Ishrana riba: poboljšanje efikasnosti hranljivih materija i korišćenja vode

Be it a semi-intensive or a totally intensive culture system, aquatic animal production depends on the availability of essential nutrients and energy supplied in the form of supplementary / complementary or complete feeds. Under any of these circumstances, the cost of these nutrient inputs remains high. Adequate nutrition is essential for the maintenance of vital functions with significant impacts on early development, growth, health, flesh quality and reproductive performance. Over the past decades, nutrition research has greatly contributed towards the remarkable development of feed-based intensive aquaculture around the world, in optimising feed quality and in the reduction of feed cost in the overall production. It is also now fully demonstrated that optimisation of the nutritional quality of the feeds and the feeding strategies can considerably improve the efficiency of fish production, environmental quality and the nutritional value of farmed fish. While knowledge of the nutritional requirements for a given production and for each of the species involved is indispensable, the supply of such nutrients in an available form will naturally vary depending upon the culture systems. Since pond culture remains by far the predominant form of aquaculture in Eastern Europe, integrated knowledge of the functioning of the pond ecosystem with precise quantification of the natural nutrient flow remains a big challenge for the fish nutritionist and the fish farmer. Development of the aquaculture is closely linked to the availability of resources: water, land, nutrient sources supplied as feeds or fertilisers. Although much progress has been made in selected sectors, there is much room for improvement of efficiency of aquaculture. Analysing the flow dynamics of major elements using reliable methods and models should facilitate our understanding how nutrients are converted into edible products of interest to the human food basket. Elemental stoichiometry is one such integrated approach not only for analysing nutrient fluxes in individual fish but also to gain quantitative knowledge on nutrient dynamics in aquaculture production systems. Given the global demand for water, reducing water use for aquatic animal production is a real challenge which needs to be addressed. This concerns both on-farm water use and feed-resources associated water use. Whether different aquatic production systems are equally “water-efficient” is another debated issue. We have very little information also as regards the virtual water-content of farmed fish and shrimp, due both to technical and conceptual reasons. Under intensive aquaculture conditions, much progress has been made to reduce our reliance on fishery-derived ingredients such as fishmeal and fish oil as protein and fat sources in feeds for fish. Inclusion of alternative protein and fat sources should also take into account the overall impacts in terms of resource and water use. Increasing efficiency in nutrient conversion and water-use are two major issues which need to be addressed to ensure aquaculture as the major supplier of animal protein to humans in the coming decades.Bilo da je reč o polu intenzivnom ili potpuno intenzivnom sistemu gajenja, proizvodnja vodenih životinja se oslanja na dostupnost esencijalnih hranljivih materija i energije koju dobijamo iz dopunske/dodatne ili kompletne hrane. O kom god sistemu gajenja da je reč, cena ovih hranljivih materija koji se koriste kao dodaci u ishrani ostaje visoka. Odgovarajuća ishrana je neophodna da bi se održale vitalne funkcije sa značajnim uticajem na rani razvoj, rast, zdravlje, kvalitet mesa i reproduktivne performanse. U proteklih nekoliko decenija, istraživanja ishrane su doprinela izvanrednom razvoju intenzivne akvakulture zasnovane na ishrani, unapređenjem kvaliteta hrane i smanjenju cene hrane u ukupnoj proizvodnji. Sada je u potpunosti dokazano da optimizacija kvaliteta ishrane i strategije ishrane mogu veoma da poboljšaju efikasnost proizvodnje ribe, kvalitet životne sredine i nutritivnu vrednost gajene ribe. Dok je znanje o potrebama za hranljivim materijama za određenu proizvodnju i za svaku vrstu u proizvodnji neophodno, dostupnost tih hranljivih materija prirodno varira u zavisnosti o kom sistemu gajenja je reč. S obzirom da je gajenje u ribnjacima sistem gajenja koji još uvek preovladava u istočnoj Evropi, integrisano znanje o načinu funkcionisanja ekosistema ribnjaka sa preciznom kvantifikacijom toka prirodnih nutrijenta ostaje veliki izazov i za nutricioniste kao i odgajivače riba. Razvoj akvakulture je blisko povezan sa dostupnim resursima: voda, zemljište, nutritivni izvori u obliku hrane ili đubriva. Iako je napredak ostvaren u određenim sektorima, još dosta treba da se radi na poboljšanju efikasnosti u akvakulturi. Analiza dinamike toka najvažnijih elemenata korišćenjem pouzdanih metoda i modela treba da nam pomogne da shvatimo kako se hranljive materije konvertuju u jestive proizvode koji su značajni za ishranu ljudi. Stehiometrija elemenata je jedan takav integrisani pristup za analizu ne samo protoka hranljivih materija kod jedinki riba već i da bi se dobilo kvantitativno znanje o dinimici nutrijenata u proizvodnim sistemima akvakulture. Ako se u razmatranje uzme potreba za vodom na globalnom nivou, smanjenje upotrebe vode u proizvodnji vodenih životinja predstavlja pravi izazov za koji treba naći rešenje. Ovaj problem se odnosi i na korišćenje vode na farmi riba kao in a korišćenje vode koje je u vezi sa izvorima hrane. Drugi problem je da li sistemi za proizvodnju u akvakulturi podjednako “koriste vodu” ? Takođe, posedujemo jako malo informacija o prividnom sadržaju vode gajenih riba i rakova, iz tehničkih i konceptualnih razloga. Pod intenzivnim uslovima gajenja u akvakulturi veliki napredak je učinjen da se manje oslanjamo na sastojke koji proističu iz ribarstva, kao što su riblje brašno i riblje ulje kao izvori proteina i masti iz hrane za ribe. Inkluzija alternativnih izvora proteina i masti takođe treba da uzme u obzir sveukupni uticaj na resurse i korišćenje vode. Povećana efikasnost konverzije hranljivih materija i korišćenje vode su dva glavna problema za koje treba da se nađe rešenje da bi akvakultura bila glavni izvor proteina životinjskog porekla u ishrani ljudi u narednim decenijama

