Article

The effect of low inclusion levels of Antarctic krill ( Euphausia superba ) meal on growth performance, apparent digestibility and slaughter quality of Atlantic salmon ( Salmo salar )

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Abstract

Two trials with Atlantic salmon (Salmo salar) were conducted to evaluate the potential of krill meal to improve feed intake. In the first experiment, after transfer to sea water, salmon smolts were fed diets added 75 or 150 g kg-1 Antarctic krill meal in substitution for fish meal for 13 weeks. The apparent digestibility coefficient for crude protein and the majority of the amino acids was significantly lower in the feeds added krill meal (around 83.5%) than in the control diet (84.9%), whereas the digestibility of crude lipids, dry matter and energy was not significantly different among the three diets. Krill meal addition resulted in higher feed intake, which led to higher growth rates and final body weights. In the second experiment, large salmon were fed a diet containing 100 g kg-1 krill meal for 6 weeks before slaughter. Their feed intake and growth performance were assessed, and fillet and visceral fat contents were measured. Salmon fed the 100 g kg-1 krill meal diet tended to eat more, resulting in significantly increased growth rates, when compared to control fish. Fish fed krill meal also had a significantly lower condition factor.

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... In addition to the high cost, the direct protein replacement of FM by KM beyond 40% may have negative effects on the growth performance. This led to the testing of low inclusion levels, for example, in a study conducted by Hatlen et al. [28], with low inclusion levels of KM. In this study, the authors determined the effect of low KM inclusions (7.5 and 15%) on feed intake and growth performance of Atlantic salmon in two trials in seawater cages [28]. ...
... This led to the testing of low inclusion levels, for example, in a study conducted by Hatlen et al. [28], with low inclusion levels of KM. In this study, the authors determined the effect of low KM inclusions (7.5 and 15%) on feed intake and growth performance of Atlantic salmon in two trials in seawater cages [28]. The low KM inclusion levels were balanced with other protein sources like soybean meal, corn, wheat, sunflower meal, and rapeseed protein. ...
... The rationale for choosing the transfer phase was to determine the effect of KM inclusion on the feed and growth depression faced by Atlantic salmon during the first few weeks after seawater transfer. The stimulating effect of KM led to significant increases in feed intake and growth rates, and the salmon smolts gained 29 and 40% more weight when fed 7.5 and 15% KM, respectively [28]. ...
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The interest for krill-based ingredients for aquaculture feed applications has increased steadily in recent years. For decades, there has been a heavy reliance on the limited sources of fishmeal and fish oil in the salmonid aquaculture industry. Further growth in farming of carnivorous fish is dependent on new feed resources becoming available. The only unexploited marine resources of significant biomass are found at lower trophic levels, of which the Antarctic krill (Euphausia superba) has a high potential. Apart from being the biggest single species biomass, Antarctic krill is also rich in nutrients, such as omega-3 polyunsaturated fatty acids, phospholipids, astaxanthin, vitamins, and minerals. This makes Antarctic krill a high-quality source of health-beneficial lipids and proteins. The present article provides an overview on the documented benefits of feeding salmonids (Atlantic salmon (Salmo salar) and rainbow trout (Oncorhynchus mykiss)) with krill products (krill meal, krill oil, and krill hydrolysate), focusing on growth performance (feed intake, growth rate, and feed conversion), fillet quality, slaughter yield, and health benefits in terms of reducing fat accumulation in liver and intestinal tissues. Besides, the article discusses possible future studies, to widen the knowledge on krill benefits in salmonids and to unravel the underlying mechanisms.
... Noteworthy are also the relatively high levels of EPA and DHA (8) , phospholipids (PL), vitamins, nucleotides and astaxanthin of krill meal (9) . Krill living in the Southern Ocean is considered a sustainable source of protein in aquafeeds (10) , and studies with carnivorous fish including Atlantic salmon have documented that krill meal may facilitate efficient reduction in the use of fishmeal in high fishmeal diets (11)(12)(13)(14)(15)(16) . For example, there are positive effects documented on feed intake and growth at different life stages without compromising fillet quality. ...
... Systemic study of krill meal in salmon diets 9 krill meal; Hatlen et al. (16) reported 11 % higher TGC and lower VF in 7 kg salmon fed 10 % dietary krill meal inclusion during 6 weeks. The lack of growth effect by dietary supplementation of krill meal in the present study may be related to the high dietary content of vegetable raw materials, unlike previous studies that used fishmeal as the major protein source. ...
... Rather the 0·6 %-units higher fillet yield (P = 0·06) and up-regulation of myofiber proteins indicate stimulated skeletal muscle growth. These results are in line with Hatlen et al. (16) who suggested that krill meal may contribute to more efficient utilisation of the feed energy for protein growth (fillet production). ...
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There is an urgent need to find alternative feed resources that can further substitute fishmeal in Atlantic salmon diets without compromising health and food quality, in particular during the finishing feeding period when the feed demand is highest and flesh quality effects are most significant. This study investigates efficacy of substituting a isoprotein (35%) and isolipid (35%) low fishmeal diet (FM, 15%) with Antarctic krill meal (KM, 12%) during three-months with growing finishing 2.3±0.3kg salmon (quadruplicate sea cages/diet). Final body weight (3.9±0.4kg) was similar of the dietary groups, but the KM-group had more voluminous body shape, leaner hearts and improved fillet integrity, firmness and colour. Ectopic epithelial cells and focal calcium deposits in intestine were only detected in the FM-group. Transcriptome profiling by microarray of livers showed dietary effects on several immune genes, and a panel of structural genes were upregulated in the KM-group, including cadherin and connexin . Upregulation of genes encoding myosin heavy chain proteins was the main finding in skeletal muscle. Morphology examination by SEM and secondary structure by FTIR revealed more ordered and stable collagen architecture of the KM-group. Free fatty acid composition of skeletal muscle indicated altered metabolism of n-3, n-6 and saturated fatty acids of the KM-group. The results demonstrated that improved health and meat quality in Atlantic salmon fed krill meal were associated with upregulation of immune genes, proteins defining muscle properties and genes involved in cell contacts and adhesion, altered fatty acid metabolism and fat deposition, and improved gut health and collagen structure.
... In addition, the concentrations of other essential amino acids, particularly isoleucine, leucine and phenylalanine,were higher in krill meal than fishmeal (Table 4). Consistently, growth performance stimulation with krill meal has been reported earlier in red swam crayfish (Gao et al., 2020), P. monodon , Atlantic salmon (Hatlen et al., 2017), P. vannamei (Nunes et al., 2011;Derby et al., 2016) and yellow croaker (Wei et al., 2019). Derby et al. (2016) reported that krill meal at 1, 3 and 6% inclusion increased the palatability and consumption of feed pellets in a concentration-dependent fashion in P. vannamei compared to the control group. ...
Article
An eight-week feeding trial was conducted to investigate the effect of dietary krill meal inclusion in diets with moderate (12%) and low (6%) fishmeal concentrations for Penaeusvannamei.Inasmuch, eight iso‑nitrogenous and isolipidic diets were formulated to contain 36% crude protein and 5.5% crude lipid. In the moderate-fishmeal diets, krill meal was included at 0, 2, 4 and 6% (called FK12:0, FK12:2, FK12:4 and FK12:6, respectively), likewise in the low-fishmeal diets, krill meal was included at the same concentrations of 0–6% (called FK6:0, FK6:2, FK6:4 and FK6:6, respectively). Shrimp with a starting body weight of 0.55 ± 0.02 g were stocked at 22 animals per tank of 350 lcapacity and fed three times daily. Results revealed that dietary krill meal and fish meal inclusion levels significantly increased growth performance (P < 0.05)and there was no significant effect on interaction between fishmeal and krill meal levels. Shrimp fed 6% krill meal diet had the highest final body weight of 11.61 g, weight gain of 11.05 g, weight gain % of 1969.38%,specific growth rate of 5.41%/d and yield of 229.42 g/tank The weight gain % and SGR showed non significant difference between 4 and 6% krill meal containing groups.Dietary change did not affect feed conversion ratio, protein efficiency ratio and apparent protein utilization(P > 0.05). Survival was significantly increased in the groups containing 6 and 4% krill meal diets compared to 0% krill meal diet (P < 0.05). Inclusion levels of krill meal showed non-significant differences in post-fed body composition except for crude lipid and crude fibre content. Fishmeal inclusion levels showed significant (P < 0.05) variation in C14:0,C16:0,C18:0,C16:1, C18:1n-9,C18:2n-6,C22:6nn-3/n-6 ratio, whereas krill meal inclusion levels showed significant variation in the all n-3 fatty acids only. Immune-related gene expression was significantly (P < 0.05) upregulated in the shrimp fed high fishmeal diets (12%) for all the analyzed genes (ProPhenoloxidase (ProPO),ProPhenoloxidase activating enzyme (PPAE), Serine Protease (SP), β-1, 3-glucan-binding protein (BGBP), Superoxide dismutase (SOD), and Hemocyanin (HC)). The dietary change led to a significant difference in both histology and haematology parameters (P < 0.05). The results inferred that krill meal could be used as a potential functional feed ingredient in Penaeus vannamei.The present study suggested beneficial effects of krill meal in shrimp diets. The levels of fishmeal inclusion (12 and 6%) also showed significant (P < 0.05) variations in various growth performance parameters. It is plausible that an inclusion level of 4% is the minimum for a measurable difference in growth performance.
