Silver Catfish Research Articles

Effects of anesthetic MS-222 on stress and reproduction of South American silver catfish (Rhamdia quelen) males

Anesthesia is a common practice used in fish research and aquaculture. It is important to understand anesthetic effects on the animal and tissues of interest to ensure validity of data and to improve animal welfare in research and fish production endeavors. The production of some captive fish species is only possible by imposing artificial reproduction procedures, and manipulation of fish for these purposes is a stressor. The purpose of this study, therefore, was to evaluate effects of different concentrations (100, 200, and 300 mg/L) of the anesthetic MS-222 (tricaine methanesulfonate) on cortisol concentrations and effects on sperm quality in Rhamdia quelen. After hormonal induction of gamete production, 28 sexually mature males were randomly assigned to treatments, and milt and blood samples were collected. Anesthesia induction time, motility rate, sperm concentration and morphology, plasma cortisol concentrations, and reproductive hormone concentrations (testosterone, 17-α-hydroxyprogesterone, and estradiol) were evaluated. Sperm motility was greater in the control than 300 mg/L treatment group but did not differ among the control, 100, and 200 mg/L groups. The estradiol concentration was greater in non- anesthetized than anesthetized Rhamdia quelen, but plasma cortisol concentrations did not differ among treatment groups (182.50 ± 42.03 ng/mL). The anesthetic MS-222 at concentrations of 100, 200, and 300 mg/L did not inhibit the stress response due to handling of Rhamdia quelen males. In addition, treatment with MS-222 was not effective in inhibiting detrimental effects on sperm quality because this treatment was associated with impaired sperm motility and lesser concentrations of plasma estradiol.

Reproductive physiology of Rhamdia quelen is improved by dietary inclusion of probiotics

This study evaluated the effects of a probiotic additive on reproductive variables of the silver catfish (Rhamdia quelen). Three hundred juveniles (initial mean weight 17.35 ± 0.97 g) were fed for 90 days with diets containing increasing levels of a probiotic additive (0.15, 0.30, 0.45 and 0.60 g/kg of feed), which consisted of a blend between Bacillus subtilis and B. cereus, both at a concentration of 4 × 1011 CFU/g, and a control diet without the additive. In males, the presence of the probiotic had an effect on relative seminal volume, sperm cells’ survival, gonadosomatic, hepatosomatic and viscerosomatic indexes, as well as transpose beat frequency, displacement velocity, motility rate and straightness of sperm cells. In females, the probiotic inclusion resulted in presented better in spawning and fertilization rates, viscerosomatic fat accumulation and development of germ cells. Additionally, the hepatic integrity and hepatocyte developmental characteristics were preserved by the presence of the probiotic additive. Thus, the inclusion of 0.60 g/kg of the probiotic could be recommended for the improvement of the reproductive performance of R. quelen.

Biomarker profile of a silver catfish Chrysicthys Nigrodigitatus in heavy metal polluted areas of the Lagos Lagoon, Nigeria

Aquatic ecosystems are usually exposed to contaminants including heavy metals from anthropogenic activities and high concentration of these metals may alter physiological function in fish muscle. Assessment of biomarker profile will provide the role of antioxidant defence enzymes in response to metal accumulation. The present study aims to find the relationship between biomarker pattern in fish muscle and the contribution of antioxidant defence enzymes to sustain balance from metal toxicity. Adult fish (Chrysicthys nigrodigitatus), water and sediment samples were taken from five sampling stations, during the wet and dry season in the Lagos Lagoon. Heavy metals (lead, cadmium, chromium, copper, zinc, iron) levels, antioxidant defence enzyme activity (superoxide dismutase, catalase, glutathione peroxidase, reduced glutathione) and malondialdehyde were analysed in fish muscle using standards methods. Heavy metal levels showed significant difference (p<0.05) in fish muscles, water and sediment, with values above recommended standard for aquatic life. PCA showed that elevated activities of antioxidant defence enzymes correlated with increase metal concentrations within the fish muscle, which may indicate possible oxidative stress. Hence, measures should be implemented and sustained in the treatment of effluents before discharging into the aquatic habitat so as to reduce stress and sustained the wild population.

