Evaluation of Fermented Soybean Meal to Replace a Portion Fish Meal on Growth Performance, Antioxidant Capacity, Immunity, and mTOR Signaling Pathway of Coho Salmon (Oncorhynchus kisutch)

Evaluation of the Effect of Dietary Manganese on the Intestinal Digestive Function, Antioxidant Response, and Muscle Quality in Coho Salmon

Manganese (Mn) is a nutritional element required for fish growth and physiology functions. In this study, we examined the effect of Mn on the intestinal digestive function, antioxidant response, and muscle quality in coho salmon (Oncorhynchus kisutch). Nine hundred salmons with initial weight approximately 0.35 g were fed with six isoproteic and isoenergetic diets formulated to contain 2.4, 8.5, 14.8, 19.8, 24.6, and 33.7 mg/kg Mn for 84 days. The result showed that the activity of trypsin and lipase was elevated, whereas α-amylase activity was not affected by various Mn diets in intestine. Dietary Mn elevated the activity of Mn-superoxide dismutase (Mn-SOD), total superoxide dismutase (T-SOD), glutathione peroxidase (GSH-PX), and catalase (CAT), but had no influence on copper/zinc-superoxide dismutase (Cu/Zn-SOD) in intestine. Dietary Mn at 8.5, 14.8, 19.8, 24.6, and 33.7 mg/kg enhanced the gene expression level of protein kinase B (Akt) and mammalian target of rapamycin (mTOR). In addition, the accumulation of Mn in muscle was enhanced with increasing levels of dietary Mn. Dietary Mn elevated the content of sodium (Na), potassium (K), magnesium (Mg), and calcium (Ca), but the content of iron (Fe) and Zn was decreased by dietary Mn in the salmon muscle. The content of fatty acids and amino acids was enhanced by various levels of dietary Mn in muscle. Moreover, a significant quadratic effect was observed on the texture of salmon muscle. The dietary Mn requirement was 16.9-25.7 mg/kg Mn to acquire the highest value of muscle texture using the quadratic regression model. The diets at 14.8 and 19.8 mg/kg Mn had a higher score of sensory evaluation for raw muscle. Our result showed that dietary Mn affected the intestinal digestion function and antioxidant response, which may further result in the change of muscle quality in coho salmon. The result will provide reference for detecting the effect of dietary micronutrients on the muscle quality of salmons.

Alternative protein sources in aquafeed: Current scenario and future perspectives

Fish meal represents the main protein source for most commercially farmed aquatic species, as it is characterized by high nutritional value and lack of anti-nutritional factors. However, its availability and the market price have been recognized as serious problems at least for over a decade, making it necessary to search for non-conventional protein sources, as an alternative to fish meals. This review aims to comprehensively examine and critically revise the use of fish meal and all alternative protein sources explored to date on the health, welfare, and growth performance of the major aquatic species commercially interesting from a global scenario. The investigation revealed that the inclusion levels of the different protein sources, plant- and animal-derived, ranged from 10 to 80 % and from 2 to 100 % respectively, in partial or complete replacement of fish meal, and generated positive effects on health, welfare, growth performance, and fillet quality. However, the results showed that above a certain level of inclusion, each protein source can negatively affect fish growth performance, metabolic activities, and other biological parameters. Moreover, it is likely that by mixing different protein sources, the combination of each ingredient causes a synergistic effect on the nutritional properties. Therefore, the future of aquatic feed formulation is expected to be based on the blend of different protein sources. Overall, the analysis highlighted the need for additional research in the field of replacing fish meals with new protein sources, given that many knowledge gaps are still to be filled on aquatic species, which deserve to be investigated.

Effects of Dietary Chitosan on Growth Performance, Serum Biochemical Indices, Antioxidant Capacity, and Immune Response of Juvenile Tilapia (Oreochromis niloticus) under Cadmium Stress