... Based on its nutritional profile, krill meal (KM) contains protein, amino acids and ash levels comparable to that of FM (Hertrampf and Piedad-Pascual, 2000;Tou et al., 2007). Noteworthy is that it presents relatively high levels of eicosapentaenoic acid (EPA; 20:5n-3) and docosahexaenoic acid (DHA; 22:6n-3) (Köhler et al., 2015), phospholipids (PLs), vitamins, nucleotides, trimethylamine N-oxide, chitin and natural astaxanthin, which has been demonstrated to stimulate the feeding appetite of fish (Everson et al., 2018), and to efficiently facilitate the reduction of FM and FO in diets (Hatlen et al., 2016;Mørkøre et al., 2020;Saleh et al., 2018;Thakara et al., 2020). ...
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A sustainable growth of the aquaculture sector implies the use of sustainable novel raw materials as replacers of the traditional fishmeal (FM) and fish oil (FO) ingredients. This fact has led to the development of sustainable and functional diets as part of a management strategy to reduce the effects on fish growth performance and health derived from low FM/FO dietary contents. In this sense, Antarctic krill (Euphausia superba) is considered a potential candidate in dietary inclusions to potentiate fish growth and health status. In this study, European sea bass (Dicentrarchus labrax) were fed a practical diet with either a 15% fishmeal content (KM0; control diet) or the same diet substituted by 30% (KM5; 5 g KM/kg diet) or 50% (KM7.5; 7.5 g KM/kg diet) Antarctic krill meal (KM) for 12 weeks in triplicates. At the end of the feeding trial, growth performance, liver morphology, liver proximate composition, lipid classes and fatty acid profiles, as well as the expression of hepatic genes related with lipid metabolism were evaluated. Fish fed KM-based diets presented higher (p < 0.05) final weight, protein and lipid efficiency ratios, specific growth rate (SGR) and improved feed conversion ratio (FCR), irrespective of the KM dietary level. Whole body and muscle proximate composition and fatty acid profiles were similar among dietary groups. Livers of European sea bass fed the experimental diets presented similar (p > 0.05) biochemical composition and fatty acid profile. However, smaller hepatocellular area and lower grade of cytoplasm vacuolization as well as a better alignment around sinusoidal spaces were found. The analyses of liver lipid classes revealed a positive correlation between the level of dietary KM and the pigmented material such as astaxanthin and free fatty acid content, as well as a negative correlation with the cholesterol levels. The expression of hepatic genes studied demonstrated a downregulation of 3-hydroxy-3-methylglutaryl-coenzyme A reductase (hmgr) and delta-6-desaturase (fads2) expression levels in fish fed KM-based diets. Besides, gene expression levels of fatty acid binding protein 7 (fabp7) and lipoprotein lipase (lpl) were significantly correlated with KM dietary levels. Altogether, these results profile KM as a potential promoter of growth and liver health in European sea bass fed low fish meal and oil diets.
... KM is a palatability enhancer in addition to suitable lipid and mineral source for fish (Goto et al., 2001;Hansen et al., 2010). Therefore, increased feed intake (FI) has been reported in fish species when diets are incorporated with KM (Hatlen et al., 2017;Yoshitomi et al., 2006). Dietary KM supplementation have been proven to improve growth, feed utilization, health status, diet digestibility and disease resistance of fish (Hansen et al., 2010;Yan et al., 2018). ...
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Protein hydrolysates and krill meal (KM) are used as protein sources in aquafeeds. The study was conducted to examine the supplemental effects of shrimp protein hydrolysates (SH) or KM in a high-plant-protein diet for red seabream (Pagrus major). A fish meal (FM)-based diet (40%) was considered as the high-FM diet (HFM) and a diet containing 25% FM and soy protein concentrate, in the expense of FM protein from HFM diet, was considered as the low fish meal (LFM) diet. Two other experimental diets (SH and KM) were prepared by including SH and KM into LFM diet at 5% inclusion levels in exchange of 5% FM from the LFM diet. A feeding trial was conducted for fifteen weeks using triplicate group of fish (Initial mean body weight, 8.47 ± 0.05 g) for a diet. Growth performance and feed efficiency of fish were significantly enhanced by HFM, KM and SH supplemented diets over those of fish fed LFM diet. Interestingly, these parameters of fish fed SH diet showed better performance than KM and HFM groups. Liver IGF-I expression of fish fed SH diet was comparable to HFM group and higher than KM and LFM diets. Protein digestibility of SH diet was significantly higher than KM, HFM, and LFM diets. Dry matter digestibility of SH diet was comparable to HFM diet and significantly higher than KM and LFM diets. Nitro blue tetrazolium and superoxide dismutase activities of HFM, SH and KM groups were significantly elevated than the LFM group and SH diet increased catalase and glutathione peroxidase activities of fish compared to KM and LFM groups. Hemoglobin level and hematocrit of fish fed SH and KM diets were significantly higher than LFM group. A diet containing 20% FM with KM is comparable to a HFM diet which contains 40% FM for red seabream. SH can be used to replace FM from red seabream diet down to 20% and fish performance can be improved better than a diet containing 40% FM. Overall, it seems that SH is more effective ingredient in red seabream diet compared to KM.
... The diets in the present experiment were supplemented with feed attractants in order to enhance their acceptability and growth performance. Nucleotides (Burrells et al., 2001), krill meal (Hatlen et al., 2017;Kousoulaki et al., 2013;Zhang et al., 2012) and soluble fish Values are represented as mean ± SEM. Raw means for the end of the feeding period with different superscript letters differ significantly (p < 0.05). ...
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Lumpfish (Cyclopterus lumpus) are widely applied as biological delousers in open net-pen farming of Atlantic salmon. As a species new to farming it is necessary to obtain a comprehensive understanding of the capacity of lumpfish to utilize plant derived feed ingredients. A feeding trial lasting for 54 days was conducted to investigate the effects of replacing fishmeal (FM) with a mix of soy protein concentrate (SPC) and pea protein concentrate (PPC) on growth, body chemical composition, and fast muscle fiber cellularity in juvenile lumpfish. Four isonitrogenous and isoenergetic diets (52 % crude protein and 14 % crude lipid) were formulated; a FM based diet was used as control (CTRL), and three experimental diets containing SPC and PPC (equal proportions of 1:1), replacing FM on weight basis at 25 % (PP25) 50 % (PP50) and 75 % (PP75). The fish grew from approximately 6.9 g to an average weight of 40.2 g in 54 days. Fish fed PP50 had significantly higher body weight, length and height compared to the other dietary groups. The whole body crude protein content of fish fed PP50 was significantly higher compared to the CTRL diet, while crude lipids were lower than those on CTRL and PP25 diets. Ash and dry matter did not differ among groups. Probability density functions showed no differences in fast muscle fiber size distributions amongst feeding groups. A higher percentage of smaller fibers in all feeding groups indicated hyperplasia was the dominant mechanism of muscle growth during the experimental period. These results suggest that a mixture of SPC and PPC can replace up to 50 % of FM in diets for juvenile lumpfish without any adverse effects on growth, chemical composition and fast muscle fiber cellularity.
... promoted growth performance and feed intake and improved the meat quality of several fish species (Hatlen et al., 2017;Suontama et al., 2007;Tibbetts, Olsen, & Lall, 2011;Yoshitomi, Aoki, & Oshima, 2007). However, Yoshitomi, Aoki, Oshima, and Hata (2006) found that supplementation with krill meal adversely affected growth performance in rainbow trout (Oncorhynchus mykiss) as a result of the accumulation of fluoride in vertebral bones. ...
