Variations in the proximate composition of muscle in cultured yellowtail Seriola quinqueradiata at different anatomical portions

In this study, we examined differences in the proximate composition of five major muscles of the yellowtail, as well as the relation between seasonal variations in the levels of crude lipids and texture of these muscles. The differences in content among these muscles and the variations in each muscle were greater for crude lipid and moisture content than for crude protein content. The crude lipid content of Musculus latero-dorsalis correlated with that of M. carinatus dorsalis, M. latero-ventralis, M. carinatus ventralis, and red muscle. In M. latero-dorsalis, the crude lipid content started to increase in October, remained high from November to January, started to decrease in March, and was low from April to June. The firmness of M. latero-dorsalis increased from October to November and started to decrease in March. Firmness decreased concurrently with decreases in crude lipid content and increased concurrently with increases in crude lipid content. The results of this study suggest that it is possible to predict the proximate compositions of other yellowtail muscles from the proximate composition of M. latero-dorsalis. Seasonal variation in crude lipid content of the M. latero-dorsalis was found, and variations in crude lipid tended to parallel those in firmness.     

Nutritional parameters of dorsal and ventral fillets in summer and winter from farmed yellowtail kingfish Seriola lalandi (Valenciennes, 1833)

The nutritional profile of dorsal and ventral portions of fillets from farmed yellowtail kingfish (YTK) (Seriola lalandi, Valenciennes, 1833) was assessed in winter and summer months to evaluate if there were differential distributions of proximate constituents, fatty acid composition and mineral content seasonally and through the dorso‐ventral axis. The proximate composition of YTK fillets varied between the two anatomical locations examined. In particular, a relatively large variation was observed in crude fat content, which decreased significantly from ventral to dorsal portions of the fillet and was inversely proportional to moisture and protein content. Higher crude fat content was also observed in the fish sampled in summer, compared to those sampled in winter. The omega 3/6 ratio remained constant between fillet portions but was significantly different between seasons (summer > winter). The index of nutritional quality for EPA and DHA was markedly different regarding to fillet portion and season (summer > winter, ventral > dorsal), and significant differences in the levels of potassium, phosphorus, magnesium and iron were also evident between the seasons examined. This study clearly shows differences in nutritional profiles of fillets from farmed YTK in South Australia relative to anatomical location and season. The increase in knowledge gained from this study may lead to improved farm management practices of YTK, which may extend to other commercially relevant species to enhance the production of premium farmed products.     

Characteristics of burnt meat in cultured yellowtail <Emphasis Type="Italic">Seriola quinqueradiata</Emphasis>

ABSTRACT:   In order to understand the characteristics of burnt meat in cultured yellowtail Seriola quinqueradiata , fish were kept at two different temperatures (13 and 30°C) and slaughtered by either spinal cord destruction (SCD) or suffocation in air (SA). Early postmortem changes during storage at 32°C were analyzed by rheological, biochemical, and histological methods. The burnt meat (with lightness parameter, L* ≥ 55) was observed at 1-h storage in the SA 30°C group, at 2 h in SCD 30°C, and at 4 h in SA 13°C; meat was normal for the SCD 13°C group until 6 h of storage. Breaking strength scores were higher for the normal meat (200 g/cm²) than burnt meat (70 g/cm²) at 4 h of storage. Expressible water content was higher for the burnt meat than for the normal meat. Adenosine triphosphate concentrations for the SCD groups were higher than for the SA counterparts. Moreover, pH decrease was much faster in the 30°C groups, showing pH 5.6 at 2 h of storage. A negative correlation between the pH and lactic acid contents in muscle ( P  < 0.001) was found. Histological analysis evidenced a larger pericellular area (40%) in the burnt samples than in the normal samples (16%). It was confirmed that a higher fish-keeping water temperature and a stressful slaughter method (faster glycolytic process) were determinative factors that influence the occurrence of burnt muscle in yellowtail, and that the effect of the former is larger than the latter.     

