Diet-fed Fish Research Articles

Growth performance and antioxidant enzyme activities in rainbow trout (Oncorhynchus mykiss) juveniles fed diets supplemented with sage, mint and thyme oils

This study evaluated effects of dietary supplementation of sage (Salvia officinalis), mint (Mentha spicata) and thyme (Thymus vulgaris) oils on growth performance, lipid peroxidation level (melondialdehyde, MDA) and liver antioxidant enzyme activities (superoxide dismutase, SOD; catalase, CAT; glucose-6-phosphate dehydrogenase, G6PD; glutathione reductase, GR; glutathione-S-transferase, GST and glutathione peroxidase, GPx) in rainbow trout (Oncorhynchus mykiss) juveniles. For this purpose, triplicate groups of rainbow trout were fed daily ad libitum with diets containing sage, mint and thyme oils at 500, 1,000 and 1,500 mg kg(-1) for 60 days. While weight gain percentage of fish fed the diets containing sage and thyme oils was significantly higher than the control group, that of fish fed mint oil was the lowest. Similarly, specific growth rate was found to be the highest in all groups of the sage and thyme oil feeding and the lowest in the mint groups. Moreover, feed conversion ratio was significantly higher in the mint oil administered groups. Survival rate was also significantly reduced in the fish fed the diet containing mint oil. It was observed that SOD, G6PD and GPx activities were significantly increased in liver tissues of all the treated fish groups compared to that of control diet-fed group. However, CAT, GST and GR activities were significantly decreased in experimental diet-fed fish groups at the end of the experiment. On the other hand, a significant reduction was found in MDA levels in the fish fed the diets with sage and thyme oils compared to control and mint diets on the 30th and 60th days of experiment. Overall, dietary inclusion of sage and thyme oils is effective in enhancing rainbow trout growth, reduction in MDA and least changing antioxidant enzyme activities at a low level of 500 mg kg(-1) diet, and they can be used as important feed supplements for rainbow trout production.

The effect of exposure to a high-fat diet on microRNA expression in the liver of blunt snout bream (Megalobrama amblycephala).

Blunt snout bream (Megalobrama amblycephala) are susceptible to hepatic steatosis when maintained in modern intensive culture systems. The aim of this study was to investigate the potential roles of microRNAs (miRNAs) in diet-induced hepatic steatosis in this species. MiRNAs, small non-coding RNAs that regulate gene expression at the posttranscriptional level, are involved in diverse biological processes, including lipid metabolism. Deep sequencing of hepatic small RNA libraries from blunt snout bream fed normal-fat and high-fat diets identified 202 (193 known and 9 novel) miRNAs, of which 12 were differentially expressed between the normal-fat and high-fat diet groups. Quantitative stem-loop reverse transcriptase-polymerase chain reaction analyses confirmed the upregulation of miR-30c and miR-30e-3p and the downregulation of miR-145 and miR-15a-5p in high-fat diet-fed fish. Bioinformatics tools were used to predict the targets of these verified miRNAs and to explore potential downstream gene ontology biological process categories and Kyoto Encyclopedia of Genes and Genomes pathways. Six putative lipid metabolism-related target genes (fetuin-B, Cyp7a1, NADH dehydrogenase (ubiquinone) 1 beta subcomplex subunit 2, 3-oxoacid CoA transferase 1b, stearoyl-CoA desaturase, and fatty-acid synthase) were identified as having potential important roles in the development of diet-induced hepatic steatosis in blunt snout bream. The results presented here are a foundation for future studies of miRNA-controlled lipid metabolism regulatory networks in blunt snout bream.