Article
This study was designed to evaluate the effect of dietary replacement fish meal supplemented with freeze‐dried powder of the Antarctic krill Euphausia superba (FDPE) on the growth performance, molting, and fatty acid composition of the Pacific white shrimp Litopenaeus vannamei (initial weight 1.27 ± 0.09 g). Four diets containing 0% (S0 group), 10% (S10 group), 20% (S20 group), and 30% (S20 group) FDPE were used in the present study. At the end of growth trial, the final body weight, weight gain rate, and specific growth rate in the S10, S20, and S30 groups were higher than those in the S0 group. The shrimp in the S10 and S20 groups exhibited better molting synchronism than those in the S0 group. The astaxanthin content in the hepatopancreas from the shrimp in the groups supplemented with FDPE was significantly higher than that in the S0 group (p < 0.05) and increased as the FDPE content in the feed increased. The shrimp in the S10, S20, and S30 groups had a higher monounsaturated fatty acid (MUFA) content in the hepatopancreas than those in the S0 group. The sum of EPA and DHA in the muscles from the shrimp in the S0 group was lower than that in the other groups. These results indicate that the dietary inclusion of 10%–20% FDPE can be used as practical diets in L. vannamei farmed under a clear water system.
... The results are in agreement with the improved growth obtained in other sparids (Chebbaki et al., 2002), as well as in other fish species fed with diets including KM or astaxanthin (Christiansen & Torrissen, 1996;Hatlen et al., 2016;Izquierdo et al., 2005;Storebakken & Choubert, 1991;Torrissen, 1986;Zhang et al., 2012). ...
Article
There is a need to find sustainable alternatives to fishmeal (FM) and fish oil (FO) in feed formulations to support the continued growth of aquaculture. FM is mostly produced from mass‐caught pelagic species, but the production has been relatively constant for several decades. The aim of this study was to investigate the potential of dietary krill meal (KM) inclusion as a sustainable alternative to FM. In view of that, a feeding trial with gilthead seabream juveniles was conducted to evaluate whether dietary KM at 3%, 6% and 9% inclusion improves growth performance in comparison with a control diet. At the end of the study, fish in the 9% KM group showed significantly higher body weight (32.76 g) compared with fish fed the control diet (30.30 g). Moreover, FM replacement by 9% KM indicated a reduction in the accumulation of lipid droplets in the hepatocytes and around the pancreatic islets. In summary, this study suggests that FM can be reduced in diets for seabream without negatively affecting growth performance, when KM is added. On the contrary, KM enhances gilthead seabream growth and reduces lipid accumulation and damage of hepatocytes, which will open an interesting innovation line to completely replace FM by alternative terrestrial protein sources and the partial inclusion of KM.
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Atlantic salmon fed for 9.5 months, diets containing medium (MF, 32%) or high (HF; 39%) fat levels with fish meal (FM) or 10% of the FM protein replaced by full-fat soybean meal (FFSM) protein were analyzed by sensory profiling. No significant differences were observed in sensory characteristics. Fish fed HF diets had more total carcass lipid, larger abdominal and myoseptal fat deposits as determined by chemical analyses, visual evaluation, and computerized X-ray tomography. CIE-1976 redness and yellowness (a∗, b∗) were higher in salmon fed HF diets, suggesting that intestinal astaxanthin absorption was facilitated by higher dietary fat content. No significant effects of dietary protein source on the amount of astaxanthin in the muscle, visual color score, proximate composition, fat deposition or sensory characteristics were observed. FFSM may partly replace FM in diets for salmonids without compromising the sensory quality.
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The main objective of this field experiment was to investigate whether ration level affected utilization of carotenoids, macronutrients, and minerals in 1,300 g Atlantic salmon (Salmo salar) during rapid growth. Salmon fed ration levels of either 1.2% or 0.6% of biomass of a commercial diet supplemented with astaxanthin and canthaxanthin (37 and 39 mg kg−1, respectively) in two consecutive 6-day feeding periods had carotenoid digestibility coefficients of 11.8% and 32.1% at the high and low feed rations, respectively. Thus, low carotenoid digestibility, but good macronutrient digestibility, may explain poor pigmentation and good feed conversion in rapidly growing salmon. Practical implications are illustrated.
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The fish gustatory system provides the final sensory evaluation in the feeding process. Unlike other vertebrates, the gustatory system in fish may be divided into two distinct subsystems, oral and extraoral, both of them mediating behavioural responses to food items brought in contact with the fish. The abundance of taste buds is another peculiarity of the fish gustatory system. For many years, morphological and electrophysiological techniques dominated the studies of the fish gustatory system, and systematic investigations of fish taste preferences have only been performed during the last 10 years. In the present review, basic principles in the taste preferences of fish are formulated. Categories or types of taste substances are defined in accordance with their effects on fish feeding behaviour and further mediation by the oral or extraoral taste systems (incitants, suppressants, stimulants, deterrents, enhancers and indifferent substances). Information on taste preferences to different types of substances including classical taste substances, free amino acids, betaine, nucleotides, nucleosides, amines, sugars and other hydrocarbons, organic acids, alcohols and aldehydes, and their mixtures, is summarised. The threshold concentrations for taste substances are discussed, and the relationship between fish taste preferences with fish systematic position and fish ecology is evaluated. Fish taste preferences are highly species-specific, and the differences among fish species are apparent when comparing the width and composition of spectra for both the stimulants and the deterrents. What is evident is that there is a strong similarity in the taste preferences between geographically isolated fish populations of the same species, and that taste preferences are similar in males and females, although at the individual level, it may vary dramatically among conspecifics. What is noteworthy is that taste responses are more stable and invariable for highly palatable substances than for substances with a low level of palatability. Taste preferences as a function of pH is analysed. There is a good correspondence between development of the gustatory system in fish ontogeny and its ability to discriminate taste properties of food items. There is also a correspondence between oral and extraoral taste preferences for a given species; however, there is no correlation between smell and taste preferences. Taste preferences in fish show low plasticity (in relation to the diet), appear to be determined genetically and seem to be patroclinous. Fish feeding motivation and various environmental factors like water temperature and pollutants such as heavy metals and low pH water may shift fish taste preferences. Comparisons between bioassay and electrophysiological data show that palatability is not synonymous with excitability in the gustatory system. The chemical nature of stimulants and deterrents in various hydrobionts is outlined. The significance of basic knowledge in fish taste preferences for aquaculture and fisheries is emphasised.
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The prediction of carcass composition of Atlantic salmon (Salmo salar) using computerized tomography (CT) data was examined. 174 fish were included in the study, and prediction equations derived by multiple linear regression (MLR) and principal component regression (PCR) were evaluated. Validation of alternative equations was done according to the relative standard error of prediction (SEP/SD), relative mean prediction error (BIAS/SD) and the correlation between chemically determined and predicted values. The potential of the CT technique for accurate and fairly unbiased predictions of percentage fat and dry matter in salmon carcasses was clearly demonstrated. SEP/SD of about 0.40, BIAS/SD less than 0.10 percentage units and a correlation between observed and predicted values of 0.92 for both compositional components were obtained for the best prediction equations. A significant prediction of protein content was not obtained.The accuracy of predicting fat and dry matter content was improved by 38% by using CT data instead of the simple carcass measurements gutted body weight and condition factor.The impact of the results on a breeding program for quality-related traits in farmed Atlantic salmon is discussed.
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Experiment 1 compared the feed training success of two genetic strains of largemouth bass (LMB). ASF strain had 69% northern and 31% Florida LMB influence, while STATION strain had 35% northern and 65% Florida LMB influence. Both strains were fed ground fish flesh, freeze dried krill (FDK), a commercial moist pellet (BIODIET™) or a dry pellet with 70% krill meal (KM-70) as starter diets. In experiment 2, fish of 0.6, 0.9 and 1.4 g or 0.2, 0.4, 0.6, 0.9, and 1.4 g initial weight were feed trained using ground fish flesh or FDK, respectively. In both experiments, fish were weaned from the starter diets to a 2 mm trout pellet using gradual feed ingredient transition (GFIT) with diets containing 80, 60, 40, 20, and 0% ground fish or 70, 50, 30, 10, and 0% krill meal. Percent fish feeding on trout pellets (feeders) among ASF bass was 32% and among STATION fish 34% (P > 0.10). Average percent feeders were 58% and 53% starting bass on FDK and ground fish, respectively, compared to only 14% feeders for bass started on KM-70 and 8% feeders among bass started on BIODIET™ (P < 0.01). In experiment 2, percent feeders increased from 7 to 52% (P < 0.01) as initial fish weight increased from 0.2 to 1.4 g for fish started on FDK. Percent feeders increased from 59 to 88% (P < 0.01) as initial fish weight increased from 0.9 to 1.4 g among fish started on ground fish. Average percent feeders was 75% when ground fish was the starter diet compared to 41% for FDK with 0.9 to 1.4 g fish (P < 0.01).
