Reduced Fish Growth Research Articles

Various effects of feeding level on ammonia tolerance in Carassius auratus under different ammonia exposure stress and the underlying mechanisms

Elevated ammonia levels in aquaculture systems could reduce fish growth and survival rates and produce a range of physiological problems. Ammonia toxicity in aquatic environments was regulated by various factors. Feeding was usually reported to help in the detoxification of fish, thereby increasing their capacity to tolerate ammonia nitrogen. However, the impact of different feeding amounts on fish in relation to ammonia exposure stress remains to be determined. To determine how feeding levels affected fish's responses to different ammonia nitrogen concentrations, two acute toxicity experiments were conducted with Carassius auratus gibelio, the major strain of gibel carp in aquaculture systems in China. In Test I, fed Carassius auratus gibelio (3 % body weight) showed a higher survival rate under a specific ammonia exposure stress. 96-h LC50 of NH3-N to 3 %F gibel carp was 1.1 times greater than that for NF (no feeding). In Test II, all fed groups (2 %F and 4 %F) under low and high ammonia stress exhibited improved ammonia detoxification, evidenced by higher liver GSase, GDH, and glutamine concentrations compared with the NF treatment. Muscle glycogen levels in feeding treatments were higher than those in NF, indicating that fed fish have more energy for ammonia detoxification. While compared with low ammonia treatment (2.70 mg L−1 TAN; NH3 0.06 mg L−1), fish exposed to high ammonia levels (26.03 mg L−1 TAN; NH3 0.57 mg L−1) demonstrated a decrease in food consumption, severe histopathological alterations in their liver, gill, and kidney, and decreased GSase, GDH, and glutamine production in the liver and brain. The results partly supported our hypothesis and suggested that increasing feeding enhances gibel carp's tolerance to ammonia nitrogen. The highest detoxification metabolism was observed under low ammonia stress. While excessive ammonia exposure could inhibit feeding and damage the detoxification organs of fish, and thus reduce the detoxification metabolism of gibel carp.

Efficacy of using plant ingredients as partial substitute of fishmeal in formulated diet for a commercially cultured fish, Labeo rohita

Reliance on fish meal can be reduced by incorporating plant-based ingredients, making aquaculture more economical, sustainable and environmental friendly. In this study, the efficacy of plant protein ingredients (PPI) such as mustard oil cake (MOC), soybean meal (SBM) and rice bran (RB) as Partial substitute of fishmeal (FM) was investigated for a commercially important fish, Labeo rohita in cages for 90 days. Three experimental diets, labeled as Diet 1, Diet 2, and Diet 3, were formulated to be isonitrogenous (with protein content ranging from 32.20 to 32.29%) and iso-caloric (with gross energy ranging from 4.12 to 4.17 kcal/g). These diets contained different proportions of PPI (45, 68, and 79%) and FM (46, 23, and 11%, respectively). Square-shaped cages with a volume of 1m3 (1 m × 1 m × 1 m) were stocked with 40 fish/m3 each with an average initial weight of 52.97 g in triplicates. Fish were hand-fed to apparent satiation twice daily for 7 days a week at a feeding rate of 5% in the initial month and 3% for the rest of the culture period. 50% of the caged fish was sampled monthly to monitor growth performance and at the termination of the experiment, all the fish was harvested to measure production economics performance. The results indicated improved growth performance and higher feed utilization at Diet 2, yielding significantly (p < 0.05) higher fish production compared to Diet 3, while these parameters were insignificant with Diet 1. By replacing FM with PPI, the total feed cost compared to Diet 1 was reduced to 20.62 and 32.76% for Diet 2 and Diet 3, respectively. The replacement of 50% FM in Diet 2 also yielded a 15.61% higher total economic net return than the Diet 1 group. However, a higher inclusion rate of PPI in Diet 3 potentially reduced fish growth, with a consequent decline of 41.61% total economic net return compared to the Diet 1 group. In conclusion, the replacement of 50% FM in Diet 2 compared to Diet 1 returned a higher benefit–cost ratio (1.72) among the feeding groups. Therefore, this FM replacement experiment suggested a 50% FM replaced diet as an unconventional, cost-effective, and readily available novel protein source without compromising the inherent nutritional quality of fish and feed in the cage culture of L. rohita. The results could be widely applicable to the fast-growing approach of cage culture technology across Asia and beyond.