Effects of dietary phospholipid level and fraction on the feed intake of non‐fish meal diet in yellowtail,Seriola quinqueradiata Temminck & Schlegel, 1845

Three feeding studies were conducted to investigate whether dietary soybean lecithin (SBL) enhanced feed intake of non‐fish meal, SPC‐based diet, in yellowtail, and also to clarify which fraction of phospholipid (PL) was effective to enhance feed intake. In experiments 1 and 2, fish were fed SBL level at 0%–5%, and it was revealed that the daily feeding rate (DFR) of fish was significantly higher for SBL 2% than for SBL 0%, while a further increase of SBL in the diet did not additionally increase the DFR. Moreover, the DFR of fish fed a diet without feeding stimulants (FS) was the lowest among the dietary treatments, indicating that the SBL does not have an effect of enhancing feed intake in yellowtail. In experiment 3, fish were fed a diet with several products containing PL at 2%. Phosphatidylcholine and phosphatidylinositol concentrations in these products positively correlated to the DFR of fish. This result revealed that these two fractions in the SBL are effective for enhancing feed intake of yellowtail when FS is present in the diet.     

Supplementation effect(s) of organic acids and/or lipid to plant protein‐based diets on juvenile yellowtail,Seriola quinqueradiata Temminck et Schlegel 1845, growth and,nitrogen and phosphorus excretion

A feeding experiment was conducted to investigate the effect of organic acids and/or lipid supplementation on growth, utilization and environmental loading of nitrogen (N) and phosphorus (P) in juvenile yellowtail fed fishmeal (FM) and plant protein (PP) diets. Six diets as FM (FM‐based), FM+P (FM with inorganic P), FM+L (FM with lipid), PP+CA (PP with citric acid), PP+L+CA (PP with lipid and citric acid) and PP+L+FA (PP with formic acid) were formulated. Yellowtails were fed each of the diets in duplicate groups; once a day, 6 days a week to near satiation at water temperature 19.0–25.0 °C for 16 weeks. Fishmeal with inorganic P gave the best growth while PP+L+FA the lowest. However, growth increased in PP+CA and PP+L+CA. Addition of lipid significantly increased N and P retention resulting in significant reduction in N and P excretion. Citric acid and FA supplementation to PP diets also increased retention of P; hence, its excretion was lowered. Thus, CA, FA and lipid in juvenile yellowtail diets can help to partially replace FM with PP sources and reduce inorganic P use to minimize environmental loading from aquafeeds.     

Seasonal changes in proteolytic enzymes of yellowtail Seriola quinqueradiata (Temminck & Schlegel; Carangidae) fed extruded diets containing different protein and energy levels

Seasonal variations in pepsin, trypsin and chymotrypsin activities and protein digestibility were studied in yellowtails (Seriola quinqueradiata) reared for 1 year with extruded diets containing different levels of protein. Trypsin and chymotrypsin storage levels in the digestive tissues of starved fish were affected by seasonal changes in water temperature. Actual digestion activities of trypsin and chymotrypsin were low at lower water temperatures, but pepsin activity in the stomach tissue was not affected by low temperatures. On the other hand, trypsin and chymotrypsin activities in the intestinal contents were higher during lower water temperature months, while pepsin activity in the stomach contents was low at lower water temperatures. Apparent protein digestibility (APD) did not differ among the dietary treatments in the higher water temperature months, while in colder months it was higher in fish fed diet 1 than in fish fed diets 2 and 3. The APD values reflected pepsin activity in the stomach contents in all sampling months. Therefore, lower APD in colder months seems to be attributed to lower protease activity in the gastric digesta, implying that enhanced pepsin secretion from the stomach tissue might improve protein digestibility and growth performance in yellowtails during winter.     

Replacement of dietary fish oil with olive oil in young yellowtail <Emphasis Type="Italic">Seriola quingqueradiata</Emphasis>: effects on growth,muscular fatty acid composition and prevention of dark muscle discoloration during refrigerated storage

Dietary fish oil (FO) was replaced by olive oil (OO) in young yellowtail Seriola quinqueradiata to investigate its effects on growth, muscular fatty acid composition and prevention of color deterioration of dark muscle during storage. Yellowtail were fed one of four diets, where FO (80 g/kg diet) was replaced by OO (0, 25, 50 and 100%) for 40 days. No significant difference in growth was seen among the diet groups. In addition, these experimental diets did not affect the proximate compositions of the dorsal muscle, ventral muscle and the liver in these fish. Serum total protein, glucose and total cholesterol levels did not show significant differences; however, serum triglyceride levels were significantly higher in fish fed 50 and 100% OO diets. Fatty acid composition of ventral muscle reflected the composition of the respective diets. Dark muscle discoloration was reduced in fish fed OO diets after 12 to 18 h during storage at 4°C. Furthermore, the redness value of fresh dark muscle increased depending on the extent of FO replacement. These results indicate that the partial or total dietary replacement of FO with OO prevents discoloration of dark muscle without affecting the growth of young yellowtail after 40 days of feeding.     

