Previous studies conducted in our lab revealed microbial assemblages to vary significantly between high (ARS-FY-H) and low fillet yield (ARS-FY-L) genetic lines in adult rainbow trout. We hypothesized that a high ARS-FY-H donor microbiome can accelerate somatic growth in microbiome-depleted rainbow trout larvae of the ARS-FY-L line. Germ-depleted larvae of low ARS-FY-L line trout reared in sterile environments were exposed to high- or low-fillet yield-derived microbiomes starting at first feeding for 27 weeks. Despite weight-normalized diets, somatic mass was significantly increased in larvae receiving high fillet yield microbiome cocktails at 27 weeks post-hatch. RNA-seq from fish tails reveals enrichment in NADH dehydrogenase activity, oxygen carrier, hemoglobin complex, gas transport, and respiratory pathways in high fillet yield recolonized larvae. Transcriptome interrogation suggests a relationship between electron transport chain inputs and body weight assimilation, mediated by the gut microbiome. These findings suggest that microbiome payload originating from high fillet yield adult donors primarily accelerates juvenile somatic mass assimilation through respiratory and mitochondrial input modulation. Further microbiome studies are warranted to assess how increasing beneficial microbial taxa could be a basis for formulating appropriate pre-, pro-, or post-biotics in the form of feed additives and lead to fecal transplantation protocols for accelerated feed conversion and fillet yield in aquaculture.

The fish diet is one of the essential factors in the development of aquaculture. The purpose of present study was to evaluate using grape pomace as a main feed ingredient on growth performance, body chemical composition, survival rate, and morphological indices of the carp (Cyprinus carpio). 200 fish with an average weight of 7 ± 0.4 g were randomly distributed in four tanks for total of 56 days. The fish were fed with a diet containing 5%, 10%, and 15% grape pomace in different feeding groups designated as G1, G2, and G3. The average daily weight gain (g), weights gain (g), and specific growth rate (%) were significantly higher (p < .05) in G3 as compared to G1 and G2 groups. The lowest feed conversion ratio was recorded in G3 group. The morphological indices, condition factors, viscerosomatic index, and hepatosomatic index were significantly higher in G3 group as compared to other treatments. The protein, fat, moisture, and ash contents in the C. carpio fillets were significantly influenced by feeding rate. The results showed that grape pomace had a positive effect on growth, survival, and nutritional indices in the carp fish. According to the obtained results, grape pomace (150 g/kg food) can be considered as the diet component for the carp fish.

Bone hydrolysates from bighead carp (Aristichthys nobilis) were prepared using Protamex and Alcalase with degrees of hydrolysis (DH) of 5%, 10% and 15%. The antioxidant activity of bone hydrolysates was evaluated in vitro and then the hydrolysates with better antioxidant activity were used to immerse bighead carp fillets through a vacuum impregnation process at concentrations of 1% and 2%. Among the six hydrolysates, fish bone hydrolyzed with Protamex at DH 10% exhibited the highest ability to scavenge 1, 1-diphenyl-2-picrylhydrazyl (DPPH) (88.79%), 2, 2\'-azino-bis-3-ethylbenzthiazoline-6-sulphonic acid (ABTS) (57.76%) and hydroxyl radicals (62.72%), as well as to chelate ferrous ions (91.46%). The hydrolysates effectively postponed freezing- and thawing-induced protein/lipid oxidation. Compared with the fillets without treatment, the impregnated fillets had higher sulfhydryl contents, greater Ca2+-ATPase activity, lower carbonyls and lower thiobarbituric acid-reactive substances (TBARS). Bone hydrolysates also have a positive effect on the texture and water-holding ability of freeze-thawed fish fillets. Fish bone hydrolysates of Protamex could serve as potential antioxidants to preserve fish fillets.

This study evaluates the differences in mineral and toxic trace element concentrations of Nile tilapia (Oreochromis niloticus) tissues from three aquatic ecosystems in Ethiopia-Lake Ziway, Lake Langano, and Gilgel Gibe reservoir-with a focus on edible (fillet) and discarded (digestive tract, gills, skin, and liver) parts. A total of sixty (n = 60) Nile tilapia samples were collected, comprising twenty (n = 20) fish from each lake, and analyzed by inductively coupled plasma mass spectrometry. All elements varied markedly among tissues and between the lakes. Some differences in element concentrations were attributed to differences in nutrient load in the ecosystems and the function of the tissues. For instance, the calcium concentrations in skin and gill were distinctly higher in fish from calcium-rich Lake Langano. The d iscarded parts were richer in essential trace elements, showing an opportunity to promote their use in human nutrition to increase the intake of important minerals. However, the accumulation of elements toxic to humans, such as aluminum, should be monitored and, in particular, controlled when rearing these fish in aquaculture.

