Aquaculture Nutrition最新文献

A nutritional bottleneck in salmonid aquaculture is the procurement of marine-derived compounds, such as essential amino and fatty acids, including omega-3 fatty acids, lysine, and methionine. Therefore, insects containing these compounds are highly promising as feed ingredients. The present study evaluates larvae of a “marine” insect (Coelopa frigida, the bristly-legged seaweed fly larvae, SWFL) reared on brown algae side streams as a feed ingredient for rainbow trout (Oncorhynchus mykiss). SWFL contained, on a dry matter basis, 60% crude protein (CP), 3.5% lysine, and 1.5% methionine, as well as 17% lipids, including 4% eicosapentaenoic acid and docosahexaenoic acid. Four isoenergetic (ca. 23 MJ kg⁻¹ gross energy) and isoproteic (ca. 45% CP) feeds were evaluated in a 10-week feeding trial. The diets included a control containing 25% fish meal, a commercial reference, and two diets substituting 40% fish meal with either SWFL or partially defatted black soldier fly larvae (BSFL) meal (Hermetia illucens). SWFL-fed fish displayed higher specific growth rates (SGR) compared to BSFL-fed fish and similar SGR compared to control and reference diet-fed fish. Feed intake in SWFL-fed fish was higher than for the control and BSFL diets and similar to the reference diet. The feed conversion ratio of fish fed the BSFL and SWFL diets was higher compared to the control, suggesting lower bioavailability of both insect meals compared to fish meals. No difference in intestinal health parameters was noted between the insect diets and the control diet, indicating good intestinal health across all treatments. However, changes in electrogenic intestinal transport were observed between the SWFL and BSFL diets, illustrating the heterogeneous effect of different insect products. Overall, SWFL meal is a promising alternative marine feed ingredient, compatible with circular production systems, as it can be efficiently cultivated using marine side streams.

Dietary betaine supplementation has been reported to alleviate the adverse effects of high-carbohydrate diets on Megalobrama amblycephala, while the regulatory mechanism remains largely unknown. In the present study, a 79-day feeding trial was conducted with 450 juvenile Megalobrama amblycephala (average weight 6.75 ± 0.10 g), which were fed with five high-carbohydrate diets (43%) supplementing betaine at 0% (CD group), 0.2% (0.2Bet group), 0.4% (0.4Bet group), 0.8% (0.8Bet group), and 1.6% (1.6Bet group), respectively. Results showed M. amblycephala in 0.8Bet group exhibited the best growth performance, indicated by the largest weight gain ratio (142.88%) and least feed conversion ratio (1.63). Moreover, liver health was promoted in 0.8Bet group, with decreased number of non-nucleated cells and less lipid accumulation, which was accompanied by the lowest hepatosomatic index (1.38%). In order to further illustrate the regulatory mechanism, metabolites assay indicated that dietary betaine supplementation significantly increased plasma contents of methionine, serine, hypotaurine, and taurine, but did not affect plasma contents of cystathionine, cystine, or cysteic acid. Accordingly, the mRNA expressions of cysteine sulfinate decarboxylase in cysteine sulfinic acid pathway and cysteamine dioxygenase (ADO) in sulfinic acid (CS) pathway, which were both involved in taurine synthesis, were also upregulated in the liver. Meanwhile, the microbial communities in M. amblycephala intestine were more stable and uniform with betaine supplementation. Therefore, dietary betaine supplementation may exert its protective roles in improving feed efficiency and liver health of M. amblycephala via promoting de novo taurine synthesis and stabilizing intestinal microbial communities.

