The sustainable development of the aquaculture industry relies on the use of alternative conventional and emergent raw materials that contributes to a circular economy and to reduce the dependency on ...fish meals and fish oils coming from oceanic fish populations. Additionally, the genetic selection of farmed fish that can display higher growth and feed utilization when fed alternative feeds, is pointed out to be a complementary valuable tool to facilitate the implementation of circular economy approaches. The main purpose of the present study was to determine the effectiveness of genetic selection for growth in European sea bass, in response to a challenge with an alternative diet that aimed to partially replaced fishmeal (FM) by poultry meal (PM) and totally replace fish oil (FO) by a blend of poultry oil (PO) with a novel microalgae oil. The two families of fish juveniles were obtained by in vitro fertilization of selected for a multi-trait including high growth (genetically selected, GS) or non-selected (wild type, WT) broodstocks and then were nutritionally challenged with a control diet that mirrored a standard commercial diet with fishmeal (20%) and fish oil (7%), or a Future diet that partially replaced the FM by PM and totally replaced the FO by a blend of rapeseed oil, PO, and a novel DHA rich-algal oil. From the second month of feeding until the end of the trial, European sea bass that was selected since for 7 generations performed better in terms of growth than the wild-type genotype, possibly related with an apparent favored feed and nutrient utilization. Furthermore, selection decreased the perivisceral fat and increased the nutritional value of flesh by increasing DHA (in g/ 100 g flesh) and ARA contents. In contrast, the dietary treatment showed little effect on fish growth performance, denoting the successful partial replacement of FM by PM and the total replacement of FO by a blend of poultry oil and an emergent microalgal oil. However, Future diet tended to reduce the ADCs of some amino acids, as well as showed an additive effect to genotype in increasing the n-3 PUFA of flesh. Altogether, our data demonstrate that multi-trait genetic selection of European sea bass improve fish plasticity to cope with the variations of ingredients in alternative feeds with low FM/FO.
•Selected European sea bass has higher plasticity to cope with the variations of dietary ingredients.•Genetic selection in European sea bass improved feed utilization, protein gain and the ADC, increasing their availability for sea bass growth.•Genetically selected fish presented significantly lower perivisceral fat than wild-type genotype.•Genetic selection increased the nutritional value of flesh, especially by increasing the DHA and ARA levels.•Future diet showed an additive effect to genotype in increasing n-3 PUFA levels of fish flesh.
•We evaluated a commercial diet for gilthead seabream that uses vegetable oils as lipid source.•We studied the effect of diet on the quality of the final product.•Changes in the fatty acid ...composition of the flesh were seen with the diets.•Higher color saturation and textural parameters values were observed with the vegetable oil diet.•The differences do not have important implications for health or sensory properties.
The long-term unsustainability of fish oil as a lipid source in aquaculture feeds has led to its progressive replacement with vegetable oils. Several studies have shown that this replacement results in a different fatty acid profile that is likely to compromise the healthy properties and quality of fish by reducing their n-3 HUFA content. In the present study, we evaluate the effect of partial replacement of fish oil with vegetable oils on the quality of the final product. Eighty-four gilthead seabream (Sparus aurata) were fed one of two different commercial diets for 19 weeks in triplicate (14 fish per tank). These diets contained either 100 % fish oil (FO diet) or a 75 % vegetable oil blend (VO diet) (50/50 mixture of soybean and rapeseed oil). After slaughter, physical-chemical analyses (Fatty Acids (FAs); flesh color; Water-Holding Capacity (WHC); pH; and Texture Profile Analysis (TPA)) and a sensory analysis were performed. Fish fed either diet displayed similar growth and feed conversion rates (SGR and FCR). The fish fed the VO diet showed an increase in muscular n-6 fatty acids, which resulted in a lower n-3/n-6 ratio. A lower presence of EPA and DHA fatty acids was also observed, although the total quantity of n-3 fatty acids was similar in both groups. With regard to fat quality, the Atherogenic Index (AI) was lower in the VO-diet group, while both groups presented a similar Thrombogenic Index (TI). The diet had some effect on quality parameters, but the changes were not very intense. The differences observed in the a* and b* chromatic parameters were not significant, but a greater and significant color saturation in the vegetable oil group was observed. No significant differences in pH and WHC were observed. Fish fed the vegetal oil diet also scored higher for hardness, springiness, gumminess and chewiness. In the sensory analysis no significant differences were observed between the two groups. The differences observed for both the fatty acid profile and the quality parameters do not appear to have any important implications in terms of either health or the sensory properties of gilthead seabream fed a vegetable oil diet.
