Paola Lupi

The effects of dietary fat and NFE levels on growing European sea bass (Dicentrarchus labrax L.). Growth rate, body and fillet composition, carcass traits and nutrient retention efficiency

European sea bass (91.5 ± 5.7 g) were randomly assigned to 12 tanks (25 fish/tank) and fed six experimental diets for 224 days according to a 3 X 2 factorial design [three crude fat levels: 11, 15 and 19% on dry matter basis, dm; 2 N-free extract (NFE) levels: 21.5 and 28.5% dm], with two replicates for each treatment. Daily feeding rate was 0.95% live weight. Final weight (339.9 g) and daily energy (11.78 kJ/fish) and protein gain (200 g/fish) were significantly higher for fish fed diets containing 19% fat. The whole body of the fish fed diets with the highest crude fat and NFE levels had significantly lower contents of moisture and protein and a higher level of crude fat. Body ash and P contents (4.41 and 0.7% wet weight) did not differ among treatments. Gross energy, protein and phosphorus retentions (29.2, 19.0 and 32.6%, respectively) and dressing percentage (89.4%) were not affected by treatments. HSI significantly decreased as dietary fat levels increased, only in fish fed diets with the highest amount of NFE. Liver fat content was significantly greater in the fish fed the highest level of NFE (35.2%) in comparison with those fed the lower level of NFE (26.0%) (P < 0.05). Percentage head and viscera (without liver) significantly decreased while percentage mesenteric and perinephric fat significantly increased with dietary fat content. Fillet percentage was significantly lower (44.1%) in fish fed diets containing 21.5% NFE, compared with those fed diets with 28.5% NFE (44.9%). Moisture decreased and lipid content increased in fillet of fish fed diets with 28.5% dietary NFE level, as dietary fat level increase. The saturated, monunsaturated and n - 6 polyunsaturated fatty acids of fish muscle significantly decreased while n - 3 PUFA levels significantly increased with increasing dietary fat content.

Preliminary results on quality and quality changes in reared meagre (Argyrosomus regius): body and fillet traits and freshness changes in refrigerated commercial-size fish

Meagre (Argyrosomus regius) intensively reared in tank by a Tuscany farm and fed commercial diets, were examined to study a) marketable and flesh nutritional traits in commercial-size fish and b) loss of freshness under refrigerated storage condition. Eighty fish, sampled in May, July and November (at 24, 26, 30 months of age) were submitted to linear measurements and weight of the most important body components. Whole fillets were analysed for moisture, lipid and fatty acid composition. Data were analysed by ANOVA (sampling date). A sub sample of fifty-four meagre (902–1840 g b.w.) was stored at 1 °C with ice cover and evaluated every 24 h after death until spoilage for the EU freshness classes, dielectric properties, rigor index, muscular and eye liquor pH, K1% freshness index. Data were analysed by regression on time after death. A small sample of meagre (n = 6) and sea bass (Dicentrarchus labrax) (n = 6), reared in analogous rearing condition in the same farm were compared by ANCOVA on body weight (average b.w. 668 g). Meagre were characterised by 1.04 condition factor, 44% fillets, 6% viscera, negligible mesenteric fat (≅1%) and 94.5% dressing yield. The head incidence increased (P < 0.01) with b.w. increase. Moisture increased while lipid decreased (P < 0.01) in fillet from July to November (74.47 vs 75.96%; 2.93 vs 2.06%). An index of thrombogenicity calculated from the quantitative fatty acid composition was very low (0.10). In comparison with sea bass of the same body weight, meagre had greater length (41.2 vs 37.6 cm), head incidence (29.9 vs 20.7%) and dressing (94.8 vs 89.2%) and lower viscera (5.2 vs 10.9%), mesenteric fat (0.9 vs 7.9%) and intramuscular fat (2.24 vs 12.78%) incidences. Meagre had a 9-day shelf-life (E class from 1st to 3rdd and A class from 4th to 7thd). Rigor index and impedance remained higher than 90% and 66, respectively until the 3rdd after death. The quality traits found for this species indicated meagre as a promising candidate for Mediterranean aquaculture.

