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1.
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2.
If osmotic stress and reduced seawater tolerance are predisposing factors for infectious pancreatic necrosis (IPN) outbreaks in farmed Atlantic salmon, increased survival by enhancing access to energy would be expected. The aim of the present study was, therefore, to increase energy access in 1-year old Atlantic salmon after sea transfer by increasing the level of dietary fat, by exchanging some of the dietary oil with more easily oxidized medium chain triacylglycerols, or by dietary supplementation of potentially energy enhancing additives such as clofibrate and tetradecylthioacetic acid (TTA). A natural outbreak of IPN occurred 8 weeks after sea transfer, and a significant dietary effect explaining 76% of the variation in mortality was observed. Relative percentage survival for the fish fed TTA in sea water was 70% when compared with the unsupplemented control, reducing mortality from 7.8 to 2.3%. Muscle fat content and plasma chloride were related to IPN mortality, suggesting that reduced hypoosmoregulatory capacity might be a predisposing factor to the onset of an IPN outbreak. Based on the observation of a threefold increase in white muscle mitochondrial fatty acid oxidizing activity by TTA, it is suggested that TTA has resulted in a re-allocation of dietary fatty acids from storage to energy producing oxidation.  相似文献   

3.
Heart and skeletal muscle inflammation (HSMI) is a transmissible disease of farmed Atlantic salmon, Salmo salar L. It is characterized by significant epi-, endo- and myocarditis, as well as myositis, particularly involving red skeletal muscle. The aetiology of HSMI is currently unresolved, though a viral cause is suspected. Since its discovery in 1999, HSMI has become an increasing problem for the Norwegian farming industry, with some farms experiencing yearly outbreaks and subsequent economic losses. In the present study an Atlantic salmon farm was studied from December 2003 to April 2005. Samples from apparently healthy as well as clinically diseased fish were collected monthly and examined histopathologically. The first fish to be diagnosed with HSMI was sampled in May, 8 months after transfer to sea. A clinical outbreak of HSMI followed in June, when all fish in the sample had lesions consistent with HSMI. Subsequent samples revealed that cardiac lesions decreased in severity 2 months after the start of the outbreak, but that multiple foci of cellular infiltration and necrosis persisted throughout the year. There appeared to be a shift in lesion location from being most severe in the compact myocardium in early stages of disease to a greater involvement of the atrium and spongy layer of the ventricle in later samples. Late samples also showed increased fibrosis of cardiac tissue. In conclusion, HSMI appears to be a severe disease with elevated mortality, morbidity close to 100% and prolonged duration.  相似文献   

4.
In the present study, the possible effect of dietary treatment on early sexual maturation in post-smolt Atlantic salmon, without any negative effect regarding growth, was investigated. The experiment was performed using 4400 individually marked (Pit tag) 1+ salmon, fed either a control diet or a diet supplemented with 0.5% tetradecylthioacetic acid (TTA) in duplicates for 3, 6 or 12 weeks after sea transfer. Compared with the control, dietary supplementation of TTA resulted in a threefold reduction in incidence of sexual mature males (0.6% vs. 1.8%). A curve-linear relationship between relative reduction in maturation and weeks of feeding TTA was found, indicating that the effect is most marked as a result of the first weeks of feeding and then levelling off. No negative dietary impact on growth was observed. As the level of fat in the muscle was reduced by dietary TTA, it seems that post-smolt supplemented dietary TTA do not accumulate high enough energy stores to start the maturation process, whereas the energy-enhancing effect of TTA due to increased fatty acid oxidation capacity may maintain the growth potential. Compared with immature salmon, sexually maturing fish revealed increased spring growth before the onset of maturation.  相似文献   