Increasing mercury bioaccumulation and biomagnification rates of Nile perch (Lates niloticus L.) in Winam Gulf, Lake Victoria, Kenya

The Nile perch (Lates niloticus L.) commercial fishery for Lake Victoria in East Africa is an important source of revenue and employment. We focused on shifts in food web structure and total mercury (THg) bioaccumulation and biomagnification in Nile perch, and lower food web items collected from Winam Gulf (Kenya) sampled 24 years apart (1998 and 2022). Stable isotope carbon (δ13C) values were higher in all species from 2022 compared to 1998. Stable nitrogen isotope (δ15N) values in baseline organisms were lower in 2022 compared to 1998. In Nile perch, δ15N values were correlated with total length, but the δ15N-length regressions were steeper in 1998 compared to 2022 except for one large (158 cm) Nile perch from 1998 with an uncharacteristically low δ15N value. Total Hg concentrations were lower in lower trophic species from 2022 compared to 1998. However, the THg bioaccumulation rate (as a function of fish length) in Nile perch was greater in 2022 compared to 1998 resulting in 24.2 % to 42.4 % higher wet weight dorsal THg concentrations in 2022 Nile perch for market slot size (50 to 85 cm) fish. The contrasting observations of increased THg bioaccumulation with size in 2022 against decreases in the rate of trophic increase with size and lower THg concentrations of lower food web items imply reduced fish growth and potential bioenergetic stressors on Winam Gulf Nile perch. All samples except 1 large Nile perch (139 cm total length collected in 2022) had THg concentrations below the European Union trade limit (500 ng/g wet weight). However, for more vulnerable individuals (women, children and frequent fish eaters), we recommend a decrease in maximum monthly meal consumption for 55–75 cm Nile perch from 16 meals per month calculated for 1998 to a limit of 8 meals per month calculated for 2022.

A class of their own? Water-soluble polymer pollution impacting a freshwater host-pathogen system

While the inclusion of synthetic polymers such as primary microplastics within personal care products have been widely restricted under EU/UK Law, water-soluble polymers (WSPs) have so far slipped the net of global chemical regulation despite evidence that these could be polluting wastewater effluents at concentrations greatly exceeding those of microplastics. Polyvinyl alcohol (PVA) and polyvinylpyrrolidone (PVP) represent WSPs with common industry and household uses, down-the-drain disposal and a direct route to wastewater treatment plants, conveying high risk of environmental leaching into freshwater ecosystems. The current study is the first investigating the impacts of predicted environmental concentrations of these WSPs on life-history traits of two freshwater species also constituting a disease model (fish - Poecilia reticulata and parasite - Gyrodactylus turnbulli). Single effects of WSPs on fish as well as their interactive effects with infection of the ectoparasite were determined over a 45-day exposure. Generally, WSPs reduced fish growth and increased routine metabolic rate of fish implying a depleted energetic budget, however these effects were dose, exposure time and polymer dependent. Parasitic infection alone caused a significant reduction in fish growth and enhanced fish routine metabolic rate. In contrast, a non-additive effect on metabolic rate was evident in fish experiencing simultaneous infection and WSP exposure, suggesting a protective effect of the two WSPs for fish also exposed to a metazoan ectoparasite. Off-host parasite survival was significantly lowered by both WSPs; however, parasite counts of infected fish also exposed to WSP were not significantly different from the control, implying more complex mechanisms may underpin this stressor interaction. Distinct detrimental impacts were inflicted on both organisms implying environmental leaching of WSPs may be causing significant disruption to interspecies interactions within freshwater ecosystems. Additionally, these results could contribute to sustainable development in industry, as we conclude PVA represents a less harmful alternative to PVP.

A case study comparing the addition of two different carbon sources in pilot scale RAS with trout with and without biofilters

