Search

The article presents a study which examines the non-specific immune responses of the head-kidney leucocytes of Senegalese sole, Solea senegalensis (Kaup), against Tenacibaculum maritimum. The function of head-kidney cells in increasing the production of reactive oxygen species (ROS) is outlined. The need to conduct further studies on the interactions between T. maritimum strains and Senegalese sole is emphasized.

Abstract: The effect of heat treatment and the presence or absence of fish skin on the volatile composition of Senegalese sole muscle was studied. The volatile profile of Senegalese sole at different storage periods was also evaluated. All samples were analysed by HS-SPME–GC–IT/MS and subjected to sensory evaluation. As expected, cooking enhanced the production/liberation of volatile compounds. Fish with the skin present, after cooking, had higher levels of sulphur compounds, 2-nonanone, ethyl octanoate and lower contents of hexanol and heptanol than skinned fish; moreover, the samples with the skin had a better overall sensory acceptability. During storage, changes on the volatile composition of Senegalese sole samples were found. The major differences were obtained after 2 weeks of storage. Compounds such as hexanal, heptanal, octanal, decanal, (E)-2-hexenal, (E)-2-decen-1-al, (E,Z)-2,6-nonadienal, benzaldehyde, 4-ethyl-benzaldehyde, 1-penten-3-ol, heptanol and (E)-2-octen-1-ol decreased after 2 weeks of storage, and other compounds, such as 3-methyl-1-butanal, 2-methyl-1-butanal, 2-heptanone, dimethyl trisulphide, dimethyl tetrasulphide and 2-methyltetrahydrothiophen-3-one increased. These differences were confirmed by sensory evaluation. Principal component analysis was applied to the chemical data. [Copyright &y& Elsevier]

Abstract: The present study evaluates the possible effects of dietary protein sources on Senegalese sole muscle volatile compounds. Senegalese sole juveniles (8g mean IBW) were fed with six extruded diets containing different protein sources: a control diet contained fish meal as the main protein source and five plant protein-based diets, in which fishmeal was replaced by increasing levels of a blend of vegetable proteins: soybean, pea, potato, wheat and corn gluten at five graded levels. The volatile profiling of the raw fish fillets was evaluated using automated HS-SPME coupled to GC–MS. Thirty-five compounds were identified and the most abundant in all samples were quantified. 1-Penten-3-ol, hexanal, 1-octen-3-ol and (E)-2-nonen-1-ol were present in the highest concentrations. Among the 20 compounds quantified, no major differences were observed in muscle volatile profile of fish fed with the different diets (p >0.05). These findings indicated that fish meal substitution by plant proteins has no major effects on sole’s muscle volatile composition. [Copyright &y& Elsevier]

A 74-day trial was undertaken to evaluate the effects of temperature (16 and 22 °C) and dietary protein/lipid ratio on the performance of juvenile Senegalese sole (mean body weight: 6.4 g). Four experimental diets were formulated to contain two protein levels (550 g kg−1 and 450 g kg−1) combined with two lipid levels (80 g kg−1 and 160 g kg−1). Growth was higher at 22 °C and within each temperature in fish fed diets 55P8L and 45P16L. Feed efficiency, N retention (% NI) and energy retention (% EI) were higher at 22 and at both temperatures in fish fed diet 55P8L. Temperature affected whole-body composition, with dry matter, protein, lipid and energy being higher and ash lower in fish kept at higher temperature. Independently of temperature, whole-body lipid, energy and ash were higher and protein was lower in fish fed the high-lipid diets. Visceral and hepatosomatic indices were not affected by diet composition but were higher in fish kept at 16 °C. Liver glycogen and lipid contents and activities of glutamate dehydrogenase, alanine and aspartate aminotransferases were not affected by diet or water temperature. Malic enzyme (ME) and glucose 6-phosphate dehydrogenase activities were higher in fish fed the low-lipid diets. ME activity was higher at lower temperature. In conclusion, increasing water temperature from 16 to 22 °C improves growth and feed efficiency of Senegalese sole juveniles; regardless of water temperature, the diet with 550 g kg−1 protein and 80 g kg−1 lipid promoted the best growth and feed efficiency. [ABSTRACT FROM AUTHOR]

Highlights: [•] Volatile profile of Senegalese sole, fed with different diets, was determined. [•] Fish meal replacement up to 75% with plant protein (PP) has no effect on sole muscle volatile composition. [•] Replacement of fish oil did not influence sensory appreciation. [•] PP diets led to the production of lower amounts of volatile compounds than vegetable oil diets. [ABSTRACT FROM AUTHOR]

