M. Mecatti

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.

Effect of Total Replacement of Dietary Fish Meal by Plant Protein Sources on Early post mortem Changes in the Biochemical and Physical Parameters of Rainbow Trout

The replacement of fish meal with plant protein sources is a major issue of interest in the aquaculture of Teleostei (Tacon, 1994). Although several studies have been undertaken over the last two decades, many questions remain about the feasibility of the total substitution of traditional protein sources. Moreover, the effects of the protein source on the quality characteristics of the product obtained have been little investigated (Médale, 2003). The aim of this study was to evaluate the effect of a diet based only on plant protein sources on the behaviour of some biochemical and physical parameters during the first 24 h after death.

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.

Contribution to the definition of the metabolic profile of farmed rainbow trout (Oncorhynchus mykiss)

Abstract The haematic outline of 339 rainbow trout (Oncorhynchus mykiss) from two different farms in the Lucca province was studied for a preliminary assessment of the metabolic profile of this species and for the investigation of the influence of some endogenous and exogenous factors on the variability of the studied parameters. The sampling time, as well as the weight, appears to have caused significant variations on most of the parameters analysed. The present study gives the annual means and the seasonal trends for each farm where the study was carried out.

Some haematochemical parameters of intensively farmed rainbow trout (Oncorhynchus mykiss)

Riassunto Alcuni parametri ematici di trote iridee (Oncorhynchus mikyss) allevate intensivamente. L’obiettivo del presente studio è quello di giungere ad una prima definizione dei valori di alcune variabili ematiche di una delle specie di maggiore interesse economico nel panorama dell’acquacoltura italiana. La determinazione del profilo metabolico (PM) di una specie non è semplice a causa dei molti fattori che influiscono sui parametri ematici, tuttavia la determinazione dei valori di riferimento è necessaria per individuare i limiti al di fuori dei quali si possono verificare contrazioni della produzione e della riproduzione.

Influence exerted by certain factors during rearing and before slaughter on post-mortem characteristics of sea bass.

The various practices adopted during rearing may cause disturbance to fish, leading to notable physiological reactions and considerably affecting their infra vitam performance, as well as the quality of the food product obtained. The aim of this work was to assess for European sea bass (Dicentrarchus labrax) the influence of the level of oxygen (DO) in the rearing water, of the density of fish in the hour prior to death, and the effect of capture repeated in the same tank 24 hours after the first capture on the values of some parameters measured at a muscular level during the first 24 hours after slaughter.

Welfare and quality of farmed trout fed high plant protein diets. 2 innovative killing method effect on stress and quality indicators

Abstract The fish stunning/slaughtering procedure has an important role both for the ethical aspect related to animal welfare and for the potential quality of the final products. Stressful harvest procedure and killing methods can negatively influence the post mortem biochemical processes with a consequent faster fish freshness loss. In particular, killing procedures causing a long agony are not humane and can shorten fish shelf life; others, more humane, can have risks for the consumers health (anaesthetics or chemical substances) or are not feasible in small/medium size fish industry (spiking and knocking). The aim of this study was to compare the traditional killing method (asphyxia - A) used for rainbow trout (Onchorynchus mykiss) with an innovative stunning/slaughtering method (two-stage electric stun: 2s at a 500Hz electric field of 2.5V/cm and then 58s at a 50Hz electric field of 0.75V/cm - E), through the study of their effects on stress and quality indicators in fish fed with traditional fish meal (FM) or innovative 80% plant protein diet (PV80). Fish (n=30) of each group (FMA, FME, PV80A, PV80E) were stored at 1°C with ice covering and analysed from 0h to 192h from death. The following analyses were done: blood parameters (only at death); rigor index (RI%) and sensorial evaluation with EU Scheme Rule 2406/96 EEC (performed by 5 judge); eye liquor and muscular pH (pHe, pHm); ATP and its degradation products in muscle; lactic acid in muscle and fillet length (FLC) and height contraction % (FHC) (at 0, 3, 6, 24h). Fillet quality appearance was evaluated by absence/presence and size of bloodstains along the midline on the left fillet. Data were analyzed by ANOVA (killing method, diet and their interaction). Asphyxiated fish (A) died within 15-30’ after prolonged struggling and agony, while innovative method stunned/killed fish (E) were immediately stunned and died in 1 minute. Asphyxiated group showed: higher values of blood glucose and muscle lactic acid; lower values of pHe and pHm at 3, 6 and 24h (P<0.01); earlier full rigor (RI 100% at 1h). RI, significantly different (P<0.001) between A and E fish until 6h after death, in E group reached 100% only at 8h. In agreement with this result, FLC of E fish showed lesser contraction both at 3 h (E 6.9 vs A 18.4%, P<0.001) and at 6h (E 13.9 vs A 18.4%, P<0.05). The same emerged for FHC at 3 h (E 0.9 vs 5.3%, P<0.001). The lower values of ATP/IMP ratio at 0, 3 (P<0.001) and 6h (P<0.01) in A fish than in E fish confirmed the stress condition of the first ones. Differences due to the diet were scarce: PV80 fish had higher pHe, pHm and inosine values at 72h (P<0.001). Fish sensorial evaluation indicated A class until 144h in all groups and B class at 192h after death, except in PV80A fish (75% in B class at 144h). As waited, some bloodstains were found in FME (26.7%) and PV80E (53.3%) fillets while A fish had negligible damages (1.7%). The bloodstains should downgraded the fillet acceptance. However, because the portion size trout are traded wholes/gutted by Italian fish industry, the problem seems less serious. The innovative killing procedure, really a fast and humane procedure, need to be improved for fillet appearance.