Browsing by Author "Fyhn, H. -J."
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- Amino acid pools of rotifers and Artemia under different conditions: Nutritional implications for fish larvaePublication . Aragão, C.; Conceição, L. E. C.; Dinis, Maria Teresa; Fyhn, H. -J.The rearing of most marine fish species still relies on live food. Amino acids (AA) are the building blocks for protein synthesis, are important energy substrates, and are involved in specific physiological functions. Thus, the AA pools (free and protein-bound) of the rotifer Brachionus rotundiformis and of Artemia parthenogenetica metanauplii were analysed, after enrichment with different diets or at different salinities. The changes in these pools were related to their impact when used as feed for the developing fish larvae. Rotifers and Artemia were enriched for 24 h in microalgae, in commercial diets, or starved for the same time period. The enrichment at different salinities was also tested using Artemia. The free AA (FAA) quantity and quality was strongly affected by the enrichment used, in both rotifers and Artemia metanauplii. The relative FAA content was significantly higher in rotifers and Artemia enriched with microalgae than in the ones enriched with commercial products, and between the different microalgae tested, the enrichment in T. chui resulted in the highest FAA content for both preys. Differences regarding the FAA quantity and quality were also found between rotifers and Artemia. With the exception of the starved preys, a higher relative FAA content was found in rotifers than in Artemia metanauplii and while the FAA pool of the rotifers was dominated by alanine, taurine was the dominant AA in the FAA pool of Artemia. Salinity had only a small effect on the FAA pool of Artemia. Concerning the protein fraction, starvation increased the relative protein content in the rotifers. Among the metanauplii, the relative protein content was affected neither by the enrichment nor by salinity, except for a significantly lower content found when the microalgae Nannochloropsis gaditana was used. The quality of the protein pool is affected by the different enrichments, but not by salinity. However, the changes in the protein-bound AA pool were less pronounced than for the FAA pool and reflect differences in the protein content and/or quality of the diet. This study showed that the AA composition of cultured zooplankton is affected by feeding regime and by salinity. The choice of the best zooplankton enrichment and/or mixture of enrichments for the different fish larval stages, should take into account the AA composition, in order to fulfil the energetic and nutritional requirements of the larvae.
- Estimated amino acid requirements during early ontogeny in fish with different life styles: Gilthead seabream (Sparus aurata) and Senegalese sole (Solea senegalensis)Publication . Aragão, C.; Conceição, L. E. C.; Fyhn, H. -J.; Dinis, Maria TeresaLittle is known about the amino acid (AA) requirements of larval fish and their possible ontogenetic changes. This paper aims to contribute to the study of these requirements in two common cultured species in Southern Europe: gilthead seabream (Sparus aurata) and Senegalese sole (Solea senegalensis). Moreover, it is intended to identify possible dietary AA imbalances occurring in normal hatchery conditions for both species. Fish larvae were reared following standard procedures and the normal feeding schemes used in hatcheries, which includes the use of live prey for several weeks. The experiments were finished once the fish were adapted to a dry feed. Samples were collected at different points for dry weight, total protein, and AA analysis. The A/E ratios [each indispensable AA content (total indispensable AA content including cysteine and tyrosine)1 1000] of fish and food were compared to identify possible dietary AA imbalances. The AA profile of both fish species changed during ontogeny, but was more stable during seabream than Senegalese sole development. This is probably linked to the marked metamorphosis observed in sole. These changes in fish larval AA profile suggest that the AA requirements change during seabream and Senegalese sole ontogenesis. Several dietary AA deficiencies were found during the ontogenetic development of both species.