Rice ethanol distillery residue as a protein source in the diet of silver catfish (Rhamdia quelen)

ABSTRACT The objective of the study was to evaluate the partial replacement of the protein of fish meal by the protein from the intermediate residue of rice ethanol distilleries in the proportions of 0%, 25%, and 50% in Rhamdia quelen. Three hundred and seventy-five fish (3.56 ± 0.6 g/7.07 ± 0.46 cm) were distributed in 15 tanks and fed three times a day for 60 days. At the end of the period, biometrics were performed to collect data and tissues, evaluating growth parameters, sonatic indices, digestive enzyme activity, plasma and hepatic metabolism, body nutrient composition, protein, and fat deposition. Fish fed the control diet showed higher feed intake (765.86 ± 53.86 g). The 50% replacement diet reduced final growth (14.27 ± 3.88 g), deposition of body protein (1.63 ± 0.05 g) and increased free liver amino acids (8.72 ± 0.41). The use of intermediate residue from rice ethanol distilleries in silver catfish diets was inefficient, requiring further studies to evaluate the protein quality of this ingredient.

Effects of chlorantraniliprole insecticide on innate immune response of silver catfish (Rhamdia quelen) naturally infected with Aeromonas hydrophila

It is well documented today that pesticides, used in crop production, may modulate the immune system of healthy fish. However, there is still only limited information regarding the effects of these anthropogenic stressors in conjunction with natural stressors (pathogens), on the innate immune responses of freshwater fish. Thus, the aim of this investigation was to compare the innate immune response of two groups of fish (Rhamdia quelen), naturally infected with Aeromonas hydrophila, exposed and unexposed to a non-lethal concentration of chlorantraniliprole (CAP) insecticide (0.0 and 1.3 μg/L/24 h). Unhealthy fish exposed to CAP showed significant higher total leukocyte counts and neutrophils percentage compared to non-exposed infected fish). However, the monocytes and eosinophils percentage significantly decreased in fish exposed to CAP. Furthermore, lysozyme activity values measured in plasma, skin mucus, gill and intestine significantly reduced in fish exposed to CAP. The CAP-induced immunomodulation may interfere on the ability of the animal to heal or fight the infection, and possible contribute to the spread of bacterial infection in fish production or environment.

Linseed protein concentrate as alternative to fishmeal in diets for silver catfish, Rhamdia quelen

AbstractA 60‐day feeding trial was conducted to evaluate the efficiency of the substitution of fishmeal (FM) with linseed protein concentrate (LPC) in the diet of silver catfish, Rhamdia quelen (6.13 g). Five isonitrogenous and isoenergetic experimental diets were formulated to replace 0, 10, 20, 30, or 40% of FM with LPC, and silver catfish were fed these diets to apparent satiation. LPC had a lower protein content compared to FM, but in vitro results showed higher protein digestibility of LPC as compared to fishmeal. There were no significant differences (p > .05) in growth, digestive somatic index, and intestinal quotient in the groups receiving LPC diets. The activity of the digestive enzymes did not differ among treatments, except for chymotrypsin, which was higher (p < .05) in the 30 and 40% LPC treatment groups. These results show that LPC protein can replace up to 40% of FM in silver catfish diets without adverse effects on growth performance.

Linseed fibers modulate the production of short-chain fatty acids and improve performance and plasma and skin mucus parameters of silver catfish (Rhamdia quelen).

