|DAVIS, D. ALLEN - Auburn University|
|SHELBY, RICHARD - US Department Of Agriculture (USDA)|
Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 10/3/2009
Publication Date: 11/3/2009
Citation: Lim, C.E., Aksoy, M., Davis, D., Shelby, R.A., Klesius, P.H. 2009. Influence of supplemental levels of fish oil and feeding duration on fillet proximate and fatty acid composition, hematology and immune response of channel catfish (Ictalurus punctatus)reared in ponds [abstract]. Asian Pacific Aquaculture 2009. paper No. 34.
Technical Abstract: Lipids of marine origin are known to contain high levels of n-3 highly unsaturated fatty acids (n-3 HUFA), eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) which have been shown to have protective effects against the development of cardiovascular diseases and rheumatoid arthritis. Lipids in farmed freshwater fish, such as channel catfish and tilapia, that are commonly fed grain-soy based diets, are low in n-3 HUFA and high in n-6 polyunsaturated fatty acid (n-6 PUFA). Earlier research has shown that n-3 HUFA content in farm-raised fish can be increased by feeding diets supplemented with marine fish oil. Increasing these fatty acids in aquaculture products could be a major factor in determining consumer acceptance. The demand of fish oil for aquafeeds has increased considerably in recent years; however, the supply has stagnated or declined. Thus, to optimize the use of this limited resource, this study was conducted to evaluate the effect of supplemental levels of menhaden fish oil and feeding duration on fillet proximate and fatty acid composition, hematology and innate immune responses of channel catfish. Triplicate groups of fingerling channel catfish (16.60 ± 0.55g) stocked in 400-m2 earthen ponds at a rate of 20,000/ha were fed a 32% protein floating catfish feed supplemented with 0, 3 or 6% of menhaden fish oil (D-1, D-2 and D-3, respectively) once daily, 6 days/week to apparent satiation for 5 months. Fish were sampled for fillet proximate and fatty acid composition after 2, 3, 4 and 5 months of feeding, and hematological and immunological assays at month 5. Dietary fish oil levels had no effect on fish production, but fish fed D-1 had significantly poorer feed efficiency than those of diets D-2 and D-3. Fillet proximate composition was not affected by dietary fish oil levels. Fillet moisture and ash decreased, whereas lipid increased with feeding duration. Fillet protein was not affected by feeding duration. Increasing dietary fish oil levels significantly increased fillet percentages of saturate, total n-3 and n-3 HUFA, but decreased total monoenes and n-6. Total fillet n-6 was not affected by feeding duration. Percentages of total saturate, n-3 and n-3 HUFA in fillets significantly decreased, but total monoenes increased with increasing feeding duration. After month 4, however, the values of these variables remained similar. When expressed in mg/g of fillet, total n-3 and n-3 HUFA progressively increased with increasing dietary levels of fish oil and feeding duration. Hematocrit, red and white blood cell count, and hemoglobin at the end of month 5 were not affected by dietary fish oil levels. Erythrocytes from fish fed diet D-3 were more resistant to hemolysis in hypotonic solutions than those fed diet D-1 and D-2. Serum protein, total immunoglobulin, and lysozyme and complement activity determined at the end of 5 months were not affected by dietary fish oil levels.