Bone health is important for a viable and ethically sound Atlantic salmon aquaculture industry. Two important risk factors for vertebral deformities are dietary phosphorus and water temperature. ...Here, we explore the interplay between these two factors during a full production of Atlantic salmon. Salmon were fed one of three diets (low 4.4–5.0 g kg−1, medium 7.1–7.6 g kg−1, or high 9.0–9.7 g kg−1 soluble phosphorus) from 3 to 500 g body weight, followed by a common diet of 7.3 g kg−1 soluble phosphorus until harvest size at 4 kg. Additional groups were included to investigate the effects of water temperatures of 10 vs 16 °C (low and high diets only) and the switching of dietary phosphorus levels (from low to medium or high, from medium to low or high, from high to low or medium), starting at seawater transfer (~100 g body weight) and lasting for 4 months (~500 g body weight). During the experimental feeding period, the low phosphorus diet caused reduced bone mineralization and stiffness and a greater prevalence of vertebral deformities, compared to the medium and high phosphorus diets. However, the prevalence of severely deformed fish at harvest was reduced by switching from the low to either the medium or high phosphorus diets for 4 months after seawater transfer, followed by rearing on the standard commercial feed. Concurrently, switching from either the medium or high to a low phosphorus diet for the same period following seawater transfer had no effect on vertebral deformities at harvest. The higher water temperature for 4 months following seawater transfer increased the severity of deformities at harvest, irrespective of dietary phosphorus. Finally, low dietary phosphorus was associated with increased fillet damage, due to ectopic connective tissue around the spine, at harvest. In conclusion, dietary phosphorus levels of 5 g kg−1 for the initial 4 months in seawater are more of a risk factor for vertebral pathologies if preceded by low, but not medium or high, dietary phosphorus in freshwater. However, dietary phosphorus levels may not play a role in temperature induced radiologically detectable vertebral pathologies. Under the reported growing conditions and diet compositions, a combination of 7.5–7.6 g kg−1 soluble phosphorus during freshwater and 5.0 g kg−1 for the first 4 months in seawater, was sufficient for normal bone health and growth in Atlantic salmon.
•Dietary phosphorus levels in salmon following seawater transfer, and in respect to seawater temperature, were evaluated•Low soluble phosphorus (LP) levels of 4.4–5.0 g kg−1, from first feeding to post smolts, resulted in poor bone health•Switching from LP to ≥7.1 g kg−1 soluble phosphorous from sea transfer mitigated some of the effects on bone health•Dietary soluble phosphorus levels of 5 and 9 g kg−1 did not interact with sea temperatures of 16 and 10 °C, on bone health.