The present study aimed to investigate leucocyte responses to inflammation as well as some innate immune parameters of Senegalese sole, Solea senegalensis, following challenge with two strains of Photobacterium damselae subsp. piscicida belonging to the European and Japanese clones described for this bacterium. Pathogenicity assays were performed to assess the virulence of each Photobacterium damselae subsp. piscicida strain for sole. Subsequently, fish were intraperitoneally injected with phosphate-buffered saline (control) or two concentrations (2 × 102 and 2 × 106 CFU mL−1) of each bacterial strain and sampled after 6 and 24 h. Results showed that the European isolate induces a higher degree of response than the Japanese strain. While blood neutrophilia and monocytosis correlated well with the increase in neutrophil and macrophage numbers in the peritoneal cavity, fish infected with the European isolate presented higher peritoneal cell numbers than fish challenged with the Japanese strain. In addition, alternative complement pathway activity and respiratory burst of head kidney leucocytes increased significantly in fish infected with the European isolate. The enhanced innate immune response displayed by Senegalese sole challenged with the European isolate is probably due to the higher degree of virulence presented by this Photobacterium damselae subsp. piscicida strain. [ABSTRACT FROM AUTHOR]

Abstract: The replacement of fish meal (FM) by increasing levels of plant protein (PP) sources 50% (PP50), 75% (PP75) and 100% (PP100) was compared to a control diet (FM) containing fish meal as the main protein source in ongrowing Senegalese sole (mean initial body weight:106g±15). These four diets were isonitrogenous and isolipidic (54% crude protein and 9% crude fat on a dry matter basis). By the end of the growth trial, groups fed PP50 and PP75 had a final body weight and daily growth index (DGI) similar to the FM fed group (200g and 0.8–0.9, respectively), whereas PP100 diet induced a significantly lower DGI (0.4). PP100 showed the highest feed conversion ratio (FCR) (2.4 vs 1.5) and the lowest protein gain (0.5 vs 0.9gkg−1ABWday−1). Nutrient intake of PP groups was statistically similar to the FM group. Apparent digestibility coefficients (ADCs) of nutrients did not differ significantly among treatments (p>0.05) and all PP diets induced lower fecal P losses than the FM group (33%). The highest PP levels (PP75 and PP100) resulted in decreased whole body lipid contents, thought PP100 showed the highest HSI and liver total lipids. In all groups, liver was the major lipid storage organ (13.96–28.57% WW). Muscle lipid content was low (1.3–1.6% WW) and did not vary significantly among treatments. Polyunsaturated fatty acid (PUFA) levels in muscle were also similar amongst dietary treatments and the two highest replacement levels (PP75 and PP100) were still effective in producing an n-3 PUFA rich product (29–30% of total fatty acids (WW)) similar to the FM group (33% of total fatty acids (WW)). Docosahexaenoic acid (DHA) was selectively retained in muscle (17–21% of total fatty acids (WW)) and neither DHA/EPA (Eicosapentaenoic acid) nor EPA/ARA (Arachidonic acid) ratios were significantly affected (p>0.05) by dietary treatments. The sensory evaluation of cooked slices showed that the replacement of marine protein sources (FM) by PP blends did not have a significant impact on the majority of the descriptors, though visual freshness and whiteness of the PP75 flesh yielded the highest scores. Our results indicate that ongrowing Senegalese sole can effectively use diets with high levels of PP sources, up to 75% of FM replacement, without impairing feed intake, growth performance and protein utilisation whilst preserving high n−3 PUFA and DHA flesh content. [Copyright &y& Elsevier]

Abstract: Effects of 55 and 45% dietary protein levels (55P and 45P diets, respectively) and temperature (12 and 18°C) on hepatic activity of superoxide dismutase (SOD), catalase, glutathione peroxidase, glutathione reductase (GR), glucose-6-phosphate dehydrogenase and lipid peroxidation (LPO) levels of Solea senegalensis juveniles were studied. Further, effects of acute thermal shocks provoked by a drop (18°C to 12°C) or a rise (12°C to 18°C) of water temperature on sole oxidative state was also evaluated. Dietary protein reduction increased LPO levels though no major alterations were found on antioxidant enzyme activities between dietary treatments. At 12°C GR activity was higher and SOD activity was lower than 18°C but LPO levels were not affected. In both thermal shock cases, LPO levels increased in 55P group, probably due to insufficient antioxidant enzyme activation. In contrast, fish of 45P group under acute exposition to warmer and colder temperature exhibited no substantial changes and a significant decrease on LPO levels, respectively, along with no major changes in antioxidant enzymes. Overall, results suggest that independently of rearing temperatures 45P group was more susceptible to oxidative stress than 55P group. Thermal shock either due to rise or drop of temperature seemed to induce oxidative stress in 55P group. [Copyright &y& Elsevier]