growth and nitrogen metabolism of sea bass fed graded levels of nucleic acid nitrogen from yeast or rna extract as partial substitute for protein nitrogen from fish meal

Some studies carried out in mammalian models have shown de novo synthesis and salvage of nucleotides to be a costly metabolic process and a dietary supplementation with nucleic acids (NA) or nucleotides has been suggested to result in a protein sparing action (Sanderson and He, 1994). On the other hand, high levels of dietary NA could have toxic effects and lead to disturbance in protein, lipid and carbohydrate metabolism in monogastric animals lacking uricase activity, an enzyme involved in NA degradation (Clifford and Story, 1976). So far, there is no clear indication of such effects in fish fed nucleic acid-enriched diets (Tacon and Cooke, 1980; Rumsey et al., 1992; Fournier et al., 2002). The aim of this experiment was to investigate growth response and N metabolism in juvenile sea bass (D. labrax) fed diets supplying graded levels of nucleic acid N from dry brewer's yeast or RNA extract as partial substitutes for protein nitrogen provided by fish meal

Parental and early-feeding effects of dietary methionine in rainbow trout (Oncorhynchus mykiss)

We studied the effect of changes in dietary methionine (Met) supply in broodstock and first-feeding rainbow trout fry (offspring). Three plant-based diets differing in Met level (deficient, adequate or in excess of the established requirement) were fed to the broodstock (male and female) for 6 months prior to spawning (diets BD, BA and BE, respectively). The offspring from the parental Met-groups was then challenged in turn with the different Met fry-diets (FD, FA and FE, respectively) for 3 weeks from first-feeding. At spawning, females fed diet BD had significantly higher plasma total and LDL-cholesterol and slightly lower plasma triacylglycerol. Diet BD reduced female (but not male) growth, weight of spawn and egg size, but had no effect on relative fecundity. The free amino acid profile of oocytes was modified, with levels of Met and Cys correlating positively with the Met-levels of broodstock diets. SAM and SAH levels in oocytes followed the same pattern, as opposed to SAM/SAH ratio. At the swim-up stage, no significant effect of parental diet on fry weight was noted, whereas survival was the highest in fry from BE-broodstock. The subsequent 21-day fry feeding with different Met levels highly affected the daily growth index with a significant interaction between the parental-diet and fry-diet effects. The expression of a number of genes regulating sulfur amino acid metabolism was modified either directly by the dietary Met supply in both broodstock liver and in whole fry (e.g. BHMT1, GR, GST pi, MsrA1) or indirectly by the parental Met intakes as seen in the swim-up fry (e.g. BHMT1, MTR, GST pi, MsrA1). Importantly, long-lasting parental effects linked to broodstock Met-intake were seen in the fry, 21-days after first-feeding and irrespective of the fry diet (CTH, MsrA1, MsrB2, SOD2). Similarly, parental effects were noted on the gene expression of both NPY and POMC feeding peptides in fry prior to exogenous feeding which persisted for POMC in the 21-day fry. Parental effects were also demonstrated on the key myogenic gene Myog, on fMHC and GDH in swim-up fry, which persisted for GDH in 21-day fry. In summary, our