This study tests the effects of feeding different vegetable oils (VO) in gilthead sea bream with the aim of improving sustainable aquafeeds. Juveniles were fed ad libitum with ten isonitrogenous ...(46%) and isolipidic (22%) diets with a 75% fish oil (FO) replacement, differing in VO composition leading to two experimental blocks: fish fed with VO blends or mono-substituted diets. Growth parameters, skin and muscle colour, muscle texture, plasma metabolites, digestive capacities, and transcript levels of intestinal lipid transport, muscle dynamics and lipid metabolism-related genes in white muscle and adipose tissue were studied. In fish fed high-palm oil diets, final body weight and mesenteric fat significantly increased, while effects were not found in hepatosomatic index, reflecting tissue-specific lipid accumulation. Relative intestinal length increased significantly with dietary soya oil (SO) content, suggesting a compensatory mechanism to improve nutrient absorption capacity. Plasma parameters showed few changes upon dietary treatments. Lipase activity was unaltered, while intestinal fatp1b expression increased in animals fed blended diets high in rapeseed oil (RO). In adipose tissue, expression of nuclear receptors pparβ and lxr was modified by dietary fatty acids (FA) profile; however, regarding lipid metabolism and β-oxidation genes, only lpl showed significant differences, suggesting that FA uptake and oxidation, but not de novo lipogenesis is what appears to determine the increase in adipose tissue mass. In fish fed blended VO diets, lpl expression showed a positive correlation with MUFA dietary content, suggesting that some FA present in RO enhance its expression, according to data from fish fed mono-substituted diets. In muscle, fish fed blended VO diets also showed a positive correlation of lpl expression with dietary MUFA, whereas in mono-substituted, it was significantly higher in fish fed SO, suggesting other mechanisms are involved in LPL regulation. Concerning β-oxidation genes in muscle, significant differences were detected in cpt1a expression for fish fed blended VO diets, whereas hadh and cpt1b were unaltered, suggesting slight FA uptake regulation in mitochondria. Expression levels of genes related to myogenic processes were not greatly modified by dietary lipid sources except for myogenin in blended VO diets-fed fish, showing a similar profile as that in body weight and opposite with the differentiation marker mhc. This study provides new information regarding the effects of dietary VO, demonstrating moderate effects in lipid homeostasis without adverse effects on growth performance, leading to a transversal view of the responses and interactions from intestine to muscle growth and flesh quality.
•Transversal view of responses from intestine, adipose tissue to muscle to dietary vegetable oils substitution in seabream.•Relative intestinal length and fatty acid transporters expression showed adaptations to specific vegetable oils.•Palm oil had positive effects on growth but caused a higher accumulation of visceral fat in this species.•High proportion of dietary MUFA could favor the lpl expression in adipose and muscle tissues.
Calpains are non-lysosomal calcium-activated neutral proteases involved in a wide range of cellular processes including muscle proteolysis linked to post-mortem flesh softening. The aims of this ...study were (a) to characterise several members of the calpain system in gilthead sea bream and (b) to examine their expression in relation to nutritional status and muscle tenderisation. We identified the complete open reading frame of gilthead sea bream calpains1-3, sacapn1, sacapn2, sacapn3, and two paralogs of the calpain small subunit1, sacapns1a and sacapns1b. Proteins showed 63-90% sequence identity compared with sequences from mammals and other teleost fishes, and the characteristic domain structure of vertebrate calpains. Transcripts of sacapn1, sacapn2, sacapns1a and sacapns1b had a wide tissue distribution, whereas sacapn3 was almost exclusively detected in skeletal muscle. Next, we assessed transcript expression in skeletal muscle following alteration of nutritional status by (a) fasting and re-feeding or (b) feeding four experimental diets with different carbohydrate-to-protein ratios. Fasting significantly reduced plasma glucose and increased free fatty acids and triglycerides, together with a significant increase in sacapns1b expression. Following 7 days of re-feeding, plasma parameters returned to fed values and sacapn1, sacapn2, sacapns1a and sacapns1b expression was significantly reduced. Furthermore, an increase in dietary carbohydrate content (11 to 39%) diminished growth but increased muscle texture, which showed a significant correlation with decreased sacapn1 and sacapns1a expression, whilst the other calpains remained unaffected. This study has demonstrated that calpain expression is modulated by nutritional status and diet composition in gilthead sea bream, and that the expression of several calpain members is correlated with muscle texture, indicating their potential use as molecular markers for flesh quality in aquaculture production.
