Effects of the total replacement of fish-based diet with plant-based diet on the hepatic transcriptome of two European sea bass (Dicentrarchus labrax) half-sibfamilies showing different growth rates with the plant-based diet

Background: Efforts towards utilisation of diets without fish meal (FM) or fish oil (FO) in finfish aquaculture have been being made for more than two decades. Metabolic responses to substitution of fishery products have been shown to impact growth performance and immune system of fish as well as their subsequent nutritional value, particularly in marine fish species, which exhibit low capacity for biosynthesis of long-chain poly-unsaturated fatty acids (LC-PUFA). The main objective of the present study was to analyse the effects of a plant-based diet on the hepatic transcriptome of European sea bass (Dicentrarchus labrax). Results: We report the first results obtained using a transcriptomic approach on the liver of two half-sibfamilies of the European sea bass that exhibit similar growth rates when fed a fish-based diet (FD), but significantly different growth rates when fed an all-plant diet (VD). Overall gene expression was analysed using oligo DNA microarrays (GPL9663). Statistical analysis identified 582 unique annotated genes differentially expressed between groups of fish fed the two diets, 199 genes regulated by genetic factors, and 72 genes that exhibited diet-family interactions. The expression of several genes involved in the LC-PUFA and cholesterol biosynthetic pathways was found to be up-regulated in fish fed VD, suggesting a stimulation of the lipogenic pathways. No significant diet-family interaction for the regulation of LC-PUFA biosynthesis pathways could be detected by microarray analysis. This result was in agreement with LC-PUFA profiles, which were found to be similar in the flesh of the two half-sibfamilies. In addition, the combination of our transcriptomic data with an analysis of plasmatic immune parameters revealed a stimulation of complement activity associated with an immunodeficiency in the fish fed VD, and different inflammatory status between the two half-sibfamilies. Biological processes related to protein catabolism, amino acid transaminations, RNA splicing and blood coagulation were also found to be regulated by diet, while the expression of genes involved in protein and ATP synthesis differed between the half-sibfamilies. Conclusions: Overall, the combined gene expression, compositional and biochemical studies demonstrated a large panel of metabolic and physiological effects induced by total substitution of both FM and FO in the diets of European sea bass and revealed physiological characteristics associated with the two half-sibfamilies

Development of digestive enzymes in larvae of Solea senegalensis, Kaup 1858

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Dietary phospholipids are more efficient than neutral lipids for long‐chain polyunsaturated fatty acid supply in European sea bass Dicentrarchus labrax larval development

International audienceAbstract We evaluated the effects of dietary lipid class (phospholipid vs. neutral lipid) and level of n−3 long‐chain PUFA (LC‐PUFA) on the growth, digestive enzymatic activity, and histological organization of the intestine and liver in European sea bass larvae. Fish were fed from the onset of exogenous feeding at 7 to 37 d post‐hatch with five isoproteic and isolipidic compound diets with different levels of EPA and DHA. Diet names indicated the percentage of EPA and DHA contained in the phospholipids (PL) and neutral lipids (NL), as follows: PL5, PL3, PL1, NL1, and NL3. Histological observations showed different patterns of lipid absorption and accumulation in the intestinal mucosa depending on the level and nature of the dietary lipid fraction. Fish fed high levels of neutral lipids (11%, NL3 diet: 2.6% of EPA+DHA in the NL fraction) showed large intracellular and intercellular lipid deposits in the anterior intestine, but no such lipid accumulation was detected when larvae were fed with low and moderate levels of EPA and DHA in the phospholipid and neutral lipid fractions of the diet (PL and NL1 diets). PL were preferentially absorbed in the postvalvular intestine, and the accumulation of marine PL was inversely correlated to their dietary level. The postvalvular intestinal mucosa and liver showed signs of steatosis; large lipid vacuoles were observed in this region of the intestine and in the liver and were inversely correlated with the level of dietary neutral lipids. The best results in terms of growth, survival, and development (maturation of the digestive system and histological organization of the liver and intestinal mucosa) were obtained in the group fed with 2.3% of EPA and DHA in the PL fraction of the diet (PL3 diet), revealing that European sea bass larvae use the LC‐PUFa contained in the PL fraction more efficiently than those from the NL fraction of the diet

Impacts of three different microdiets on Florida Pompano, Trachinotus carolinus, weaning success, growth, fatty acid incorporation and enzyme activity

