Title: Implementation of rendered fats in aquaculture feeds: maximizing ability to tailor nutritional value of cultured finfish while minimizing reliance on marine resources

Principle Investigator: Jesse Trushenski

Year: 2008

Scientific Abstract:
Objective 1 was designed as a screening study to determine which of the rendered fats evaluated held the most promise for use in the context of finishing strategies for rainbow trout. Each of the rendered fats assessed yielded equivalent growth and growth efficiency. Given that no differences in production performance were observed among the fats, we selected beef tallow based on 1) the minimal impact this fat had on fillet composition in Objective 1, and 2) the more favorable price and widespread availability of this fat source relative to the other rendered fats we evaluated. In Objective 2, greater levels of fish oil sparing (50-100% fish oil replacement) with beef tallow were evaluated in combination with finishing periods of different durations. The feeding trial for Objective 2 revealed no significant differences in growth performance among the treatments: All fish reached a marketable size (~1.25 lbs.) by the time of harvest, and weight gain (1000-1200% gain over the course of the trial) and feed conversion ratio (FCR; 1.4-1.7) were good, regardless of whether the fish were fed diets containing fish oil, beef tallow, or blends of these lipids exclusively or in combination with a finishing feed. Tissue analysis revealed that fillets with equivalent levels of beneficial HUFA may be produced by feeding rainbow trout beef tallow-based feeds according to one of several schemes. For example, 75% of dietary fish oil can be replaced with beef tallow in the grow-out feed if a 4-week finishing period is used. Alternatively, beef tallow can be used to completely replace fish oil in rainbow trout feeds if a 12-week finishing period is used to restore HUFA levels. Taken together, these results indicate that beef tallow may be used rather extensively in rainbow trout culture without concern for reduced production performance or the loss of fillet nutritional value. Lay publications describing these results are planned in order to encourage the aquafeed industry to consider greater use of rendered fats, particularly beef tallow, in rainbow trout feeds.

Publications:
Potential, Implications and Solutions Regarding the Use of Rendered Animal Fats in Aquafeeds

Growth Performance, Tissue Fatty Acid Composition, and Consumer Appeal of Rainbow Trout Reared on Feeds Containing Terrestrially Derived Rendered Fats

Growth Performance and Tissue Fatty Acid Composition of Rainbow Trout Reared on Feeds Containing Fish Oil or Equal Blends of Fish Oil and Traditional or Novel Alternative Lipids