This study was aimed to investigate the effects of replacing dietary fish meal (FM) with defatted yellow mealworm (Tenebrio molitor) meal (DYM) on growth performance, intestinal health, serum immune, and antioxidant indexes of juvenile Chinese mitten crab (Eriocheir sinensis). Four hundred juvenile Chinese mitten crabs (4.94 ± 0.08 g) were randomly distributed into five groups in quadruplicate (20 crabs per tank), and each group was fed with diets that replaced FM with DYM at 0% (CON, containing 200 g/kg FM), 25% (DYM25), 50% (DYM50), 75% (DYM75), and 100% (DYM100) for 8 weeks, respectively. The results showed that the growth, serum immune and antioxidant indexes, digestive enzyme activities, intestinal histology, and microbiota composition of DYM25, DYM50, and DYM75 groups all reached the similar level as the CON group. While when 100% fishmeal was replaced, significantly decreased the final body weight (FBW), weight gain (WG), serum alkaline phosphatase (AKP), acid phosphatase (ACP), lysozyme (LZM), glutathione peroxidase (GSH-Px), total antioxidant capacity (T-AOC), and total superoxide dismutase (T-SOD) activities, hepatopancreas protease activity, mid-intestine folds height and number (P < 0.05), significantly increased the feed conversion ratio (FCR), serum malondialdehyde (MDA) content, and the abundance of intestinal harmful bacteria Shewanella (P < 0.05). Overall, these results suggest that 75% dietary FM (150 g/kg) can be effectively replaced by DYM without negative impact on the growth performance, intestinal health, serum immune, and antioxidant indexes of juvenile E. sinensis.

An 8-week feeding trial was conducted to investigate the effects of host-associated Bacillus megaterium R32 and stachyose on the intestinal mucosal defense system of turbot (Scophthalmus maximus. L). Three isonitrogenous and isolipidic diets were formulated: control diet (C), control diet with 1.0 × 10⁸ CFU/g B. megaterium R32 (RC), and 1.0 × 10⁸ CFU/g B. megaterium R32 + 1.5% stachyose (RS) supplementation separately. The results showed that diets RS and RC significantly inhibited the expression of cell development and apoptosis-related genes (β-catenin, CyclinD1, BAX, Bid); diets RS and RC significantly increased the expression of intestinal tight junction protein claudin-4, while RS group significantly decreased the expression of myosin light chain kinase; diets RS and RC significantly decreased the expression of proinflammatory factors (IL-13, IL-15, IFN- γ), diet RS also significantly decreased the expression of TNF-α and AP-1, and increased the expression of TGF-β. 16s rRNA gene sequencing results showed that diets RS and RC significantly decreased the abundance of conditional pathogenic bacteria (Corynebacterium, Desulfovibrio, Escherichia-Shigella). Among them, the abundance of Bacillus in the RS group was the highest. It is concluded that the combination of stachyose and B. megaterium R32 had a more positive effect on intestinal cell development and barrier function and strengthened the intestinal mucosal defense system of turbot.

This review paper provides an in-depth analysis of the current status, challenges, and strategies for improvement within the fish feed industry in East Africa, focusing on Kenya, Uganda, Tanzania, and Rwanda. Aquaculture production in these countries is experiencing steady growth, driven by increasing demand for fish and fish products for both nutritional and economic purposes. Despite the market facilitating the transition from extensive to semi-intensive and moderately intensive farming systems across the four countries, the sector’s progress is hampered by a lack of sustainable, locally produced, high-quality, and cost-effective fish feeds tailored to different developmental stages of fish. Despite the evident need, there is a notable scarcity of comprehensive reviews addressing the regional perspective of fish feed due to heightened cross-border trade driven by the soaring demand and increased installation of cages in Lake Victoria, as well as in inland dams and reservoirs. This paper addresses critical challenges, such as regional scarcity and limited access to quality feed ingredients, regulatory obstacles, insufficient quality control measures, infrastructure constraints, and a lack of awareness and understanding of feed management and formulation. To overcome these challenges, the paper recommends fostering collaboration to establish a robust regional fish feed supply chain, investing in research and development initiatives, advocating for policy reforms and regulatory support, and compliance with East African Community quality standards for fish feed. Moreover, there is an urgent need to enhance human resource capacity through training and extension services, promote public investment support, strengthen sector institutions and industry associations, conduct training and awareness programs for feed providers, and improve storage facilities to maintain feed quality. The paper provides policymakers with valuable insights to inform targeted interventions that will catalyze positive transformation within the fish feed industry in East Africa.