BACKGROUND: Fish gut microbial assemblages play a crucial role in the growth rate, metabolism, and immunity of the host. We hypothesized that the gut microbiota of rainbow trout was correlated with breeding program based genetic selection for muscle yield. To test this hypothesis, fecal samples from 19 fish representing an F2 high-muscle genetic line (ARS-FY-H) and 20 fish representing an F1 low-muscle yield genetic line (ARS-FY-L) were chosen for microbiota profiling using the 16S rRNA gene. Significant differences in microbial assemblages between these two genetic lines might represent the effect of host genetic selection in structuring the gut microbiota of the host.
RESULTS: Tukey\'s transformed inverse Simpson indices indicated that high muscle yield genetic line (ARS-FY-H) samples have higher microbial diversity compared to those of the low muscle yield genetic line (ARS-FY-L) (LMM, χ2(1) =14.11, p < 0.05). The fecal samples showed statistically distinct structure in microbial assemblages between the genetic lines (F1,36 = 4.7, p < 0.05, R2 = 11.9%). Functional profiling of bacterial operational taxonomic units predicted characteristic functional capabilities of the microbial communities in the high (ARS-FY-H) and low (ARS-FY-L) muscle yield genetic line samples.
CONCLUSIONS: The significant differences of the microbial assemblages between high (ARS-FY-H) and low (ARS-FY-L) muscle yield genetic lines indicate a possible effect of genetic selection on the microbial diversity of the host. The functional composition of taxa demonstrates a correlation between bacteria and improving the muscle accretion in the host, probably, by producing various metabolites and enzymes that might aid in digestion. Further research is required to elucidate the mechanisms involved in shaping the microbial community through host genetic selection.

Trichlorfon is an organophosphate insecticide that is widely used on fish farms to control parasitic infections. It has been detected in freshwater ecosystems as well as in fishery products. There is a growing body of evidence to suggest that certain feed additives may reduce or prevent pesticide-induced toxicity in fish. The aim of the present study was to determine whether acute exposure to trichlorfon would alter bioenergetic homeostasis and alter fatty acid profiles in muscles of silver catfish (Rhamdia quelen). We also sought to determine whether rutin prevents or reduces these effects. Cytosolic and mitochondrial creatine kinase (CK) and activities of complexes II-III and IV in muscle were significantly inhibited by exposure to 11 mg/L trichlorfon for 48 h compared to effects in the unexposed group. Total content of polyunsaturated fatty acids (omega-3 and omega-6) were significantly lower in muscle of silver catfish exposed to 11 mg/L trichlorfon for 48 h than in the unexposed group. Addition of 3 mg rutin/kg feed increased CK activity and prevented inhibition of complex IV activity, as well as preventing all alterations of muscle fatty acid profiles elicited by exposure to trichlorfon. No significant differences were observed between groups with respect to muscle adenylate kinase or pyruvate kinase activities, as well as total content of saturated and monounsaturated fatty acids. Our findings suggest that exposure (48 h) to 11 mg trichlorfon/L water inhibits cytosolic and mitochondrial CK activity in muscle. Trichlorfon also affects activities of complexes II-III and IV in respiratory chain, with important consequences for adenosine triphosphate production. The pesticide alters fatty acid profiles in the fish and endangers human consumers of the product. The most important finding of the present study is that inclusion of rutin improves bioenergetic homeostasis and muscle fatty acid profiles, suggesting that it reduces trichlorfon-induced muscle damage.