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The objective of this study was to determine the effect of feed intake on the apparent digestibility coefficient (ADC) of astaxanthin including the major geometrical E/Z-isomers in Atlantic salmon (Salmo salar). Atlantic salmon (50 per pen, initial weight 2 kg) were kept in 125 m3 sea pens equipped with an excess feed collection system to monitor and quantify accurate feed intake, and subjected to three treatments in triplicate. All salmon were fed the same diet supplemented with 47 mg astaxanthin per kg. Two treatments were fed full or restricted rations corresponding to 100 or 40% of apparent satiation, respectively, with a switch in ration between two consecutive feeding periods (14 and 3 d, respectively), whereas the control treatment was fed to 100% of apparent satiation during both periods. The corresponding feed intakes were 0.45 and 0.16% of biomass for salmon fed 100% or 40% of apparent satiation, respectively. Faeces were collected by stripping at the end of each feeding period and ADCs of astaxanthin were determined by an indirect method using yttrium oxide (Y2O3) as an indigestible marker. Feed intake and astaxanthin ADC were negatively correlated (R2 = 0.64; p = 0.0001). Astaxanthin ADC was 1.5 times higher at the low compared to the high ration level (p < 0.05), but due to the low feed intake the total amount of digested astaxanthin was only about 50% of that in fish fed to satiation. The ADCs of the all-E and 13Z-isomers of astaxanthin were similar and considerably higher than for 9Z-astaxanthin (p < 0.05). The amount of digested astaxanthin/TGC (estimated thermal growth coefficient) decreased with increasing feed intake. Estimates of astaxanthin retention indicated that a higher feed intake cause a lower muscle concentration of astaxanthin compared to that obtained at low feed intakes due to the lower digestibility. Blood samples were collected at the end of the second feeding period to examine possible relationships between plasma carotenoids, feed intake and ADC. Salmon without faeces in the hindgut had a lower plasma astaxanthin concentration compared to salmon with faeces in the hindgut (p < 0.05). In conclusion, feed intake and astaxanthin ADC are negatively correlated, and may thus explain reductions in muscle retention of Atlantic salmon.
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Appetite and growth are suppressed for up to 30 days in Atlantic salmon smolts following transfer to seawater. This exceeds the period of osmoregulatory adaptation which is complete within 10 days. The restoration of feeding is independent of fish size. Daily food intake and the rate of evacuation of digesta in individual fish are independent of the duration of seawater adaptation but appeared to be positively related to water temperature. After the initial period of suppression of appetite, the temperature-specific growth rate of seawater-adapted smolts is not significantly different from that of freshwater-adapted smolts and temperature appeared to exert a far greater influence on growth in smolts than salinity. However, after 3 months post-transfer to seawater, there are differences in body composition which suggested metabolism favouring lipid deposition in freshwater-adapted post-smolts and protein deposition in seawater-adapted fish. Lipid deposition may be of adaptive value to fish overwintering in freshwater where food is more limited than in the sea.
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Feeding behavior is stimulated when fish are fed diets supplemented with Antarctic krill, Euphausia superba, meal. An electrophysiological method was used to study the olfactory and gustatory responses of sea bream, Pagrus major, to extracts of krill meal, non-muscle krill meal, and white fish meal. It was observed that the non-muscle krill meal elicited the strongest responses; non-muscle krill meal gave about 1.5 times and krill meal 1.2 times the response of the white fish meal. Amino acid analysis of the meals indicated that non-muscle krill meal was high in sarcosine, proline, glutamic acid, arginine and glucosamine. These amino acids are believed to be the cause of the gustatory and olfactory responses observed. Several diets containing these amino acids were tested for feeding stimulation in sea bream. It was shown that sea bream feeding was stimulated mainly by proline, glycine and glucosamine.
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Dietary (n-3) long-chain PUFA [(n-3) LCPUFA] ameliorate several metabolic risk factors for cardiovascular diseases, although the mechanisms of these beneficial effects are not fully understood. In this study, we compared the effects of dietary (n-3) LCPUFA, in the form of either fish oil (FO) or krill oil (KO) balanced for eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) content, with a control (C) diet containing no EPA and DHA and similar contents of oleic, linoleic, and alpha-linolenic acids, on ectopic fat and inflammation in Zucker rats, a model of obesity and related metabolic dysfunction. Diets were fed for 4 wk. Given the emerging evidence for an association between elevated endocannabinoid concentrations and metabolic syndrome, we also measured tissue endocannabinoid concentrations. In (n-3) LCPUFA-supplemented rats, liver triglycerides and the peritoneal macrophage response to an inflammatory stimulus were significantly lower than in rats fed the control diet, and heart triglycerides were lower, but only in KO-fed rats. These effects were associated with a lower concentration of the endocannabinoids, anandamide and 2-arachidonoylglycerol, in the visceral adipose tissue and of anandamide in the liver and heart, which, in turn, was associated with lower levels of arachidonic acid in membrane phospholipids, but not with higher activity of endocannabinoid-degrading enzymes. Our data suggest that the beneficial effects of a diet enriched with (n-3) LCPUFA are the result of changes in membrane fatty acid composition. The reduction of substrates for inflammatory molecules and endocannabinoids may account for the dampened inflammatory response and the physiological reequilibration of body fat deposition in obese rats.
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A study of the variables in techniques for alkaline hydrolysis of proteins and for chromatographic analysis of the products has led to a method for the accurate determination of tryptophan. Quantitative recoveries of tryptophan are obtained when proteins (1 to 5 mg) are hydrolyzed at 110° or 135° in 0.6 ml of 4.2 n NaOH containing 25 mg of starch. The hydrolysis is performed in polypropylene liners sealed inside glass tubes evacuated to below 50 µm of mercury. Ion exchange chromatography of tryptophan on Beckman PA-35 resin (column height 8 or 12 cm) has been accomplished in 30 to 50 min with pH 5.4 buffer, 0.21 n in Na⁺. The details in the procedure which make possible complete recovery of tryptophan include: (a) addition of the sample at pH 4.25 instead of at pH 2.2 in order to avoid loss of tryptophan in citrate buffer at acid pH; (b) the use of NaOH instead of Ba(OH)2 to avoid loss of tryptophan by adsorption on BaSO4 or BaCO3; (c) the inclusion of starch as the most effective antioxidant tested; and (d) chromatography with a buffer which separates tryptophan from Nε-(dl-2-amino-2-carboxyethyl)-l-lysine, which can be formed in significant quantities during alkaline hydrolysis. Molar calculations of protein concentrations are based on the results from analysis of an acid hydrolysate run parallel with the alkaline hydrolyses. Integral values (100 ± 3%) have been obtained for the expected number of tryptophan residues in tryptophyl-leucine, human serum albumin, porcine pepsin, sperm whale apomyoglobin, and in bovine α-chymotrypsin, trypsin, deoxyribonuclease, and serum albumin. Since carbohydrate does not interfere, the procedure is applicable to foods and has been tested on normal and opaque-2 maize meals and on wheat flours.
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Of the truly abundant polysaccharides in Nature, only chitin has yet to find utilization in large quantity. Chitin is the second most abundant natural biopolymer derived from exoskeletons of crustaceans and also from cell walls of fungi and insects. Chitin is a linear beta 1,4-linked polymer of N-acetyl-D-glucosamine (GlcNAc), whereas chitosan, a copolymer of GlcNAc (approximately 20%) and glucosamine (GlcN, 80%) residues, is a product derived from de-N-acetylation of chitin in the presence of hot alkali. Chitosan is, in fact, a collective name representing a family of de-N-acetylated chitins deacetylated to different degrees. Both chitin/chitosan and their modified derivatives find extensive applications in medicine, agriculture, food, and non-food industries as well. They have emerged as a new class of physiological materials of highly sophisticated functions. Their application versatility is a great challenge to the scientific community and to industry. All these are the result of their versatile biological activity, excellent biocompatibility, and complete biodegradability in combination with low toxicity. Commercial availability of high-purity forms of chitin/chitosan and the continuous appearance of new types of chitin/chitosan derivatives with more and more useful and specific properties have led to an unlimited R&D efforts on this most versatile amino polysaccharide, chitin to find new applications, which are necessary to realize its full potential. Incidentally, this too has become an environmental priority. No doubt, chitin is surely an undisputed biomolecule of great potential.