Dietary histidine requirement to reduce the risk and severity of cataracts is higher than the requirement for growth in Atlantic salmon smolts, independently of the dietary lipid source

The present study was carried out to investigate whether the dietary histidine requirement to reduce cataract development is higher than that for growth in Atlantic salmon smolts (Salmo salar L.) after seawater transfer and whether dietary vegetable oils contribute to cataractogenesis. Duplicate groups of salmon smolts were fed ten experimental diets with either fish oil (FO) or a vegetable oil (VO) mix replacing 70% FO and histidine at five target levels (10, 12, 14, 16 and 18g His/kg diet) for 13 weeks after seawater transfer. The VO diet-fed fish exhibited somewhat inferior growth and feed intakes compared with the FO diet-fed fish, irrespective of the dietary histidine concentration. Both cataract prevalence and severity were negatively correlated with the dietary histidine concentration, while lens N-acetyl-histidine (NAH) concentrations were positively correlated with it. The fatty acid profiles of muscle, heart and lens reflected that of the dietary oils to a descending degree and did not affect the observed cataract development. Muscle, heart and brain histidine concentrations reflected dietary histidine concentrations, while the corresponding tissue imidazole (anserine, carnosine and NAH) concentrations appeared to saturate differently with time. The expression level of liver histidase was not affected by the dietary histidine concentration, while the liver antioxidant response was affected in the VO diet-fed fish on a transcriptional level. The lowest severity of cataracts could be achieved by feeding 13·4g His/kg feed, independently of the dietary lipid source. However, the present study also suggests that the dietary histidine requirement to minimise the risk of cataract development is 14·4g His/kg feed.

Impact of UV-B Radiation on the Physiology of Freshwater Carp Labeo rohita Larvae and Evaluation of UV-B Protective Properties of Seeds of Achyranthes aspera and Vitamin C

Effect of harmful UV-B radiation and their remedial measures have been studied in Labeo rohita (rohu) larvae. Larvae were fed with four different diets: D1 and D2 contained 0.1 and 0.5 % Achyranthes aspera seeds, respectively; D3 contained 800 mg vitamin C/kg diet, and D4 contained control diet. After 50 days, all groups were exposed to UV-B radiation (80 μW/cm2). One batch of control diet-fed fish was exposed to UV-B (D4Ex), and the other group remained unexposed (D4UEx). Survival rate of rohu was significantly (P < 0.05) higher in D2 when compared to others. Among the exposed groups, highest average weight was recorded in D2 (103 ± 4 mg). Total tissue protein concentration was higher in exposed groups compared to the unexposed one. Glutamic oxaloacetic transaminase (GOT) and glutamate pyruvate transminase (GPT) levels were minimum in unexposed control diet-fed fish. Vitamin C provided protection against lipid peroxidation which was evident from the lowest level of thiobarbituric acid reactive substance in exposed fish (D3). Significantly (P < 0.05) higher nitric oxide synthase level in fish fed with Achyranthes aspera seeds (0.5 %) supplemented diet showed the immunomodulatory property of the seeds. A combination of vitamin C and seed may be more UV-B protective for carp larvae.

Effect of plant-based feed ingredients on osmoregulation in the Atlantic salmon lens

Lenses of adult Atlantic salmon fed with a plant oil and plant protein-based diet (plant diet) were compared to lenses of fish fed a diet based on traditional marine ingredients (marine diet) with respect to biochemical composition and functionality ex vivo. After 12 months of feeding, plant diet-fed fish had smaller lenses with higher water contents and lower concentrations of histidine (His) and N-acetylhistidine (NAH) than fish fed with the marine diet. Cataract development in both dietary groups was minimal and no differences between the groups were observed. Lens fatty acid and lipid class composition differed minimally, although a significant increase in linoleic acid was observed. The lenses were examined for their ability to withstand osmotic disturbances ex vivo. Culture in hypoosmotic and hyperosmotic media led to increase and decrease of lens volume, respectively. Lenses from plant diet-fed fish were less resistant to swelling and shrinking, released less NAH into the culture medium, and accumulated His and NAH at higher rates than lenses from marine diet-fed fish. Culture in hypoosmotic medium resulted in higher cataract scores than in control and hyperosmotic medium. mRNA expression of selected genes, including glutathione peroxidase 4 and SPARC (secreted protein acidic and rich in cysteine), was affected by diet and osmotic treatment. It can be concluded that lenses of farmed Atlantic salmon are affected by the diet composition, both in biochemical composition and physiological functionality in relation to osmoregulation.