In this study, water quality and fish performance of traditional RAS with nitrifying biofilters were compared with systems operated under heterotrophic N assimilation (HET-N), a process where bacteria consume ammonium directly for growth and thereby remove dissolved N excreted from the fish, using three different modes of carbon addition. Using twelve identical pilot scale RAS, four treatment groups were established in triplicate: RAS with autotrophic biofilters (Control), RAS with autotrophic biofilters and acetate addition (BF RAS +Acetate), RAS without biofilter with acetate addition (BF RAS -Acetate) and RAS without biofilter and a biopellet reactor (Biopellet RAS). The nine RAS with carbon addition all had lower levels of nitrate and orthophosphate at the end of the trial compared to the three control RAS (approx. 70% less NO3- in the Biopellet RAS and 72% less PO43- in BF RAS -Acetate). Without biofilters installed, both BF RAS -Acetate and Biopellet RAS maintained acceptable water quality parameters during their respective start-up phases and were fully developed in under 3 weeks. The addition of acetate to the water caused an expected formation of bioflocs in the systems, and a significant increase in bacterial activity and turbidity. Substantial feed spill was observed in RAS with acetate addition. The absence of bacterial accumulation and no increase in turbidity in the water in Biopellet RAS suggest that the processes primarily occurred within the reactor. The overall fish mortality was <1%, however, both types of RAS with acetate addition led to reduced fish growth (7.4–20%) compared to the control RAS and the RAS with biopellets. Biopellets were found to reduce dissolved N and P, and had a fast start up time without deteriorating water quality, thereby showing promising traits for use in RAS.

Impacts of microplastic on fisheries and seafood security — Global analysis and synthesis

This review paper collected, collated, analysed, interpreted, synthesised, and documented the research investigations conducted on microplastic (MPs) pollution impacts on seafood organisms (including fish, sharks, shrimps, lobsters, crabs, oysters, mussels, and seaweeds) during the last ten years (2012−2022) covering fifty-seven locations/countries in the world. MPs contaminated 926 seafood species comprising 895 finfish, 09 crustaceans, 20 molluscs and 02 seaweeds. Seafood from Asia was found to be most contaminated with MPs. High MP contamination/ingestion was revealed in several seafood organisms. The ingestion of MPs can reduce fish growth and fish fitness, leading to reduced yield/fish production. Fish and seafood play a significant role in supporting the economy, employment, food sources, and livelihoods of people across the globe, which can be threatened due to the contamination of seafood organisms with MPs. MPs have bioaccumulated in fish skin, gills, stomachs, liver, intestine, and muscles as well as dry fish and canned fish. Hence, the consumption of MP-contaminated fresh fish, whole fish, dried fish or canned fish poses risks as it may be a pathway of MP transfer to humans. MPs can increase the health risks to seafood fish consumers since there is a probability that high risks pollutants adsorbed on MPs (heavy metals, pesticides, and oil compounds) can transfer to humans via the food chain. Several of the chemicals (heavy metals, DDT, PAHs) adsorbed onto MPs are carcinogenic. MPs have also been detected in fish meals, therefore, farmed livestock such as aquaculture fish and chicken fed to fish meals can be exposed to MPs and ultimately to humans. Preventive and safety measures are suggested to reduce the exposure of MPs to humans. In addition, several policy strategies are recommended to reduce the impacts of plastic waste and plastic pollution on the environment, aquatic biota, wildlife, seafood and human health.

Dietary oleic acid supplementation improves feed efficiency and modulates fatty acid profile and cell signaling pathway in European sea bass (Dicentrarchus labrax) juveniles fed high-lipid diets

Diets with high-lipid levels may reduce fish growth, feed intake and increase fat deposition, jeopardizing fillet quality and shelf-life, which may be of major concern for the final consumer. To mitigate these potentially harmful effects, several nutritional strategies have been applied, including the use of functional ingredients. In this study, European sea bass (initial body weight 21.4 g) were fed six isonitrogenous (45% crude protein) diets with 16% and 22% lipid levels and supplemented with oleic acid (OA) at 0, 1, and 2% as a functional ingredient.Increasing dietary lipid levels did not affect fish growth performance, feed intake, and feed utilization. Independently of lipid level, dietary OA supplementation decreased feed intake and increased feed efficiency and Nitrogen (N) retention (% N Intake). Whole-body composition, hepatosomatic and visceral somatic indexes were not affected by dietary composition. The liver and muscle lipid contents were also not affected by dietary composition.The liver fatty acid profile was not affected by dietary lipid level, but monounsaturated fatty acid (MUFA) content decreased while polyunsaturated fatty acid (PUFA) content decreased with dietary OA supplementation. In the muscle, PUFA content decreased with dietary lipid levels, particularly C18:2n-6 (LA) and C20:2n-6. Dietary OA supplementation increased muscle MUFA, particularly OA (C18:1n-9), and reduced PUFA content. Compared to fish fed with 1OA diets, fish fed with 2OA diets presented a decreased area covered by lipids in the liver.Dietary OA supplementation increased hepatic glucose-6-phosphate dehydrogenase (G6PDH) activity and decreased malic enzyme (ME) activity, while no differences were observed in the activity of fatty acid synthase (FAS) and enzymes related to β-oxidation. Moreover, dietary OA supplementation decreased mechanistic target of rapamycin (mTOR) protein levels, while protein kinase B (Akt) and the phosphorylated state levels of both Akt and mTOR were not affected by dietary composition. Overall, dietary OA supplementation decreased feed intake and improved feed efficiency, without affecting growth performance, contributing to mitigate the potentially harmful effects of high-lipid diets in European sea bass.