Quality outline of European sea bass (Dicentrarchus labrax) reared in Italy: shelf life, edible yield, nutritional and dietetic traits

Abstract The final product quality of European sea bass was outlined through some results on (1) quality traits in a large range of body size (80–1580 g weight) and (2) changes in sensorial and objective quality parameters during shelf life, as influenced by the rearing system, storage and stress. More than 500 European sea bass of commercial size were used in several trials. All fish were subjected to linear and weight measurements. In most trials, sea bass were stored at 4 or 1 °C with ice cover and evaluated every 24 h after death until spoilage for the EU freshness classes and for a large number of physical and chemical quality traits (rigor index, dielectric properties, muscle and eye liquor pH, water-holding capacity (WHC), water, protein, ash, total, neutral and polar lipids, cholesterol, fatty acids, malonaldehyde, adenine nucleotides and biogenic amines). Fillets showed on the average isometric growth, but the dorsal muscle grew faster and the ventral one slower than the body weight. A moderate corpulence increase in fish shape during growth emerged. The size range from 500 to 940 g—when incidences of fillets and dorsal muscle were higher than 48% and 31% and that of viscera was lower than 10%—can be suggested for having sea bass with the better edible portion yield. Protein and ash contents of muscle remained constant with body weight increase, while moisture and cholesterol content decreased; total lipid moderately increased along with the triglyceride incidence. On the whole, the muscular fatty acid pattern determined good indexes of atherogenicity (IA) and mostly of thrombogenicity (IT). Sea bass stored at 4 or 1 °C with ice cover had a 6- and 10-day shelf life, respectively. In the first 2 and 3 days, respectively, sea bass were Extra (always with 100% rigor index) and had Fish Tester values decreasing to 64 or 73, respectively, and negligible levels of malonaldehyde (MDA) and biogenic amines. In the following 2 and 3 days, respectively, sea bass became A fish (good quality), with decrease of rigor index (IR) and Fish Tester (FT) and slight increase in malonaldehyde and putrescine contents. In the following 2 and 4 days, respectively, sea bass became B fish (bad quality), with further decrease of rigor index and Fish Tester and moderate increase of malonaldehyde and putrescine. Thereafter, fish were unfit for human consumption. No difference in quality parameter of fish reared in aerated (4.3 ppm O2) or hyperoxic (9.3 ppm) conditions was found. Stress shortened the pre- and post-rigor phase and shelf life.

Milk fatty acid composition, rumen microbial population, and animal performances in response to diets rich in linoleic acid supplemented with chestnut or quebracho tannins in dairy ewes

The aim of the study was to evaluate milk fatty acid (FA) profile, animal performance, and rumen microbial population in response to diets containing soybean oil supplemented or not with chestnut and quebracho tannins in dairy ewes. Eighteen Comisana ewes at 122±6 d in milking were allotted into 3 experimental groups. Diets were characterized by chopped grass hay administered ad libitum and by 800 g/head and day of 3 experimental concentrates containing 84.5 g of soybean oil/kg of dry matter (DM) and 52.8 g/kg of DM of bentonite (control diet), chestnut tannin extract (CHT diet), or quebracho tannin extract (QUE diet). The trial lasted 4 wk. Milk yield was recorded daily, and milk composition and blood parameters were analyzed weekly. At the end of the experiment, samples of rumen fluid were collected to analyze pH, volatile fatty acid profile, and the relative proportions of Butyrivibrio fibrisolvens and Butyrivibrio proteoclasticus in the rumen microbial population. Hepatic functionality, milk yield, and gross composition were not affected by tannin extracts, whereas milk FA composition was characterized by significant changes in the concentration of linoleic acid (CHT +2.77% and QUE +9.23%), vaccenic acid (CHT +7.07% and QUE +13.88%), rumenic acid (CHT -1.88% and QUE +24.24%), stearic acid (CHT + 8.71% and QUE -11.45%), and saturated fatty acids (CHT -0.47% and QUE -3.38%). These differences were probably due to the ability of condensed versus hydrolyzable tannins to interfere with rumen microbial metabolism, as indirectly confirmed by changes in the relative proportions of B. fibrisolvens and B. proteoclasticus populations and by changes in the molar proportions of volatile fatty acids. The effect of the CHT diet on the milk FA profile and microbial species considered in this trial was intermediate between that of QUE and the control diet, suggesting a differential effect of condensed and hydrolyzable tannins on rumen microbes. Compared with control animals, the presence of B. fibrisolvens increased about 3 times in ewes fed CHT and about 5 times in animals fed QUE. In contrast, the abundance of B. proteoclasticus decreased about 5- and 15-fold in rumen liquor of ewes fed CHT and QUE diets, respectively. The use of soybean oil and a practical dose of QUE or CHT extract in the diet of dairy ewes can be an efficient strategy to improve the nutritional quality of milk.

