Antonio Lorenzo

Influence of the EPADHA ratio in rotifers on gilthead seabream (Sparus aurata) larval development

Abstract A feeding experiment was carried out to investigate the influence of the eicosapentaenoic acid (EPA, 20:5n − 3) to docosahexaenoic acid (DHA, 22:6n − 3) ratio ( EPA DHA ) on 17-day-old Sparus aurata larval development. Larvae were fed rotifers (Brachionus plicatilis) enriched with four different lipid emulsions containing the same amount of total n − 3 highly unsaturated fatty acids (n − 3 HUFA) but different EPA DHA ratios. The different EPA DHA ratios of the emulsions gave rise to different ratios in the enriched rotifers. Furthermore, increments of the EPA DHA ratio in rotifers produced a decrease in larval growth performance, so that larvae fed rotifers containing the highest EPA DHA ratio showed the poorest growth rate. The analysis of fatty acids from larvae showed that there was a significant linear relationship between EPA DHA ratio in their total polar lipids (TPL) and larval growth. At the same time, when the EPA DHA ratio increased in rotifers, there was an increase in total n − 3 HUFA in larvae total neutral lipid (TNL), which was mainly due to the accumulation of EPA. Results obtained in the present study suggest that for the same level of total n − 3 HUFA, larval growth performance can be improved by a decrease in EPA DHA ratio in rotifers, indicating the importance of DHA during the first days of S. aurata larval development.

Influence of broodstock gilthead seabream (Sparus aurata L.) dietary fatty acids on egg quality and egg fatty acid composition throughout the spawning season

The influence of broodstock dietary lipids on egg quality and egg fatty acid composition throughout the spawning season of gilthead seabream was investigated. For this purpose, the fish were fed for 7 months either a control diet (diet C) or a diet deficient in n−3 highly unsaturated fatty acids (n−3 HUFA) but rich in both oleic (18:1n−9) and linolenic (18:3n−3) acids (diet D). Eggs spawned by both groups of fish were sampled at the beginning, middle and end of the spawning season and the fatty acid composition of their neutral (NL) and polar lipids (PL) determined. In the early season, percentages of fertilized and hatched eggs, relative proportions of NL and PL as well as their fatty acid compositions, were not affected by the lipid composition of the broodstock diet. However, the eggs spawned during the middle and late seasons showed marked differences among the two groups of fish, clearly reflecting the influence of dietary fatty acids. This influence was more evident in the neutral lipid fraction than in the polar lipids. No correlation was found between the number of buoyant eggs and eicosapentaenoic (20:5n−3, EPA), docosahexaenoic (22:6n−3, DHA) fatty acids or total n−3 HUFA contents in egg phospholipids. However, a negative correlation was detected when percentages of fertilized eggs were compared with the levels of 18:1n−9, 18:3n−3 and with the ratio 18:1n−9/n−3 HUFA present in the phospholipids. Our results indicate the importance of maintaining not only the level of n−3 HUFA in egg membrane phospholipids, but also the balance between n−3 HUFA and other fatty acids such as 18:1n−9 and 18:3n−3, in order to obtain a high spawning quality.

Lipid and fatty acid composition of ovaries from wild fish and ovaries and eggs from captive fish of white sea bream (Diplodus sargus)

Abstract The fatty acid composition of ovaries from wild white sea bream and ovaries and eggs of captive white sea bream were investigated to estimate the fatty acid requirements of this species. The total lipid (TL) content in wild fish ovaries was similar to that found in ovaries and eggs from captive fish. The general pattern of the fatty acid distribution in lipid of ovaries from wild fish and ovaries and eggs from captive fish was similar. In total lipid, no significative differences in total monoenes, n −6, n −3 and n −3 highly unsaturated fatty acids (HUFA) were found. However, the relative percentage of specific fatty acids differed between wild and captive fish. Thus, arachidonic acid (20:4 n −6, AA) percentage was higher in wild ovaries than in ovaries and eggs from captive fish, whereas eicosapentaenoic acid (20:5 n −3, EPA) showed the opposite trend. In consequence, wild fish presented a lower EPA/AA ratio in their ovaries when compared with ovaries and eggs of captive fish. These differences were extended to all lipid classes studied (triacylglycerol (TG), phosphatidylcholine (PC) and phosphatidylethanolamine (PE)). The present study suggests that essential fatty acids, specially EPA and AA of the diet supplied to the captive white sea bream broodstocks, do not seem to be in an appropriate proportion for this species.