This study was conducted to evaluate the prebiotic action of distinct linseed fibers on diets for silver catfish (Rhamdia quelen) juvenile. For this, soluble and insoluble fractions of linseed fiber were concentrated separately and combined in four ratios (1:0.5, 1:1, 1:2, 1:4), which were added in diets and evaluated along with a control diet. After 45days receiving the experimental diets, the animals were submitted to biometry for data collection and samples. The experimental design was completely randomized, data were submitted to analysis of variance, and the means were compared by Tukey's test (P < 0.05). Fish performance was higher for the group that received the 1:2 and 1:4 diets. The production of intestinal acetic acid was higher in fish fed on the 1:2 diet, and butyric acid was higher with 1:4 diet and the propionic acid with the control diet. The control diet led to lower counts of goblet cells. Total proteins and globulins in plasma, mucoprotein, total immunoglobulins, and cutaneous mucus pH were higher in fish fed on diets 1:2 and 1:4. Cortisol levels and intestinal pH were lower in these treatments. The linseed fiber intake increased total plasma immunoglobulins and plasma alkaline phosphatase activity and in mucus. It was concluded that the use of 1:2 and 1:4 soluble fiber/insoluble linseed in the diet beneficially modulates the production of short-chain fatty acids in the digesta, with reflection on growth performance, number of goblet cells in the intestinal epithelium, and improvement in plasma and skin mucus parameters of fish.

Ethanolic extract of Hyptis mutabilis (Rich.) Briq.: An effective sedative and antioxidant agent in fish

The goal of this study was to evaluate the anesthetic potential of an ethanolic extract of Hyptis mutabilis and its effects on behavior, biochemistry, ionic balance, and oxidative stress biomarkers of silver catfish (Rhamdia quelen) after 24-h exposure. Additionally, its chemical composition was determined by high performance liquid chromatography coupled with a diode array detector and tandem mass spectrometry (HPLC-DAD-MS/MS) to identify its bioactive compounds. The concentration range of 50–500 mg L−1 induced only partial loss of equilibrium (14–2 min) in fish. There was quick recovery (about 5 min) with 50 and 100 mg L−1, while not all animals recovered within 30 min exposure to the higher concentrations. Fish exposed to 100 mg L−1 maintained a sedative level during the long-term experiment. There were lower plasma glucose and lactate levels in fish exposed to the extract compared with the control group (water). There were net Na+ and K+ influxes after exposure to the extract, while Cl− effluxes were observed in all groups (treated or not). Ammonia excretion decreased in animals exposed to extract, and creatinine elimination did not change. Fish exposed to 100 mg L−1 showed higher catalase and glutathione S-transferase activities in the kidney, while glutathione-dependent peroxidase activity increased in the liver. Lipid peroxidation in the kidney did not differ among experimental groups, while there were lower levels in the liver of juveniles exposed to the extract. There was no mortality or side effects in any of the experiments. Rosmarinic acid (53.76 ± 0.13 mg g−1 extract) and rutin (5.75 ± 0.28 mg g−1 extract) were identified in the extract based on standards. In conclusion, the ethanolic extract of H. mutabilis is a promising fish sedative at 100 mg L−1. Its use for long-term exposure showed a good safety margin and ability to prevent stress. Hence, it can be proposed for use in the transport of aquatic animals.

Replacement of corn by rice grits, with or without phytase supplementation, in diets for silver catfish ( Rhamdia quelen ) juveniles

Replacement of corn by rice grits, with or without phytase supplementation, in diets for silver catfish ( <i>Rhamdia quelen</i> ) juveniles

Protective effects of diet containing rutin against trichlorfon-induced muscle bioenergetics disruption and impairment on fatty acid profile of silver catfish Rhamdia quelen

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.

Effects of reduced protein level and dietary amino acid supplementation on growth, body composition and intestinal morphometry of silver catfish ( Rhamdia quelen )

The reduction in the protein level and the supplementation of lysine (Lys) and methionine (Met) in the diet were evaluated in the performance and intestinal morphometry of silver catfish (Rhamdia quelen). The study was used in a completely randomized design for 63 days, where 320 fish (26.33 ± 0.40 g) were distributed in 20 tanks (250 L, 16 fish each) and fed until the apparent satiety was reached. Five diets were formulated, a positive control [38% of crude protein (CP) (38CP)], a negative control [34% of CP (34CP)] and three test diets [34% of CP supplemented with Lys (34L), 34% of CP supplemented with Met (34M) and 34% of CP supplemented with Lys plus Met (34LM)]. Final weight and condition factor were greater in fish fed the 34LM diet than in those fed the 34CP diet (p < .05). Body lipid deposition was lower in fish fed the 34CP diet than other diets (p = .0002). In the fillet, there was a lower deposition of lipids in fish fed with 34L diet than in fish fed with 34M and 34LM diets (p <.0001). Fish fed the 34LM diet had a higher AA content in the plasma than those fed 34L and 34CP diets (p < .0001). The lower villus height was observed in fish fed the 34L diet compared to the 38CP diet (p = .021). It is possible to reduce 4% of the CP level in silver catfish diets with supplementation of Lys and Met.

