|Li, Earcho - BEIJING NORMAL UNIVERSITY|
Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 4/15/2012
Publication Date: 6/4/2012
Citation: Li, E., Lim, C.E., Shoemaker, C.A., Klesius, P.H. 2012. Growth, body composition, immune response and resistance to Streptococcus iniae of hybrid tilapia, Oreochromis niloticus x O. aureaus, fed diets containing various levels of linoleic and linolenic acids [abstract]. XV International Symposium on Fish Nutrition and Feeding, Molde, Norway. P. 231.
Technical Abstract: The effects of various levels of dietary linoleic (LA) and linolenic acids (LN) on growth, body proximate and fatty acid composition, immune response and resistance to Streptococcus iniae of juvenile, sex-reversed all-male hybrid tilapia, Oreochromis niloticus x O. areaus, were evaluated. A basal purified diet (34% crude protein and 3.2 kcal DE/g) supplemented with 6% coconut oil (diet 1, 0.12% LA and 0% LN) and nine test diets in which coconut oil was replaced by safflower oil to provide 0.5, 1.0 and 2% of LA (diets 2-4), flaxseed oil to obtain 0.5, 1.0 and 2% of LN (diets 5-7), and a combination of safflower oil and flaxseed oil to provide LA and LN, each at levels of 0.25, 0.50 and 1.00% (diets 8-10) were formulated. Since flaxseed oil also contains LA, diets 5, 6 and 7 contain, in addition to LN, 0.26, 0.40 and 0.69% LA, respectively. Each diet was fed to juvenile hybrid tilapia (3.89 ± 0.11 g) in triplicate aquaria twice daily to apparent satiation for 10 weeks. Fish fed the control diet had the lowest weight gain (WG) but were not significantly different (P>0.05) from those fed diets 2 and 6. Fish fed diet 3 had the highest WG, but no differences were found when compared with those fed diets 2, 4-5 and 7-10. There were no significant (P>0.05) differences among dry matter feed intake, feed efficiency ratio and survival of fish in all treatments. Whole body proximate composition (moisture, protein, lipid and ash) did not differ (P>0.05) among fish in different treatments. Fatty acid (FA) composition of whole fish is generally a reflection of dietary FA. Whole body total n-6 fatty acids (n-6 FAs) increased with increasing dietary levels of n-6 FAs. There was also a trend of increasing body n-3 FAs content with increasing dietary levels of n-3 FAs, but the values peaked at a dietary concentration of about 1%. Tilapia accumulated higher levels of n-6 than n-3 as the body ratios of n-6 to n-3 greatly increased relative to dietary ratios (diets 5-10). No differences (P>0.05) were observed among hematological and immunological parameters, the average number of days to first mortality after S. iniae challenge and cumulative mortality14 days post-challenge of fish receiving various dietary treatments. The current study indicates that the presence of either LA or LN will satisfy the essential FA requirement of hybrid tilapia since fish fed diets containing sufficient levels of only LA or LN in combination with LA grew at similar rate. However, compared to LN, LA appears to have better growth promoting effect. Quadratic broken line analysis of WG shows that 1.14% dietary LA is required for maximum growth of hybrid tilapia.