Effect of increasing docosahexaenoic acid content in weaning diets on survival,growth and skeletal anomalies of longfin yellowtail (Seriola rivoliana,Valenciennes 1833)

Five isoproteic (54.8%) and isolipidic (24.1%) microdiets, which varied in their docosahexaenoic acid (DHA) content (0.25%, 0.75%, 1.64%, 1.99% and 3.17%; dw), were manufactured to determine its effects on longfin yellowtail Seriola rivoliana larvae in terms of fish biological performance, whole body fatty acid profile and incidence of skeletal anomalies from 30 dah (11.31 ± 1.79 Total Length, TL) to 50 dah (19.80 ± 0.58 mm TL). The inclusion of dietary DHA up to 3.17% (dw) improved larval resistance to air exposure, although DHA did not significantly affect fish final growth or final survival. Indeed, high levels of dietary DHA (1.99% and 3.17%, dw) tended to increase the incidence of skeletal anomalies in S. rivoliana larvae, albeit no significant differences were observed. Furthermore, the occurrence of severe anomalies such as kyphosis and lordosis, was mainly associated to the larvae fed the highest levels of dietary DHA. In terms of survival, increasing dietary DHA levels did not significantly affect longfin yellowtail survival rate, despite a tendency for enhanced survival. The results of the present study proved that the inclusion of dietary DHA in inert diets up to a 3.17% (dw) and a DHA/EPA ratio above 3.1 increased the final survival and stress resistance in S. rivoliana larvae.     

The importance of dietary HUFA for meagre larvae (Argyrosomus regius; Asso, 1801) and its relation with antioxidant vitamins E and C

Despite the interest of meagre (Argyrosomus regius) as a fast‐growing candidate for Mediterranean aquaculture diversification, there is a lack of information on nutrition along larval development. Importance of highly unsaturated fatty acids (HUFA) and the antioxidant vitamins E and vitamin C has not been investigated yet in this species. Six diets with two levels of HUFA (0.4% and 3% dw), two of vitamin E (1500 and 3000 mg kg^?1) and two of vitamin C (1800 and 3600 mg kg^?1) were fed to 15 dah meagre larvae. Larval growth in total length and dry body weight was significantly lowest in larvae fed diet 0.4/150/180 and showed few lipid droplets in enterocytes and hepatocytes and lower HUFA contents than the initial larvae. Increase in dietary HUFA up to 3%, significantly improved larval growth and lipid absorption and deposition. Besides, among fish fed 3% HUFA, increase in vitamin E and vitamin C significantly improved body weight, as well as total lipid, 22:6n‐3 and n‐3 fatty acids contents in the larvae. Thus, the results showed that 0.4% dietary HUFA is not enough to cover the essential fatty acid requirements of larval meagre and a high HUFA requirement in weaning diets is foreseen for this species. Besides, the results also pointed out the importance of dietary vitamin E and C to protect these essential fatty acids from oxidation, increase their contents in the larvae and promote growth, suggesting high vitamin E and C requirements in meagre larvae (higher than 1500 and 1800 mg kg^?1 for vitamin E and vitamin C respectively).     

Effect of Density at Harvest on the Growth Performance and Profitability of Hatchery‐reared Spotted Rose Snapper,Lutjanus guttatus,Cultured in Floating Net Cages

This study evaluated the effect of the density at harvest on the performance and profitability of hatchery‐reared spotted rose snapper cultured in cages. The fish were stocked at harvest densities of 15, 20, and 22 kg/m³ in cages of 222 and 286 m³. More than 39,000 snapper fingerlings with an initial weight of 14 g were stocked. The fish were fed an extruded diet and cultured over a 360 d period. The thermal growth coefficient ranged from 0.04 to 0.05 and survival was 95% for all treatments, with the highest final weight (436.8 g) observed for fish reared at a density of 20 kg/m³. The allometric value b indicated that hatchery‐raised, cage‐cultured snapper were heavier than their wild counterparts. The major costs were feed (ranging from 44.7–45.9%), labor (22.4–32.6%), and seed costs (20.2–26.1%). The total production cost ranged from US$ 6.5 to US$ 7.5/kg. The baseline scenario was not economically feasible. However, a 10% increase in the sales price resulted in increases in the internal rate of return (183%) and net present value (US$ 97,628.9). These results suggest that L. guttatus has the potential for commercial production in cages.     