Vitamin C supplementation in aquaculture activities

Neste estudo, investigaram-se os efeitos de diferentes níveis de vitamina C na dieta de peixes com biomarcadores de estresse oxidativo e parâmetros hematológicos em jundiás. Os juvenis foram divididos em três grupos e alimentados com diferentes quantidades de vitamina C: 1) 0, 2) 500 e 3) 1.000 mg kg-1. Dez peixes por grupo foram coletados em 0, 14 e 28 dias após o início do experimento. A atividade da catalase hepática aumentou no grupo 1 após 28 dias. A atividade da GPx nas brânquias diminuiu em todos os grupos, e a GPx hepática aumentou nos grupos alimentados com vitamina C. A atividade hepática da SOD e os níveis de NPSH nas brânquias e no fígado não foram afetados. Em todos os grupos, a atividade GST diminuiu nas brânquias e aumentou no fígado. Os níveis de peroxidação lipídica diminuíram no fígado e nas brânquias para os grupos 2 e 3. Os resultados deste estudo indicam que ambas as dietas, com 500 ou 1.000 mg/kg de vitamina C, contribuíram para diminuir o dano oxidativo de Rhamdia quelen, sugerindo que a suplementação de vitamina C no presente modelo experimental pode ser útil na aquicultura para superar possíveis mudanças oxidativas induzidas por condições ambientais adversas.

Behavioral impairment and neurotoxic responses of silver catfish Rhamdia quelen exposed to organophosphate pesticide trichlorfon: Protective effects of diet containing rutin

Trichlorfon is an organophosphate pesticide used extensively for controlling ectoparasites in aquaculture. Studies have found that trichlorfon caused environmental pollution and severe neurotoxic effects in several freshwater species. Feed additives such as flavonoids may reduce or prevent pesticide-induced toxicity in fish. The aim of the present study was to determine whether acute exposure to trichlorfon impairs behavior and causes oxidative damage in brains of silver catfish (Rhamdia quelen). We also sought to determine whether rutin would be capable of preventing or reducing these effects. Silver catfish were divided into four groups: groups A and C received basal feed, while groups B and D received feed containing 3 mg rutin/kg diet for 21 days. After 21 days, groups C and D were exposed for 48 h to a nominal concentration of 11 mg trichlorfon/L water. Fish exposed to trichlorfon showed significantly longer distances travelled and swimming performances than did unexposed fish. Cerebral levels of reactive oxygen species and lipid peroxidation were significantly higher in fish exposed to trichlorfon than in unexposed fish, while cerebral superoxide dismutase, catalase, glutathione peroxidase, and acetylcholinesterase (AChE) activities were significantly lower. Taken together, our findings suggest that dietary supplementation rutin completely prevented all alterations elicited by trichlorfon, except for cerebral AChE activity; the latter remained significantly lower compared to the unexposed group. In summary, rutin prevents trichlorfon-induced neurotoxicity in silver catfish.