5.
Heart and skeletal muscle inflammation (HSMI) is a transmissible disease causing mortality in farmed Atlantic salmon, Salmo salar L. It is characterized by epi-, endo- and myocarditis and myocardial necrosis, as well as myositis and necrosis of red skeletal muscle. The present paper describes two infection experiments, with the aim of further exploring the infectivity and pathogenesis of HSMI. In both experiments, Atlantic salmon were intraperitonally injected with putatively infective material. The first experiment was carried out in fresh water, using cardiac tissue, blood plasma and cell cultured material as inoculates. In the second experiment, various tissues sampled from fish in the mid-outbreak phase were used to inoculate experimental fish in sea water. Also, cardiac tissue sampled before and after the outbreak phase was used. Finally, cardiac tissue pre-treated with chloroform was tested. In both experiments, all inoculates resulted in cardiac inflammation during the study period of 8 weeks. Early cardiac changes included perivasculitis and endocarditis, which were observed from 1–3 weeks post-challenge (p.c.). Focal myocarditis first appeared 3 weeks p.c., and the number of fish showing myocardial changes at 8 weeks p.c. was high in all groups. A possible mechanism for the development of HSMI is discussed.  相似文献   

6.
Wax esters (WE) in copepods constitute huge natural marine lipid resources, which can contribute as future lipid source in formulated diets in aquaculture, and thereby reduce the pressure on use of marine resources at higher trophic levels. The present study was undertaken to investigate factors affecting WE digestibility, including production of bile and lipases in Atlantic salmon fed diets containing high proportions of oil derived from copepods. Individually tagged postsmolt Atlantic salmon (initial weight 250 g) were distributed into three dietary groups in triplicate tanks and fed either a fish oil supplemented diet or diets where 50% or 100% of the fish oil was replaced with oil extracted from Calanus finmarchicus . WE accounted for 30.7% or 47.7% of the lipids in these latter diets, respectively. Over the 100 day feeding period, the salmon fed the fish oil diet displayed a significantly higher specific growth rate (SGR; 0.74) than fish fed the 100% Calanus oil diet (SGR; 0.67). The apparent digestibility coefficient of total lipid and total fatty acids was significantly higher in salmon fed the fish oil and the mixed diet compared to fish fed the pure Calanus oil diet. However, the fish appeared to enhance the lipid digestive capacity by increasing bile volume and the lipolytic activity. It is concluded that the digestion of WE in Atlantic salmon is poorer than for triacylglycerols. However, the digestive capacity is increased by elevating the bile content and lipase activity. At very high levels however, WE of lipid between 37.5% and 47.7%, are there no more compensation and WE utilisation decreases.  相似文献   

7.
This study was conducted to determine the effects of feeding increasing lipid concentrations (310, 380 and 470 g kg–1 lipid on dry weight) in diets based mainly on herring byproducts to Atlantic salmon Salmo salar . The diets were isonitrogenous, varying in dietary lipid content at the expense dietary starch. Average fish weight increased from 1.2 kg in April to 2.2–2.7 kg at the end of the feeding trial in September. Significantly greater growth was found in fish fed either the 380 g kg−1 or the 470 g kg−1 lipid diets compared with the 310 g kg−1 lipid diet. Muscle lipid content increased in all dietary groups on a wet weight basis from 7.7 ± 1.4% to 12 ± 3% in salmon fed the 310 g kg−1 lipid diet, and to 16 ± 2% in salmon fed the 380 g kg−1 and 470 g kg−1 lipid diets. In fish of similar weight there was a positive correlation between dietary lipid and muscle lipid concentrations. Low concentrations of muscle glycogen were detected in fish fed each of the diets, while muscle vitamin E concentrations slowly decreased as muscle lipid increased. Muscle fatty acid composition reflected dietary fatty acid profiles, containing similar percentages of total saturated, monoenic and n-3 fatty acids (20:5n-3 and 22:6n-3) in fish from all dietary treatment groups. However, a higher ratio of n-3/n-6 was found in muscle from fish fed the 470 g kg−1 lipid diet compared with the other two groups. Blood chemistry values varied somewhat, but all values were within normal ranges for Atlantic salmon of these sizes.  相似文献   