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A procedure is described for the testing of feeding response to dietary attractants by juvenile rainbow trout Oncorhynchus mykiss, The fish were maintained in a controlled environment with minimum visual and auditory stimulation. They were fed once daily following a scotoperiod of 12 h. Feed consumption was recorded over a period of 4 min at successive 1-min intervals. The feeding response could be assessed as early as 2 min after dispensing feed. The attractants examined to test the procedure were hydrolysates of krill, These were supplied to the control diet in liquid or dried form, as a component of the pellets or as a surface dressing. There was a positive response to the krill hydrolysate, which was greater when the attractant was applied to the surface of the pellets. Incidental to the development of the technique was the observation that the use of feeding attractants may modify feeding behavior to reduce feed wastage, The technique affords a rapid, sensitive, and repeatable method for evaluating feeding attractants.
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Freeze-dried krill (FDK) and krill meal were evaluated as dietary components during feed training of 1-g largemouth bass. Freeze-dried krill, dry pellets with 0, 18, 25, 36, 50, 54, and 75% krill meal, and a commercial moist pellet (BIODIET™) were compared as starter diets. Fish were fed the starter diets in training periods of 4 to 13 days. Percent fish feeding (feeders) on FDK ranged from 79 to 95% and was higher than percent feeders on other starter diets (P < 0.01). Percent feeders on FDK increased from 79 to 91% as FDK was fed from 4 to 13 days (P < 0.01). Percent feeders on dry pellets increased from 1 to 28% as krill meal levels in dry pellets increased from 0 to 75% (P < 0.01). Percent feeders on BIODIET™ ranged from 9 to 12%. After training, feeders on the starter diets were weaned to dry pellets. Gradual feed transition and gradual feed ingredient transition were compared as strategies to wean fish from FDK to dry pellets. Gradual feed transition is the progressive replacement of the starter diet with the final diet. Gradual feed ingredient transition replaces a particular starter diet by a sequence of feeds containing decreasing amounts of the main component of the starter diet until the final diet is reached. Among fish trained on FDK, 65% weaned to dry pellets after gradual feed ingredient transition compared with only 28% after gradual feed transition (P < 0.01). Fish trained on FDK for 4 days weaned better to dry pellets compared with fish fed FDK for 7 days or longer (P < 0.05). Fish trained once on FDK or fish trained on FDK that did not wean from FDK to dry pellets and were retrained on FDK were weaned to a dry trout pellet using gradual feed ingredient transition. Semi-moist/soft or dry/hard weaning diets with krill meal were evaluated. Percent feeders on trout pellets among fish trained once on FDK was 68 to 71% compared with 33 to 39% for bass trained twice on FDK (P < 0.01). Texture of the weaning diets did not affect percent feeders on trout pellets (P > 0.10).
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The objectives of this study were to determine which indicators were most responsive to suboptimal phosphorus intake in fingerling rainbow trout, and to observe the magnitude of these changes over time. Fish with an initial mean weight of 1.8 g were hand-fed one of five semipurified wheat-gluten based diets containing between 0.23%–1.16% dietary phosphorus, or a fish meal control diet (1.8% P) for 8 weeks. Phosphorus, calcium and magnesium concentrations in whole body, skin (with scales), and plasma were measured bi-weekly. Alkaline phosphatase activity was determined in plasma and in a crude intestinal homogenate. There was no correlation between dietary phosphorus concentration and body weight of rainbow trout. Of all tissues and metabolites examined, skin was the most responsive to differences in dietary phosphorus concentration. Dietary treatment had a significant effect on the concentrations of ash, phosphorus, calcium and magnesium in rainbow trout skin at weeks 4 and 8. Whole body ash, phosphorus, calcium, and magnesium concentrations were also highly responsive to graded levels of dietary phosphorus at week 8. Rainbow trout fed suboptimal phosphorus diets had significantly lower plasma phosphorus concentrations and alkaline phosphatase activity, and significantly higher whole body lipid than those fed adequate phosphorus diets. Alkaline phosphatase activity of the intestinal homogenate was not significantly correlated with dietary phosphorus intake.
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Methods of feed digestibility determination in fish were reviewed. The indicator method, using chromic oxide, was judged most suitable, but the best method of sampling faeces was uncertain. Rainbow trout (Salmo gairdneri, Richardson) were fed an experimental diet containing 1% chromic oxide. Faeces were collected by two stripping methods, and gut contents were obtained by dissection from five zones of the alimentary canal. Analyses of feed, faeces, and gut contents were made, and digestibility of protein, fat, carbohydrate, ash and gross energy calculated. It was concluded that absorption occurs in all parts of the alimentary tract, and that it is important to limit the stripping of faeces for analysis in digestibility studies to the hindmost part of rectum, i.e. from the ventral fin to anus.
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A simple and inexpensive method for determining daily feed intake of groups of fish in tanks is described. The method is based on the collection of waste feed from the effluent water and consists of an effective drainage system and a wire mesh collector. This technique is dependent upon the use of feed with good physical stability. The daily feed intake of fish in a tank is calculated by the difference between the amount fed and the amount of waste feed collected (corrected for leaching losses). The system can be combined with any type of feeding method in which sinking pellets are used. It allows accurate intake measurements for research purposes or can be used in commercial operations for adjusting feeding level without knowledge about biomass in the tank or water temperature. Use of the method has revealed large variations in daily feed intake of groups of Atlantic salmon fed continuously.
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Farmed Atlantic cod with a mean weight of 4.8 kg were maintained for 9 weeks in sea cages and fed diets where the dietary fishmeal component was substituted with increasing proportions (0%, 22%, 63% and 100%) of meal from Antarctic krill, Euphausia superba. Wild-caught cod were included in the study as external control. At termination of feeding, all fish were slaughtered and muscle pH was immediately recorded. The fish were then stored on ice for three days and assessed for muscle pH and objective (skin and fillet colour, and fillet texture) and subjective (sensory evaluation) quality criteria. Replacement of fishmeal with krillmeal in the diets resulted in the skin colour above and below the lateral line to be more red than the control group without krillmeal substitutions, even though this difference was not significant, and with more yellow hue. Additions of krillmeal increased the muscle whiteness and yellow hue compared with the control group and wild fish. There was no difference in red hue between the groups. Muscle pH, texture or sensory attributes were unaffected by dietary inclusion level of krillmeal. Wild-caught cod deviated in several aspects from the farmed cod. It is concluded that the replacement of fishmeal with Antarctic krillmeal in the diets two months before slaughter did not move the sensory attributes more towards wild fish.
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An increase in mortalities, due to the failure of some smolts to feed after transfer to sea cages, has been observed in many fish farms during the last 2 years. In the present study mortalities were as high as 9–5% and the majority of these appeared 7–9 weeks post-transfer. Comparisons of length-weight relationships between the initial group of smolts released in the cage and at 3-, 6- and 8-wcek intervals after transfer showed that a proportion of the fish had lost weight. The condition factor of individually measured fish also confirmed that with increasing time after transfer some fish were in a much poorer condition. The feeding of smolts after transfer was not related to their size. The fork length distribution of feeding and non-feeding fish showed that feeding fish were recruited from all size classes of the initial population. The lack of appetite in smolts after transfer was demonstrated by the reduced number of fish feeding and by the amount of food consumed. In the first week after transfer only 10% of the fish were feeding in the sea cage, increasing to 65% after 5 weeks. In the tanks (where there were no failed smolts) 95% of the smolts were feeding within 5 weeks after transfer, whereas in the sea cage it took 8 weeks before this figure was reached.
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Feeding trials were carried out to examine substances that could be used as supplements in low-protein/high-lipid diets to improve protein digestion of yellowtails (Seriola quinqueradiata) during winter. Dietary supplementation with synthetic or natural (krill and squid extracts) feeding stimulants (FS) improved feed intake and growth performance of yellowtails. Moreover, the apparent protein digestibility (APD) and pepsin, trypsin and chymotrypsin secretions in fish fed diets supplemented with the different FS were superior to those in fish fed the control diet. These findings suggest that the dietary inclusion of either synthetic or natural FS is a potential tool for improving protein digestion at low water temperatures, and may provide a promising solution for the winter growth retardation experienced in yellowtail culture.