Effects of dietary phosphorus deficiency on the growth performance, hepatic lipid metabolism, and antioxidant capacity of Yellow River Carp Cyprinus carpio haematopterus.

The study aimed to evaluate the effects of phosphorus (P) deficiency in diets on growth performance, hepatic lipid metabolism, and antioxidant capacity in Yellow River Carp Cyprinus carpio haematopterus. In this study, 72 healthy experimental fish (initial weight=12.0 ± 0.1g [mean±SE]) were randomly selected and distributed to two groups, with three replicates in each group. The groups were fed either a P-sufficient diet or a P-deficient diet for 8 weeks. The P-deficient feed significantly decreased the specific growth rate, feed efficiency, and condition factor of Yellow River Carp. Fish that were fed the P-deficient feed demonstrated higher contents of triglyceride, total cholesterol (T-CHO), and low-density lipoprotein cholesterol in the plasma and a higher T-CHO content in the liver compared to the P-sufficient diet group. In addition, the P-deficient diet significantly reduced the catalase activity level, decreased the glutathione content, and increased the malondialdehyde content in the liver and in the plasma. Furthermore, P deficiency in the diet significantly downregulated the messenger RNA expression of nuclear erythroid 2-related factor 2 and peroxisome proliferator-activated receptor α, whereas it upregulated the messenger RNA expression of tumor necrosis factor α and fatty acid synthase in the liver. Dietary P deficiency reduced fish growth performance, induced fat deposition and oxidative stress, and impaired liver health.

High water temperature raised the requirements of methionine for spotted seabass (Lateolabrax maculatus).

This study evaluated the effects of dietary methionine level and rearing water temperature on growth, antioxidant capacity, methionine metabolism, and hepatocyte autophagy in spotted seabass (Lateolabrax maculatus). A factorial design was used with six methionine levels [0.64, 0.85, 1.11, 1.33, 1.58, and 1.76%] and two temperatures [moderate temperature (MT): 27 ℃, and high temperature (HT): 33 ℃]. The results revealed the significant effects of both dietary methionine level and water temperature on weight gain (WG) and feed efficiency (FE), and their interaction effect was found on WG (P < 0.05). In both water temperatures tested, fish WG increased with increasing methionine level up to 1.11% and decreased thereafter. The groups of fish reared at MT exhibited dramatically higher WG and FE than those kept at HT while an opposite trend was observed for feed intake. Liver antioxidant indices including reduced glutathione and malondialdehyde (MDA) concentrations, and catalase and superoxide dismutase (SOD) activities remarkably increased in the HT group compared to the MT group. Moreover, the lowest MDA concentration and the highest SOD activity were recorded at methionine levels between 1.11% and 0.85%, respectively, regardless of water temperatures. Expression of methionine metabolism-related key enzyme genes (mat2b, cbs, ms, and bhmt) in the liver was increased at moderate methionine levels, and higher expression levels were detected at MT compared to HT with the exception of ms gene relative expression. Relative expression of hepatocyte autophagy-related genes (pink1, atg5, mul1, foxo3) and hsp70 was upregulated by increasing methionine level up to a certain level and decreased thereafter and increasing water temperature led to significantly enhanced expression of hsp70. In summary, HT induced heat stress and reduced fish growth, and an appropriate dietary methionine level improved the antioxidant capacity and stress resistance of fish. A second-order polynomial regression analysis based on the WG suggested that the optimal dietary methionine level for maximum growth of spotted seabass is 1.22% of the diet at 27 ℃ and 1.26% of the diet at 33 ℃, then 1.37g and 1.68g dietary methionine intake is required for 100g weight gain at 27 ℃ or 33 ℃, respectively.

Effect of Autolyzed Yarrowia lipolytica on the Growth Performance, Antioxidant Capacity, Intestinal Histology, Microbiota, and Transcriptome Profile of Juvenile Largemouth Bass (Micropterus salmoides).