不同年龄野生和养殖兴凯湖翘嘴鲌肌肉营养成分分析

为评定营养价值、建立种质标准以及研制人工配合饲料,对2龄、4龄和6龄兴凯湖翘嘴鲌(Culter alburnus)野生和养殖群体的肌肉营养成分和营养品质进行了分析比较,结果显示,2龄兴凯湖翘嘴鲌野生和养殖群体肌肉营养成分含量无显著差异(P>0.05);4龄、6龄野生群体的水分和粗蛋白含量显著高于养殖群体(P<0.05),粗脂肪含量显著低于养殖群体(P<0.05)。与常见养殖鱼类相比,野生兴凯湖翘嘴鲌Ca和P含量较高。野生和养殖群体的氨基酸组成一致,甘氨酸含量最高,谷氨酸和赖氨酸次之。4龄、6龄野生群体氨基酸总量(TAA)、必需氨基酸总量(EAA)和鲜味氨基酸含量显著高于养殖群体(P<0.05)。结果表明,兴凯湖翘嘴鲌野生与养殖群体蛋白质含量较高,均含有丰富的氨基酸,具有较高的营养价值和食用价值;野生群体肌肉营养价值和肉味鲜美程度明显优于养殖群体,且随年龄增长差异更鲌加明显。在配制兴凯湖翘嘴鲌人工饲料时,应适当添加限制性氨基酸蛋氨酸和胱氨酸,以提高其营养价值;适当添加甘氨酸和谷氨酸,以提高养殖鱼体风味。     

An evaluation of increasing linolenic acid level in the diet of Macrobrachium nipponense: Lipid deposition,fatty acid composition and expression of lipid metabolism‐related genes

To determine the effects of linolenic acid (LNA, 18:3n‐3) in oriental river prawn (Macrobrachium nipponense), an 8‐week feeding experiment was conducted using six isonitrogenous and isoenergetic semi‐purified diets containing 0.07 g/kg (control), 7.3 g/kg, 16.6 g/kg, 20.2 g/kg, 27.3 g/kg and 36.3 g/kg LNA. The hepatopancreas lipid content decreased significantly when dietary LNA content was >20.2 g/kg. Fatty acid analysis revealed that the percentage of 18:3n‐3 in the hepatopancreas significantly increased with increasing dietary LNA levels, while 20:5n‐3, 22:5n‐3 and 22:6n‐3 levels in the hepatopancreas decreased in a curvilinear manner as dietary LNA increased. Additionally, qRT‐PCR results revealed that hepatopancreas mRNA expression of acetyl‐CoA carboxylase (ACC) decreased with increasing dietary LNA, while the greatest carnitine palmitoyl transferase‐1(CPT1) mRNA expression was observed in the 2.73 g/kg and 36.3 g/kg groups. Furthermore, hepatopancreas mRNA expression of acyl‐CoA delta‐9 desaturase (SCD) and fatty acyl elongase 6(elovl6) was downregulated when prawns fed the diets containing >20.2 g/kg LNA. These results indicate that dietary 18:3n‐3 could decrease lipid deposition through increased fatty acid β‐oxidation and modulated fatty acid synthesis, and alter fatty acid composition by regulating fatty acyl elongase and fatty acyl desaturase mRNA expression in the M. nipponense.     