Influence of dietary n − 3 highly unsaturated fatty acids levels on juvenile gilthead seabream (Sparus aurata) growth and tissue fatty acid composition

Abstract Gilthead seabream juveniles (11.5 ± 0.2 g mean weight) were fed diets containing different levels of n − 3 highly unsaturated fatty acids (n − 3 HUFA) for 8 weeks. The fatty acid composition of neutral and polar lipids from gills, liver, muscle and brain, as well as fish performance were studied. In tissues sampled at the commencement of the feeding study 16:0, 18:1 n − 9 and n − 3 HUFA were the most abundant of the saturated, monounsaturated and polyunsaturated fatty acids, respectively. In both polar and non-polar lipids, the initial ratio of eicosapentaenoic acid (EPA) to docosahexaenoic acid (DHA) in the neutral fraction of all tissues examined was approximately 1:2, whereas in the polar fraction of muscle, liver and gills the ratio comprised between 1:1.5 and 1:1. When the fish were fed a diet with a very low content of n − 3 HUFA (0.19%), a marked decrease in these fatty acids occurred in the neutral fraction, while the reduction in the polar fraction was more moderate in all the tissues. In these fish the relative losses of EPA and DHA were similar in the neutral fraction of the lipids of the gills, muscle and liver, whereas in the polar fraction these values were only similar in muscle and liver. Growth and feed efficiency were higher in fish fed a diet containing 1% n − 3 HUFA. Further elevation of the dietary n − 3 HUFA level from 1% to 1.5% resulted in a worsening of those parameters. It is concluded that the requirement of n − 3 HUFA of gilthead seabream of 11–30 g weight is at least 1 % of the dry diet.

Influence of n-3 highly unsaturated fatty acid deficiency on the lipid composition of broodstock gilthead seabream (Sparus aurata L.) and on egg quality

A feeding experiment was conducted on gilthead seabream (Sparus aurata) broodstock to investigate the incidence of n-3 highly unsaturated fatty acids (n-3 HUFA) dietary deficiencies on the lipid composition of female liver, gonads and eggs, in relation to spawning quality. Broodstock were fed a control (C) diet or a n-3 HUFA deficient (D) but linolenic acid rich diet. After 20 weeks of feeding, the results showed that levels of total neutral (TNL) and total polar (TPL) lipids of female gonads and eggs were independent of diet. However the fatty acid composition of phosphatidylcholine (PC), phosphatidylethanolamine (PE) and phosphatidylinositol (PI) of female liver, gonads and eggs in the two groups of fish showed marked differences, reflecting the influence of fatty acid levels in the broodstock diets. This influence was even higher in TNL than in the phospholipid classes examined. In fish fed n-3 HUFA deficient diet, fatty acid composition of TNL of female gonads and eggs reflected the diet more than liver. A higher egg production in broodstock fed C diet (1.8% n-3 HUFA in diet) was extended to spawning quality such as percentages of fertilised and hatched eggs.

Effect of different levels of n−3 highly unsaturated fatty acids on growth and fatty acid composition of juvenile gilthead seabream (Sparus aurata)

The requirements of juvenile gilthead seabream for n−3 highly unsaturated fatty acids (n−3 HUFA) were studied by feeding fish with diets containing 4 different levels of n−3 HUFA ranging from 0.76 to 2.94% of the diet. Juvenile fish weighing 42.5 ± 0.21 g were randomly divided into 12 groups of 15 fish and pair fed the 4 experimental diets for 8 weeks. No mortality was observed during the feeding trial, but significant differences were found in growth rate and biochemical composition of the fish. Fish fed low dietary n−3 HUFA (0.76% of the diet) showed poor growth rates and low feed efficiency ratios, but these parameters improved by the elevation of the n−3 HUFA levels in the diet up to 1.9%. Fish fed the lowest n−3 HUFA diet showed the highest levels of crude lipid in the liver and gills. Muscle and gill phospholipids were generally less influenced by the type of diet than the liver. Results of this experiment suggest that with dietary lipid contents of 8–10%, the requirements for essential fatty acids of juvenile gilthead seabream is about 1.9% n−3 HUFA of the dry diet.

Growth and survival of cuttlefish (Sepia officinalis) of different ages fed crustaceans and fish. Effects of frozen and live prey

Abstract Three feeding experiments, using live mysid shrimp, grass shrimp or fish fry as prey for 1-, 30- and 60-day-old cuttlefish were conducted to determine the efficiency of each dietary source in relation to cuttlefish size and age. Additionally, a fourth experiment using fish fry and grass shrimp, but previously frozen, was also conducted. The results showed that when 1-day-old cuttlefish were fed mysids, grass shrimp or fish for 4 weeks, mysids were the best prey, but only during the first week. From this moment until the end of the experiment, the best growth rate was when cuttlefish were fed grass shrimp. Cuttlefish fed fish fry showed the poorest growth rate throughout the experiment. Similarly, cuttlefish aged 30 or 60 days fed grass shrimp or fish fry had the best growth rates when fed grass shrimp. When cuttlefish were fed live fish, survival increased with size of cuttlefish (73.3%, 91.7% and 100% for 1, 30 and 60 days cuttlefish, respectively). In the fourth experiment, using frozen diets, overall acceptance of each diet (feeding rates) was the same for fish and shrimp. However, lower growth was obtained when cuttlefish were fed fish compared to grass shrimp. This lower growth was due to a lower food conversion (28% vs. 41%). Since cephalopod paralarvae and juvenile most likely need prey rich in polyunsaturated fatty acids (PUFA), phospholipids and cholesterol, and a moderate content in neutral lipids, we have analyzed the biochemical compositions of the different prey to evaluate the influence of this factor on growth and survival.