The purpose of the present research was to evaluate the effect of diets supplemented with activated yeast, crude chitin, and chitosan on the growth, immune, and antioxidant response of freshwater prawn Cryphiops (Cryphiops) caementarius. Adult male prawns were kept in individual culture vessels installed in aquarium tanks. The basal diet (control) was supplemented with activated Saccharomyces cerevisiae yeast (60 g/kg), crude chitin (20 g/kg), and chitosan (1 g/kg). Each dietary treatment consisted of three replicates. The diet supplemented with activated yeast causes greater growth, as well as a greater number of total hemocytes (82.54 × 10⁵ cells/mL), semigranular (59 × 10⁵ cells/mL), and granular (18.67 × 10⁵ cells/mL) hemocytes and without atypical hemocytes. Furthermore, a higher number of hemocytes positive for prophenoloxidase (98%), a shorter hemolymph clotting time (42.87 s), a higher activity of acid phosphatase (12.50 U/mL) and glutathione-S-transferase (GST) (0.186 U/mL) were also observed in dietary yeast group. On the contrary, there were no differences in the activity of superoxide dismutase (SOD) enzyme in prawns from any dietary treatment. Results from this research demonstrate for the first time that the diet containing activated yeast increases the growth and immune response of the freshwater prawn through a significant increase in hemocyte and acid phosphatase levels, a decrease in hemolymph clotting time, and a greater number of proPO-positive hemocytes. However, activated yeast is not effective in increasing the activity of antioxidant enzymes SOD and GST. Therefore, the activated yeast diet can be useful to improve the aquaculture production of C. (C.) caementarius and possibly of other commercially important crustaceans.

The aim of this study was to reveal the effects of yeast culture replacing fish meal (FM) or chicken meal (CM) on the growth performance, serum biochemical indexes, intestinal digestive enzyme activities, hepatic antioxidant, and hepatic and intestinal histology of bullfrog (Lithobates catesbeianus). The basal diet contained 100 g/kg FM and 100 g/kg CM, and then yeast culture was used to decrease FM or CM level to 75 and 50 g/kg with yeast culture inclusion of 32 and 64 g/kg, respectively, resulting in five groups of isonitrogenous diets (control, FM75, FM50, CM75, and CM50). A total of 450 bullfrogs (45.5 ± 0.4 g initial weight) were fed the five diets for 50 days. (1) The FM50 group presented significantly lower weight gain, condition factor, hind leg index, and higher feed conversion ratio than the control group, while the other three groups of FM75, CM75, and CM50 showed no significant difference in growth performance when compared to the control group. (2) The serum triglyceride content of FM50 group was significantly lower, while the alkaline phosphatase activity was significantly higher than those of the control group. The serum total cholesterol levels were significantly lower in the CM50 group compared to the control group. (3) In intestinal digestive enzyme activities, the trypsin and α-amylase activities in the CM75 and CM50 groups, the trypsin activity in the FM75 group, and lipase activity in the CM50 group were all significantly higher than those in the other groups. (4) The replacement of 50% FM with yeast culture (FM50 and CM50 groups) promoted the total antioxidant capacity in the liver, but compared to the control group, the intestinal villi height and muscularis propria thickness in the FM50 group were significantly lower. There was no difference (P > 0.05) in liver histology among all the groups. In conclusion, in a basal diet containing 100 g/kg FM and 100 g/kg CM, 32.0 and 64.0 g/kg yeast cultures could successfully replace 25% of dietary FM and 50% of dietary CM without negative effects on the growth performance, serum biochemical indexes, and hepatic and intestinal health of bullfrogs.