Dietary lipid levels affect lipoprotein clearance,fatty acid transport,lipogenesis and lipolysis at the transcriptional level in muscle and adipose tissue of large yellow croaker (Larimichthys crocea)

To investigate the effect of dietary lipid levels on lipid metabolism in muscle and adipose tissue of large yellow croaker (Larimichthys crocea), fish (average body weight 150.0 g) were fed to one of three diets with a low (6%), moderate (12%, the control diet) or high (18%) crude lipid level for 10 weeks. The expression of genes related to lipoprotein clearance (lpl, ldlr, lrp1 and srbi), fatty acid transport (cd36, fatp1, fabp3 and fabp11), lipogenesis (fas and dgat2) and lipolysis (atgl, cpt1 and aco) in muscle and adipose tissue was analysed. In muscle of fish fed the low‐lipid diet, the expression of lpl, lrp1, fas, dgat2 and atgl was significantly downregulated, whereas fabp3 and fabp11 were significantly upregulated compared with those fed the control diet. In muscle of fish fed the high‐lipid diet, the expression of lpl, ldlr, lrp1, cd36, fabp3, fas and dgat2 was significantly decreased, while fabp11 expression was significantly increased compared with those fed the control diet. Compared with the control group, only a significant downregulation of fabp3 expression in adipose tissue was observed in the low‐lipid group. In the high‐lipid group compared with the control group, the expression of ldlr, fabp11, dgat2, atgl and aco in adipose tissue was significantly upregulated, whereas cpt1 expression in adipose tissue was significantly downregulated. These results indicated that the expression of the selected key genes related to lipid metabolism was tissue‐specific regulation by dietary lipid levels in large yellow croaker.     

Potential of meat meal to replace fish meal in extruded dry diets for barramundi, Lates calcarifer (Bloch). II. Organoleptic characteristics and fatty acid composition

The organoleptic quality of barramundi fed for 66 days on pelleted diets containing varying amounts of fish meal and meat meal was determined in two experiments (E1 and E2). Each compared four diets: a 430 g kg^?1 crude protein (CP) control diet (containing 35% Chilean anchovy fish meal); two diets containing high inclusions (40% or more) of meat meal; and a proprietary barramundi diet. In E1, the two meat meal diets contained 10% Chilean fish meal whereas the two meat meal diets in E2 had no marine protein ingredients. Panellists identified and rated the colour of flesh, and scored odour, flavour and texture characteristics and overall liking on structured graphic line scales (0–100). Fish fed the high‐meat meal diets were sweeter and firmer than those fed the high‐fish meal control diet in E1 (P < 0.05). Scores for fishy flavour were also highest for the meat meal diets and lowest for the proprietary diet. In both E1 and E2, scores were high (> 60) for overall liking and low (< 10) for undesirable odours and tastes. Exclusion of all sources of marine protein from the diet in E2 did not detract from the sensory value of the fish. The influence of diet on the fatty acid profile of the fish was examined in E2. Compared with fish fed the control diet, the neutral lipid fraction of those fed the meat meal diets had higher proportions of saturated and short‐chain monounsaturated fatty acids at the expense of longer chain fatty acids, especially 22:6n‐3. Polar lipids showed only subtle dietary effects, which were confined to the long‐chain unsaturated fatty acids.     

Lipid content and fatty acid composition in female American shad,Alosa sapidissima,at different stages of ovarian development under reared conditions

The fatty acid accumulation in broodstock influences the fecundity of spawners as well as egg quality. A comprehensive understanding of the lipid and fatty acid changes in broodstock during the reproductive period can increase our knowledge of the nutritional requirements in artificial breeding programs. The study assessed the lipid and fatty acid compositions of muscle, liver and ovary of American shad at different stages of reproductive development under reared conditions. The results indicated that there were significant differences in lipid content among ovary, liver and muscle. Mean total lipid levels in ovary, liver and muscle were 15.92%–10.87%, 13.62%–6.89%, 10.39%–6.11% respectively. During the development season, the total lipid content in muscle in stages V and VI were significantly lower than those in stages II and III. The total lipid content in liver in stages IV, V and VI was significantly lower than in stages II and III, whereas the total lipid content in the ovary increased significantly as the gonad developed and reached its highest value at stage V. From II to VI stage, the liver content of docosahexaenoic acid (DHA) decreased and the ovarian content of DHA increased, whereas the content of eicosapentaenoic acid (EPA) remained relatively constant. The content of C16:0 and C18:1n‐9 decreased in muscle and liver, but significantly increased in ovary. It is therefore suggested that the lipids were preferentially transferred from muscle and liver to ovary beginning in stage IV as the gonad matured. At stage IV, the lipid transfer accelerated, and saturated and unsaturated fatty acids, such as C16:0, C18:1n‐9, DHA, EPA and arachidonic acid, were selectively transferred to and conserved in ovaries.