Sublethal effects of triclosan and triclocarban at environmental concentrations in silver catfish (Rhamdia quelen) embryos

Although banished in some countries, triclosan (TCS) and triclocarban (TCC) have been detected in surface waters in concentrations ranging from ng L−1 to μg L−1 and have shown to affect non-target organisms posing risk to aquatic ecosystems. However, the majority of the studies consider higher levels of these chemicals and single exposure effects to investigate their potential risks, rather than using environmentally relevant concentrations and their binary mixture. In this study, the toxicity of TCS and TCC, and their binary mixture was assessed in catfish embryos (Rhamdia quelen, a south American native species) exposed to environmental concentrations during 96 h. Organisms were evaluated through the endpoints of developmental abnormalities (spine, fin, facial/cranial and thorax), biochemical biomarkers related to oxidative stress responses: catalase (CAT), superoxide dismutase (SOD), glutathione-S-transferase (GST) activities, protein carbonylation (PCO) and neurotoxicity by acetylcholinesterase activity (AChE). The data showed that TCS caused fin abnormalities, decrease of SOD activity and increase of AChE activity in the catfish embryos of 96hpf. On the other hand, TCC and the binary mixture showed a higher abnormality index for the 96hpf embryos, and an induction of CAT and GST activities for the mixture treatment. The results obtained were able to show potential, but not severe, toxicity of TCS and TCC even in low concentrations and a short period of exposure. The relevance of studies approaching real scenarios of exposure should be reinforced, considering environmental concentrations of chemicals, interactions of contaminants in complex mixtures and the use of a native species such as R. quelen exposed during initial stages of development.

Quercetin attenuates endocrine and metabolic responses to oxytetracycline in silver catfish (Rhamdia quelen)

This study aimed to verify whether dietary quercetin protects against the detrimental effects induced by oxytetracycline (OTC) administration in silver catfish (Rhamdia quelen). Fish were divided into different experimental groups that received OTC and/or quercetin, either during 14 or 21 days. To determine the endocrine system stress response, we have measured the brain mRNA expression levels of corticotropin-releasing hormone (crh), proopiomelanocortins (pomca and pomcb) and some of the pituitary hormones (growth hormone [gh], somatolactin [sl], and prolactin [prl]). We have also quantified the levels of cortisol as well as some metabolites (glucose, glycogen, lactate, and triglycerides) in the plasma. Moreover, the enzymatic activity of hexokinase, phosphorylase (active GPase), fructose-biphosphatase (FBP), glycerol-3-phosphate dehydrogenase, glucose-6-phosphate dehydrogenase, and glutamate dehydrogenase (GDH) and gill Na+/K+-ATPase were measured. The results demonstrated that OTC activates the silver catfish stress response by increasing the plasma cortisol and decreasing the glucose levels at 14 and 21 days. Additionally, OTC also altered the fish hepatic metabolic status as demonstrated by an increase in triglycerides levels and the enzymatic activity of both FBP and GDH after 14 days. OTC also stimulated Na+/K+-ATPase activity in the gill after 14 days and altered the hypophyseal expression of gh (at 14 and 21 days) and prl (at 14 days). The co-treatment with 1.5 g of quercetin could prevent most of the alterations caused by OTC, strongly suggesting quercetin as a beneficial compound when added to the fish diet.

Rutin-added diet protects silver catfish liver against oxytetracycline-induced oxidative stress and apoptosis

It is unknown whether the flavonoid rutin can protect the silver catfish liver in response to exposure to a known stressor, such as the prophylactic usage of the antimicrobial agent oxytetracycline. Thus, the current study aimed to assess the effect of rutin incorporation into the silver catfish diet formulation on oxytetracycline-induced liver oxidative stress and apoptosis. Fish were split into four groups as follows: control, rutin (1.5 g kg diet−1), oxytetracycline (0.1 g kg diet−1) and rutin+oxytetracycline (1.5 g kg diet−1 and 0.1 g kg diet−1, respectively). After two weeks of feeding with the different diets (standard, rutin-, oxytetracycline and rutin+oxytetracycline-added diets), fish were euthanized to collect the liver. Although the rutin-added diet was unable to recover glutathione peroxidase activity, ascorbic acid and reduced glutathione (GSH) levels, which were depleted due to oxytetracycline consumption, it markedly diminished the oxidized glutathione (GSSG) content, thus decreasing the GSSG to GSH ratio, an important index of oxidative stress. It also increased glutathione reductase and markedly augmented glucose-6-phosphate dehydrogenase activities, which were declined after oxytetracycline ingestion. Furthermore, the rutin-added diet reestablished superoxide dismutase and catalase activities and reduced lipid peroxidation, nitric oxide and superoxide anion levels as well, all changes resulting from oxytetracycline consumption. Finally, it also prevented oxytetracycline-induced apoptosis through increasing heat shock protein 70 and markedly decreasing high mobility group box 1 and, consequently, reducing cleaved caspase-3 protein levels. Therefore, in conclusion, the incorporation of this flavonoid to the silver catfish diet protected the liver against oxytetracycline-induced liver oxidative stress and apoptosis.

