Effects of dietary n−3 polyunsaturated fatty acids on lipid and fatty acid composition and haematology of juvenile Arctic charr Salvelinus alpinus (L.)

Abstract

The effect of dietary n-3 and n-6 polyunsaturated fatty acids (PUFAs) on juvenile Arctic charr Salvelinus alpinus (L.) were investigated with respect to essential fatty acid (EFA) deficiency and lipid metabolism using one commercial and 12 casein-based test diets. Arctic charr with mean weight of 1.6g were fed test diets for 12 weeks at 10°C. At the end of the feeding, blood, liver, muscle and whole fish were sampled to determine haematocrit, haemoglobin, water content, lipid and fatty acid composition. Charr fed diets containing 0-1.0% n-3 PUFAs showed typical EFA deficiency signs: fatty liver or elevated water content in whole body or substantial accumulation of 20:3n-9 in liver polar lipids. These signs were less apparent or disappeared when charr were fed diets containing ≥ 2.0% 18:3n-3. No correlation was found between dietary PUFAs and haematocrit or haemoglobin values. Significant changes in fatty acid composition of liver polar lipids in charr fed dietary PUFAs indicate that charr can convert 18:3n-3, 18:2n-6 and 20:5n-3 into long-chain PUFAs. While charr had a direct incorporation of dietary 22:6n-3 into liver and muscle there appears to be preferential utilization of n-3 PUFAs for elongation and desaturation. The conversion of 18:4n-3 was less in muscle than in livers. These findings, combined with data on growth and feed efficiency reported previously by Yang and Dick (1993), indicate that charr require 1-2% dietary 18:3n-3 (dry weight). Small amounts of dietary 18:2n-6 (up to 0.7%) did not have detrimental effects on charr.

Effects of dietary linolenic acid on growth, fatty acid composition, immune function and antioxidant status of juvenile blunt snout bream,Megalobrama amblycephala

“…Using second-order polynomial regression models, the dietary LNA requirements of juvenile blunt snout bream were estimated to be 17.5 and 15.6 g/kg based on SGR and FER respectively. These levels were similar to those reported for white fish (Coregonus lavaretus) (Thongrod, Takeuchi, Satoh & Watanabe, 1989), Arctic charr (Salvelinus alpinus) (Yang, Tabachek & Dick, 1994), and channel catfish , but higher to those reported for yellowhead catfish (Tan et al, 2009) , 1991) and Japanese eel (Anguilla japonicas) (Takeuchi, Arais, Watanabe & Shimma, 1980). The different LNA requirements are probably attributed to the fish species and size, experimental conditions and data analysis (Tocher, 2010;Zhang et al, 2006).…”

Growth, immune response and resistance toAeromonas hydrophilaof darkbarbel catfish, Pelteobagrus vachelli(Richardson), fed diets with different linolenic acid levels

“…Lower weight gain and SGR of fish fed the control diet (0% linolenic acid) in our study is likely due to a deficiency of linolenic acid. EFA deficiency can occur, leading to poor growth performance in other freshwater fish, such as Oncorhynchus mykiss (Castell, Sinnhuber, Wale & Lee ), Coregonus laveratus (Watanabe, Thongrod, Takeuchi, Satoh, Kubota, Fujimaki & Cho ), O. masou (Thongrod, Takeuchi, Satoh & Wantanabe ), Salvelinus alpinus (Yang, Tabachek & Dick ) and Salmo salar (Ruyter, Rosjo, Einen & Thomassen ) when n‐3 PUFA is deficient in diets. The reported n‐6 fatty acids requirements for O. nilotica are 0.5% (Takeuchi, Satoh & Watanabe ).…”

“…Lower weight gain and SGR of fish fed the control diet (0% linolenic acid) in our study is likely due to a deficiency of linolenic acid. (Yang, Tabachek & Dick 1994) and Salmo salar (Ruyter, Rosjo, Einen & Thomassen 2000) when n-3 PUFA is deficient in diets. The reported n-6 fatty acids requirements for O. nilotica are 0.5% (Takeuchi, Satoh & Watanabe 1983).…”

“…In this study, 1.3% linolenic acid was determined by broken-line analysis to be optimal for growth of dark barbel catfish, which is similar to previous reports of catfish species. The reported linolenic acid requirements are 1.0-2.0% for I. punctatus ) and S. alpinus (Yang et al 1994) and 1.0% for S. glanis (Borgut et al 1998).…”

Metabolism of n−3 and n−6 fatty acids in Atlantic salmon liver: Stimulation by essential fatty acid deficiency

“…In the present study, the high ratio (3.5) of 20:3n-9 to 22:6n-3 in the total lipid fraction of hepatocytes from salmon fed the EFA-deficient diet, together with the appearance of swollen pale livers and fin erosion, indicates an EFA-deficient status. The latter two symptoms are known signs of EFA deficiency in fish (27,28). Even though no dietary n-6 fatty acids were available to fish from either of the two dietary groups, the percentage of the n-6 fatty acids 20:4 and 22:5 was higher in hepatocytes from fish fed the EFA-deficient diet as compared to hepatocytes from fish fed the n-3 supplemented diet.…”