Alternatives to the use of native vegetable oils (VO) as fish oil (FO) replacers in aqua feeds were evaluated. Acid oils are a free fatty acid (FFA)-rich by-product mainly from the refining of VO. ...Re-esterified oils are the final product of a chemical esterification reaction between acid oils and glycerol, and have less FFA and more mono- and diacylglycerols (MAG and DAG), known for being good emulsifiers, than crude VO. Therefore, they could have a higher nutritive value than that of the native and acid oils. In two earlier studies in rainbow trout (Trullàs et al., 2015, 2016), diets including acid and/or re-esterified VO resulted in total fatty acid apparent digestibility coefficients above 95%. Moreover, no negative effects on growth, plasma biochemical parameters and morphology of tissues were observed when compared to the native oil diet. For all these reasons, the present study aimed at assessing their effects on the final quality of fillets of rainbow trout. Triplicate groups of rainbow trout were fed eight experimental diets containing 15% of different types of experimental rapeseed oils in addition to 5% of FO during 72days. The experimental rapeseed oils were native (RNO), acid (RAO), re-esterified (REO), or blends (66% RN-33% RAO/33% RN-66% RAO or 66% REO-33% RAO/33% REO-66% RAO). Commercial FO was used for the control diet (F). The colorimetric analysis resulted in significant differences only in b* and C* in both fresh and thawed fillets, as well as in significant correlations between the colorimetric parameters among diets. For the total fat content, fillets of fish fed the control diet obtained the highest values, which were higher than those of fish fed diets containing RNO and the blend 66% REO-33% RAO. No differences in texture, liquid holding capacity, and TBARS were found among fillets of fish fed the different diets. Regarding tocopherol concentrations in fillets, α-tocopherol was significantly higher (P<0.05) in fillets of fish fed the control diet than in those fed RA/RE, while β+γ-tocopherol was significantly lower in fillets of fish fed C than in the rest. Even though the aforementioned differences were found, they did not seem to be relevant concerning the final quality of fillet.
•Re-esterified and acid vegetable oils could be sustainable and economically advantageous replacers for fish oil and native vegetable oils.•There was an interest in assessing the effects of re-esterified and acid rapeseed oils on the quality of fillets, in light of their previous good results in fatty acid digestibility, growth and plasma parameters.•Diets including 15% of rapeseed acid or re-esterified oils as a single or blended fat source do not seem to produce relevant changes in the flesh quality of rainbow trout.
Manganese (Mn) is an essential metal for fish and requirements have been established for several finfish but not for gilthead sea bream. Thus, the present study aims to establish the optimal dietary ...supplementation level of Mn in gilthead sea bream fingerlings fed vegetable based diets.
Gilthead sea bream fingerlings (weight 12.6 ± 1.5 g, mean ± S.D.) were fed five practical diets high in vegetable ingredients (fish meal: 10%, fish oil: 6%). The diets were supplemented to contain 19, 27, 30, 41 and 66 mg Mn kg−1 as MnSO4. Four hundred and fifty sea bream fingerlings were randomly distributed in 15 tanks and fed one of the five diets until apparent satiation three times per day for 42 days. Growth parameters including feed intake, thermal growth coefficient and feed conversion ratio were calculated. At the end of the trial, samples were taken for biochemical, mineral, histological and gene expression analyses.
After the feeding trial, fish almost tripled their weight, but dietary Mn levels did not affect growth parameters or survival. The high fish meal substitution levels led to high Mn contents in the basal diet (19 mg Mn kg−1 diet), that seemed to be sufficient to promote sea bream growth. Body lipid composition, protein and ash were not affected by the dietary Mn. Similarly, whole body, liver and vertebrae mineral contents were not affected by Mn supplementation. Morphological characteristics of liver had no significant differences among dietary Mn levels. However, increase of Mn contents beyond 30 mg Mn kg−1 down-regulated mnsod expression. Expression of cat gene was not affected.
Overall, results suggest that the Mn content present in the basal diet (19 mg Mn kg−1) was sufficient to cover the requirements in juvenile gilthead sea bream fed practical plant-based diets, although results from oxidative status markers might point out the need to increase supplementation levels beyond this point when fish are under conditions that may affect their oxidative status.