Efeito da aveia em dietas com fitase para o jundiá sobre desempenho, composição corporal e histologia intestinal

Este estudo avaliou a inclusão de aveia em dietas suplementadas com fitase para jundiá sobre: desempenho zootécnico, composição corporal e morfologia intestinal. Foram utilizados 168 juvenis de jundiá com peso e comprimento médio de 4,51 ± 0,59g e 8,11 ± 0,54 cm, respectivamente, distribuídos aleatoriamente em 24 unidades experimentais. O experimento foi realizado em esquema fatorial 4x2 em triplicata, no qual o primeiro fator foram os níveis crescentes de inclusão de aveia em substituição ao milho de 0, 33, 66 e 100%. O segundo fator foi a inclusão ou não de fitase (0 e 1500 Uf kg-1). Houve interação entre os fatores para o ganho em peso e taxa de crescimento específico, onde os peixes alimentados com 66% de substituição de aveia por milho na dieta suplementada, com fitase, apresentaram melhores resultados. No que diz respeito a composição corporal, os valores de umidade dos peixes alimentados com 100% de substituição de aveia por milho, sem fitase, foram os que apresentaram os menores valores para esta variável. Houve influência da aveia para a composição proteica corporal, no qual os peixes alimentados com dietas contendo substituição total do milho pela aveia apresentaram os maiores valores. Os peixes alimentados com a enzima fitase apresentaram maior composição lipídica corporal. Não foram verificadas diferenças na morfologia intestinal dos jundiás alimentados com as dietas testadas. Sugere-se que a utilização de fitase em dietas para o jundiá não afeta os parâmetros avaliados. Com exceção dos níveis de substituição de 33%, com fitase, e 66%, sem fitase, a substituição do milho pela aveia em dietas para o jundiá pode ser realizada sem que ocorram prejuízos sobre o desempenho produtivo, composição corporal e histologia intestinal. Ainda, a substituição de milho por aveia em 66%, com fitase, resulta em maior ganho em peso.

Growth, hematology, metabolism, and oxidative parameters of silver catfish (Rhamdia quelen) fed diets containing Lippia alba leaf

The dietary addition of Lippia alba essential oil has been studied in fish, showing excellent results against lipid peroxidation. The objective of this study was to evaluate the compounds present in the plant and the growth, hematology, metabolism, and oxidative parameters of silver catfish fed diets containing L. alba leaf. The experimental design was completely randomized with 500 silver catfish distributed in 5 treatments and 4 replicates in a water recirculation system. The treatments tested were: control (without leaf inclusion); 0.5; 1; 1.5 and 2% inclusion of L. alba leaf powder. All diets tested had the same composition matrix, containing 37.49% crude protein and 10.04% lipids. Leaf compounds have been found that may have great antioxidant capacity such as caffeic acid, verbascoside, and calceolarioside E. However, some compounds present in the leaf may cause damage to fish performance such as malic acid and quinic acid. Fish fed diets containing L. alba leaf presented lower growth and changes in hematological parameters compared to control fish. At the higher levels of L. alba leaf inclusion, undesirable metabolic changes occurred as increased plasma alanine aminotransferase activity, indicating liver damage. The presence of L. alba leaf in diets resulted in decreased muscle lipid peroxidation and increased the amount of non-protein thiols in the gills and muscle. This indicates that the plant leaves have antioxidant potential in fish. Therefore, at the tested levels, the addition of L. alba leaf powder in diets for juveniles of silver catfish is not recommended. Summary statementThis article is interesting because it assesses the inclusion of natural products in fish diets, resulting in improved health.