Body traits and chemical composition of muscle in the common carp (Cyprinus carpio L.) as influenced by age and rearing environment

To investigate body traits and muscle chemical composition in common carp as influenced by age and rearing environment, 2000 fry were stocked in two earthen ponds (300 m2): warm (W), with warm water (refluent from a thermal power station) at about 10 °C above natural temperature, and natural (N), with water from Lake Trasimeno. Because of the different growth rate, W subjects were sampled 3 times (at 12, 15 and 18 months of age) while N-subjects were sampled only once (at 15 months of age). The W 12-month-old fish weighed on average 102 g while N-fish did not reach this weight even at 15 months. At this age, the W subjects showed, in comparison with N-subjects, higher body weight (143 vs. 85 g), component weights, linear measurements (20.94 vs. 17.8 cm), fins (1.80 vs. 1.63g) and filleting remnants (12.80 vs. 11.25%) and lower incidence of skin and head index; no differences resulted in proximate analysis, but muscles of W-fish were richer in saturated fatty acid and in n − 3 PUFA content and showed a higher n-3n-6 PUFA ratio. By comparison with the 15-month-old subjects collected in October 1992, the 12-month-old W-subjects, collected in July 1992, showed lower fin (0.59 vs. 1.8%), viscera (7.6 vs. 10.2 %) and head (20.36 vs. 22.92%) percentages but higher gill (4.27 vs. 3.24%), filleting remnant (14.99 vs. 12.80%), skin (3.92 vs. 3.37%) and dressing (92.4 vs. 89.79%) percentages. The 18-month-old W-subjects, collected in January 1993, did not differ significantly from the 15-month-old subjects either in body weight (154 vs. 143 g) or in the other traits studied, excluding the incidence of viscera (12.01 vs. 10.21%) and gills (2.69 vs. 3.34%), respectively, in the older subjects. Intramuscular lipid content decreased from July according to a seasonal trend. Allometric coefficient showed tachyauxesis for viscera, pectoral and pelvic fins, skin and total muscle and bradyauxesis for filleting remnants and head.

Effect of Rearing System on Body Traits and Fillet Quality of Meagre (Argyrosomus Regius, Asso 1801) Chilled for a Short Time

The purpose of this study was to evaluate qualitative traits of meagre (Argyrosomus regius) from two different rearing systems (land-based tank filled with geothermal water vs offshore sea cage) and after short-term storage at chilling temperature (1, 2, or 3 days). Fish originated from the same batch were fed the same diet. Morpho-biometric traits, L*, a*, and b* colour parameters, texture, free water, proximate composition, total lipids, fatty acids, iron, and selenium contents were analyzed in the fillets. Most parameters were affected by rearing system. Compared to tank-reared fish, caged fish were shorter, poorer in visceral fat, and had higher incidence in cavity content and liver, lower incidence in gonads and head. Caged fish also had softer fillets in the epaxial site, which showed a higher tendency towards greenish colour. Caged fish also showed higher lipid content but lower Fe and Se content. Tank-reared fish fillets were more abundant in PUFAn-3, mainly due to DHA (18.54 vs 12.95%; P<0.001) and consequently showed the best healthiness indexes. Minimal changes, mostly involving colour and texture, were detected during the first three days of refrigerated storage. During storage, no significant modification of the parameters investigated could be ascribed to the rearing system.

