title: Replacement of dietary fish oils by alpha-linolenic acid-rich oils lowers omega 3 content in tilapia flesh.
abstract: A 20-week feeding trial was conducted to determine whether increasing linolenic acid (18:3n-3) in vegetable oil (VO) based diets would lead to increased tissue deposition of 22:6n-3 in Nile tilapia (Oreochromis niloticus). Five isonitrogenous and isoenergetic diets were supplemented with 3% of either linseed oil (LO), a mixture of linseed oil with refined palm olein oil (PO) (LO-PO 2:1) and a mixture of refined palm olein oil with linseed oil (PO-LO 3:2) or with fish oil (FO) or corn oil (CO) as controls. The PO-LO, LO-PO and LO diets supplied a similar amount of 18:2n-6 (0.5% of diet by dry weight) and 0.5, 0.7 and 1.1% of 18:3n-3, respectively. Increased dietary 18:3n-3 caused commensurate increases in longer-chain n-3 PUFA and decreases in longer-chain n-6 PUFA in the muscle lipids of tilapia. However, the biosynthetic activities of fish fed the LO-based diets were not sufficient to raise the tissue concentrations of 20:5n-3, 22:5n-3 and 22:6n-3 to those of fish fed FO. The study suggests that tilapia (O. niloticus) has a limited capacity to synthesise 20:5n-3 and 22:6n-3 from dietary 18:3n-3. The replacement of FO in the diet of farmed tilapia with vegetable oils could therefore lower tissue concentrations of 20:5n-3 and 22:6n-3, and consequently produce an aquaculture product of lower lipid nutritional value for the consumer.
authors.affiliation: Institute of Aquaculture, University of Stirling, Stirling, FK9 4LA, Scotland.
authors.forename: Ioannis T
authors.initials: IT
authors.lastname: Karapanagiotidis
authors.forename: Michael V
authors.initials: MV
authors.lastname: Bell
authors.forename: David C
authors.initials: DC
authors.lastname: Little
authors.forename: Amararatne
authors.initials: A
authors.lastname: Yakupitiyage
mesh_terms: D000821:Animal Feed / Q000032:analysis*; D000818:Animals; D017756:Aquaculture; D004042:Dietary Fats, Unsaturated / Q000008:administration & dosage / Q000378:metabolism; D015525:Fatty Acids, Omega-3 / Q000032:analysis* / Q000378:metabolism*; D043371:Fatty Acids, Omega-6 / Q000032:analysis / Q000378:metabolism; D005231:Fatty Acids, Unsaturated / Q000032:analysis; D005395:Fish Oils / Q000008:administration & dosage / Q000378:metabolism*; D005396:Fish Products / Q000032:analysis; D008043:Linseed Oil / Q000008:administration & dosage / Q000378:metabolism; D009132:Muscles / Q000737:chemistry / Q000378:metabolism*; D009751:Nutritional Requirements; D009753:Nutritive Value; D000073878:Palm Oil; D010938:Plant Oils / Q000008:administration & dosage / Q000378:metabolism; D011897:Random Allocation; D017210:Tilapia / Q000378:metabolism*; D017962:alpha-Linolenic Acid / Q000008:administration & dosage / Q000378:metabolism*
chemical_list: D004042:Dietary Fats, Unsaturated; D015525:Fatty Acids, Omega-3; D043371:Fatty Acids, Omega-6; D005231:Fatty Acids, Unsaturated; D005395:Fish Oils; D010938:Plant Oils; D017962:alpha-Linolenic Acid; D000073878:Palm Oil; D008043:Linseed Oil