results demonstrate that dietary Met levels of rainbow trout broodstock affect various traits in the offspring, some of which persisted during the first weeks of exogenous feeding. Further studies need to evaluate the long-term persistence of the parental effects over time and to elucidate the mechanisms, whether epigenetic or not. Statement of relevance: Determining the multiple effects of dietary methionine levels on reproductive, growth performance and metabolism in offspring will help improve formulations of low fish meal feeds for rainbow trout at sensitive life cycle stages. (C) 2016 Elsevier B.V. All rights reserved.EU [288925]F.C.T., Portugal - Fundo Social Europeu (POCH) and National Funds [SFRH/BPD/108389/2015]info:eu-repo/semantics/publishedVersio

Modulation of the IgM gene expression and IgM immunoreactive cell distribution by the nutritional background in gilthead sea bream (Sparus aurata) challenged with Enteromyxum leei (Myxozoa)

The aim of the present work was to determine if a plant protein-based diet containing vegetable oils (VO) as the major lipid source could alter the distribution of IgM immunoreactive cells (IRCs) and the IgM expression pattern in the intestine and haematopoietic tissues of gilthead sea bream (GSB) (. Sparus aurata) challenged with the myxosporean Enteromyxum leei. In a first trial (T1), GSB fed for 9 months either a fish oil (FO) diet or a blend of VO at 66% of replacement (66VO diet) was challenged by exposure to parasite-contaminated water effluent. All fish were periodically and non-lethally sampled to know their infection status. After 102 days of exposure, samples of intestine and head kidney were obtained for IgM expression and immunohistochemical detection (IHC). Additional samples of spleen were taken for IHC. Fish were categorized as control (C, not exposed), and early (E), or late (L) infected. The 66VO diet had no effect on the number of IgM-IRCs in any of the tissues or on IgM expression in C fish, whereas the infection with E. leei had a strong effect on the intestine. A combined time-diet effect was also observed, since the highest expression and IRCs values were registered in the posterior intestine (Pi) of E-66VO fish. A positive correlation was found between IgM expression and the presence of IgM-IRCs in the Pi. The effect of the time of infection was studied more in detail in a second trial (T2) in which samples of Pi were taken at 0, 24, 51, 91 and 133 days after exposure to the parasite. A significant increase of the IgM expression was detected only in parasitized fish, and very late after exposure. These results show that the duration of the exposure to the parasite is the most determinant factor for the observed intestinal IgM increased phenotype which gets magnified by the feeding of a high VO-based diet. © 2012 Elsevier Ltd.This work was funded by EU through projects AQUAMAX (FOOD-CT-2006-16249; Sustainable Aquafeeds to Maximise the Health Benefits of Farmed Fish for Consumers) and ARRAINA (Advanced Research Initiatives for Nutrition & Aquaculture, FP7/2007/2013; grant agreement n° 288925), and by the Spanish Ministry of Science and Innovation (MICINN) through the project AGL2009-13282-C02-01. Additional funding was obtained from the “Generalitat Valenciana” (research grant PROMETEO 2010/006). I. E. received a Spanish PhD fellowship (FPI) from MICINN.Peer Reviewe

