Date of Award
Master of Science
Sparing fish oil (FO) in aquafeeds, especially diets intended for marine carnivores, is essential for the continued economic and environmental sustainability of aquaculture. Plant- and animal-derived lipids may successfully replace FO so long as diets are otherwise formulated to contain adequate amounts of essential fatty acids, including the long-chain polyunsaturated fatty acids (LC-PUFAs) required by many marine carnivorous species. Whereas growth performance may not be affected by these alternative lipids, tissue fatty acid profiles, including that of the edible fillet products, are often distorted and contain less of the LC-PUFAs many seafood consumers desire. Saturated fatty acid (SFA)-rich lipids, such as fully hydrogenated soybean oil (SO), tend to have a less overt effect on fillet composition and LC-PUFA loss in comparison with alternative lipids rich in C18 polyunsaturated fatty acids (C18 PUFAs). However, SFA-rich lipids may be somewhat less digestible. To address this digestibility limitation, two studies were conducted to evaluate 1) increasing inclusion levels of partially hydrogenated SO (a monounsaturated fatty acid [MUFA]-rich lipid with presumably higher digestibility) in place of fully hydrogenated SO, and 2) supplementing fully hydrogenated SO-based feeds with emulsifiers as a means of enhancing diet utilization, growth performance, and fillet LC-PUFA retention in California Yellowtail (Seriola dorsalis). In both studies, diets containing only fully hydrogenated SO yielded tissues with equivalent levels of LC-PUFAs in comparison to diets containing menhaden FO. Replacing 60% of fully hydrogenated SO with partially hydrogenated SO resulted in numeric increases in production performance (weight gain and specific growth rate [SGR]), with minimal accumulations of trans fats in edible tissues. Whereas emulsifiers including casein, whey protein, and monoglycerides can be added to SFA-rich fully hydrogenated SO diets to potentially improve digestibility, no production performance benefit was realized in California Yellowtail; the addition of mixed bile acids, however, significantly impaired performance. In summary, the use of SFA-rich fully hydrogenated SO is an effective strategy for minimizing the negative effects of FO sparing on California Yellowtail fillet composition, but limitations associated with reduced SFA digestibility must be addressed in order to optimize utilization and effectiveness of SFA-rich aquafeeds.
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