The improper components of formulated feed can cause the intestinal dysbiosis of juvenile largemouth bass and further affect fish health. A 28 day feeding trial was conducted to investigate the effect of partially replacing fish meal (FM) with autolyzed Yarrowia lipolytica (YL) on juvenile largemouth bass (Micropterus salmoides). We considered four diets—control, YL25, YL50, and YL75—in which 0%, 25%, 50%, and 75% of the FM content, respectively, was replaced with YL. According to results, the weight gain rate (WGR) and specific growth rate (SGR) of the fish with the YL25 and YL50 diets were significantly higher than the WGR and SGR with the control diet, while the YL75 diet significantly reduced fish growth and antioxidant enzymes activities, and shortened the villus height in the intestinal mucosa. The 16S rRNA analysis of the intestinal microbiota showed that the relative abundance of Mycoplasma was significantly increased with the YL25 and YL50 diets, while the Enterobacteriacea content was increased with the YL75 diet. Moreover, our transcriptome analysis revealed that certain differentially expressed genes (DEGs) that are associated with growth, metabolism, and immunity were modulated by YL inclusion treatment. Dietary YL25 and YL50 significantly reduced the mRNA level of ERBB receptor feedback inhibitor 1 (errfi1) and dual-specificity phosphatases (dusp), while the expression of the suppressor of cytokine signaling 1 (socs1), the transporter associated with antigen processing 2 subunit type a (tap2a), and the major histocompatibility complex class I-related gene (MHC-I-l) were sharply increased with YL75 treatment. We determined that the optimum dose of dietary YL required for maximum growth without any adverse influence on intestinal health was 189.82 g/kg (with 31.63% of the fishmeal replaced by YL), while an excessive substitution of YL for fishmeal led to suppressed growth and antioxidant capacity, as well as intestinal damage for juvenile largemouth bass.

Enhancing replacement of fishmeal with corn protein concentrate by blending with soy protein concentrate and supplementing attractants in the diets of red hybrid tilapia

The objective of this study was to investigate the potential of enhancing the dietary substitution of fishmeal (FM) with corn protein concentrate (CPC) in the diets of red hybrid tilapia, Oreochromis sp., by blending CPC with soy protein concentrate (SPC) and adding betaine-HCl and dried basil leaves (DBL; feeding attractants). Seven isonitrogenous diets [FM100-CPC0-SPC0 (control); FM25-CPC75-SPC0 (75% of FM replaced by CPC); FM25-CPC50-SPC25 (50% and 25% of FM replaced by CPC and SPC, respectively); FM25-CPC50-SPC25B (with 0.5% betaine and 2% DBL); FM0-CPC100-SPC0 (100% diet protein from CPC); FM0-CPC75-SPC25 (75% and 25% of FM replaced by CPC and SPC, respectively) and FM0-CPC75-SPC25B (with 0.5% betaine and 2% DBL)] were formulated. Triplicate groups of tilapia fingerlings (average initial weight, 7.31 ± 0.03 g) were fed one of the diets for 56 days. The effects of high dietary levels of plant protein concentrate (PPC) on growth, nutrient utilization, body composition, body colouration and gut histology of tilapia were investigated. High levels of dietary CPC significantly (p < 0.05) reduced fish growth and feed intake. Blending CPC with SPC restored the growth performance of tilapia at the 75% PPC inclusion level. The addition of palatability enhancers further improved the growth of tilapia fed high PPC-based diets.

Pre-treatment of Ulva rigida improves its nutritional value for European seabass (Dicentrarchus labrax) juveniles