In this study, three microdiets were tested on weaning of Florida pompano larvae: Otohime, Gemma and a reference diet LR803. The experimental system was stocked with 11-day-old larvae, which were co-fed micro-diets and live food from 11 dph to 17 dph then micro-diets only until 28 dph. Survival from 11 dph to 28 dph was similar for all treatments, with an average of 33%. At the end of the trial, the Gemma larvae were significantly longer and heavier than those larvae fed the other diets. Significant differences were observed in fatty acid composition of the diets and larvae between treatments. The Gemma larvae incorporated the lowest amount of eicosapentaenoic acid (EPA), docosahexaenoic acid (DHA) and arachidonic acid (ARA). However, they had the highest DHA/EPA and ARA/EPA ratios, which is in agreement with the concept that the proportions of polyunsaturated fatty acids could be of greater importance than their absolute amount. Results from the enzyme analysis suggest that fishmeal is suitable as the main protein source for Florida pompano larvae. This study gives new insights on Florida pompano early nutritional requirements and demonstrated the full functionality of the pancreas at 16 days post hatch, opening possibilities of an earlier weaning time

Dietary TAG source and level affect performance and lipase expression in larval sea bass ( Dicentrarchus labrax )

International audienceAbstract The influence of dietary TAG source (fish oil, triolein, and coconut oil) and level (7.5 and 15% of the diet) on growth, lipase activity, and mRNA level was studied in sea bass larvae, from mouth opening until day 24 and from day 37 to 52. Fish oil and triolein induced better growth in both experiments, this being significant at a higher dietary level. Coconut oil significantly decreased growth at the higher level, possibly as the result of an excessive supply of medium‐chain TAG. Growth was not related to lipase specific activity, suggesting a production in excess to dietary needs. Body lipid content was positively related to dietary lipid level and was affected by lipid quality. In addition, larval FA composition generally reflected that of the diet. The source of dietary lipid, but not the quantity, was shown to affect lipase activity significantly. Coconut oil diets induced the highest lipase activity, whereas the effect of fish oil was age dependent‐it was similar to coconut oil at day 24 but induced the lowest lipase activity in 52‐d‐old larvae. The differential lipase response was probably caused by differences in the FA composition of the diet, related to the specificity of lipase toward FA differing in chain length and degree of saturation. No significant differences were found in lipase/glyceraldehyde‐3‐phosphate dehydrogenase mRNA, which suggests the existence of a posttranscriptional regulation mechanism

Effects of a mix of Bacillus sp. as a potential probiotic for Florida pompano, common snook and red drum larvae performances and digestive enzyme activities

This study examined the effect of a commercial mix ofBacillussp. on survival, growth and digestive enzyme activities of Florida pompano, red drum and common snook. Larvae were fed either live feed enriched with Algamac 3050 (Control), Algamac 3050 and probiotics (PB), or the previous diet combined with a daily addition of probiotics to the tank water (PB+). Survival was not affected by the treatments for any of the species. At the end of the pompano and snook trial, standard lengths of larvae from the PB and PB+ treatments were significantly greater than for the control larvae. Microbiological analyses were performed at the end of the pompano trial, and numbers of presumptive Vibrio were not a concern in the system. For both pompano and snook, trypsin-specificactivity was higher in PB and PB+ larvae compared with the control larvae. Similarly, alkaline phosphatase activity was higher for the pompano larvae fed the PB and PB+ treatments and for the snook larvae fed the PB+ treatment compared with the control larvae. This experiment suggests that a mix ofBacillussp. can promote growth through an early maturation of the digestive system during the early larval stages of pompano and snook

Maturation of the digestive system of Downs herring larvae (Clupea harengus, Linnaeus, 1758): identification of critical periods through ontogeny

Digestive system functionality is a key process linked to larval recruitment and survival. However, little is known about organ development and enzyme maturation of the digestive system of North Sea Atlantic herring (Clupea harengus). In this study, herring larvae were reared at 13 °C from hatching to 69 day post hatch, covering four developmental stages: (1) yolk sac (8–9 mm), (2) pre-flexion (9–14 mm), (3) flexion (12–18 mm) and (4) post-flexion stages (15–30 mm). Combined histological (semi-quantitative scoring) and enzyme analyses (pancreatic and intestinal) showed that developmental stages are strongly linked to physiological changes. The larvae lack a functional stomach and use the intestine as the primary site of digestion which is mainly supported by pancreatic enzyme activity. The intestine acquired adult enzymatic digestive features with a functional brush border at the end of the flexion stage and pyloric ceca started to develop during the post-flexion stage. The transition from pre-flexion to flexion stage and the end of the post-flexion stage are energetically taxing periods as indicated by a reduced number and size of liver vacuoles. Based on these findings, we consider these moments as critical periods, where herring larvae could be dramatically affected by suboptimal feeding conditions in the field. This implies that pre-flexion stage larvae with low or no liver reserves may not be able to proceed to the next developmental stage. Hence, the level of energy storage in first-feeding larvae needs to be examined for its use as a field indicator of survival and development

Effects of the total replacement of fish meal and fish oil by plant sources on the hepatic transcriptome of European sea bass (Dicentrarchus labrax)

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