Morphological characteristics and chemical composition of muscle in the mirror carp (Cyprinus carpio var. specularis) as influenced by body weight

Abstract The evolution of morphological traits and muscle chemical composition during growth was analysed by allometric or normal regression (on body weight or total length or total lipid) utilizing a preliminary series of data obtained from mirror carps ranging from 39 to 2776 g body weight. The fish came from earthen ponds fed with warm water (refluent from a thermal power station) at about 10 °C above natural temperature. As regards allometric coefficients of components on body weight, gills (0.70) and filleting remnants (0.85) were the earliest growing while viscera (1.18) and skin (1.11) were the latest. Isoauxesis resulted for fins, excluding pelvic fins that were later growing (1.08). As regards relative growth of lengths and thicknesses on total body length, head length (0.82) was the earliest and abdomen (1.15) and trunk lengths (1.12) were the latest growing; all body thicknesses showed tachyauxesis, particularly on the hind-portions. As regards the chemical composition of muscle, cholesterol (mg/100 g) and the C20:4 and C22:6 percentages showed a linear decreasing trend with increasing body weight, while the opposite resulted for C18:1, SFA and MUFA content. Lipid, C16, C16:1, C20:5 and n − 3 PUFA content presented a decreasing trend followed by an increase, while C18:2 and n − 6 PUFA content showed the opposite behaviour. Intramuscular lipid content influenced the chemical composition of muscle: as lipid content increased, C18:1 also increased, while C18:2 and n − 3 PUFA decreased; C14, C16:1 and MUFA showed an increasing trend followed by a decreasing phase, while C16, C18, C20:4, C22:6, SFA and n − 6 PUFA showed the opposite.

Morphological, nutritional and safety traits of bluefin tuna (Thunnus thynnus) reared in floating cages

To evaluate the influence of fattening on morphological, nutritional and safety characteristics, two lots of bluefin tuna were sampled before (November: 2 ♀, 4 ♂) and after 5 months of fattening (April: 5 ♀, 5 ♂). The specimens, after death, were refrigerated and analysed at different times over the period of a week for morphological and flesh physico-chemical parameters in six muscle sites. Tuna sampled in April had greater body weight (44.04 vs 36.41kg), trunk length (52.21 vs 48.22cm) and minimum and maximum circumferences (13.74 vs 12.77 and 94.90 vs 89.10cm). No differences in other linear measures or body components were found. Fattening did not influence flesh colour or total lipid content, producing small differences in its chemical composition: greater C18:0, C18:1n9 and PUFAn6 percentages; higher putrescine and histamine (0.489 vs 0.335 and 0.666 vs 0.370mg/kg) but lower spermine and spermidine (10.598 vs 17.387 and 2.420 vs 3.928mg/kg) levels. Large differences in physico-chemical parameters were found between muscle sites and a significant interaction between sampling date and muscle site indicated non homogeneous changes in chemical composition of dorsal, ventral and red muscle after fattening. Sex only influenced fat content in viscera (♀ 12.84 vs ♂ 9.84%).

First haematic results for the sea bass (Dicentrarchus labrax) metabolic profile assessment

Abstract The assessment of blood reference ranges of farmed fish can be extremely useful in improving production and product quality. A first attempt to establish the normality ranges for the most important haematochemical parameters of farmed sea bass was carried out by analysing the trend of Haematocrit, Glucose, Total Protein, Albumin, Globulin, Total Cholesterol and some electrolytes in 353 sea bass farmed with two different farming systems within 1 year. A strong seasonal effect was found with regard to each parameter; the role of some environmental conditions was evaluated; and some reference ranges were proposed for the culturing methods considered.

Physico-Chemical Traits of Raw and Cooked Fillets of Rainbow Trout (Oncorhynchus Mykiss) from Different Strains and Farms

Fillets and cooking yields, water holding capacity, textural properties, colour, proximate composition, collagen and fatty acids of five strains (1T1, 1T2, 1T3, USA, UK) of rainbow trout, Oncorhynchus mykiss, reared in three farms (F1, F2, F3), were measured before and after cooking. Physico-chemical parameter of the strains greatly differed both in raw and cooked state. 1T2 and USA recorded the highest yields. 1T2 distinguished from the other strains, showing lowest values of hardness, chewiness, gumminess and springiness. It also had brighter and less pigmented flesh with low fat, mainly in the raw state. USA strain showed the most valuable traits in terns of texture and colour, and had higher fat and collagen content in flesh. The physico-chemical profile of each strain was differently modified by cooking. USA strain maintained a positive texture and colour profile after cooking and its quality was the best.