Silver catfish (Rhamdia quelen) breeders fed on crude glycerin-containing diets exhibited metabolic alterations and increased sperm concentration

This study aimed to evaluate the effects of the inclusion of crude glycerin in silver catfish (Rhamdia quelen) broodstock diets on their growth, characteristics of fresh and cryopreserved sperm, blood biochemical parameters, and tissue centesimal composition. A total of 150 males (52.8 ± 2.93 g) and 225 females (53.4 ± 3.38 g), reared in 15 excavated 16 m2 nursery tanks, were included in the study. The fish were fed rations containing 300 g digestible protein (DP) kg−1 and 12.55 MJ digestible energy (DE) kg−1 diet, and five different crude glycerin levels (0, 40, 80, 120, and 160 g kg−1). Male growth and reproductive parameters, the DNA integrity in fresh sperm, as well as the characteristics of cryopreserved sperm were evaluated 12 months after the start of the experiment. Blood samples were also obtained to quantify the calcium, triglyceride, glucose, total protein, aspartate aminotransferase, alanine aminotransferase, alkaline phosphatase, total cholesterol, and high-density lipoprotein (HDL) cholesterol plasma levels, and to evaluate the erythrocyte DNA integrity. Fish were euthanized and dissected to evaluate the hepatosomatic (HSI), viscerosomatic (VSI), and gonadosomatic (GSI) indices, and to evaluate the centesimal composition of the organs and tissues. There was an increase (p < .05) in the sperm concentration of animals fed the highest level of crude glycerin. The other seminal and spermatic parameters from fresh or cryopreserved sperm remained unchanged (p > .05). Among blood parameters, the total cholesterol and total protein levels were augmented (p < .05) in fish fed rations containing 80 g glycerin kg−1, while the calcium level decreased (p < .05) in fish fed 160 g crude glycerin kg−1. The growth was not altered (p > .05). Increases were observed in the muscle dry matter and ash and testicular raw protein contents (p < .05) in the group fed the ration with the highest crude glycerin level; in contrast, the muscle protein levels were decreased (p < .05). The preliminary results showed that Rhamdia quelen males fed the highest crude glycerin dietary levels led to metabolic alterations which increased protein deposition in the testis and increased sperm concentration, without damages on growth or survival. The higher sperm concentration will allow to producing more doses of cryopreserved sperm.

Diphenyl diselenide‐loaded nanocapsules in silver catfish feed enhance growth, improve muscle antioxidant/oxidant status and increase selenium deposition: Advantages of nanotechnology for fish health

The aim of this study was to determine whether feed supplementation with nanoencapsulated Ph2Se2 would improve the growth performance of silver catfish and would maintain or improve the muscle antioxidant system. Final mean weight (p = .031), weight gain (p = .014) and specific growth rates (p = .045) were significantly higher in supplemented fish than in the control group. Muscle reactive oxygen species (p = .0001) levels were significantly lower in supplemented fish than in the control group. Also, muscle hydrogen peroxide (p = .0001) and lipid peroxidation (p = .0001) levels were significantly lower in supplemented fish than in the control group. Muscle antioxidant capacity against peroxyl radical (p = .00001) levels were significantly higher in fish supplemented with both Ph2Se2 forms (free or nanocapsules) than in the control group, while muscle superoxide dismutase (p = .001) and catalase (p = .0001) activities were significantly higher in supplemented fish than in the control group. Finally, selenium (Se) deposition (p = .00001) was significantly higher in the muscle of fish supplemented with free and nanoencapsulated forms compared with the control; and deposition levels were significantly higher in fish supplemented with Ph2Se2-loaded in nanocapsules compared with the free form. Based on this evidence, Ph2Se2-loaded in nanocapsules improves silver catfish performance and antioxidant/oxidant status. The greater content of Se (1.22 µg/g muscle) in the muscle of fish fed with dietary Ph2Se2-loaded nanocapsules indicates that it may be considered a nutraceutical for fish.