FEED ADDITIVES
Spicing up aquafeeds: A novel strategy to mitigate reduced fish oil dietary inclusion, showcased in seabream fed a low fish oil-high poultry oil diet Alberto Ruiz, Enric Gisbert, IRTA, Thiago Raggi, Sofia Morais, LUCTA S.A.
The fish oil challenge Availability and cost of fish oil has become a main bottleneck for the growth of the aquaculture sector, and for maintaining the end-quality and welfare of farmed fish. Fish oil provides energy and essential nutrients, including n-3 long-chain polyunsaturated fatty acids (LC-PUFA), mainly eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), cholesterol and fat-soluble vitamins. A steady growth of aquaculture production, with declining or stagnant fish oil production in the last two decades, has only been possible through the gradual replacement of fish oil with other fats, mostly of vegetable origin. However, the dietary level of fish oil is reaching, or has already reached, its lower limit in most industries, and cannot be further reduced without significant negative effects on fish performance, health, and end-quality. Most of these impacts are associated with the anti-inflammatory, cardioprotective, and lipotropic role of omega-3 fatty acids (particularly of n-3 LC-PUFA). Conversely, omega-6 (highly abundant in plant oils) have opposite effects. Commercially viable alternative sources of omega-3 are emerging in the industry, but cost and volumes are still limiting for use in most species, markets, or production stages. Therefore, new strategies are urgently needed to optimize the efficiency of the use of fish oil and
alternative omega-3 sources. Formulation and supplementation strategies to aid in the strategic use of fish oil The overall composition and fatty acid class balance of fish oil have been given less attention than its level of omega-3. The principal fatty acids of most commercial fish oils used in aquafeeds are 14:0, 16:0, 16:1n-7, 18:1n9, EPA and DHA, and they typically contain 25-30% saturated fatty acids (SFA), 20-50% monounsaturated fatty acids (MUFA) and 20-45% polyunsaturated fatty acids (PUFA), of which most are omega-3. Replacing fish oil with vegetable oils greatly changes the dietary fat profile, most notably by reducing SFA and increasing omega-6 levels concurrently with omega-3 reduction. The physiological consequences of these imbalances are magnified by the fact that omega-3 and omega-6 are competitively metabolized by the same set of enzymes, and the metabolites of these enzymatic conversions perform antagonistic functions. On the other hand, SFA and MUFA are preferential substrates for metabolic energy production, sparing LC-PUFA, notably EPA and DHA, from catabolism. Several fish studies have already demonstrated that this omega-3 sparing effect can increase LC-PUFA in the edible fraction and/or reduce the dietary levels needed to satisfy essential fatty acid requirements. Hence, optimized formulation strategies should aim to reduce
Aquafeed: Advances in Processing & Formulation Vol 16 Issue 1 2024
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