Dietary medicinal plant extracts improve growth, immune activity and survival of tilapia Oreochromis mossambicus

The effects of supplementing diets with acetone extract (1% w/w) from four medicinal plants (Bermuda grass Cynodon dactylon, H(1), beal Aegle marmelos, H(2), winter cherry Withania somnifera, H(3) and ginger Zingiber officinale, H(4)) on growth, the non-specific immune response and ability to resist pathogen infection in tilapia Oreochromis mossambicus were assessed. In addition, the antimicrobial properties of the extract were assessed against Vibrio alginolyticus, Vibrioparahaemolyticus, Vibrio mimicus, Vibrio campbelli, Vibrio vulnificus, Vibrio harveyi and Photobacterium damselae. Oreochromis mossambicus were fed 5% of their body mass per day for 45 days, and those fed the experimental diets showed a greater increase in mass (111-139%) over the 45 days compared to those that received the control diet (98%). The specific growth rate of O. mossambicus fed the four diets was also significantly greater (1.66-1.93%) than control (1.52%) diet-fed fish. The blood plasma chemistry analysis revealed that protein, albumin, globulin, cholesterol, glucose and triglyceride levels of experimental fish were significantly higher than that of control fish. Packed cell volume of the blood samples of experimental diet-fed fish was also significantly higher (34.16-37.95%) than control fish (33.0%). Leucocrit value, phagocytic index and lysozyme activity were enhanced in fish fed the plant extract-supplemented diets. The acetone extract of the plants inhibited growth of Vibrio spp. and P. damselae with extracts from W. somnifera showing maximum growth inhibition. A challenge test with V. vulnificus showed 100% mortality in O. mossambicus fed the control diet by day 15, whereas the fish fed the experimental diets registered only 63-80% mortality at the end of challenge experiment (30 days). The cumulative mortality index for the control group was 12,000, which was equated to 1.0% mortality, and accordingly, the lowest mortality of 0.35% was registered in H(4)-diet-fed group.

Dietary Lactosucrose Decreases Hepatic and Plasma Lipid Contents in a Marine Teleost, Red Sea Bream Pagrus major

The aims of this study were to confirm the effects of dietary lactosucrose (LS), a fermentable oli- gosaccharide, on plasma and liver lipid levels in red sea bream. Fish were assigned to two groups and fed either a commercial diet or a commercial diet supplemented with 0.24% LS for two months. Fish fed LS had lower liver lipid contents than did control diet-fed fish (P< 0.001). Levels of plasma cholesterol and triglyceride but not HDL-cholesterol in fish fed LS were signifi- cantly lower than in control fish (P< 0.001). The above results indicate that the dietary fermentable saccharide LS affected lipid metabolism in this fish.

Effect of dietary EE/NFE ratio on sensorial traits of shi drum

A four months growth trial was carried out in order to evaluate the quality traits of juvenile shi drum (Umbrina cirrosa) fed two isonitrogenous and isoenergetic diets having a different EE/NFE ratio (LOW, 0.7 vs. HIGH, 1.1). Compared to HIGH diet, LOW one was formulated increasing the replacement of fish oil with cereal products and soybean meal. At the end of the feeding trial (2 replicate per dietary treatment), 26 fish for each thesis were sorted according to live weight and submitted to chemical and sensorial analysis. Dietary treatments showed similar productive performance. The relative high inclusion of carbohydrates in substitution of lipids did not affect proximate composition of whole body and dorsal fillet. Among sensorial traits, LOW diet-fed fish evidenced a significant lower trunk exudation and fillet lightness. Results of this research showed that shi drum is a suitable candidate for Mediterranean marine aquaculture and its dietary formulation might include at least the NFE amount tested in this trial.