8.
Heart‐ and skeletal muscle inflammation (HSMI) caused by infection with Piscine orthoreovirus (PRV) is one of the most common viral diseases in farmed Atlantic salmon (Salmo salar) in Norway, and disease outbreaks have been reported in most countries with large‐scale Atlantic salmon aquaculture. Currently there is no vaccine available for protection against HSMI, partly due to the lack of a cell line for efficient virus propagation. Erythrocytes are the primary target cells for PRV in vivo and a potential source for isolation of PRV particles. In this study, PRV was purified from infected erythrocytes, inactivated and used in a vaccination trial against HSMI. A single immunization with adjuvanted, inactivated PRV induced protection against HSMI in Atlantic salmon infected by virus injection 6 weeks later, while a moderate protection was obtained in fish infected through natural transmission, i.e. cohabitation. The PRV vaccine significantly reduced PRV loads and histopathological lesions typical for HSMI compared to the unvaccinated control group. This is the first demonstration of protective vaccination against PRV, and promising for future control of HSMI in Atlantic salmon aquaculture.  相似文献   

9.
Early sexual maturation of male chinook salmon (maturation 1 to 4 years prior to females in the same age class) results in reduced effectiveness of stock enhancement programs and a financial loss to the salmon farming industry. Previous studies in Atlantic salmon have shown that the age of maturity in males is affected by growth and/or body energy stores, but the relative roles of these two factors are not well understood. Therefore, an experiment was designed to determine when spermatogenesis was initiated, to characterize the endocrine changes during the onset of puberty in male salmon, and to determine if the level of whole-body lipid affects the incidence of early male maturation in a wild stock (Yakima River) of 1+ spring chinook salmon. Fry were fed a commercial diet from February until August and were then divided into groups of 320 fish (mean weight, 5.6 g) and fed one of five experimental diets (two replicate groups/diet) containing 4%, 9%, 14%, 18% or 22% lipid and 82%, 77%, 73%, 69%, or 65% protein for 13 months. Fish were reared on natural photoperiod and ambient temperature (6°C to 16°C), and pair-fed to a level based on the tank with the lowest feed consumption. Fish were weighed monthly and sampled to determine body composition, pituitary follicle-stimulating hormone (FSH) and luteinizing hormone (LH) levels, plasma insulin-like growth factor I (IGF-I) levels, and stage of gonadal development.

Throughout the experimental period the mean fish weight was similar among treatment groups. However, from December through the end of the experiment in the following September, maturing males were significantly larger than nonmaturing fish. Initial lipid levels in 0-age experimental fish were near 6%, which is similar to wild fish of the same stock and age captured in the Yakima River during August. Fish fed diets containing more than 4% lipid increased in whole-body lipid content during the first 2 months of feeding and then maintained at relatively constant levels during the course of the experiment. Whole-body lipid levels for the dietary treatment groups averaged 5.6%, 7.1%, 8.2%, 9.4%, and 9.6% from October through the following September.

Based on histological examination of the testes of experimental fish, type B spermatogonia and primary spermatocytes were first observed in some of the yearling males during November. These were designated maturing males. Pituitary FSH levels were significantly higher in maturing than nonmaturing males at this time and for the remainder of the study. Pituitary FSH levels increased as spermatogenesis proceeded in maturing fish, whereas pituitary LH levels increased in maturing 1+ males only during July and August, when testes were in late stages of spermatogenesis and in September during spermiation. Plasma IGF-I levels were significantly higher in maturing males than nonmaturing fish from December through the end of experiment. Since maturing males were significantly larger than nonmaturing fish of both sexes from December through September, the difference in IGF-I levels could be due to differences in growth or due to maturation.