Dietary effects on insulin and glucagon

34 p., 5 tables, 2 figures and bibliographyThe effects of dietary amino acid profile (based on muscle (M) or whole body composition (WB) and the balance between indispensable (IAA) and dispensable amino acids (DAA) in the diet, on plasma levels of insulin and glucagon, were analysed in rainbow trout and gilthead sea bream. Plasma insulin values (baseline and 6 h postfeeding) were higher in trout than in sea bream, but the relative postfeeding increase was more pronounced in sea bream. Within the same dietary amino acid profile, diets with lower IAA/DAA, had a lower effect on the postfeeding secretion of insulin in both species. Circulating levels of glucagon (baseline and postfeeding relative increases) were higher in sea bream. In trout, diets with WB amino acid profile had a greater secretory effect on postfeeding glucagon than did diets with M profile, while gilthead sea bream showed an inverse response to circulating glucagon with respect to diet. Muscle insulin and insulin growth factor-I binding parameters were not affected by the dietary regimen. The postfeeding glucagon response depends on both the dietary AA profile and the fish species, while that of insulin seems to be more uniform, and is affected in a similar way regardless of the species.This study was funded by the European Union (Q5RS-2000–30068) “Perspectives of Plant Protein Use in Aquaculture” and by the Centre de Referencia de Recerca Desenvolupament en Aqüicultura de la Generalitat de Catalunya (CRA-2003–2.2/ 333038)

Long-term effect of parental selenium supplementation on the one-carbon metabolism in rainbow trout (Oncorhynchus mykiss) fry exposed to hypoxic stress

This study evaluated how different forms of selenium (Se) supplementation into rainbow trout broodstock diets modified the one-carbon metabolism of the progeny after the beginning of exogenous feeding and followed by hypoxia challenge. The progeny of three groups of rainbow trout broodstock fed either a control diet (Se level: 0·3 µg/g) or a diet supplemented with inorganic sodium selenite (Se level: 0·6 µg/g) or organic hydroxy-selenomethionine (Se level: 0·6 µg/g) was cross-fed with diets of similar Se composition for 11 weeks. Offspring were sampled either before or after being subjected to an acute hypoxic stress (1·7 mg/l dissolved oxygen) for 30 min. In normoxic fry, parental Se supplementation allowed higher glutathione levels compared with fry originating from parents fed the control diet. Parental hydroxy-selenomethionine treatment also increased cysteine and cysteinyl–glycine concentrations in fry. Dietary Se supplementation decreased glutamate–cysteine ligase (cgl) mRNA levels. Hydroxy-selenomethionine feeding also lowered the levels of some essential free amino acids in muscle tissue. Supplementation of organic Se to parents and fry reduced betaine-homocysteine S-methyltransferase (bhmt) expression in fry. The hypoxic stress decreased whole-body homocysteine, cysteine, cysteinyl-glycine and glutathione levels. Together with the higher mRNA levels of cystathionine beta-synthase (cbs), a transsulphuration enzyme, this suggests that under hypoxia, glutathione synthesis through transsulphuration might have been impaired by depletion of a glutathione precursor. In stressed fry, S-adenosylmethionine levels were significantly decreased, but S-adenosylhomocysteine remained stable. Decreased bhmt and adenosylmethionine decarboxylase 1a (amd1a) mRNA levels in stressed fry suggest a nutritional programming by parental Se also on methionine metabolism of rainbow trout.publishedVersio

Modifications of intestinal nutrient absorption in response to dietary fish meal replacement by plant protein sources in sea bream (Sparus aurata) and rainbow trout (Onchorynchus mykiss)

