No abstract

The efficiency of diets with the inclusion of Spirulina for Siberian sturgeon weaning has been tested. Three isoproteic and isoenergetic diets were formulated with an increasing level of Indian strain Spirulina (SP 40%, SP 50% and SP 60%); the diets were tested against a control diet without microalgae. The results show that Spirulina inclusion improves growth and that an inclusion level of 50% gave the greatest growth rate, a better favourable feed conversion rate and the highest protein efficiency. The fatty acid composition of fillets showed differences between the experimental and control diets: an increase in the Spirulina level induces increases in palmitic and linoleic acids and a decrease in the myristic acid. The control diet was characterized by high levels of eicosapentaenoic and docosahexaenoic acids. At the end of the experiment, statistical differences appeared in the fatty acid profile of the sturgeon fillet, mainly concerning high content of monounsaturated fatty acid and polyunsaturated fatty acid in the sturgeon fillets. If the problems related to the high production costs are solved, Spirulina could prove a good partial substitute fish meal.

Purslane is an excellent source of omega-3 fatty acids, amino acids and vitamins. The aim of this research was to study the effect of different nitrogen levels and NO 3 − -N/NH 4 + -N ratios in the nutrient solution on the yield and on the oxalic acid content and fatty acid profile in purslane grown in a soilless culture system. Two experiments were carried out to test different levels of nitrogen: (1) 8-12-16 mmol L −1 and (2) 0-12-24-36 mmol L −1 . A third experiment was carried out maintaining the N level fixed (12 mmol L −1 ) but varying the NO 3 − -N/NH 4 + -N ratio: 60:40, 40:60, 0:100. The results indicated that plants grew with increasing nitrogen level up to 36 mmol L −1 . Nitrogen supplied in both NO 3 − and NH 4 + forms produced bigger plants than N supplied in NH 4 + form only. Nitrogen did not significantly influence the polyunsaturated fatty acid content in the canopy. Significant trends were found for α-linolenic acid (LNA; 18:3 n-3) and linoleic acid (LA; 18:2 n-6), indicating a favorable accumulation of omega-3 fatty acids with increasing N; palmitic acid decreased by increasing N and by switching the NO 3 − /NH 4 + ratio towards the NH 4 + level in the nutrient solution, but using 0:100 NO 3 − /NH 4 + , decreased plant quality. Increasing N lowered oxalic acid production and palmitic acid content, enhancing purslane nutritional quality. Keeping a high N level in the nutrient solution with a 40:60 NO 3 − /NH 4 + ratio would give the best results in terms of yield, oxalic acid concentration and fatty acid profile.

Abstract. The aim of this research was lo evaluate the effect of density and feeding level (initially 8 or 16kg/m3 and 1·3% or 2% of present biomass respectively) on productive traits, meat composition and water quality output in farmed rainbow trout, Oncorhynchus mykiss (Walbaum). Individual fish growth shows significant differences in relation to density and feeding level; feed conversion rate is positively Influenced by the lower feeding level and low rearing density. At low density, specific growth rate, protein efficiency ratio and coefficient of variation of individual final weights are more favourable than at high density. Dry matter and lipid composition of meat are positively affected by feeding level; whereas no differences are recorded on the amino acid and fatty acid profiles. Water quality shows differences due to density (NO3 and NH4+) and feeding level (NO2, NH4+ and P).

The aim of this study was to evaluate the performances and the flesh quality of Pagellus bogaraveo fed with diets containing rice protein concentrate [RPC, 70% crude protein (CP) and 10% ether extract]. Three isoproteic and isoenergetic (CP 47%, 22 MJ/kg DM) diets were formulated with an increasing level of RPC: 0%, 20% and 35%. The fish (mean weight 75 g) from the Messina Straits were randomly distributed in 12 tanks (3 diets x 4 replications, 10 fish/tank). The daily ratio (1.5% of the fish biomass) was updated every 15 days. Biomass gain showed an opposite trend to the RPC diet inclusion. No differences appeared in the somatic indexes. Differences appeared between fatty acid profiles of the dorsal muscle. Fatty acid of series n-6 increased and fatty acid of series n-3 decreased in fillets of fish fed with increasing levels of RPC. The inclusion of RPC in the diets, as a partial replacement of fish meal (20%), is possible without affecting the growth performance and fillet quality.

The Giant red shrimp (GRS, Aristaeomorpha foliacea) is a seafood product that is highly appreciated on the Italian market. This work aims at investigating whether a close relationship can be established amongst the area of origin, sex and the GRS quality.

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The aim of this research was to evaluate the e⁄ciency of diets with Spirulina and plant oils (POs) inclusion for white sturgeon weaning and their effects on the fatty acid (FA) composition of ¢sh £esh. Three isoproteic (45%) and isoenergetic (21MJ kg À1 DM) diets were formulated: one ¢sh meal-based diet integrated with ¢sh oil (FMO) and two 40% Spirulina meal-based diets integrated with corn (SPC) or soybean (SPS) oils respectively. One hundred and thirty-¢ve white sturgeon ¢ngerlings (mean weight 17.5 g) were stocked randomly in nine ¢breglass tanks. At the end of the trial, which lasted 71 days, the growth performance traits and somatic indexes were determined. The chemical composition, gross energy and FA pro¢le were determined on the ¢sh ¢llets. No signi¢cant e¡ects were observed for the growth performances or ¢llet chemical composition. The FA pro¢le of the ¢llets re£ected those of the diets. In particular, the ¢llets of the ¢sh fed with the SPC and SPS diets were lower in n-3 FA, due to the substitution of ¢sh oil (FO) with POs. It is possible to replace FO and meal in sturgeon; therefore, Spirulina meal integrated with POs could be a good alternative to sturgeon diet.