The percentage of maturing males was significantly influenced by whole-body lipid, increasing from 34% in fish fed the 4% lipid diet to 45% in fish fed the 22% lipid diet. These data suggest that whole-body lipid levels influenced the incidence of maturation of male spring chinook salmon. In addition, both endocrine and histological indicators suggest that maturation was initiated in males approximately a full year prior to the time the fish will spawn.  相似文献   


10.
Effects of dietary tetradecylthioacetic fatty acid (TTA) on muscle fat, development of gonads and early sexual maturation in S0 Atlantic salmon during the first year in sea were investigated. TTA (0.5% w/w) was added to the feeds for 8 weeks in the spring. In May, at the end of the TTA‐feeding period, the fish in the TTA group had significantly (P < 0.05) less fat (10.1%) stored in muscle compared with the control group (10.8%). In September, mean male gonadosomatic index (GSI) in maturing fish in the TTA group was found to be lower compared with the maturing fish in the control group (P = 0.05). On the basis of GSI values, male sexual maturation in September was 10.0% vs. 14.4% for the TTA and the control group respectively. Thus, relative to the control group, the incidence of male sexual maturation in the TTA group was reduced by about 1/3 (P = 0.002). Production data was not affected by dietary supplementation of TTA. This study reveals that TTA significantly reduces the incidence of male sexual maturation in S0 Atlantic salmon. A significant elimination model of TTA in fish muscle that takes into account, the growth rate of the fish was further developed in this study.  相似文献   

11.
The effects of feeding three natural frozen diets, grass shrimp (Palaemonetes sp.), crayfish (Procambarus clarkii) and fish (Sardina pilchardus) and two semi‐humid artificial diets (based on fish or shrimp powder) to the cuttlefish, Sepia officinalis, were analysed. Growth rate and feeding rate [FR; % body weight (BW) day?1] and food conversions (FC, %) were determined. Cuttlefish fed shrimp grew larger (3.8% BW day?1) and had the highest FC, followed by those fed crayfish, and sardine. The highest FR was obtained for cuttlefish fed crayfish (10.5% BW day?1). Although both artificial diets were accepted, none produced growth. Digestive gland‐to‐body weight ratio (DG/BW ratio) was calculated for animals fed each diet. A positive correlation (r = 0.94) between cuttlefish ingestion FR and DG weight was obtained. Mortality occurred mainly during the last week, and some cannibalism occurred among cuttlefish fed artificial diets. Finally, lipid composition of diets, DG and mantle of each group were analysed. Sardine diet was characterized by high levels of triacylglycerol (TG), whereas the main difference between shrimp and crayfish was the higher n‐3/n‐6 ratio found in shrimp. Changes in the lipid composition of DG were related to diet, but did not correlate with growth data. A strong loss of TG in the DG of artificial diets groups was notable. No differences in mantle lipid composition among the natural diets were found, but artificial diet groups showed higher contents of neutral lipids in their mantle respect to natural diets. According to results obtained, crayfish (P. clarkii) could be used as an alternative prey for rearing S. officinalis compared with shrimp. Artificial diets showed the worst effects in growth and mortality as well as the stronger influence on DG and mantle lipid composition of cuttlefish.  相似文献   

12.
Duplicate groups of juvenile coho salmon (Oncorhynchus kisutch) were fed daily to satiation one of four “dry” diets. Diets contained either 35 (LP) or 51% (HP) protein and either 12 (LL) or 17% (HL) lipid on a dry matter basis. Additional groups received the same diets supplemented with 1 ppm 17α-methyltestosterone (MT). Most of the eight treatments were administered for 294 days (July to April).Fish fed HP diets grew faster in weight than those fed LP diets. MT supplementation significantly enhanced growth regardless of diet composition. Appetite was greatest in fish fed LP diets; MT supplementation increased appetite in July and August. Protein efficiency ratios (PER) during these months were inversely related to dietary protein and directly related to lipid content. These trends in PER were, in most instances, reversed during September and October, but a distinct trend was not evident in subsequent months. Groups fed MT diets had increased PERs between July and October.Dietary protein content did not affect proximate composition of fish sampled in November; however, high dietary lipid content of MT-free diets was associated with low body moisture, protein and ash and with high lipid content. These effects on body composition were usually reduced when the diets contained MT. In April, body protein content of fish fed non-supplemented diets was directly related and lipid content inversely related to dietary protein-calorie ratio. MT supplementation of the LP-LL diet increased body protein and ash content, number of β cells in the pituitary, and thyroid activity (histological assessment). Lipid deposition in omentum, liver and whole body was decreased.In April, osmoregulatory ability of fish fed LP diets with MT was impaired. However, hormone withdrawal for 14 days restored normal ability.It is concluded that manipulation of dietary protein, lipid and MT content can significantly improve protein utilization and thus offers a means to lower food costs in coho culture.  相似文献   