The widespread use of commercial feeds with high-fat content in aquaculture may lead to oxidative stress and inflammation in fish during culture, which may cause changes in fish muscle texture. Therefore, mitigating oxidative stress and inflammation during fish farming holds paramount importance in improving fish muscle quality. In this study, we investigated the effect of different dietary levels of chlorogenic acid (CGA; 0, 100, 200, 400, 800, 1600 mg/kg diet, P1–P6) in commercial diets on the muscle of blackspotted croaker (Protonibea diacanthus) through an 8-week feeding trial in open sea cages. The results showed that high dietary CGA levels (P5–P6) could significantly reduce muscle oxidative stress and inflammation (P < 0.05). Muscle toughness (hardness, chewiness, shear force, and gumminess) improved significantly as CGA levels increased (P < 0.05). It was also observed that the gap of muscle fiber was significantly reduced, while the muscle fiber density was significantly increased with the increase of CGA level (P < 0.05). Notably, dietary CGA also had a significant effect on collagen content in the muscle (P < 0.05), which may also be a crucial factor affecting muscle texture. Furthermore, it was found that the reduction of inflammation and increase of collagen deposition in muscle by dietary CGA may be related to the upregulation of transforming growth factor beta (TGF-β) signaling pathway. Finally, it can be concluded that a dietary CGA supplementation of 1173.11 mg/kg is suggested for the aquaculture of P. diacanthus, based on the muscle texture quality.

Experimental diets were formulated including the suitable lipid level (10%, PC), the high-lipid level (16%, HL), and HL containing sodium acetate diets (HS). Three diets were fed golden pompano (Trachinotus ovatus) (initial body weight: 12.88 ± 0.03 g) for 8 weeks. The results showed HL diets significantly increased hepatosomatic index (HSI) and abdominal fat percentage (ASF), aggravated liver lipid deposition, and caused blood metabolic disorder and liver damage (P < 0.05). Moreover, the fish fed HL diets significantly decreased intestinal villus number (VN) and muscular layer thickness (MLT) (P < 0.05), accompanied with an increased trend in the relative abundance of intestinal pathogenic bacteria such as Mycoplasma and Photobacterium. However, the fish fed HS diets significantly decreased the HSI and AFP, relieved hepatic lipid deposition, improved blood and liver metabolism, and intestinal morphology in comparison to the fish fed HL diets (P < 0.05). More importantly, sodium acetate addition improved intestinal microbiota by inhibiting the proportion of pathogens (Mycoplasma and Vibrio) and increasing the abundance of probiotics (Bacteroidales_S24-7_group_norank, Cetobacterium, Bacteroides, and Lachnospiraceae_NK4A136_group). Furthermore, there was a strong correlation between these bacteria (Mycoplasma, Vibrio, Lachnospiraceae_NK4A136_group, Bacteroidales_S24-7_group_norank, Bacteroides, and Cetobacterium) and main physiological indices. In conclusion, sodium acetate improved blood performance, alleviated hepatic lipid deposition induced by HL diets, and boosted the growth and intestinal health for golden pompano.

This study investigated how dietary myo-inositol affects osmoregulation, carbohydrate and lipid metabolism, immunity, and antioxidant properties in Penaeus vannamei under long-term low-salinity conditions. A two-factor (2 × 3) orthogonal approach was used with three different concentrations of dietary myo-inositol (0, 1,200, and 2,000 mg/kg) at two dietary carbohydrate levels: normal carbohydrate or high carbohydrate (HC). Six experimental diets were formulated, and a feeding trial was carried out for 42 days. The interaction of myo-inositol with an HC diet significantly improved shrimp survival, weight gain, and specific growth rates. Dietary myo-inositol increased the contents of Na⁺, K⁺, and Ca²⁺ in the serum and reduced the ion loss caused by low-salinity stress. In addition, a lack of myo-inositol can lead to loosening of gill filament connections and thinning or disappearance of the cuticle. However, myo-inositol supplementation protected the structural and functional integrity of the shrimp gills and significantly enhanced the ion transport capacity (P < 0.05). Two-factor analysis showed that myo-inositol concentration was affected by dietary carbohydrate levels, and an HC diet enhanced myo-inositol biosynthesis in shrimp gills (P < 0.05). The concentrations of myo-inositol are highest in the gills and lowest in the liver and pancreas. Moreover, dietary myo-inositol can improve the immune function and antioxidant capacity of P. vannamei. The results also indicated that under sustained low-salinity stress, high levels of carbohydrates cannot relieve the stress caused by low-salinity conditions and can even affect the healthy growth of P. vannamei. Under HC levels, adding dietary myo-inositol significantly improved glycogen and lipid deposition in hepatopancreas tissue and enhanced carbohydrate utilization and osmotic adjustment ability in P. vannamei under chronic low-salinity stress.