FCR) were obtained in fish fed 1% HY diet than that of fish fed 0% HY diet (P < 0.05). Fish fed 0.25% HY diet showed the lowest value of hepatopancreas somatic indices (HSI) and significantly lower than that of fish fed 0% HY diet (P < 0.05). Meanwhile, protein and ash in the whole-body content of fish fed 1% HY diet was significantly higher than that of fish fed 0%-0.5% HY diets. Serum immunological parameters showed that the lysozyme (LZM) activity and Complement C3 content were significantly increased by dietary supplementation of 0.5%-1% HY (P < 0.05). However, dietary supplementation with 0.125%-1% HY significantly decreased the activity of myeloperoxidase (MPO) (P < 0.05). Antioxidant status in serum and liver was significantly enhanced by dietary supplementation of 0.25%-1% HY through the remarkably improved superoxide dismutase (SOD) activity both in serum and liver, the raised total antioxidative capacity (T-AOC) of serum as well as the notably reduced malondialdehyde (MDA) content in the liver (P < 0.05). However, T-AOC in the liver was not significantly influenced among all diet treatments (P > 0.05). Villi height and intraepithelial lymphocytes (IEFs) of mid-intestine were significantly higher in fish fed 0.5%-1% HY diets (P < 0.05). The challenge test demonstrated the enhanced protection against Streptococcus iniae strain by the obtained higher cumulative survival rate. In conclusion, dietary supplementation of 1% HY could maintain the better growth performance, nutrient composition as well as immune response and antioxidant capacity for juvenile Nile tilapia.