Macroalgae are promising ingredients for aquafeeds, but their recalcitrant polysaccharide structure limits their wide use. To disrupt this structure, different physical (ultra-sounds, autoclave, microwaves), chemical (acid, alkaline), and biotechnological (solid-state fermentation, SSF; SSF followed by sequential hydrolysis, SSF-SH) treatments were carried out in Ulva rigida. The chemical composition, morphological microstructure, release of reducing sugars, soluble protein, and phenolic compounds were evaluated in the final products.All treatments increased U. rigida protein content, while lipid content increased after autoclave, ultra-sound, microwave, and SSF treatments. SSF-SH treatment was more effective in disrupting the cellulose and hemicellulose fractions, resulting in a higher reducing sugars release. The alkaline treatment was more efficient in reducing lignin content and increasing phenolic compounds, antioxidant activity, and soluble protein of U. rigida.The most promising products were then included at 5 % in diets for European seabass (Dicentrarchus labrax) juveniles. Crude, ultra-sound, alkaline, and SSF-SH-treated U. rigida reduced fish growth, while SSF-treated U. rigida resulted in similar growth as the positive control (fish meal-based diet). Feed intake was reduced in all experimental groups, but the feed efficiency of fish fed SSF-U. rigida diet and the protein efficiency ratio of fish fed crude, alkaline, and SSF-treated U. rigida were higher than the positive control. The highest total alkaline proteases activity was achieved with the crude U. rigida diet, while no differences were observed in fish fed the positive control, ultra-sound, and SSF diets.Overall, of the processing methods tested, the most efficient was SSF, which improved feed efficiency of European seabass juveniles fed U. rigida-including diet without affecting growth performance.

Effect of permethrin and cypermethrin on oxygen consumption of a fresh water fish, H. fossilis

Fish provide a high caloric diet to a large number of people all over the world but indiscriminate use of these pollutants has reduce fish growth synthetic pyrethroids may decrease nutritive value, as well as, there compounds may also rich to human body through fish flesh and will cause toxicity to human being also. Two sources of oxygen are potentially available to fishes while most use only dissolved oxygen; others have the ability to obtain oxygen from the atmosphere. All breathing fishes also use dissolved oxygen to some extent, under toxic condition, the oxygen supply becomes deficient and number of poisons become more toxic increasing the amount of poison being exposed to the animal. The fish breathe more rapidly and the amplitude of respiratory movement will increase. The result of the present study suggest that the altered rates of respiration of fresh water fish may serve as a rapid biological monitor of the pesticides exposure to important components of fresh water fish community.

Application of poultry by‐product meal in diets of obscure pufferfish ( Takifugu obscurus )

The relative shortage of fishmeal is challenging the sustainable development of aquaculture industry. A 56-day feeding trial was conducted to evaluate the efficacy of fishmeal replacement by poultry by-product meal (PBM) in juvenile obscure pufferfish. The basal diet with 45% (dry matter) fishmeal was used as the control diet, and in the four experimental diets PBM was added into the control diet to replace fishmeal at the level of 15% (PBM15), 30% (PBM30), 45% (PBM45) and 60% (PBM60) respectively. Each diet was fed to triplicate tanks, each of which was stocked with 30 fish. PBM30 did not significantly affect the growth performance, nutrient apparent digestibility coefficient, proximate composition, amino acid profile, muscle texture and serum biochemical indices (p > 0.05). PBM45 did not significantly (p > 0.05) affects the weight gain, but reduced the feed efficiency ratio (p < 0.05). PBM60 resulted in significantly reduced fish growth (p < 0.05). PBM-supplemented diets resulted in lower contents of long chain-polyunsaturated fatty acid in the liver, but higher deposition of C18:1n-9 and C18:2n-6 in experimental fish (p < 0.05). In conclusion, replacing 30% fishmeal with PBM in the diet did not compromise the growth performance, feed utilisation, health status and muscle texture of farmed obscure pufferfish.

Mooseer (Allium hirtifolium) boosts growth, general health status, and resistance of rainbow trout (Oncorhynchus mykiss) against Streptococcus iniae infection

In large-scale aquaculture, the fast growth rate of fish is positively influenced by feed additives such as medicinal plants. This is however; infectious disease may reduce fish growth and cause devastating economic loss. The present study investigated in vitro antibacterial efficacy of Mooseer (Allium hirtifolium) extract against Streptococcus iniae and its in vivo effects on growth, biochemical parameters, innate immunity of rainbow trout (Oncorhynchus mykiss). Therefore, six experimental diets were designed to include different levels of Mooseer from zero (as control), 5, 10, 15, 20, and 25 g per kg diet respectively referred to as M1 to M5. Results from the antibacterial evaluation showed that Mooseer extract inhibits S. iniae growth with MIC and MBC values of 128 and 256 μg ml−1. Appreciable results were obtained in the groups supplemented with Mooseer. Mooseer enhanced growth performance, and modulated serum biochemical and immunological parameters (total protein, albumin, triglyceride, glucose, cortisol, cholesterol, lysozyme, Ig, ACH50, ALP, and protease activity), and liver enzymes (ALT, AST and ALP). The greatest effects were found for higher doses of Mooseer supplementation (M4 and M5). Meanwhile, results from the survival rate of fish challenged with S. iniae showed higher survival in M2 and M4 treatments. The present findings suggest the beneficial use of Mooseer in rainbow trout diet, with 20 g kg−1 inclusion as the recommended dose.