Optimum krill phospholipids content in microdiets for gilthead seabream (Sparus aurata) larvae

The aim of the present study was to determine the optimum dietary levels of krill phospholipids (KPL) for sea bream (Sparus aurata) larvae, and its influence on larval development and digestive enzymes activity. Larvae were fed five formulated microdiets with five different levels of KPL. Complete replacement of live preys with the experimental microdiets for seabream larvae produced high survival and growth rates, particularly in fish fed the highest levels of KPL. In the present study, increase in dietary KPL up to 120 g kg^?1 (100 g kg^?1 total PL) significantly improved larval survival and growth, whereas further increase did not improve those parameters. An increase in alkaline phosphatase, trypsin and lipase activity with the elevation of KPL up to 120 g kg^?1 was also found denoting a better functioning of digestive system. Besides, there was a linear substrate stimulatory effect of dietary KPL on phospholipase A2 activity. Finally, increasing dietary KPL lead to better assimilation of n‐3 HUFA especially eicosapentaenoic acid, reflected in the higher content of these fatty acids in both neutral and polar lipids of the larvae. In summary, KPL were found to be an excellent source of lipids for seabream larvae. Optimum inclusion levels of this ingredient in microdiets to completely substitute live preys at this larval age were found to be 120 g kg^?1 KPL.     

Regulation of growth, fatty acid composition and delta 6 desaturase expression by dietary lipids in gilthead seabream larvae (Sparus aurata)

The Δ6 and Δ5 desaturases and elongases show only very limited activity in marine fish, and little is known of the possibility of enhancing Δ6 desaturase gene expression in these fish. The use of plant oils in marine fish diets is limited by their lack of n−3 highly unsaturated fatty acids (HUFA) despite an abundant content of the 18C fatty acid precursor linoleic and α-linolenic acids. The objective of the present study was to determine the ability of larval gilthead seabream to utilize vegetable oils and assess the nutritional regulation of Δ6 desaturase gene expression. Seventeen-day-old gilthead seabream larvae were fed during a 17-day period with one of four different microdiets formulated with either sardine fish oil (FO), soybean, rapeseed or linseed oils, respectively, or a fifth diet containing defatted squid meal and linseed oil. Good larval survival and growth, both in terms of total length and body weight, were obtained by feeding the larvae either rapeseed, soybean or linseed oils. The presence of vegetable oils in the diet increased the levels of 20:2n−9 and 20:2n−6, 18:2n−9, 18:3n−6, 20:3n−6 and 20:4n−6, in larvae fed rapeseed and soybean oils in comparison to those fed FO. In addition, a sixfold increase in the relative expression of Δ6 desaturase-like gene was found in larvae fed rapeseed and soybean oils, denoting the nutritional regulation of desaturase activity through its gene expression in this fish species. However, feeding linseed oil did not increase the expression of the Δ6 desaturase gene to such a high extent.     

The potential of pet‐grade poultry by‐product meal to replace fish meal in the diet of the juvenile spotted rose snapper Lutjanus guttatus (Steindachner, 1869)

A 12‐week feeding trial was conducted to examine the replacement of fish meal with pet‐grade poultry by‐product meal (PBM‐PG) in the spotted rose snapper Lutjanus guttatus diet. Five experimental diets were formulated to contain graded levels of PBM‐PG at proportion of 250, 500, 75 or 900 g kg^?1. The control diet contained sardine fish meal as the main protein source. Four groups of 15 randomly assigned L. guttatus juveniles were fed to satiation 3 times day^?1. Except for the fish fed the PBM‐PG90 diet, the growth performance, survival and feed utilization efficiency of the experimental fish were not significantly lower than those of the control fish. The dietary level of PBM‐PG did significantly affect the haematological characteristics (P < 0.05). The dietary dry matter and protein apparent digestibility coefficients (ADCs) decreased with increasing dietary PBM‐PG. High values for lipid ADCs were observed in all diets, with significant differences among the dietary treatments. The fish whole‐body protein, moisture, lipid and ash contents were not affected by the inclusion of dietary PBM. These results indicate that high‐quality terrestrial PBM can successfully replace more than half of the marine fish meal protein in the L. guttatus diet.     

