Monounsaturated fatty acids (MUFA)-rich and n-6 polyunsaturated fatty acid (n-6 PUFA)-rich vegetable oils are increasingly used as fish oil replacers for aquafeed formulation. The present study investigated the fatty acid metabolism in juvenile European sea bass (Dicentrarchus labrax, 38.4 g) fed diets containing fish oil (FO, as the control treatment) or two different vegetable oils (the MUFA-rich canola/rapeseed oil, CO; and the n-6 PUFA-rich cottonseed oil, CSO) tested individually or as a 50/50 blend (CO/CSO). The whole-body fatty acid balance method was used to deduce the apparent in vivo fatty acid metabolism. No effect on growth performance and feed utilization was recorded. However, it should be noted that the fish meal content of the experimental diets was relatively high, and thus the requirement for n-3 long-chain polyunsaturated fatty acid (n-3 LC-PUFA) may have likely been fulfilled even if dietary fish oil was fully replaced by vegetable oils. Overall, relatively little apparent in vivo fatty acid bioconversion was recorded, whilst the apparent in vivo β-oxidation of dietary fatty acid was largely affected by the dietary lipid source, with higher rate of β-oxidation for those fatty acids which were provided in dietary surplus. The deposition of 20:5n-3 and 22:6n-3, as % of the dietary intake, was greatest for the fish fed on the CSO diet. It has been shown that European sea bass seems to be able to efficiently use n-6 PUFA for energy substrate, and this may help in minimizing the β-oxidation of the health benefiting n-3 LC-PUFA and thus increase their deposition into fish tissues.

Brown trout Salmo trutta (~1 g) were fed four casein-gelatin based diets with different lipid resources for 6 weeks. The sources of dietary lipid were menhaden oil (MO diet), hazelnut oil (HO diet,), a blend of linseed oil and soybean oil (1:1) (LO+SO diet), and soybean lecithin (LE diet). Feeding trial was conducted in a recirculating water system at 13±0.2°C. Fish fed LO+SO diet demonstrated the highest growth performance while those fed HO diet had the lowest growth rate (P<0.05). The fatty acid profiles of fish reflected the fatty acid composition of the diets. High level of docosahexaenoic acid (22:6n-3, DHA) in whole body lipids of fish fed LO+SO diet corresponded with the high level of linolenic acid (18:3n-3, LNA) in the lipids of this diet. Fish fed LE diet which was rich in linoleic acid (18:2n-6, LA) had the highest level of arachidonic acid (20:4n-6 , ARA) in their body. The results suggest that the efficiency of elongation and desaturation of C18 fatty acids depends on the dietary lipid source and brown trout has capacity to transform LA and LNA to ARA and DHA, respectively. Growth depletion in fish fed HO diet might be caused by essential fatty acid deficiency.Keywords: Brown trout, Salmo trutta, lipids, fatty acids, growth. Balık Yağı Yerine Kullanılan Farklı Diyetsel Bitkisel Yağların Kahverengi Alabalık (Salmo trutta) Yavrularında Büyüme ve Yağ Asidi Kompozisyonuna Etkisi ÖzetMevcut çalışmada yaklaşık 1 g ağırlığındaki kahverengi alabalık yavruları 6 hafta süre ile kazein-jelâtin tabanlı yemlerle beslenmiştir. Yemlerde yağ kaynağı olarak balık (ringa) yağı (MO diyeti), fındık yağı (HO diyeti), soya yağı-keten tohumu yağı karışımı (1:1) (LO+SO diyeti) ve soya lesitini (LE diyeti) kullanılmıştır. Kapalı devre su sisteminde yürütülen çalışma boyunca sıcaklık 13±0,2°C olarak gerçekleşmiştir. Çalışma sonunda LO+SO yemi ile beslenen balıklar diğer yemlerle beslenen balıklara göre önemli derecede yüksek büyüme performansı göstermiştir (P<0,05). En düşük büyüme HO yemi ile beslenen balıklarda görülmüştür. Tüm vücuda ait toplam yağların nötral ve polar lipit fraksiyonlarının yağ asidi içerikleri yemlerin yağ asidi içeriklerini yansıtmıştır. Yüksek düzeyde linolenik asit (18:3n-3, LNA) içeriğine sahip LO+SO diyeti ile beslenen balıkların vücudunda, dokozahekzaenoik asit (22:6n-3, DHA) miktarında artış görülmüştür. Benzer şekilde en yüksek araşidonik asit (20:4n-6, ARA) içeriği, 18:2n-6 (linolenik asit, LA) bakımından zengin olan LE diyeti ile beslenen balıklarda görülmüştür. Mevcut çalışmanın sonuçları, kahverengi alabalıkta yemlerdeki yağ kaynağına bağlı olarak LA ve LNA in sırasıyla ARA ve DHA e dönüştürebildiğini göstermektedir. Fındık yağı ile beslenen balıklardaki düşük büyümenin esansiyel yağ asidi eksikliğinden kaynaklandığı düşünülmektedir.Anahtar Kelimeler: Kahverengi alabalık, Salmo trutta, yağlar, yağ asitleri, büyüme.

No abstract

No abstract

No abstract