Effect of the partial replacement of fish meal and oil by vegetable products on performance and quality traits of juvenile shi drum (Umbrina cirrosa L.)

A four-month growth trial was carried out in order to evaluate performance and quality traits of juvenile shi drum fed with two isonitrogenous and isoenergetic diets having different amounts of vegetable products (Vegetable diet vs. Control diet). Compared to the Control diet, the Vegetable diet was formulated by increasing the replacement of fish meal (14%) with soybean and cereal products, and fish oil (12%) with a mixture of vegetable oil. On June, 4 groups of 225 fish (2 replicates per dietary treatment) were sorted according to live weight and reared in fibreglass tanks over a four- month long experimental period. Fish were hand fed to apparent satiety. Offered feed, growth parameters and feed efficiency were recorded as productive performance. At the end of the trial (October) biometric, chemical and reological traits were examined to assess fish quality. The dietary treatments showed similar productive performance. The relatively high inclusion of vegetable sources led to a significant modification of body shape, mesenteric fat and viscera weight. Among quality traits, Vegetable diet-fed fish demonstrated a significantly lower whole body and fillet crude protein content. Yellowness value of the cooked fillet was significantly lower in the Control diet-fed fish, whereas fillet texture was similar. The results of this research showed that shi drum is a suitable candidate for Mediterranean marine aquaculture and its dietary formulation might include at least the amount of vegetable sources used in this trial.

Effect of dietary fat level on carcass traits and flesh quality of European Sea Bass (Dicentrarchus labrax) from mariculture

The study aimed at evaluating the effect of the reduction of dietary fat on juvenile European sea bass nutritional value and quality traits. Fish were reared in floating cages (Trieste Gulf, Italy) from July (11) to October (10). Two isoproteic diets were compared: LF (low fat, EE = 19.4%) vs. HF (high fat, EE = 24.6%). No significantly different growth performance was observed. LF diet-fed fish were characterized by the reduction of celomatic fat (not edible fraction) and by the increase in dressing percentage. The tested dietary fat level also affected both fillet and epiaxial white muscle proximate composition, resulting in a significantly lower fillet lipid concentration in LF diet-fed fish. Dietary treatment influenced cooked fillet colour and texture probably as a consequence of the different intramuscular fat deposition. Fillet from HF-fed fish, in fact, presented higher lightness (L*) value and lower instrumental strengthness.

Growth and feed conversion of juvenile winter flounder (Pleuronectes americanus) in relation to different protein-to-lipid levels in isocaloric diets

Abstract Winter flounder show good potential for culture in Atlantic Canada. Information about their nutritional requirements is necessary in order to be able to formulate cost-effective feeds that produce acceptable growth rates. Fish meal, the principal protein source in most fish feeds, is one of the more expensive ingredients. Reduction of the amount of protein in diets would reduce the cost of feed. Therefore, a 10-week feeding trial was conducted with juvenile winter flounder (initial weight 0.8 g) in order to determine the effect of reducing digestible protein-to-energy levels in diets on specific growth rates (SGR), feed efficiency (FE) and respiration rates. Experimental diets were formulated to contain dietary protein-to-lipid levels of 50:10%, 45:15% and 40:20%. There were significant differences in final weights and percent weight gain among all three dietary treatments. Winter flounder fed the 50:10 diet (26.6 mg kJ −1 digestible protein to energy) had the highest specific growth rate (2.1±0.2% weight day −1 ), which was significantly greater ( P −1 (1.1±0.3% day −1 ), but not significantly different from those that fed the 45:15, 23.5 mg kJ −1 diet (1.7%). The 50:10 diet-fed fish had a feed efficiency ratio (0.7±0.1) which was significantly better than the 40:20 group (0.2±0.1, P P =0.06), the protein efficiency of the 50:10 diet-fed fish tended to be higher than the other two groups.