The effects of partial (75%; diet PP75) and total (100%; diet PP100) replacement of fish meal by plant protein sources on the intestinal nutrient absorption of gilthead sea bream and rainbow trout were examined over a 12-week growth trial. The diets comprised a mixture of plant ingredients (corn gluten meal, wheat gluten, extruded peas and rapeseed meal) and met the amino acid requirements of the fish. A third group of fish on a fish meal diet was used as a control for comparative purposes. Diets were tested in triplicate and fish were fed twice a day until visual satiation. At the end of the trial, we measured amino acid (L-leucine, L-lysine, L-phenylalanine, Lalanine and L-proline) and D-glucose absorption at short term (6 h) and long-term (36 h and 48 h in rainbow trout and sea bream respectively) post-feeding by means of brush border membrane vesicles obtained from pyloric caeca, proximal intestine and distal intestine. The absorption pattern at 6 h post-feeding was modified in both species in response to fish meal replacement. In PP75-fed trout absorption was delayed from pyloric caeca to proximal and/or distal intestinal segments, thus total absorption capacity was maintained in this group. On the contrary, total uptake was significantly decreased in trout fed the PP100 diet and in sea bream on both PP75 and PP100 diets. Glucose transport capacity was increased in both experimental sea bream groups and in PP75 trout. Long-term transport capacity was up-regulated for both species. Our results show that intestinal nutrient absorption is modified in response to the use of high levels of plant protein sources and that these changes are species-specific

Parental selenium nutrition affects the one-carbon metabolism and the hepatic dna methylation pattern of rainbow trout (Oncorhynchus mykiss) in the progeny

Selenium is an essential micronutrient and its metabolism is closely linked to the methionine cycle and transsulfuration pathway. The present study evaluated the effect of two different selenium supplements in the diet of rainbow trout (Onchorhynchus mykiss) broodstock on the one-carbon metabolism and the hepatic DNA methylation pattern in the progeny. Offspring of three parental groups of rainbow trout, fed either a control diet (NC, basal Se level: 0.3 mg/kg) or a diet supplemented with sodium selenite (SS, 0.8 mg Se/kg) or hydroxy-selenomethionine (SO, 0.7 mg Se/kg), were collected at swim-up fry stage. Our findings suggest that parental selenium nutrition impacted the methionine cycle with lower free methionine and S-adenosylmethionine (SAM) and higher methionine synthase (mtr) mRNA levels in both selenium-supplemented treatments. DNA methylation profiling by reduced representation bisulfite sequencing (RRBS) identified differentially methylated cytosines (DMCs) in offspring livers. These DMCs were related to 6535 differentially methylated genes in SS:NC, 6890 in SO:NC and 7428 in SO:SS, respectively. Genes with the highest methylation difference relate, among others, to the neuronal or signal transmitting and immune system which represent potential targets for future studies.publishedVersio

Evaluating dietary supply of microminerals as a premix in a complete plant ingredient-based diet to juvenile rainbow trout (Oncorhynchus mykiss)

Two basal diets M0 and V0 were formulated with marine and plant based ingredient composition. Seven experimental diets were prepared from the two basal diets namely M0, M100, V0, V30, V60, V100 and V150 by incorporating different levels of a micromineral premix (Cu, Fe, Mn, Se and Zn). Triplicate groups of rainbow trout (initial weight: 20 g) reared at 17°C were fed one of each diet to apparent visual satiation over 12 weeks. Among the V diet fed fish, growth and feed intake exhibited maximal response at V60 level of premix inclusion; Apparent availability coefficient of Fe, Cu and Zn decreased linearly with increasing level of premix whereas apparent availability coefficient of Mn and Se was unaffected. The available dietary concentration in basal V0 diet was for Fe, 20.6; Cu, 2.8; Mn, 6.5; Zn, 17.3 and Se, 0.195 (in mg/kg DM) and in the M0 diet for Fe, 63.3; Cu, 5.2; Mn, 2.9; Zn, 35.2 and Se, 0.87 (in mg/kg DM). In reference to NRC (Nutrient requirements of fish and shrimp. Washington, DC: National Research Council, The National Academies Press, 2011) recommendations, the V0 basal diet accounted for 34.3%, 92.9%, 53.9%, 115% and 130.2% and the contribution from M0 diet for 105.5%, 173.3%, 24.2%, 234.7% and 580% of the minimal dietary inclusion levels of Fe, Cu, Mn, Zn and Se to rainbow trout, respectively. However, data on whole body mineral contents showed that normal levels were maintained only for Cu and Mn through supply from basal V0 diet. For Zn and Se, available supply even from the highest supplemented diet (V150) was not sufficient to maintain normal body mineral levels of rainbow trout in the present study. On the whole, optimal dietary inclusion levels of microminerals are altered while using fishmeal-free diets for rainbow trout