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Abstract— The main objective of this study was to determine the effect of different levels of krill meal (KM) as a feed attractant in juvenile Nile tilapia fed soybean (SBM) diets on growth performance, feed utilization, and body composition. Fish of an initial average weight 0.8 × 0.01g were stocked in 18 glass aquaria (80 L each) at a rate of 25 fish per aquarium. Fish meal (FM 20% of the diet) was used as the sole source of animal protein in the control (Diet 1). Diets 2 to 6 had (SBM) protein with various levels of krill meal (0.0,1.5,3.0,4.5, and 6.0%, diets 2-6 respectively). Test diets were fed to satiation to triplicate groups of Nile tilapia four times daily for 20 wk. Fish fed krill meal supplemented diets had significantly (P < 0.05) better growth performance compared with fish fed the unsupplemented and FM control diets. The krill meal increased growth of Nile tilapia by 31.9% compared to control diets (average Anal wet weight, 14.15 × 0.95 g and 10.72 × 0.2 g, respectively). Moreover, weight gains were not significantly different for fish fed diets with different levels of krill meal. Feed utilization parameters such as feed intake, feed conversion ratio, protein efficiency ratio differed significantly for fish fed krill meal diets compared with control. Digestibility of nutrient and energy of diets increased with increasing levels of krii meal. The incorporation of krill meal in diets significantly affected the protein, fat, ash, and energy of whole body composition. These results suggest that supplementation of krill meal at 1.5% in the diets of Nile tilapia as attractant or stimulant may lead to increased feed intake, growth performance, and feed utilization. Soybean meal can completely replace fishmeal in diets for juvenile tilapia.
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A total of six isoprotein and isolipid diets for Atlantic salmon, Salmo salar L., were prepared substituting from 0 to 100% of fish meal protein (0–68% of diet by dry weight) with meal from Antarctic krill (Euphausia superba). The feed produced from high inclusion levels of krill meal had lower ability to absorb lipid during vacuum coating than fish meal. Both amino acid and fatty acid compositions of the diets were fairly similar. The experiment commenced using salmon averaging 500 g and ended at a mean weight of 1500–1800 g (140 days of feeding). Moderate amounts of krill meal (20–60% of krill protein) in the diets increased growth during the first 71 days of feeding compared with the fish meal control, while no growth difference was observed during the last 69 days of feeding. This may, at least in parts, be explained by a feed-attractant function of the krill meal. Muscle dry weight and lipid concentrations were unaffected by the diet. Feed conversion rate increased with high levels of krill meal in the diets (e.g. for the last period from 0.94 in the 0% diet to 1.26 in the 100% diet). This indicates that the fish were able to compensate by eating more to maintain growth. The apparent digestibility coefficients of dry matter and protein were not influenced by diet, but both faecal moisture and lipid had a tendency to increase at the highest inclusion level (all protein from krill meal). This may be related to chitin in the krill diet that is known to decrease lipid absorption and induce diarrhoea (increased water content in faeces). Chitin was not utilized to any major extent. Welfare parameters such as blood haemoglobin, red blood cell counts, plasma protein, cholesterol, triacylglycerols and glucose levels were unaffected by diets. Clinical indicators of cellular damage (alanine aminotransferase and aspartate aminotransferase) were similar indicating no diet-induced tissue damage during the trial.
Article
The effects of partial replacement of fish meal (FM) with meal made from northern krill (Thysanoessa inermis), Antarctic krill (Euphausia superba) or Arctic amphipod (Themsto libellula) as protein source in the diets for Atlantic salmon (Salmo salar L.) and Atlantic halibut (Hippoglossus hippoglossus L.) on growth, feed conversion, macro-nutrient utilization, muscle chemical composition and fish welfare were studied. Six experimental diets were prepared using a low-temperature FM diet as control. The other diets included northern krill where 20, 40 or 60% of the dietary FM protein was replaced with protein from northern krill, and two diets where the FM protein was replaced with protein from Antarctic krill or Arctic amphipod at 40% protein replacement level. All diets were iso-nitrogenous and iso-caloric. Atlantic salmon grew from 410 g to approximately 1500 g during the 160 day experiment, and Atlantic halibut grew from 345 g to 500–600 g during the 150 day experiment. Inclusion of krill in the diets enhanced specific growth rate in salmon, especially during the first 100 days (P < 0.01), and in a dose–response manner in halibut for over the 150 day feeding period (P < 0.05). Feed conversion ratio did not differ between dietary treatments, and no difference was found in dry matter digestibility, protein digestibility and fish muscle composition. Good growth rates, blood parameters within normal ranges and low mortalities in all experimental treatments indicted that fish health was not affected either Atlantic salmon or Atlantic halibut fed the various zooplankton diets.
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A method for identifying and confirming the efficacy of feeding stimulants and deterrents is described. Feeding studies carried out using Atlantic salmon, Salmo salar L., have shown that the addition of squid extract as a stimulant to feeds may lead to modification of feed intake, and may ameliorate the negative effects of unpalatability when fish are presented with medicated diets.
Article
This study examined the long-term effects of a feeding deterrent, oxytetracycline (OTC), and a feeding stimulant, squid extract, on feed intake, growth and dry matter (DM) digestibility in Atlantic salmon, Salmo salar L. Fish were fed one of four diets for 9 weeks: 1. commercial feed formulation (basic); 2. BM (basic plus 20 g kg−1 OTC); 3. BMS (BM plus 10 g kg−1 squid extract); 4. BS (basic plus 10 g kg−1 squid extract). OTC initially reduced the palatability of the feed, but the fish seemed to become accustomed to the taste of OTC over time. Addition of squid extract to the medicated feed (BMS) seemed to mask the aversive taste of OTC, but the effect on feed consumption was of short duration. Addition of squid extract to the basic feed (BS) had no significant effect on feed intake, growth or feed digestibility. The growth of fish fed medicated diets (BM and BMS) was depressed, probably as a consequence of reduced feed digestibility. The two additives led only to temporary changes in feed acceptability, but both growth and DM digestibility were affected by OTC. Thus, we suggest that short-term studies may be inadequate to test whether deterrent or stimulant properties of feed ingredients are of practical importance in feed formulation.
Article
The main objective of the present study was to evaluate the effect of using three different crustacean meals (Tysanoessa inermis, Euphausia superba, Themisto libellula) on product quality of Atlantic salmon (Salmo salar L.). In order to do this, a total of six iso-protein, iso-lipid and iso-carotenoid diets were prepared. Two experimental diet series were prepared. In the first series, a control feed (K0) was compared with diets where 20%, 40% and 60% of the fish meal protein were replaced with protein from Northern krill T. inermis (K20, K40 and K60, respectively). In the second series, control feed (K0) was compared with diets where 40% of the dietary protein was replaced by protein from T. inermis (K40), Antarctic krill E. superba (AK40) and the Arctic amphipod T. libellula (AMP40). The salmon groups were fed the various diets for 160 days and the average weight of the fish increased from 410 g to around 1500 g. Fish given diets containing krill displayed a general better growth compared with the ones given pure fish meal diet. Replacing fish meal protein with protein from the crustacean sources had, in general, only minor effects on the flesh quality measured both by technical and sensory methods. However, some significant effects were noted. Postmortem muscle pH was generally lower (P < 0.05), for K20, K40, AMP40 in fish fed crustacean diets compared with those receiving the control diet. Increasing the replacement level of non-fish meal protein from Northern krill (K20, K60) significantly reduced the rigor contraction. Fish given K20 had a slightly firmer meat texture, measured as resistance to post-rigor compression, especially when compared with K60 (P < 0.05). Fish from the K20 and AMP40 groups had a deeper red flesh coloration [both light reflection (A*-value and chroma) and flesh astaxanthin concentration] than fish fed K0 and higher inclusions of krill meal. The groups with the highest astaxanthin flesh content also showed the best growth and had the highest feed intake. Finally, a sensory panel analysis differed slightly from the technical measurements in that K0, rather than K20 was given the highest score for hardness and colour. In comparison with K0, AK40 got the lowest salty taste and hardness scores from the panellists relative to the control fish (P < 0.05). Despite minor effects on the present quality measures, it is concluded that meal from three different crustacean species can successfully replace fish meal up to 60% with Northern krill, and 40% of Antarctic krill and amphipod meal of dietary proteins.
