Nutrition and feeding in striped bass Morone saxatilis larvae: Lipid and fatty acid requirements and microencapsulated diets

There has been a growing interest in the commercial aquaculture of striped bass, Morone saxatilis. Little is known, however, about the nutritional requirements and feeding physiology of striped bass larvae. The objectives of this study were (a) to evaluate the efficiency of the live food enrichment techniques in studying the nutritional requirements for polyunsaturated fatty acids (PUFA), phospholipids and free amino acids, (b) to determine the ontogenetic changes of lipolytic enzymes, and (c) to develop a microencapsulated diet for striped bass larvae as full or partial replacement of live food. Three enrichment techniques, namely, microencapsulated fish oil, yeast/fish oil emulsion and unicellular algae, Chlorella sp. were evaluated for their efficiency in improving the n-3 PUFA content of Artemia nauplii to striped bass larvae. The enrichment of the Artemia nauplii appeared to increase the eicosapentaenoic acid content and enhance the growth of the striped bass larvae. The uptake and metabolism of &\sp{14}&C-glycine or &\sp{14}&C-phosphatidylcholine labeled liposomes by freshly hatched Artemia nauplii were investigated as a new technique for amino acid and phospholipid. The results of this study suggest that liposomes may be used to enrich Artemia nauplii with phospholipids and free amino acids. Ontogenetic changes of triacylglycerol hydrolase, wax ester hydrolase and phospholipase A&\sb2& were determined in the fertilized eggs and premetamorphosed larvae of striped bass and the larval food Artemia using radioassays. It was estimated that first feeding striped bass larvae had the capacity to digest 47% of their daily lipid ingestion. A complex protein-walled microcapsule (CWC) was prepared by incorporating lipid-wall capsules containing highly water soluble nutrients along with other dietary materials in a cross-linked protein-wall microcapsule. In vitro experiments indicated that the CWC was digested by the crude enzyme extract from striped bass larvae or purified porcine pepsin and trypsin. Diet acceptability, growth and survival of striped bass larvae fed complex protein-walled microcapsules were investigated in two separate experiments. In both experiments, the acceptability of microencapsulated diets was high. Neither microencapsulated diet support growth when solely fed to the larvae. The results of this study suggested that CWC can be used for partial replacement (60%) of live food without any significant effect on growth and survival of striped bass larvae

Fish larval nutrition and feed formulation: knowledge gaps and bottlenecks for advances in larval rearing

Despite considerable progress in recent years, many questions regarding fish larval nutrition remain largely unanswered, and several research avenues remain open. A holistic understanding of the supply line of nutrients is important for developing diets for use in larval culture and for the adaptation of rearing conditions that meet the larval requirements for the optimal presentation of food organisms and/or microdiets. The aim of the present review is to revise the state of the art and to pinpoint the gaps in knowledge regarding larval nutritional requirements, the nutritional value of live feeds and challenges and opportunities in the development of formulated larval diets.Norwegian Ministry of Fisheries; Research Council of Norway [CODE-199482, GutFeeling-190019]; Spanish Ministry of Science and Innovation MICINN + FEDER/ERDF [AGL2007-64450-C02-01, CSD2007-0002]; project HYDRAA [PTDC/MAR/71685/2006]; Fundacao para a Ciencia e a Tecnologia (FCT), Portugal; FEDER; EC [LIFECYCLE- 222719]; EU RTD [FA0801]info:eu-repo/semantics/publishedVersio

Enrichment of Artemia nauplii in vitamin A, vitamin C and methionine using liposomes

Several types of liposomes were used to enrich Artemia nauplii in vitamin A, vitamin C and free methionine. In a first experiment, unilamellar liposomes formulated with krill phospholipid extract and retinyl palmitate demonstrated their capability to enhance the retinol content of Artemia nauplii. Furthermore, the increase in retinol was related to the amount of retinyl palmitate included in the liposomes as vitamin A source. These findings yield the possibility of using such vesicles to bioencapsulate simultaneously both vitamin A and essential fatty acids present in the krill phospholipid extract. A second enrichment was carried out with unilamellar liposomes composed of soybean phosphatidylcholine and loaded with sodium ascorbate as vitamin C source. Our results did not show that vitamin C content in the nauplii could be increased using unilamellar liposomes. This was most likely due to the degradation of the vitamin C during enrichment as well as the ascorbate leakage. Finally, a third experiment assessed enrichment in free methionine using liposomes of different lamellarity (unilamellar or multilamellar) and composed of either soybean phosphatidylcholine or dipalmitoyl phosphatidylcholine, both combined with cholesterol as a membrane stabilizer. Results indicated that multilamellar liposomes represent a useful tool to deliver methionine to Artemia nauplii. Enhanced protection given by their multiple bilayers in comparison to unilamellar liposomes could account for the higher ability displayed by multilamellar vesicles for free methionine bioencapsulation

Oxidative stability and changes in the particle size of liposomes used in the Artemia enrichment

The oxidative stability and the particle size of several types of liposomes were assessed in order to characterize their behaviour when submitted to the aggressive conditions of the Artemia enrichments. Results show that all liposomes tested in this study were much more oxidatively stable than a commercial product based on fish oil emulsion. Whereas the initial thiobarbituric acid reactive substances (TBARS) concentration in the emulsion was only slightly higher than in liposomes, the concentration of TBARS in the emulsion increased up to values three orders of magnitude above those registered by liposomes after 21 h of incubation. Among the different liposome formulations, results indicate that vesicles composed of phospholipids containing long-chain highly unsaturated fatty acids (krill phospholipid extract) were generally less stable than those composed of shorter length-chain and more saturated acyl chains. In regards to the particle size changes during enrichment, all liposomes maintained their original size during the experimental period when incubated without nauplii. In the presence of nauplii, liposomes did not exhibit notable changes in their size, except for unilamellar vesicles prepared by the extrusion methodology and formulated with soybean phosphatidylcholine. The implications of the results on the capability of liposomes to be used in Artemia nauplii enrichments are discussed

The Fatty Acid Profile of the Marine Cephalopod Loligo vulgaris

Squids and their by-products are widely used as pre-spawning feeds in marine fish hatcheries. Therefore, we studied the fatty acid composition of mantle tissue, arms, fins, and gonads of the marine cephalopod, Loligo vulgaris, from a broodstock nutrition point of view. Docosahexaenoic (DHA) and eicosapentaenoic (EPA) acids represented nearly half (>45%) of the total fatty acids, with DHA the most abundant fatty acid in all investigated tissues. The fatty acid profile of the gonads differed significantly from those of the mantle, arms, and fins; EPA was present in a sig- nificantly higher proportion (20%), perhaps indicating its important role in reproduction. Results indicate that Loligo vulgaris and its by-products can be an important nutritional component of broodstock feeds, serving as a major source of DHA and EPA