[Show abstract][Hide abstract] ABSTRACT: Fish larvae present high amino acid requirements due to their high growth rate. Maximizing this growth rate depends on providing a balanced amino acid diet which can fulfil larval amino acid nutritional needs. In this study, two experimental microencapsulated casein diets were tested: one presenting a balanced amino acid profile and another presenting an unbalanced amino acid profile. A control diet, live feed based, was also tested. Trials were performed with larvae from 1 to 25 days after hatching (DAH). Microencapsulated diets were introduced at 8 DAH in co-feeding with live feed and at 15 DAH larvae were fed the microencapsulated diets alone. Results showed a higher survival for the control group (8.6 ± 1.3% versus 4.2 ± 0.6% and 3.2 ± 1.8%) although dry weight and growth were similar in all treatments. The proportion of deformed larvae as well as the ammonia excretion was lower in the group fed a balanced diet than in the unbalanced or control groups (38.3% deformed larvae in control, 30% in larvae fed unbalanced diet and 20% on balanced diet group). Furthermore, larvae fed the microencapsulated diets presented higher docosahexaenoic acid and arachidonic acid levels. This study demonstrates that dietary amino acid profile may play an important role in larval quality. It also shows that balanced microencapsulated diets may improve some of the performance criteria, such as skeletal deformities, compared to live feeds.
[Show abstract][Hide abstract] ABSTRACT: Dietary amino acids imbalances have been described when fish larvae are fed rotifers, what may lead to a reduction in growth rate. The tube-feeding technique can be used to assess the effect of free amino acid short term supplementation. In this study supplementation of tryptophan, methionine and arginine were tested in Diplodus sargus. Single crystalline (14)C amino acids as well as a mix of (14)C amino acids were used as tracers to compare results of individual amino acids metabolism with the average of all amino acids. The results show low absorption efficiencies for tryptophan (70%) and arginine (80%) and similar absorption for methionine (90%) when compared with the average of all amino acids. Supplementation of these amino acids seems to be viable but it did not result in higher retention compared to the amino acid mix. This means that tryptophan, methionine and arginine are probably not the limiting amino acid when Diplodus sargus larvae are fed rotifers. However, supplementation in these IAA may be required for their roles as precursors of important molecules other than proteins, in order to improve larval quality and/or performance.
[Show abstract][Hide abstract] ABSTRACT: Dietary amino acid imbalances are likely to happen when fish larvae are fed live food. This can lead to reduced growth as well as decreased larval quality. The tube-feeding technique can be used to assess the effect of free amino acid supplementation at short term and determine whether a given amino acid is deficient in the diet. In this study supplementation of lysine and tyrosine were tested in Diplodus sargus larvae fed rotifers in order to determine its effect on the metabolism of these amino acids. Supplementation was done using rotifers enriched with liposomes boosted with free amino acids. Single crystalline 14C amino acids as well as a mixture of 14C amino acids were used as tracers to compare results of individual amino acid metabolism with the average of all amino acids. The results showed low absorption efficiencies for both tyrosine and lysine when compared to the average of all amino acids. A lower relative 14C retention was found when D. sargus larvae were fed tyrosine enriched rotifers and tube-fed 14C tyrosine, indicating that tyrosine was not a limiting amino acid. On the other hand, lysine supplementation had a similar retention percentage in the treatments with and without lysine supplementation. Based on the tube-feeding studies with lysine and tyrosine supplementated rotifers neither lysine nor tyrosine affected protein synthesis in a way to indicate that these amino acids are insufficient in D. sargus larvae fed rotifers.