BACKGROUND: Due to excellent nutritional properties of fish and fish products, dietitians recommend their larger share in the diet, for both the prevention and treatment of diet-related diseases. In this context particular attention should be given to fish eggs (roe). The aim of the study was to compare the content of selected minerals and trace elements in the roe and muscle tissue of aquaculture-reared rainbow trout. Moreover, the extent to which an edible portion of 100 g of fish product (roe or fillet) satisfies the requirements for these elements in adult consumers (women and men) and children was determined.
METHODS: The research material was represented by 20 farmed rainbow trout females (Oncorhynchus mykiss). In muscle tissue and roe the proximate composition, energy value, and nutritional quality index were examined. Concentrations of K, Na, Ca, Mg, Zn, Fe, Mn and Cu were determined by flame atomic absorption spectrometry analysis. The levels of minerals and trace elements in fish products were used to calculate the percentages of the recommended dietary reference values for adults and children in portion of 100 g.
RESULTS: The roe had higher content of 7 elements including, Zn (29.40 ± 1.38, 27.74-30.91 mg/kg), Mn (1.66 ± 0.08, 1.55-1.73 mg/kg), Fe (11.17 ± 0.35, 10.75-11.60 mg/kg), Cu (1.24 ± 0.04, 1.21-1.30 mg/kg), Ca (546.90 ± 23.68, 522.02-578.96 mg/kg), Mg (546.97 ± 23.68, 522.02-578.96 mg/kg), Na (403.61 ± 5.53, 397.29-407.57 mg/kg) compared to muscle tissue, respectively, Zn (2.73 ± 0.97, 0.94-3.77 mg/kg, Mn (0.22 ± 0.10, 0.14-0.46 mg/kg), Fe (2.19 ± 1.44, 1.02-5.50 mg/kg), Cu (0.24 ± 0.06, 0.17-0.36 mg/kg), Ca (164.07 ± 71.72, 93.24-306.32 mg/kg), Mg (240.00 ± 73.37, 127.92-316.41 mg/kg), Na (273.37 ± 99.65, 183.93-524.41 mg/kg). In turn, the muscle tissue contained 3 times as much K (5159.87 ± 974.70, 4004.63-6343.91 mg/kg) as the roe (1713.65 ± 58.68, 1643.97-1764.14 mg/kg). The roe covered the recommended nutrition standards (population reference intake, PRI and adequate intake, AI) to a greater extent than the fillet for all analysed trace elements and minerals except K. For children, the contribution of roe to the reference intake of such elements as Mg, Zn, Fe, Mn and Cu was particularly high. Therefore the roe should be considered as a source of Mg for all consumer groups, and as high in Zn for women and children. The suggested portion of fillet and roe provided only 2-3 % of the daily requirement for Na.
CONCLUSIONS: Despite the differences found, both roe and fillet from rainbow trout are a good source of analysed elements. The results indicate the need to continue research in order to determine the influence of other factors on the content of minerals and trace elements in roe and the possibility of using gonads to enrich other food products with elements.

The effect of carp feeding with n-3 PUFA-enriched feed (Schizochytrium sp. meal or salmon oil) on nutritional quality indicators (proximal composition, fatty acid profile of fat) and culinary quality (color parameters, texture, sensory properties) was evaluated. Highly significant effects of carp nutrition on chemical composition and fat characteristics, L* and a* color parameters, muscle fiber size, endomysium thickness, moisture and taste of fillets were determined. Fillets obtained from carps fed with the experimental feed contained less protein and more crude fat and had larger muscle fibers, but scored more highly in the sensory evaluation of moisture and fishy taste. In the fat of carp fed the enriched feed, a greater share of total PUFA, n-3 PUFA, total EPA and DHA, n-3/n-6 ratio, and a smaller share of total MUFA were observed compared with control fish. However, no effect of nutrition on the texture of carp fillets, assessed either instrumentally or using sensory methods, was found. The use of Schizochytrium sp. meal as a source of EPA and DHA gave much better results than salmon oil, as it allowed a higher content of these valuable fatty acids to be achieved, without compromising quality.

The present study studied the effects of fish gelatin (FG) incorporated with grape seed extract (GSE) through vacuum impregnation (VI) on refrigerated tilapia (Oreochromis niloticus) fillets over 12 days. The VI of FG-GSE significantly improved the quality of the fish by decreasing drip loss, texture changes, and microbial survival. It also delayed protein oxidation by inhibiting the formation of disulphide bonds and carbonyl groups, and maintaining a higher sulfhydryl content and Ca2+-ATPase activity. Regarding myofibril degradation, FG-GSE maintained their secondary structure by increasing the ratio of α-helices and β-sheets (70.88-75.51%). Atomic force microscopy further revealed that the FG-GSE coating preserved the myofibril nanostructure by maintaining their length, width, and height. Overall, the synergistic effects of VI with 3% FG and 0.9% GSE suggested a promising approach for fillet preservation.