Serological tests in relation to the viability,fertility and localization of hydatid cysts in cattle,sheep, goats and swine

A serological study of intermediate hosts (cattle, sheep, goats and swine) of Echinococcus granulosus was carried out by means of the indirect haemaglutination (IHA) and flocculation with latex (LA) tests, relating them with the organs invaded, and the fertility and viability of the cysts.In cattle a sensitivity of 75% and 21.05% of non-specific reactions was given by IHA, while the LA gave 66.7 and 17.54%, respectively. In the sheep, the IHA gave 79.16 and 20%, and the LA, 75 and 15%. In the goat, the IHA gave 76 and 22%, and the LA 71.43 and 16%. Finally, in the pig, the IHA gave 75 and 22%, and the LA, 66.6 and 14.16%.The IHA was more sensitive in detecting hepatic cysts in the cow, and pulmonary cysts in the goat, while in the sheep and the pig there were no significant differences. The LA was more sensitive in detecting hepatic cysts in the cow, goat and pig, while there were no significant differences in sheep.The differences in serum titers by the IHA and the LA tests with respect to the viability and the fertility of the cysts in the hosts, were not significant.     

Supplementation of Citric Acid and Amino Acid Chelated Trace Elements in Low‐Fish Meal Diet for Rainbow Trout Affect Growth and Phosphorus Utilization

This study was conducted to evaluate the effect of citric acid (CA) and amino acid chelated trace elements (AA) on the growth, phosphorus (P) utilization efficiency and loading in rainbow trout fed a diet formulated with a low‐fish meal (FM) concentration. A low‐FM basal diet with or without monocalcium phosphate supplementation served as positive and negative control correspondingly. Dietary treatments consisted of the basal diet supplemented either with 1% CA, AA (equivalent to 40 Zn, 20 Mn, and 4 Cu mg/Kg of diet instead of inorganic trace element mix) or a combination of both. Duplicate groups of 35 fish (13.2 g) were fed until apparent satiation during 12 wk. Group of fish fed diets supplemented with 1% CA or AA had a final growth and feed utilization similar to that observed in fish fed the positive control diet (P > 0.05). P absorption was increased with the addition of CA or AA. P retention efficiency rates for these diets were higher in comparison with the rest of the treatments consequently showing the lowest P loading values (P < 0.05). The results indicate that addition of 1% CA or AA, to a low‐FM diet without inorganic P supplementation enhanced fish growth, P retention, and decreased P load to the environment.     

Sensory evaluation of farmed sharpsnout seabream (Diplodus puntazzo)

The first attempts at applying aquacultural techniques to sharpsnoutseabream (Diplodus puntazzo) have proved very promising.One of the factors to keep in mind when analysing the viability of a speciesforindustrial farming is that of consumer acceptance of the product, a variablethat can be measured by sensory evaluation tests. To that end, 107 participantsfrom a number of work centres were assessed with hedonic sensory tests usingsharpsnout seabream samples. For reference purposes, the tasting also includedgilthead seabream samples. Participants were asked to fill out a questionnairethat included questions concerning their preferences for any one fish. Weanalysed the sensory attributes of both fish species using a hedonic scale, andalso their acceptability (disposition to purchase) to consumers. The resultsproved fairly encouraging with a view to sharpsnout seabream large-scaleproduction. All attributes tested in the sensory profile analysis werepositively rated. About 60% of the surveyed population would consider buyingsharpsnout seabream at a price similar to that of gilthead seabream (10∈),and 85% found it to be pleasing to the eye. Aside from flavour, its texture,juiciness and fat level are the most important appraisal attributes. Efforts toimprove the organoleptic characteristics of the species should focus mainly onthese attributes.     

Segregation and associations of enological and agronomic traits in Graciano × Tempranillo wine grape progeny (Vitis vinifera L.)

The main objective of this research was the evaluation of the variability present in a segregating wine grape population derived from a cross between Graciano × Tempranillo, two Spanish varieties, in order to select improved genotypes with potential for producing high-quality wines in a climate change scenario. For that purpose, the phenotypic segregation of 16 agronomic traits related to production and phenology and 11 enological traits related to technical and phenolic maturity was studied in the progeny for three consecutive years. All traits presented transgressive segregation and continuous variation. Year effect was significant for all traits except total, extractable and skin anthocyanins content. However, a high level of genotype consistency for enological traits was revealed by repeatabilities and correlations between years. Significant correlations among traits were observed but most associations were weak. Furthermore, the CAPS (Cleaved Amplified Polymorphic Sequence) marker for the VvmybA genotype was tested to determine whether it would be useful in indirect selection for berry anthocyanins content. The results showed that the number of homozygous and heterozygous genotypes for the functional colour allele adjusted to a 1:1 segregation ratio, and that homozygous genotypes had significantly higher anthocyanins content. Principal component analysis found eight variables that contributed up to 80 % of the phenotypic variability present in the population. Seven groups of hybrids were distinguished based on ripening time, cluster weight, berry weight and anthocyanins content by cluster analysis; and fourteen genotypes were pre-selected for further research.