The effects of fish oil-enriched diets on growth, feed conversion and fatty acid content of red hybrid tilapia, Oreochromis sp

Vitamin E amelioration of oxidative stress and low immunity induced by high-lipid diets in hybrid grouper (♀ Epinephelus fuscoguttatus × ♂ E. lanceolatu)

The experiment was conducted to investigate the effects of vitamin E (VE) on growth, oxidative stress and immunity for hybrid grouper (♀ Epinephelus fuscoguttatus × ♂ E. lanceolatu) fed high-lipid diet. Six groups of iso-protein (50.23%) and iso-lipidic high-lipid (15.36%) experimental diets were prepared by adding 0 (basic diet control), 0.01%, 0.02%, 0.03%, 0.04%, 0.05% α-tocopherol respectively in basic diet. Each treatment consisted of 3 replicates and 30 fish (10.20 ± 0.02 g) in each replicate for 8 weeks. The results showed that: 1) compared with the control group, the growth performance of grouper was not affected by the addition of VE in high-lipid diet, but the specific growth rate (SGR) in high VE dose (0.6%) group were significantly decreased compared with 0.02% and 0.03% groups. 2) Adding VE to high-lipid diet can alleviate the hepatic oxidative damage caused by high-lipid diet, and significantly improve the serum and liver antioxidant enzyme activity. 3) Compared with the control group, appropriate VE significantly increased the expression of liver anti-inflammatory factors TGF-β and IL10, and significantly decreased the expression of proinflammatory factors IL8 and IL6. In conclusion, adding appropriate amount of VE into high-lipid diet can improve antioxidant capacity and immunity of grouper, we speculated that VE may alleviate lipid peroxidation by improving antioxidant capacity to reduce the inflammatory response. In combination with the results of the current study, we recommend an additional dose of 0.02%-0.03% of α-tocopherol in this experiment under high-lipid conditions.

Dietary fish oil replacement by linseed oil: Effect on growth, nutrient utilization, tissue fatty acid composition and desaturase gene expression in silver barb (Puntius gonionotus) fingerlings

Silver barb (Puntius gonionotus) is considered a promising medium carp species for freshwater aquaculture in Asia. This study in silver barb was carried out to evaluate the effects of total or partial substitution of dietary fish oil (FO) with linseed oil (LO) on growth, nutrient utilization, whole-body composition, muscle and liver fatty acid composition. Fish (12.1±0.4g of initial body weight) were fed for 60days with five experimental iso-proteinous, iso-lipidic and iso-caloric diets in which FO (control diet) was replaced by 33.3%, 50%, 66.7% and 100% LO. Final weight, weight gain, percent weight gain, SGR decreased linearly (p<0.001) with increasing LO levels in the diets. Dietary LO substitution levels did not significantly (p>0.05) affect the feed conversion ratio (FCR), protein efficiency ratio (PER) and whole body proximate composition. Furthermore, enhanced level of LO increased α-linolenic acid (ALA; 18:3n3) and linoleic acid (LA; 18:2n6) and decreased eicosapentaenoic acid (EPA; 20:5n3) and docosahexaenoic acid (DHA; 22:6n3) in muscle and liver. To understand the molecular mechanism of long chain-polyunsaturated fatty acid (LC-PUFA) biosynthesis, we cloned and characterized the fatty acyl Δ6 desaturase (Δ6 fad) cDNA and investigated its expression in various organs/tissues following replacement of FO with LO in the diet. The full-length Δ6 fad cDNA was 2056bp encoding 444 amino acids and was widely expressed in various organs/tissues. Replacement of FO with LO increased the expression of Δ6 fad mRNA in liver, muscle and intestine but no significant difference was found in the brain.

Impact of dietary fatty acids on muscle composition, liver lipids, milt composition and sperm performance in European eel

In order for European eel aquaculture to be sustainable, the life cycle should be completed in captivity. Development of broodstock diets may improve the species' reproductive success in captivity, through the production of high-quality gametes. Here, our aim was to evaluate the influence of dietary regime on muscle composition, and liver lipids prior to induced maturation, and the resulting sperm composition and performance. To accomplish this fish were reared on three "enhanced" diets and one commercial diet, each with different levels of fatty acids, arachidonic acid (ARA), eicosapentaenoic acid (EPA), and docosahexaenoic acid (DHA). Neutral lipids from the muscle and liver incorporated the majority of the fatty acid profile, while phospholipids incorporated only certain fatty acids. Diet had an effect on the majority of sperm fatty acids, on the total volume of extractable milt, and on the percentage of motile sperm. Here, our results suggest that the total volume of extractable milt is a DHA-dependent process, as we found the diets with the highest DHA levels induced the most milt while the diet with the lowest DHA level induced the least amount of milt. The diet with the highest level of ARA induced medium milt volumes but had the highest sperm motility. EPA also seems important for sperm quality parameters since diets with higher EPA percentages had a higher volume of milt and higher sperm motility. In conclusion, dietary fatty acids had an influence on fatty acids in the tissues of male eel and this impacted sperm performance.