Cofeeding of phospholipids to turbot Scophthalmus maximus L. larvae as a tool to reduce live food consumption

The possible benefits of feeding a formulated diet, together with Artemia , to first-feeding turbot larvae were investigated. Five dietary regimes were used: control ( Artemia only), cofeeding with a diet rich in phospholipid (PL) from bovine brain, cofeeding with a diet rich in free fatty acids (FFA) from the same source, cofeeding with a commercial diet (Lansy A2), and a formulated feed only (PL-rich diet). All treatments with artificial diets and the control treatment that received Artemia exclusively gave a similar survival rate of the fish at day 29. Cofeeding with artificial diets resulted in a lower growth rate than the control treatment. Cofeeding the larvae with PL-rich or FFA-rich diets did not affect the pigmentation or resistance to salt stress of the larvae. Complete substitution of Artemia by the phosholipid diets from day 20, however, resulted in severe stress and pigmentation problems. Cofeeding might have interesting features for application since it may reduce the amount and cost of live food and also offer to the fish larvae essential nutrients that are not contained in sufficient amounts in the (enriched) live food.     

Effect of Dietary Essential Fatty Acids and Vitamins on Egg Quality in Turbot Broodstocks

Varying egg quality is one of the main factors interfering with the reliable performance of marine fish hatcheries. As larval performance during the first period largely depends on the availability of essential nutrients, the endogenous provision of these nutrients through the egg stages, and possibly parental diet, might be an important tool in improving hatchery output. Therefore, several feeding experiments were conducted on turbot (Scophthalmus maximus) broodstock reared under production conditions at two commercial facilities in France: France Turbot (FT) and Sepia Conseil (SC). Diets varied mainly in essential fatty acids (-3 HUFA), Vitamins C and E, and were fed for 2–3 months prior to the reproductive season. Egg quality parameters, i.e. fertilization and hatching rate, egg and oil droplet diameter, and biochemical composition, were monitored for each female during its total reproductive phase.Egg size during the reproductive cycle showed a low variability among females receiving the same treatment, but became significantly smaller as the season progressed. The same occurred for the oil globule in the non-vitamin supplemented groups, whereas it significantly increased in the vitamin-supplemented groups. However, these observations could not be correlated with any of the hatching or fertilization characteristics. The egg dimensions also varied as a function of the diet supplied, i.e. high HUFA levels in the broodstock diet resulted in a significant increase of egg diameter, oil globule diameter as well as fertilization rate. Interestingly, the control groups, with the lowest fertilization rate, had the highest hatching percentage, significantly higher than the HUFA/non-vitamin enriched groups.Using non-selected sources of trash fish as a food source at SC resulted in low levels of ascorbic acid (AA) in the eggs compared to the administration of an optimal quality batch of mackerel at FT. Enrichment of the trash fish with ascorbate-2–polyphosphate (ApP) resulted in a tripling of the AA content. Extra enrichment of the FT control diet did not further increase the levels in the eggs, suggesting that a saturation level was obtained. The major fatty acids in turbot eggs as well as freshly hatched larva are 16:0, 18:1-9, 20:5-3 and 22:6-3, but no obvious changes in their pattern could be detected for the different broodstock treatments. However, the level of 20:4-6 was significantly higher in the control group of FT, and showed a high correlation with the hatching percentage of the eggs obtained from the various broodstock treatments.