Abstract: A growth trial with Senegalese Sole (Solea senegalensis Kaup, 1858) juveniles fed with diets containing increasing replacement levels of fishmeal by mixtures of plant protein sources was conducted over 12weeks. Total fat contents of muscle, liver, viscera, skin, fins and head tissues were determined, as well as fatty acid profiles of muscle and liver (GC-FID analysis). Liver was the preferential local for fat deposition (5.5–10.8% of fat) followed by fins (3.4–6.7% fat). Increasing levels of plant protein in the diets seems to be related to increased levels of total lipids in the liver. Sole muscle is lean (2.4–4.0% fat), with total lipids being similar among treatments. Liver fatty acid profile varied significantly among treatments. Plant protein diets induced increased levels of C16:1 and C18:2 n−6 and a decrease in ARA and EPA levels. Muscle fatty acid profile also evidenced increasing levels of C18:2 n−6, while ARA and DHA remained similar among treatments. Substitution of fishmeal by plant protein is hence possible without major differences on the lipid content and fatty acid profile of the main edible portion of the fish – the muscle. [Copyright &y& Elsevier]

Abstract: A growth trial was conducted to evaluate the growth potential and nutrient utilization of Senegalese sole fed diets containing increasing replacement levels of dietary fishmeal (FM) by mixtures of plant protein (PP) sources. Six extruded isonitrogenous and isolipidic diets (55% crude protein and 8% crude fat on a dry matter basis) were fed to juvenile sole (mean initial body weight: 8g±0.06) during 92days. A reference diet containing FM as the main protein source (Control) was compared with five PP based-diets with increasing PP levels: 25% (PP25), 35% (PP35), 45% (PP45), 60% (PP60) and 75% (PP75). PP45, PP60 and PP75 diets were supplemented with crystalline amino acids to simulate the level present in the Control diet. The environmental impact of the tested diets was assessed through the determination of N and P budgets and calculating approximate Fish-in:Fish-out (Fi:Fo) ratios. Fish fed PP25 and PP75 reached a final body weight and daily growth index (DGI) similar to the Control group (P>0.05). Diet PP45 displayed the lowest DGI (0.8 vs 1.3%), lowest protein efficiency ratio (1.03 vs 1.8) and highest FCR (1.7 vs 1.01). The dietary treatments with highest percentage of FM replacement (PP60 and PP75) displayed similar FCR values as the Control (1.2–1.0). Apparent digestibility coefficients (ADCs) of protein varied between 77 and 85% and were not significantly affected by the PP inclusion level. Whole body protein and energy content did not differ significantly among treatments, but protein gain was significantly higher in the Control group compared to PP35, PP45 and PP60 groups. The results indicate that Senegalese sole can effectively cope with plant protein-based diets, but growth rate and nutrient gain mainly depend on the selection of adequate plant protein blends, rather than on the plant protein incorporation level. Sole fed the highest PP level (PP75) showed good growth performance, efficient dietary nutrient utilization and a lower Fi:Fo ratio compared to the Control. The present results clearly show that increasing FM replacement level can have a positive environmental impact as reduces P fecal waste and the fishmeal used per kg of sole produced. [Copyright &y& Elsevier]

A study was undertaken to determine the dietary protein level for optimal growth performance and body composition of juvenile Senegalese sole. Five experimental extruded diets were formulated to contain increasing levels of protein [430, 480, 530, 570 and 600 g kg−1 dry matter (DM)] and a constant lipid level, ranging from 100 to 130 g kg−1 DM. Triplicate groups of 35 sole (initial body weight: 11.9 ± 0.5 g) were grown over 84 days in 60-L tanks supplied with recirculated seawater. Fish were fed by means of automatic feeders in eight meals per day. At the start and end of the trial, whole-body samples were withdrawn for proximate composition analysis. At the end of 84 days of experimental feeding, daily weight gain and specific growth rate in fish fed diets P43 and P48 were significantly lower than those found in fish fed higher protein level diets (P53, P57 and P59). Similarly, feed efficiency was also significantly lower in fish fed diet P43 than in fish fed all other dietary treatments. Sole juveniles fed lower protein level diets (P43 and P48) showed a significantly lower protein content than fish fed the higher dietary protein level treatments (P53, P57 and P60). Changes within the tested dietary protein levels did not affect significantly protein productive value or total nitrogen (N) losses in fish. However, daily N gain was significantly higher ( P < 0.05) in fish fed diets P53 and P60 than in fish fed the lowest protein level diet (P43). Data from the present study indicate that diets for juvenile Senegalese sole should include at least 53% crude protein to maintain a good overall growth performance. Based on a second-order polynomial regression model, the daily crude protein requirement for maximum whole-body N gain as estimated here for Senegalese sole juveniles was 6.43 g kg−1 body weight day−1 which corresponds to a value of 1.03 g N intake kg−1 body weight day−1. If the present data are expressed on a dietary crude protein concentration basis, the allowance for maximum protein accretion (N gain) would be met by a diet containing a crude protein level of 600 g kg−1. [ABSTRACT FROM AUTHOR]