•The effects of dietary Mn in plant based feeds for gilthead sea bream was studied.•The high Mn contents in the basal diet was sufficient to promote sea bream growth.•Dietary Mn contents beyond 30 mg Mn kg−1 down-regulated MnSOD expression.•Overall other parameters remained unaffected by the dietary Mn content.•Under high oxidative stress, markers suggest the need to increase Mn levels.
In this study, the intestinal microbiota of farmed Atlantic salmon (Salmo salar L.) was examined with traditional culture-based techniques, and by molecular analysis of the 16S rDNA. The aim of the ...study was to evaluate the use of cultivation-based and molecular-based techniques, and compare the results obtained by the two methods. Samples were collected from the fore-, mid- and hind-gut, respectively. PCR and denaturing gradient gel electrophoresis (DGGE) analyses were performed on DNA extracted directly from the gut content and from bacteria cultivated on Tryptic Soy Agar (TSA). Population fingerprints of the predominant microbiota were generated by DGGE analysis of universal V3 16S rDNA PCR amplicons, and distinct bands from DGGE were sequenced. Results show that the salmon intestine was dominated by Lactobacillus spp., Lactococcus sp., Bacillus sp., Photobacterium phosphoreum, Acinetobacter sp., Pseudomonas sp. and Vibrio sp. Molecular analyses of samples from direct DNA extraction enabled detection of lactic acid bacteria. Prior cultivation detected Vibrio sp., Acinetobacter sp. and Pseudomonas sp., which were not detected by the direct analyses. In addition to the PCR–DGGE approach, 50 TSA isolates from the hind-gut were pure cultured and identified by partial sequencing of the 16S rDNA. Vibrio spp. and P. phosphoreum dominated among these isolates. The data provided demonstrate the use of PCR–DGGE as an alternative method for studying the intestinal microbiota of fish.
Systemic Granulomatosis (SG) affects the majority of cultured meagre (Argyrosomus regius). This pathological condition, whose aetiology is still not known, is identified by multiple granulomas in a ...variety of organs that become calcified and necrotic with time. The available evidence supports the hypothesis that SG is a metabolic disorder associated with nutritional imbalances, and the present study examined the role of dietary vitamin D3, minerals (Ca, P) and plant-protein sources in the development of the disease. The use of plant-protein in the diet formulation exacerbated the progression of SG, while vitamin D3 did not prevent its occurrence. On the other hand, the severity of SG was improved by increasing the P content in the feed. However, the exact irritant that causes this inflammatory response in meagre is still unknown and more research needs to examine other nutritional factors.
•Systemic granulomatosis (SG) is a newly described disease that affects the majority of cultured meagre.•The aetiological factor of SG is unknown; however there is evidence that it may be a metabolic disorder.•Dietary vitamin D3 did not affect the development of the disease while high P content in the diet improved the condition•Fishmeal replacement by plant proteins affected negatively the progression of the disease
Gilthead seabream (Sparus aurata Linnaeus, 1758 (Perciformes, Sparidae)) is an important aquaculture species in the Mediterranean Sea basin. Yet, quantitative data on its dentition under standard ...farming conditions are currently lacking. Furthermore, it is unknown if the dentition can adapt to food of different sizes. Here, we describe the lower jaw dentition of juvenile S. aurata fed a standard pellet size (4 mm) and present a detailed analysis of 11 representative teeth. Overall, the number of teeth showed large individual variation, but it was not significantly related to fish length. Considerable left-right differences were observed, without clear side dominance. We also assessed the influence of feeding S. aurata a smaller (2 mm) or larger (6 mm) pellet size. Four months of feeding with different pellet sizes did not cause detectable differences in total tooth number on the dentaries at the time of harvest, nor in size of the teeth assumed to be most relevant in food processing. If and how different pellet sizes may nevertheless affect digestion, and eventually fish health, is subject for further studies.
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