| Research Abstract |
This study was investigated the requirement and nutritional role of marine fish larvae for icosapentaenoic acid (EPA) and docosahexaenoic acid (DHA).
At first, different stages of larval fish such as striped jack, yellowtail, cod were collected and analysed their fatty acid compositions. Only DHA content in three species was decreased immediately after hatching. This result suggests that fish larvae during 5-10mm size (total length) may require high amount of DHA.
Secondly, the experiment was conducted to find out a suitable lipid type for enrichment by comparing the incorporation of lipid and n-3highly unsaturated fatty acids (n-3HUFA) in Artemia nauplii between various types of oil, such as ethylesters (EE), triglycerides (TG), methyl esters (ME), and free fatty acids (FFA) containing about 43% of n-3HUFA, using the so-called direct method. It is concluded that a maximum incorporation of n-3HUFA in Artemia can be obtained by enrichment with EE for 24h and that EE or ME are very quickly
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incorporated into TG fractions. Then these Artemia were fed on larval striped knife jaw and red sea bream to compare the dietary value of Artemia enriched with various types of oil, based on the growth, survival and chemical compositions of both fish larvae. The result indicated that the dietary value of Artemia to both species was effectively improved by enrichmewith TG, ME, and EE, especially with EE.
In next, dietary value of Artemia enriched with EE type of EPA and DHA for larval yellowtail and red sea bream was investigated. Both larval yellowtail and red sea bream fed on nauplii enriched with EPA showed good growth and high survival rate, however quite low activity tests were observed. On the other hand, fish fed DHA enriched Artemia showed high feed performances, incl. high activity tests. Thus, it is clearly indicated that larval fish require DHA in order to receive good growth and health.
Finally, two feeding experiments were conducted to compare the essential fatty acids (EFA) value between EPA and DHA in juvenile red sea bream and striped jack. Both fish fed a diet without supplemental EFA showed low feed efficiency and high morthlity. The requirement of EPA and DHA was estimated to be around 1% and 0.5% in diet for juvenile red sea bream, respectively. The EFA efficiency of DHA was also found to be twice as high as that of EPA. On the other hand, the experiment on the EFA of juvenile striped jack have demonstrated that : 1) DHA is more effective than EPA as EFA ; 2) requirement for DHA alone is about 1.7% in diet.
This study was clearly demonstrated that marine fish larvae require DHA as EFA and physiological purpose. Less
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