13.
在水温13~14 ℃下,将平均体质量(1.07±0.3) g的亚东鲑幼鱼养在100 cm×100 cm×60 cm圆形玻璃缸循环水系统中,密度为159尾/m^( 3) ,水深约40 cm,投喂添加0%、0.1%、0.2%、0.5%、 1.0% 、1.5%和2.0%β-葡聚糖的饲料饲养60 d,研究β-葡聚糖对亚东鲑幼鱼存活及生长的影响。试验结果显示,不同含量β-葡聚糖对亚东鲑幼鱼存活率差异不显著,均为100%;平均质量增长率0.5%试验组最大,显著高于其他各组( P <0.05),平均体长增长率0.5%试验组最大,与0.2%、0.5%、1.5%试验组之间差异不显著,显著高于其他各组( P <0.05),0%试验组平均体长增长率最小;特定生长率0.5%试验组最高,显著高于其他各组( P <0.05),0%试验组最低;肝体指数依次递减,0%试验组最大,与 0.1% 、 0.2% 和0.5%试验组之间差异不显著,但显著高于其他各组( P <0.05);肥满度0.1%、0.2%、 0.5% 、 1.0% 试验组之间差异不显著,显著高于其他各组( P <0.05),0%试验组最小;摄食率0.1%试验组最高,随着β-葡聚糖添加量增加依次递减,但各试验组之间差异不显著;食物转化率0.5%试验组最高,与1.0%、 1.5% 、2.0%之间差异不显著,显著高于其他各组( P <0.05),0%试验组最低。肠道脂肪酶、胰蛋白酶和淀粉酶活性均随β-葡聚糖含量增加呈先增后减变化趋势,说明β-葡聚糖能够提升肠道消化酶活性。综上所述,饲料中添加0.5%β-葡聚糖对亚东鲑存活与生长效果较好。  相似文献   

14.
A two-factor study was conducted to evaluate the effects of dietary riboflavin and lipid levels on the growth, health performance and riboflavin status of Atlantic salmon ( Salmo salar ). Atlantic salmon parr were fed four fishmeal-based diets with or without supplementation of 20 mg riboflavin kg–1, at two lipid levels, 150 or 300 g kg–1. Each diet was fed to triplicate tanks of fish for 12 weeks. Unsupplemented diets contained between 6 and 8 mg riboflavin kg–1. There were no significant differences in growth as a result of riboflavin supplementation. No mortality or histomorphological changes in eye tissues were observed. Dietary treatments did not affect blood haemoglobin values. After 12 weeks, muscle lipid content seemed to be reduced by riboflavin supplementation irrespective of dietary lipid level. Riboflavin status of whole body, muscle, liver, kidney and eye lenses is reported. Saturation levels of riboflavin in liver and muscle were reached with unsupplemented diets. The concentrations of riboflavin and lipid in liver were negatively correlated. There was a tendency of higher whole body riboflavin concentration in fish fed high-lipid diets. Based on growth, absence of deficiency signs and maximal tissue saturation of riboflavin, it can be concluded that the requirement for riboflavin was met by the natural riboflavin content in the raw materials of the feed. However, independent of dietary lipid level, dietary riboflavin supplementation may increase lipid utilization in rapidly growing salmon parr.  相似文献   