Article
The aim of this study was to identify the effect of growth, size and season on the flesh quality of Atlantic salmon (Salmo salar). Following smoltification, two groups of size sorted 0+ and 1+ smolts (four treatment groups in all) were measured for body weight and length in January, June and October 2002. The fish were stored on ice for 4 days before filleted and samples taken for flesh colour, fat/dry content, end pH, gaping score and texture shear force. Large fish upon smoltification grew faster during the first year at sea, while smaller fish grew faster during the second year at sea, resulting in similar weight at slaughter. Season showed the main influence on quality, where fish slaughtered in October had harder texture, higher fat content and redder colour compared to previous samples (P < 0.05). There were only minor differences between the fish slaughtered in January and June (P > 0.15). No significant differences (P > 0.05) were detected as an effect of size or smoltification age when effects of season were accounted for in the statistical model. We conclude that the observed variation in quality was an effect of changes in growth with season. We recommend that actions aimed to halter growth prior to slaughter could be an effective control measure to reduce seasonal quality variations.
Article
Feed intake, growth and ionoregulation of Atlantic salmon (Salmo salar L.) were studied in fish fed diets either with or without squid extract supplementation in combination with transfer from fresh water to seawater (SW) at different times during parr–smolt transformation (10 April, 3 May and 19 June). Water temperature was held at approximately 8 °C. All groups of fish showed a temporary depression in feeding and growth after SW transfer. The depression was most severe in fish transferred in April, intermediate in fish transferred in May and shortest in fish transferred in June. Nevertheless, squid extract resulted in increased feeding and growth, especially in fish transferred to SW in June, providing evidence that squid extract contains substances that serve as feeding stimulants. The results indicate that there may be a potential to improve SW performance of salmon by adding squid extract to feed. The results also indicate that Atlantic salmon may be transferred to SW over a relatively long period during spring, but to minimise the duration of appetite depression, late transfer may be preferable. Individual feeding rates following short-time SW exposure were not correlated with plasma chloride concentrations in any of the groups, indicating that appetite suppression is not a direct result of osmo-ionoregulatory failure.
Article
The aim of the study was to investigate how the replacement of LT-fish meal by a 3.5:1 mixture of an experimentally produced partially deshelled krill meal (PDKM) and a pea protein concentrate (PPC) affected growth rate, digestibility of main nutrients and minerals, fluoride accumulation and histology in Atlantic salmon (Salmo salar). Five extruded diets were fed to salmon with an average weight of 546 g, distributed into 15 tanks equipped with flow through sea water. During extrusion, increased krill meal resulted in increased lipid content in the feed mash and subsequently decreased pellet expansion and decreased pellet water stability. The salmon had an optimum growth rate with a PDKM/PPC inclusion of 400 g kg− 1. Starch digestibility decreased and lipid digestibility increased with increasing PDKM/PPC inclusion. Fluoride in faeces increased linearly with increasing dietary fluoride levels. Plasma cholesterol decreased with increased PDKM/PPC inclusion, whereas no major differences were seen for triglycerides, free fatty acids, glucose, or bile acids. Fish fed increased dietary PDKM/PPC showed an increased prevalence of mild to moderate nephrosis.
Article
The aim of this study was to non-invasively determine fat and pigment concentrations in salmon muscle based on visible and near infrared (VIS/NIR) spectroscopy measurements of live/whole fish and fillets, and by means of digital photography (DP) of fillets. The fish used were two populations of farmed Atlantic salmon (Salmo salar L.) consisting of 46 salmon averaging 0.7 kg (range 0.17–1.7 kg, Group S) and 30 salmon averaging 2.3 kg (range 1.4–4.1 kg, Group L). Chemical analyses (fat and pigment content) and computerized tomography, CT (fat content) were used as reference methods. Group L was analysed in the live state (VIS/ NIR), after gutting (VIS/NIR and CT), and as fillets (VIS/NIR and DP). Group S was analysed in the gutted state (VIS/NIR) and as fillets (VIS/NIR and DP). VIS spectroscopy predictions of pigment in whole salmon from Group S were obtained with a root mean square error of prediction (RMSEP) of 0.9 mg kg − 1 astaxanthin, and a correlation between VIS spectroscopy predicted and chemically measured pigment of r = 0.85 (p b 0.0001). The fat concentration was determined by the NIR spectroscopy in live fish with RMSEP = 1.0 fat% unit, and a correlation with chemical reference values of r = 0.94 (p b 0.0001). Fat predictions from NIR spectroscopy correlated also well with predictions from CT analyses, r = 0.95 (p b 0.0001). VIS spectroscopy and DP were equally well suited to determine pigment concentrations in salmon fillets, with prediction errors of only 0.4 mg kg − 1 astaxanthin, and a correlation with chemically determined pigment of r = 0.92 (p b 0.0001). The results obtained in the present study are the first to demonstrate successful non-invasive pigment predictions in whole salmon using VIS/NIR spectroscopy, and the possibility for simultaneous, rapid and non-destructive quantification of fat and pigment concentrations.
Article
Atlantic salmon, Salmo salar, were fed four levels of dietary fat (256, 308, 346 and 389 g kg−1 of diet) for 138 days, with the purpose of studying quality characteristics in raw and smoked fish fillets. Dietary fat levels up to 346 g kg−1 resulted in increased fat content of the raw fillets. The dietary fat levels had a less systematic effect on perceived fatness of the smoked fillets and caused a trend towards better odour and flavour. The fat content of raw fillets was significantly (P≤ 0.05) correlated to lower smoke odour, greater rancid flavour, fatness, and a yellower hue of the smoked fillets. Astaxanthin levels of the raw fillets varied between 6 and 11 mg kg−1 of fillet and were significantly (P≤ 0.05) correlated with greater intensity of smoke odour, lower off-odour, and less whiteness, greater colour intensity and a redder hue of the smoked fish. It is proposed that salmon fillets can be graded according to weight, fat content and colour values prior to smoking to obtain more standardized quality characteristics of the final product after processing.
Article
Sensory-evaluated hardness of smoked Atlantic salmon (Salmo salar L.) was correlated with various response variables from instrumental texture analysis of raw or smoked cutlets (25 mm thick) using 4 different probes: 12.5- and 23- mm-dia cylinders, a Warner-Bratzler blade, and a 25.4-mm-dia sphere. Sensory hardness correlated significantly with analyses using all mechanical methods, but it was most accurately predicted by the 12.5-mm-dia cylinder in raw salmon (force and area at 90% compression; r = 0.70, P < 0.0001), and by the 23-mm-dia cylinder in smoked salmon (force at 90% compression and the area from origo to the 1st significant break; r = 0.63 to 0.64, P < 0.0001).
Article
The marine crustacean krill (order Euphausiacea) has not been a traditional food in the human diet. Public acceptance of krill for human consumption will depend partly on its nutritive value. The aim of this article is to assess the nutritive value and potential health benefits of krill, an abundant food source with high nutritional value and a variety of compounds relevant to human health. Krill is a rich source of high-quality protein, with the advantage over other animal proteins of being low in fat and a rich source of omega-3 fatty acids. Antioxidant levels in krill are higher than in fish, suggesting benefits against oxidative damage. Finally, the waste generated by the processing of krill into edible products can be developed into value-added products.
Article
In the wild, parr of Atlantic salmon, Salmo salar L., normally show aggressive, territorial behaviour, whereas smolts form non-aggressive schools. In order to study changes in feed acquisition in hatchery reared Atlantic salmon smolts, individual feed intake and hypoosmoregulatory capacity were monitored during smolting and seawater acclimation, using X-radiography and 24 h seawater challenge tests. In both the seawater transferred fish and the control fish remaining in freshwater, weight-specific feed intake and specific growth rates increased during the spring. One week after seawater transfer, there was a temporary decrease in feed intake and an increase in the number of non-feeding salmon. Four weeks after transfer, the fish had compensated for the growth suppression, and there were no differences in weight, feed intake and growth rates. Feed intake was weakly correlated with hypoosmoregulatory capacity, both in freshwater and after seawater transfer. There were no changes in the coefficient of variation in feed intake during smolting and seawater acclimation, and there was no relationship between weight, feed intake or growth in the freshwater phase and the subsequent feed intake in seawater. The study indicated that the decrease in feed intake after seawater transfer may not be explained as a behavioural change in social interactions, but rather as a transient acclimation to seawater.