[Show abstract][Hide abstract] ABSTRACT: The riboflavin enrichment of the marine microalga Tetraselmis suecica and the transfer of this vitamin to higher trophic levels of the aquatic food chain such as the rotifer Brachionus plicatilis and the larvae of two species of sparids: white sea bream and gilthead sea bream were studied. The preliminary experiment consisted of determining the concentration of riboflavin added to T. suecica cultures to achieve a maximum quantity of this vitamin in the microalgal cells. Seven concentrations were tested in triplicate: 0 (control), 2.5, 5, 10, 20, 40 and 80 ng ml− 1; the results showed that the 10 ng ml− 1 was the optimum concentration that the microalgae accumulated 4.29 ± 0.19 pg cell− 1, 21.2 ± 0.35 ng ml− 1 and 19.4 ± 0.56 μg g− 1 (dry weight) of riboflavin. Control and enriched microalgal cultures were used for feeding the rotifer B. plicatilis. Control and enriched rotifers were used for feeding white sea bream and gilthead sea bream larvae. Rotifers fed on enriched microalgal cultures accumulated significantly (P < 0.05) more riboflavin than those fed the control culture after 24 h of enrichment (17.7 ± 1.3 and 13.7 ± 1.2 μg g− 1 (dw), respectively) and after 24 h of starvation (10.2 ± 44 1.1 and 5.6 ± 0.4 μg g− 1 (dw), respectively). In both species of sparids, those larvae fed enriched rotifers contained significantly more riboflavin than those fed control rotifers, the vitamin B2 content in control and enriched white sea bream larvae was 21.7 ± 2.7 and 29.2 ± 1.3 μg g− 1 (dw), respectively, and in control and enriched gilthead sea bream larvae it was 5.5 ± 1.0 and 7.3 ± 0.05 μg g− 1 (dw), respectively. Significant differences in length and survival of white sea bream larvae were observed. In the present study, riboflavin enrichment of microalgal cultures resulted in higher levels of this vitamin in both rotifers and fish larvae.
[Show abstract][Hide abstract] ABSTRACT: The indispensable AA profile of fish carcass has been commonly used as a good indicator of fish amino acids requirements. Amino acids composition of the whole body tissue of Diplodus puntazzo was determined for the larval ages of 5, 9, 12, 17, 25 and 35 days after hatching (DAH).No significant differences were found during this species ontogeny for any indispensable amino acid although for dispensable amino acids, significant differences were found for glutamate and glutamine (p = 0.003), aspartate and arparagine (p = 0.027) and serine (p = 0.027).In order to obtain the ideal dietary amino acid profile, bioavailability was determined using 15N-labelled rotifers together with GC-C-IRMS. High relative bioavailabilities were found for isoleucine, leucine and valine, meaning these amino acids are retained more efficiently. On the contrary, alanine, glutamate and aspartate presented a lower bioavailability when compared to lysine.Histidine appeared to be the first limiting amino acid at 4 days after hatching (DAH) when larvae were fed rotifers. At 12, 25 and 35 DAH the first limiting amino acid seemed to be threonine.Comparing amino acid profiles, with and without taking into account the relative bioavailability data, accentuated differences were found for methionine and leucine.Using larval amino acid profiles corrected with relative amino acid bioavailability enables an estimation of the ideal dietary amino acid profile for Diplodus puntazzo.
[Show abstract][Hide abstract] ABSTRACT: The indispensable AA profile of fish carcass has been commonly used as a good indicator of fish amino acids requirements. Amino acid composition of the whole body tissue of Diplodus sargus was determined for the larval ages of 0, 2, 5, 8, 12, 17, 25, 35 and 45 days after hatching (DAH). No significant differences were found during this species ontogeny, except for phenylalanine. A comparative analysis of amino acid profiles from larvae and respective diet was performed. Low correlation was found to rotifers (R2 approximately 0.5), while higher correlations were found for Artemia nauplli, metanauplii (R2 approximately 0.8) as well as for the dry feed. These results suggest that D. sargus are subjected to higher nutritional imbalances during the first 10 days of feeding when larvae are fed on rotifers alone. Arginine, threonine, lysine, cysteine and histidine appeared to be limiting amino acids at 2, 12, 25 and 45 DAH, respectively. Similar results were reported in literature for Sparus aurata and Solea senegalensis, although D. sargus diets seem to have more amino acids in deficiency as well as more severe differences between larval and diet amino acid profiles. To solve these apparent nutritional imbalances, amino acid supplementation should be considered. The use of inert diets in early larvae ages seems to be most adequate as live feed supplementation appears to be more difficult.