15.
The present experiment reports on the effects of inositol supplementation from 0 to 1600 mg kg−1 to a fishmeal-based diet on growth, inositol retention, proximate composition (dry matter, protein and lipid) and blood chemistry in Atlantic salmon, Salmo salar L., fry during a 28-week feeding experiment. Growth was affected to a minor extent, and only during the first 4 weeks of the experiment. Mortality was low and not related to dietary inositol. The inositol concentration in whole fish and liver was affected by dietary inositol supplementation. Proximate composition of whole fish was similar among dietary groups, except for positive correlations between dry matter, lipid and protein and dietary inositol supplementation after 8 weeks. Analyses of hepatic lipid classes after 8 weeks showed non-significant differences among the groups, mostly explained by somewhat reduced total hepatic lipid accumulation with increasing dietary inositol. Triacylglycerol and phosphatidylcholine accounted for 80% and 8–10% of the hepatic lipids (approximately 80 mg lipid g−1 wet weight) in all groups. Blood haemoglobin was positively correlated and plasma triacylglycerol was negatively correlated to dietary inositol supplementation at week 28, while plasma protein and cholesterol were unaffected. The present results indicate that the requirement of Atlantic salmon fry for inositol is covered through the natural content of inositol in practical feed ingredients at around 300 mg inositol kg−1. It may, however, be advisable to supplement starter diets with moderate amounts of inositol, around 200 mg kg−1, to compensate for fluctuations in inositol concentrations in natural ingredients, leaching loss of inositol from the diet and for any potential increased inositol requirement in salmon fry.  相似文献   

16.
The purpose of this study was to determine the effect of AQUI‐S® (5.0 mg/L) sedation compared with nonsedation on the primary (plasma cortisol), secondary (osmoregulation), and tertiary (mortality) stress responses in Atlantic salmon smolts during transport and transfer to sea. AQUI‐S sedation during on‐ and off‐loading sufficiently reduced the primary stress response to lower mortality (2.5%) during transfer to sea compared with unsedated fish, which experienced a mortality rate above 11.5%. The unsedated fish experienced an acute mortality, which only stabilized 16 d after the transport. None of the secondary stress responses measured in this experiment could contribute in explaining this phenomenon, with the possible exception of plasma magnesium. While osmolality and chloride increased in both groups during the experiment, it did not seem to be related to the difference in the primary stress response documented in the sedated and unsedated groups. It instead appeared to be an effect of the salinity change from freshwater to seawater after transport. Plasma magnesium differed between the groups, while plasma magnesium in the AQUI‐S‐sedated group returned to prestress levels 12 h after transport. The unsedated group showed no such recovery even 1 wk after transport, which may indicate a disturbance in hydromineral balance and give plausible explanation for delayed mortality this group experienced. AQUI‐S shows promise as a stress‐reducing sedative for Atlantic salmon smolts and if used properly could improve animal welfare and survivability during and after common aquaculture‐related incidents.  相似文献   

17.
The present paper reports the results of a 1 year experiment using Atlantic salmon with a starting weight of 1.7 kg, and final weight of 7.4 to7.8 kg dependent of diet group. The experiment aimed to evaluate a direct production method of feed where landings from fishing vessels are used directly in feed processing. The dietary compositions followed the natural rhythm in lipid level of the catches of herring in the North Sea (Catch group) adjusted to be stable throughout one season only, and compared to a control diet (constant composition throughout the year) and a designed diet (opposite to the natural biorhythm of salmon lipid stores) (diet group Design). Four seasons were defined: spring (March, April, May), summer (June July August), autumn (September, October, November), winter (December, January, February). All diets varied in protein and lipid due to the adjustment according to season. The experiment was run in triplicate sea cages for each diet, using natural light and temperature regimes (21°N). All diet groups showed equal growth throughout each season, except for the Catch group during autumn showing lower SGR-values. SGR values varied significantly also between seasons for all diet groups, ranging from 0.29 during spring to 0.81 during autumn. Feed conversion ratio varied dependent on season and the dietary protein to energy ratio, at all seasons except winter. Quite a large variation between diet groups and seasons were registered in condition factor. Whole body lipid varied between seasons, as a consequence of dietary lipid levels, and increased as fish weight increased. After autumn growth only, whole body protein levels were significantly lower in the Catch group compared to the two other diet groups. Muscle lipid levels did not vary as a consequence of fish size alone, but varied substantially between seasons in both the Catch and Control groups, but not in the Design group. Muscle alpha-tocopherol and fatty acid profile varied due to diet in spring and autumn seasons, but with minor variations due to diet in summer and winter periods. Only minor influences from diet were registered in liver and heart compositions. Haematological parameters and plasma nutrient values ranged within normal values for salmon, and together with close to no mortality throughout the experiment, fish health was concluded to be good in all diet groups at all seasons. However, plasma asparagine aminotransferase (ASAT) values were quite high during summer and autumn, especially in the control group. These results point to the need of optimizing antioxidant composition of diets during the summer and early autumn season. Overall results show the possibility to obtain acceptable production results when feeding Atlantic salmon a diet adjusted to each season, as long as the fish protein to energy (P:E) requirements are met, further that total body lipid stores varied more than muscle lipid concentrations, and that the lipid levels were highly dependent on season, diet composition and fish size.  相似文献   

