Effects of partial substitution of dietary fish oil with blends of vegetable oils, on blood leucocyte fatty acid compositions, immune function and histology in European sea bass (Dicentrarchus labrax L.)

Abstract

Within a decade or so insufficient fish oil (FO) will be available to meet the requirements for aquaculture growth. Consequently, alternative sources are being investigated to reduce reliance on wild fish as a source of FO. Vegetable oils (VO) are a feasible alternative to FO. However, it is important to establish that alternative dietary lipids are not only supplied in the correct quantities and balance for optimal growth, but can maintain immune function and prevent infection, since it is known that the nutritional state of the fish can influence their immune function and disease resistance. A way of maintaining immune function, while replacing dietary FO, is by using a blend of VO rather than a single oil. In this study, juvenile European sea bass (Dicentrarchus labrax) were fed diets with a 60 % substitution of FO with a blend of rapeseed, linseed and palm oils. Two oil blends were used to achieve a fatty acid composition similar to FO, in terms of energy content, and provide a similar balance of SFA, MUFA and PUFA. Fish were fed the diets for 64 weeks, after which time growth and fatty acid compositions of liver and blood leucocytes were monitored. The impact of the dietary blends on selected innate immune responses and histopathology were also assessed, together with levels of plasma prostaglandin E 2 . The results suggest that potential exists for replacing FO with a VO blend in farmed sea bass feeds without compromising growth, non-specific immune function or histology.

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

“…In addition to absolute ARA levels, the balance between ARA and EPA (precursor to the lesspotent eicosanoids, 3-series prostanoids and 5-series leukotrienes) in the tissues appears to influence physiological status in aquatic species. Given the relationship between dietary FA composition and tissue profile, it is not surprising that replacing fish oil with various plant-derived lipids influences eicosanoid production [58] and, in turn, processes regulated by eicosanoids such as immune function [56,[59][60][61] . However, most of these studies, in spite of having compared feeds with radically different fatty acid profiles, have reported moderate or conflicting immunological effects.…”

Determination of Hematological Status as Health Indicator of European Sea Bass (Dicentrarchus labrax L.) Fed Different Dietary Fatty Acids

“…As stated in a previous study, the use of n-6 and n-3 (PUFA) and MUFA fatty acids as an alternative and source of energy led to significant effects in the immune system and supported macrophage activity of fish (Barros et al, 2002;Montero et al, 2005;Mourente et al, 2007;Montero and Izquerdo, 2010). Mourente et al (2007) stated that the use of vegetable derived lipids as an alternative to fish oil yielded optimal growth and feed cycle and can also optimize immune system functions of fishes if it is included in the right amounts.…”

“…There have been numerous studies into the effects of balanced diet contents on hematological parameters (Robinson and Daniels, 1987;Mourente et al, 2007;Wassef et al, 2007).…”

“…In similar studies conducted on different marine species, peripheral blood leukocytes and functions were affected by the fatty acid profile of the diet. (Sheldon and Blazer, 1991;Montero et al, 2003;Mourente et al, 2007). Mourente et al (2007) mentions the study of plant oils are used as an alternative to fish oil, important changes have been determined from the non-specific immune system.…”

Dietary effect of varying linseed oil compositions on growth response, survival and polyunsaturated fatty acid levels in Tilapia (Oreochromis niloticus)

“…In addition, studies have reported considerable success in partial or total replacement of FO with VO in many fish species (Ng, 2005;Turchini et al, 2009Turchini et al, , 2010. Moreover, recent studies have also evaluated the effects of replacing highquality FO with VO sources on growth performance, fatty acid profile or health parameters of fishes, such as gilthead seabream (Sparus aurata) (Menoyo et al, 2004) and European sea bass (Dicentrarchus labrax L.) (Mourente et al, 2007). However, the extent of the effect is determined by the vegetable oil source and level of dietary replacement.…”