Digestive tract morphology and enzyme activities of juvenile diploid and triploid Atlantic salmon (Salmo salar) fed fishmeal-based diets with or without fish protein hydrolysates.

Triploid, sterile Atlantic salmon (Salmo salar) could make a contribution to the development of the farming industry, but uncertainties about the performance and welfare of triploids have limited their adoption by farmers. In this study, we compared the ontogeny of digestive tract morphology and enzyme activities (pepsin, trypsin, chymotrypsin, alkaline phosphatase and aminopeptidase) of diploid and triploid Atlantic salmon. Fish were fed diets based on fishmeal (STD) or a mix of fishmeal and hydrolysed fish proteins (HFM) whilst being reared at low temperature from start-feeding to completion of the parr-smolt transformation. Fish weights for each ploidy and feed combination were used to calculate thermal growth coefficients (TGCs) that spanned this developmental period, and the data were used to examine possible relationships between enzyme activities and growth. At the end of the experiment, faeces were collected and analyzed to determine the apparent digestibility coefficients (ADCs) of the dietary amino acids (AAs). Digestive tract histo-morphology did not differ substantially between ploidies and generally reflected organ maturation and functionality. There were no consistent differences in proteolytic enzyme activities resulting from the inclusion of HFM in the diet, nor was there improved digestibility and AA bioavailability of the HFM feed in either diploid or triploid fish. The triploid salmon had lower ADCs than diploids for most essential and non-essential AAs in both diets (STD and HFM), but without there being any indication of lower intestinal protease activity in triploid fish. When trypsin-to-chymotrypsin activity and trypsin and alkaline phosphatase (ALP) ratios (T:C and T:ALP, respectively) were considered in combination with growth data (TGC) low T:C and T:ALP values coincided with times of reduced fish growth, and vice versa, suggesting that T:C and T:ALP may be used to predict recent growth history and possible growth potential.

The effects of fish meal replacement with ultra-micro ground mixed plant proteins (uPP) in practical diet on growth, gut and liver health of common carp (Cyprinus carpio)

Plant proteins are widely used for fish meal replacement in aquafeeds, but anti-nutritional factors in plant protein reduce fish growth performance and impair fish health. The present work aimed to study the effects of improving fish meal replacement percentage with ultra-micro ground mixed plant proteins (uPP) on growth, gut and liver health of common carp. Carps were fed with a practical basal diet with partial fish meal replacement by plant proteins or the basal diet supplemented with 2.5 % or 5% uPP for 16-week. Results indicated that uPP addition did not affect growth and survival of common carp at a supplementation level up to 5% (p > 0.05). However, 5% uPP up-regulated the intestinal expression of inflammation related genes (p < 0.05) and reduced HIF-1α expression (p < 0.05). Moreover, dietary 5% uPP increased serum ALT (p = 0.06) and AST level (p < 0.05) and up-regulated liver expressions of inflammation related genes (p < 0.05). The Simpson diversity index of gut microbiota was lower in 5% uPP group compared to control (p < 0.05). The relative abundance of Fusobacteria and Cetobacterium was lower (p < 0.05), while Proteobacteria including Shewanella and Citrobacter was higher in the 5% uPP group compared to control (p < 0.05). In contrast, 2.5 % uPP did not increase inflammatory and injury parameters in fish intestine and liver, but rather improved the expression of occludin and defensin in the intestine compared with control (p < 0.05). Moreover, no significant differences were found in gut microbiota between 2.5 % uPP group and control. Together, our study suggests that low-level uPP addition can be adopted to further improve fish meal replacement, while dietary 5% uPP impairs gut and liver health of common carp and negatively affects intestinal microbiota.