18.
Based on the regulatory effects of body fat on appetite and seasonal variations in fat deposition and growth of Atlantic salmon, the present study tested the hypothesis that body fat content prior to declining day length in the autumn can significantly modulate growth rate. The growth rate of salmon (mean initial body weight, BW = 2.3 kg) with different muscle fat content prior to autumn, subjected to natural photoperiod and temperature, during a 7‐month period (mean final BW = 6.6 kg) was studied. In August, three fish groups (HF, LF and 0.5LF group) with significantly different muscle fat content (HF = 16.4%, LF = 13.2% and 0.5LF = 11.3%), individually marked with PIT‐tag, were mixed into the four net‐pens and fed a standard high‐energy diet until March the following year. The muscle fat content prior to the autumn had a highly significant (p < .0001) effect on growth during the 7‐month main‐dietary period, even after identical fat stores among the groups were restored, indicating a more complex explanation than just a lipostatic regulation mechanism. Mean thermal growth coefficients were HF = 2.9, LF = 3.4 and 0.5 LF = 3.9, resulting in increased final weight gain for LF and 0.5LF of 590 g and 980 g, respectively, compared to the HF group. The LF groups obtained a significantly higher homogeneity in BW and shape than HF‐fed fish in March, optimizing automatic gutting and filleting at slaughter. The improved growth response among the LF groups by reducing lipid levels can potentially be utilized in closed and semi‐closed production units where photoperiod can be manipulated.  相似文献   

19.
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20.
This study assessed refined canola oil (CO) as a supplemental dietary lipid source for juvenile fall chinook salmon, Oncorhynchus tshawytscha, parr with respect to possible effects on their growth and osmoregulatory performance and body composition. Diets with equal protein ( 57%) and lipid ( 19%) content (dry weight basis) were supplemented with lipid from either anchovy oil (AO) or CO with AO so that CO comprised 0 (0CO), 11% (11CO), 22% (22CO), 33% (33CO), 43% (43CO) or 54% (54CO) of the dietary lipid content. Triplicate groups of juvenile chinook salmon were fed their prescribed diets for 104 days in freshwater (FW) and 31 days in seawater (SW) after a 4-day transition period. Dietary fatty acid compositions reflected the different proportions of AO and CO in the supplemental lipid. Diet treatment had no effect on fish growth, feed intake, feed efficiency, protein utilization, fish mortality or terminal whole body water and ash percentages. Whole body lipid percentages were higher in 11CO and 43CO fish than in 33CO fish and in 11CO fish versus 22CO fish. Whole body protein percentages were highest in 33CO, 43CO and 54CO fish and lowest in 0CO and 22CO fish. Terminal whole body fatty acid compositions were influenced strongly by the dietary fatty acid compositions. Haematocrit and muscle water percentages were not affected consistently and plasma Na+ and Cl− concentrations were unaffected by diet treatment in FW or 24-h seawater challenges during FW residency. Also, diet treatment had no effect on the physiological parameters after SW residency. We conclude that dietary treatment had no effect on fish growth performance under our experimental conditions. Also, the dietary inclusion of CO neither facilitated nor impaired the transfer of chinook salmon parr to seawater. Thus, CO was found to be an excellent and cost-effective source of supplemental dietary lipid for culture of juvenile fall chinook salmon during freshwater residency.  相似文献   

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