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Essential fatty acids nutrition and its effects on immune responses of the juvenile grouper, Epinephelus malabaricus.

by Wu, Feng-Cheng

Abstract (Summary)
Essential fatty acids nutrition and its effects on immune responses of the juvenile grouper, Epinephelus malabaricus Feng-Cheng Wu (Advisor: Dr. Houng-Yung Chen) Institute of Marine Biology, National Sun Yat-sen University Kaohsiung 804 Taiwan. A series of three experiments was conducted to study the essential fatty acids nutrition and its effects on immune responses (IR) of the juvenile grouper, Epinephelus malabaricus. All experimental diet contained 10 g/100 g diet supplemental lipids from various sources. A reference diet was used in all experiments and contained natural oil mixture of cod liver oil, linseed oil, and safflower oil at a rate of 2:1:1 (wt/wt/wt). In experiment 1, juvenile grouper (11.8 ¡Ó 0.7 g) were fed for 12 wks on one of the seven experimental diets, control diet and the reference diet to investigate dietary requirement for docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA) and effects on IR of grouper. Seven experimental diets contained 1 g/100 g diet of DHA and EPA in various combinations and 9 g/100 g diet of tristearin. The control diet contained 1 g/100 g diet of trilinolenin and trilinolein (3:1, wt/wt). The results indicate that there was a significant difference among dietary treatments in growth, phagocytosis and leucocytes proliferation, when stimulated by Con A and PHA-P but not by LPS. However there was no difference in survival rate and relative liver weight. Enhanced growth was observed when the dietary DHA/EPA was greater than 1, indicating that DHA was superior to EPA in promoting fish growth. DHA is the only member in the family of (n-3) highly unsaturated fatty acid (HUFA) that stimulates phagocytic functions of leucocytes and T cell proliferation of the juvenile grouper. In experiment 2, juvenile grouper (11.3 ¡Ó 0.6 g) were fed for 12 wks on one of the eight experimental diets or the reference diet to investigate dietary requirement for linolenic acid (LNA) and linoleic acid (LA), as well as effects on nonspecific IR of grouper. The test diets were supplemented with LNA or LA at a rate of 1 or 2 g LNA or LA/100 g diet or 2 g/100 g diet of LNA and LA in various ratios (3, 1.4, 0.7 and 0.4). Tristearin was used to fill the lipid supplemental level to 10 g/100 g diet. The results show that enhanced growth and optimal non-specific cellular IR were observed when the grouper were fed on the diet having the highest LNA/LA ratio (3:1) or on the diets supplemented with LNA. But the enhancement was not different (P>0.05) from that of the reference diet group. Thus, incorporating 2 g/100 g LNA/LA (3:1, wt/wt) in diet ensures adequacy of the grouper for essential fatty acid. In experiment 3, juvenile grouper (13.2 ¡Ó 0.9 g) were fed on one of the six experimental diets in the 2 ¡Ñ 3 factorial design or on the reference diet for 12 wks to investigate dietary requirement for (n-3)HUFAs and arachidonic acid (AA), as well as effects on IR of grouper. Two levels of (n-3)HUFAs (1 or 2 g/100 g ) in combination with 3 levels of AA (0, 1 or 2 g/100 g) were tested. The results show an enhanced growth when optimal concentrations of AA and (n-3)HUFA were incorporated to the diets. Liver (n-6)HUFAs concentration reflects IR of the juvenile grouper. Interaction of AA and (n-3)HUFAs in affecting fish growth and IR was insignificant (P>0.05), and concentrations of dietary (n-3)HUFAs or AA did not significantly affect fish survival rate. The results of the 3 experiments show that the grouper will benefit most in growth and IR when their diets contain 1 g/100 g diet of (n-3)HUFA and 1 g/100 g diet of AA, when (n-3)HUFA is a mixture of DHA and EPA at a ratio of 3:1 (wt/wt).
Bibliographical Information:

Advisor:Houng-Yung Chen; Shi-Yen Shiau; Yun-Yuan Ting; S. S. Shin; Y. L. Song; M. S. Su; Ming-Chen Tung

School:National Sun Yat-Sen University

School Location:China - Taiwan

Source Type:Master's Thesis

Keywords:immune nutrition grouper essential fatty acid responses fish

ISBN:

Date of Publication:07/12/2002

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