Neurobehavioral, apoptotic, and DNA damaging effects of sub-chronic profenofos exposure on the brain tissue of Cyprinus carpio L.: Antagonistic role of Geranium essential oil

Currently, the contamination of water with different insecticides like profenofos (PFF) is a critical concern in the aquatic ecosystem. There are limited studies available on the negative impacts of PFF on common carp fish (Cyprinus carpio L.). Therefore, the existing study was designed to investigate the effect of PFF exposure (1/10 of the 96 h-LC50) on the neurobehavior, growth performance, chemical composition, oxidative status, DNA damage, apoptotic status and histological indices of the brain and gill tissues. In addition, this study seeks to detect the ability of geranium essential oil (GEO) dietary supplementation to mitigate the negative impacts of PFF. Accordingly, a total of 120 healthy fish were divided into four groups: the control group, fed on basal diet only; the other groups were fed on a basal diet supplemented with 400 mg kg–1 GEO, basal diet and PFF in water (PFF group), and supplemented diet with GEO and PFF in water (GEO + PFF), respectively, for 60 days. The results showed that PFF significantly reduced fish growth performance, crude protein, and lipid contents. It caused several behavioral alterations including spiral movement, decreased activeness, and changes in feeding behavior. Moreover, PFF increased the DNA tail length, tail moment, and the level of 8-hydroxy-2′-deoxyguanosine. Histologically, PFF induced a wide array of circulatory, inflammatory, regressive and progressive alterations in the brain and gill tissues. PFF significantly downregulated Bcl-2 and upregulated caspase-3 immuno-expression in both organs. Further, it considerably depleted the antioxidant enzymes, including superoxide dismutase, catalase, and glutathione peroxidase. The GEO supplementation did not reach the respective control values but markedly improved most of the behavioral, physical, biochemical, oxidative, apoptotic, and inflammatory markers, altered by PFF exposure. It also protected the gill and brain tissues from the branchial and encephalopathic effects of PFF. These findings suggest that GEO dietary supplements could be advantageous for mitigating PFF negative impacts and presenting a promising feed additive for common carp in aquaculture.

Partial substitution of fishmeal with soybean protein-based diets for dourado Salminus brasiliensis

Cost and environmental restrictions limit the use of fishmeal (FM) in aquafeeds and plant protein (PP) sources. Soybean by-products are important alternative; however, their antinutritional factors may reduce fish growth. This study evaluates the effect of FM substitution for PP (soybean meal and soy protein concentrate) in diets of dourado (Salminus brasiliensis), a promising species for fish farming and empirically considered highly tolerant to PP-based diets. A control diet was formulated to contain 20 % of fishmeal and 61 % of plant protein (SBM) and other five diets with decreasing FM graded levels (16 %, 12 %, 8 %, 4 %, 0 %), which were replaced by soybean protein concentrate (SPC), comprising six treatments and four replicates. Fifteen dourados (6.73 ± 0.2 g) were stocked into 200 L tanks in a recirculating system, fed with experimental diets three times a day to apparent satiation for 90 days. Growth performance, food conversion ratio, protein efficiency ratio and protein retention efficiency of fish were impaired when FM substitution exceeded 13.05 % (the broken line analysis method). Histological analysis of intestinal mucosa showed a decrease in villus height when fishmeal was totally replaced by PP, which probably impaired digestive functions of fish and reflected in a severe loss on growth performance.

Interactive Effects of Hypoxia and Temperature on Consumption, Growth, and Condition of Juvenile Hybrid Striped Bass

AbstractProductive tributary reservoirs can become suboptimal environments for fish during summer because of hypolimnetic hypoxia (≤3 mg O2/L) and high epilimnetic temperatures that reduce access to quality habitat for growth. We conducted a laboratory experiment using a 3 × 3 × 2 (temperature × dissolved oxygen [DO] × fish size) complete factorial design to examine the effect of DO concentration and temperature on consumption, growth, and proximal body composition of juvenile hybrid Striped Bass (Striped Bass Morone saxatilis × White Bass M. chrysops), which are commonly stocked into North American reservoirs and for which tolerances to environmental conditions are not fully known. Our study demonstrates that consumption and growth of juvenile hybrid Striped Bass were affected by an interaction between temperature and DO. Specifically, low DO conditions negatively affected consumption, especially at high temperatures. By contrast, growth was largely unaffected by DO, except at high temperatures when low DO reduced fish growth. Temperature and DO did not interact to cause changes in energy density or moisture content, although temperature did independently affect the moisture content of hybrid Striped Bass tissues. The change in moisture content was lowest for fish exposed to high temperatures, suggesting a negative effect of temperature on fish condition. Collectively, our experimental findings provide useful information for modeling the energetics of hybrid Striped Bass and assessing reservoir habitat quality, which can help guide decision making regarding stocking.