n-3 HUFA requirement of larval gilthead seabream Sparus aurata when using high levels of eicosapentaenoic acid

Abstract A feeding experiment on n-3 highly unsaturated fatty acids (n-3 HUFA) requirement in gilthead seabream, Sparus aurata , larvae was carried out using rotifers containing different percentages of n-3 HUFA, ranging from 0.16% to 7.42% on a dry weight basis (DWB). The enriched rotifers showed a direct relationship between their n-3 HUFA contents and the n-3 HUFA concentration in the emulsified lipids. The n-3 HUFA level in fish increased gradually to the elevation of the n-3 HUFA percentage in rotifers. The larvae fed on rotifers containing a low percentage of n-3 HUFA showed poor growth and high mortality. Larval growth, survival and activity were effectively improved by the elevation of the n-3 HUFA levels in rotifers to 5.53% DWB. When the level of these fatty acids in rotifers reached the amount of 7.42%, larval growth, survival and activity were negatively affected. In this treatment the larval eicosapentaenoic acid (EPA) assimilation rate was higher than that found for the docosahexaenoic acid (DHA). These results suggest that, in our experimental conditions, the n-3 HUFA requirement for larval gilthead seabream is about 5.5% in DWB of rotifers.

Effect of dietary supplementation with shrimp on skin pigmentation and lipid composition of red porgy (Pagrus pagrus) alevins

A feeding experiment was conducted on red porgy alevins to investigate the influence of dietary supplementation with shrimp on pigmentation and lipid composition of carcass (muscle and skin) and eyes. To this purpose, red porgy alevins with an initial mean weight of 2.8±1.3 g were divided into six groups. Three groups were fed gilthead seabream commercial pellet (P, 100% pellet), whereas the other three were fed with the commercial pellet and shrimp Pleisonika sp. (PS, 88% pellet:12% shrimp) to provide the diet with a source of carotenoids. After 4 months of feeding, the results showed that PS-fish groups displayed a pink-coloured skin similar to that of the wild fish, whereas P-fish groups showed a dark-grey-coloured skin. Furthermore, a higher total content of carotenoids was found in carcass and eyes from PS-fish groups with respect to P-fish groups. No significant differences in growth, survival or other gross external signs were found between treatments. Total lipid (TL), triacylglycerol (TG), phosphatidylcholine (PC) and phosphatidylethanolamine (PE) of red porgy carcass exhibited a specific fatty acid profile. However, the general patterns of the fatty acid distribution in lipids of carcass and eyes from both groups of fish (P and PS) were similar, and only slight differences were found mainly in carcass for some of the fatty acids. We conclude that the natural carotenoids supplied by the shrimp were effectively assimilated by the red porgy and allowed the cultured fish to acquire a skin coloration similar to that of wild fish.

Improvement of the nutritional value of rotifers by varying the type and concentration of oil and the enrichment period

Abstract Several enrichment conditions (type and concentration of oil in culture medium and time of enrichment) were tested in order to study their influence on rotifer ( Brachionus plicatilis ) lipid and fatty acid composition as well as on its population profile. Rotifers pre-fed on bakers yeast ( Saccharomyces cerevisiae ) were enriched with lipid emulsions containing triacylglycerols (TAG) or methyl ester (ME) mixtures at three different concentrations. Rotifers were sampled after 0 (yeast-fed rotifer), 3, 6, 12 and 24h enrichment. At every concentration and time assayed, the highest lipid levels were obtained when using TAG. In spite of the differences existing in saturated and monounsaturated fatty acid composition between the enrichment emulsions, rotifers tended to maintain the level of these fatty acids independently of the enrichment period and oil concentration. Increasing the enrichment period rather than the amount of oil present in the medium was found to be more efficient in increasing the n − 3 highly unsaturated fatty acids ( n − 3 HUFA) level in rotifers. Rotifers reflected a better incorporation of eicosapentaenoic acid (EPA, 20:5 n − 3) than of docosahexaenoic acid (DHA, 22:6 n − 3), regardless of the ratio between both fatty acids in the emulsions. The use of ME as an enrichment source produced greater mortality in egg-carrying females than when using TAG.