The objective of this study was to examine the effects of varying levels of dietary chitosan supplementation on mitigating cadmium stress and its influence on growth performance, serum biochemical indices, antioxidant capacity, immune response, inflammatory response, and the expression of related genes in juvenile Genetically Improved Farmed Tilapia (GIFT, Oreochromis niloticus). Five groups of juvenile tilapias (initial body weight 21.21 ± 0.24 g) were fed five diets with different levels (0%, 0.5%, 1.0%, 1.5%, and 2.0%) of chitosan supplementation for 60 days under cadmium stress (0.2 mg/L Cd2+). The findings indicated that, compared with the 0% chitosan group, dietary chitosan could significantly increase (p < 0.05) the final weight (Wf), weight gain rate (WGR), specific growth rate (SGR), daily growth index (DGI), and condition factor (CF), while the feed conversion ratio (FCR) expressed the opposite trend in juvenile GIFT. Dietary chitosan could significantly increase (p < 0.05) the activities (contents) of cholinesterase (CHE), albumin (ALB), lactate dehydrogenase (LDH), alkaline phosphatase (ALP), acid phosphatase (ACP), and lysozyme (LZM), while glutamic pyruvic transaminase (GPT), glutamic oxaloacetic transaminase (GOT), and complement 3 (C3) in the serum of juvenile GIFT expressed the opposite trend. Dietary chitosan could significantly increase (p < 0.05) the activities of superoxide dismutase (SOD) and catalase (CAT) and significantly decrease (p < 0.05) the activities (contents) of glutathione S-transferase (GST), glutathione peroxidase (GSH-Px), and malondialdehyde (MDA) in the serum of juvenile GIFT. Dietary chitosan could significantly increase (p < 0.05) the activities (contents) of CAT, GST, GSH-Px, and total antioxidant capacity (T-AOC) and significantly decrease (p < 0.05) the contents of MDA in the liver of juvenile GIFT. Dietary chitosan could significantly increase (p < 0.05) the activities (contents) of SOD, GSH-Px, T-AOC, Na+-K+-ATPase, and Ca2+-ATPase and significantly decrease (p < 0.05) the activities (contents) of CAT, GST, and MDA in the gills of juvenile GIFT. Dietary chitosan could significantly up-regulate (p < 0.05) the gene expression of cat, sod, gst, and gsh-px in the liver of juvenile GIFT. Dietary chitosan could significantly up-regulate (p < 0.05) the gene expression of interferon-γ (inf-γ) in the gills and spleen and significantly down-regulate (p < 0.05) the gene expression of inf-γ in the liver and head kidney of juvenile GIFT. Dietary chitosan could significantly down-regulate (p < 0.05) the gene expression of interleukin-6 (il-6), il-8, and tumor necrosis factor-α (tnf-α) in the liver, gills, head kidney, and spleen of juvenile GIFT. Dietary chitosan could significantly up-regulate (p < 0.05) the gene expression of il-10 in the liver, gills, head kidney, and spleen of juvenile GIFT. Dietary chitosan could significantly up-regulate (p < 0.05) the gene expression of transforming growth factor-β (tgf-β) in the liver and significantly down-regulate (p < 0.05) the gene expression of tgf-β in the head kidney and spleen of juvenile GIFT. In conclusion, dietary chitosan could mitigate the impact of cadmium stress on growth performance, serum biochemical indices, antioxidant capacity, immune response, inflammatory response, and related gene expression in juvenile GIFT. According to the analysis of second-order polynomial regression, it was found that the optimal dietary chitosan levels in juvenile GIFT was approximately 1.42% to 1.45%, based on its impact on Wf, WGR, SGR, and DGI.

Excessive Substitution of Fish Meal with Fermented Soybean Meal Induces Oxidative Stress by Impairing Glutathione Metabolism in Largemouth Bass (Micropterus salmoides)

The application of fermented soybean meal (FSBM) is an effective strategy to alleviate the shortage of fish meal (FM) in aquaculture. However, an excessive substitution ratio often reduces fish growth and induces liver oxidative stress, while the mechanism remains poorly understood. Here, an 8-week feeding trial was conducted in largemouth bass (initial weight: 6.82 ± 0.09 g) to establish an oxidative stress model by replacing 50% of FM with FSBM (fermented by Bacillus subtilis). The results showed that FSBM substitution significantly reduced the growth performance of largemouth bass, including the weight gain rate and specific growth rate. Moreover, FSBM significantly reduced the contents of essential amino acids and total free amino acids in muscle, along with the mRNA expression of amino acids and small peptide transporters. Enzyme activity detection and liver sections showed that FSBM substitution caused liver oxidative stress, indicating the successful construction of an oxidative stress model. An integrated analysis of transcriptomic and metabolomic data revealed that FSBM substitution impaired glycine, serine and threonine metabolism, as well as glutathione metabolism. In addition, the ratio of reduced glutathione (GSH) to oxidized glutathione (GSSG) was decreased in the FSBM group, which may explain the mechanism of oxidative stress caused by FSBM substitution. Considering that glycine is an important component of glutathione synthesis, key genes involved in glycine metabolism (glya, gnmt and agxt) and dietary glycine supplementation should be valued to improve the availability of FSBM. This study reveals for the first time the importance of non-essential amino acids in improving the utilization of plant-based protein sources and provides original insight for the optimization of aquatic feeds.

The Effects of Fermented Feed on the Growth Performance, Antioxidant Activity, Immune Function, Intestinal Digestive Enzyme Activity, Morphology, and Microflora of Yellow-Feather Chickens

This experiment was conducted to investigate the effects of fermented feed on growth performance, antioxidant activity, immune function, intestinal digestive enzyme activity, morphology, and microflora of yellow-feather chickens. A total of 240 one-day-old female yellow-feathered (Hexi dwarf) chickens were randomly divided into two treatment groups, with six replicates per group and 20 chickens per replicate. The control group (CK) received a basal diet, whereas the experimental group was fed a basal diet of +2.00% fermented feed (FJ). The trial lasted for 22 days. Compared with the CK, (1) the growth performance was not affected (p > 0.05); (2) immunoglobin a, immunoglobin g, immunoglobin m, interleukin-1β, and interleukin-6 were affected (p < 0.05); (3) liver superoxide dismutase, glutathione peroxidase, and catalase were higher (p < 0.05); (4) trypsin activity in the duodenum and cecal Shannon index were increased (p < 0.05); (5) the relative abundance of Actinobacteriota in cecum was increased (p < 0.05); (6) the abundance of dominant microflora of Bacteroides as well as Clostridia UCG-014_norank were increased (p < 0.05). In summary, the fermented feed improved the growth performance, antioxidant activity, immune function, intestinal digestive enzyme activity, morphology, and microflora of yellow-feather chickens.