Article
Acclimation of Atlantic salmon (Salmo salar L.) smolts to sea water at low temperatures has been studied in groups of fish transferred directly from fresh water (6°C) to sea water at 2°, 4° and 6°C. Temperatures were maintained until day 54 when water temperature was switched to ambient (approximately 7°C) in all groups. The following parameters were monitored on days 8, 29, 50 and 72 after transfer: plasma osmolality and electrolyte concentrations, gill Na+–K+ ATPase activity, individual feed intake and growth. By the end of the experiment cumulative mortality was 18.1%, 12.5% and 5.0% in the groups of smolt transferred to sea water at 2°, 4° and 6°C, respectively. Plasma osmolality and the concentrations of chloride and sodium were inversely related to water temperature, but values for all groups (osmolality: 324–344 mosM kg−1; [Cl−]: 147–162 mM; [Na+]: 164–171 mM) fell within the range considered to be normal for seawater-acclimated salmonids. Gill Na+–K+ ATPase activity increased in all groups of fish following transfer to sea water, the rate of increase being correlated with water temperature. Feed intake and growth were very low for the first few weeks following the transfer of the fish from fresh to sea water, but increased thereafter. On day 50 the percentages of nonfeeding fish were 23%, 5% and 1% in the groups of smolt transferred to sea water at 2°, 4° and 6°C, respectively. Accordingly, highest rates of feed intake and growth were recorded for the fish held at the highest temperature. The results indicate that Atlantic salmon smolts are more tolerant of low seawater temperatures than earlier believed, and the negative effects of low temperature upon feeding and growth do not seem to be directly related to an impaired ability of the fish to hypoosmoregulate.
Article
This study was performed to evaluate the effect on fish growth performance by replacing fish meal with a blend of vegetable protein sources. Atlantic salmon were fed eight diets where the percentage of protein from fish meal to vegetable protein varied from 85.1%, 68.6%, 51.9% to 34.7%, respectively. The experimental groups were fed in triplicate for 11 weeks, increasing fish weight from about 128 g at start to 450 g in the end. The vegetable protein blend was composed of full-fat soybean meal and corn gluten meal at a 1:2 ratio. Four percentages of fish meal to vegetable protein blend were used in four diets using LT fish meal or medium quality fish meal. All diets were extruded and balanced to be equal in gross energy, crude protein, lipid, carbohydrate, lysine and phosphorus. A significant positive linear correlation between fish meal inclusion and fish growth, feed efficiency and digestibility of protein, lipid and energy was observed in diets containing high quality fish meal. The difference in growth corresponded to a difference in final weight of 13.3% comparing diets with 85.1% and 34.7% fish meal protein. A significant positive correlation between fish meal inclusion and growth and feed efficiency was also observed in diets containing medium quality fish meal. No difference in growth was found between treatments containing the two fish meal qualities (P=0.06). However, feed intake was significantly higher and feed efficiency lower for fish fed medium quality compared to high quality fish meal. Protein, amino acid and energy digestibilities were reduced with increased dietary vegetable protein blend inclusion. Protein efficiency ratio (PER) and net protein value (NPV) were also positively linearly correlated to dietary fish meal percentage, and significant reductions in PER and NPV of 10% were observed as dietary fish meal protein decreased from 51.9% to 34.7%. NPV were in average 6.5% higher in fish fed diets containing high quality fish meal compared to medium quality fish meal. No difference in chemical composition of the fish was observed for any of the diets. A difference in performance was observed for fish meal quality and vegetable blend. The effect of reduced fish meal quality could be explained by reduced digestibility of protein and amino acids. This was compensated by a similar increase in feed intake, reducing NPV for medium quality fish meal. Increased inclusion of vegetable blend affected growth performance and reduced digestibility, but was not compensated by increased feed intake.
Article
Fifty adult 1–8 kg Atlantic halibut were subjected to computerised X-ray tomography (CT) to evaluate CT as a non-destructive measure of relative size of fat deposits and lean tissue, and to estimate fat content. Preliminary examinations of dissected tissues showed a clear separation and no overlap in CT values for pure fat deposits and lean tissue. The estimated proportions of fat deposits and lean tissue (area%) varied significantly between five CT-scans collected in the longitudinal direction of the halibut, and the scan across the longitudinal mid-line was considered to be the most relevant for the whole halibut fillet. Fat percentage of a cutlet determined after ethyl acetate extraction correlated well (r2=0.85, P<0.001) with CT measured fat deposit area (%), which shows that CT can be used as a non-destructive method to predict fat content in halibut.
Article
This study investigated long-term effects on nutrient digestibility and protein and lipid growth of soy protein and lipid levels used in commercial grower diets for Atlantic salmon. Two series of extruded diets were formulated to contain either 45% protein and 32% lipid (medium fat) or 40% protein and 39% lipid (high fat). Each series consisted of six diets in which a soy protein source partially replaced low-temperature (LT) dried fish meal (FM): FM only (control), soy protein concentrate (SPC, 30% of crude protein, CP); SPC added 0.2% dl-methionine (30% of CP, SPC+met); dehulled, defatted soybean meal (HP-SBM, 20% of CP); full-fat (FF) SBM (10% of CP), and; defatted SBM (10% of CP). Each diet was fed to triplicate groups of 0.56-kg salmon kept in sea pens. The experiment lasted 235 days, during which the salmon reached 2.5 to 2.8 kg. Growth was slower in the FM-control and HP-SBM treatments than in the other treatments. The HP-SBM diet induced enteritis in the distal intestine of the salmon and, at day 215, the apparent digestibilities of nitrogen, lipid and energy were lower in the HP-SBM treatments than in all other treatments. Except a slightly reduced muscle protein concentration in the HP-SBM treatment, no effects of dietary soy were detected on final body composition. Salmon fed the high-fat diets reached on average 122 g higher final weight than those fed the medium-fat diets; however, 91 g of this was in the form of lipid, and corresponded with enlarged deposits of visible fat.
Article
This article reviews the nutritional value of different species of krill and the results of feeding experiments with krill for salmonids. Krill is a protein-rich and moderately fatty feedstuff. The nutritional value of protein from krill is high. The nutritional value of the lipids depends on whether the krill specimen utilizes glycerols or waxes as energy stores. Krill is a good source for essential fatty acids, and contains carotenoids. It is considered to be a palatable feed ingredient. Krill contains much ash and is bulky due to the chitin-containing carapace. Feeding experiments with salmonids have shown that krill can be successfully utilized as a source of protein, energy and flesh-pigmenting carotenoids. In addition, although the fluoride content of krill is high, this mineral does not accumulate in the edible portions of the fish.
Article
Relevance of fat content and fillet shape of Atlantic salmon for quality and yield during smoking processing was investigated. Fat content significantly influenced quality of raw and smoked products, although the interactions varied according to the raw material used and smoking temperature. In raw and smoked fillets, increasing fat content coincided with increasing L* and b*-values and decreasing fat holding capacity. In smoked salmon, fat content also correlated positively to the a*-value, smoke-intensity-/wood-fire flavor and fatty texture, and negatively to water holding capacity and shear-force. Weight loss during salting and smoking decreased with increasing fat content, and voluminous shaped fillets gave higher yield than slim fillets.
Article
We designed a general-purpose computer program, Osiris, for the display, manipulation, and analysis of digital medical images. The program offers an intuitive, window-based interface with direct access to generic tools. Characterized by user-friendliness, portability, and extensibility, Osiris is compatible with both Unix-based and Macintosh-based platforms. It is readily modified and can be used to develop new tools. It is able to monitor the entries made during a work session and thus provide data on its use. Osiris and its source code are being distributed, free of charge, to universities and research groups around the world.
Article
We studied the effects of increasing dietary concentrations of each of the following amino acids on growth, feed intake, feed conversion ratio and composition of gain in rainbow trout in six dose-response experiments: L-lysine, L-tryptophan, L-histidine, L-valine, L-leucine and L-isoleucine. Semipurified diets containing 20.1 MJ digestible energy/kg dry matter, with wheat gluten and crystalline amino acids as sole sources of amino acids, were fed to rainbow trout [initial mean body weight (BW) 40-51 g, depending on the amino acid studied]. In one series of 24 diets, lysine concentration ranged from 4.5 to 58.0 g/kg dry matter; in five further series of 12 diets each, concentrations ranged from (in g/kg dry matter): tryptophan, 1.3 to 5.6; histidine, 2.6 to 13.5; valine, 6.2 to 34.2; leucine, 10.0 to 42.0 and isoleucine, 5.0 to 15.3. Each diet was fed to a group of 20 fish for 53-64 d, depending on the amino acid studied. Dry matter intake, weight gain, feed conversion ratio, protein concentration of gain and total protein deposition followed exponential response functions. To achieve 95% of the maximum protein deposition, dietary concentrations of 27.7 g lysine, 2.0 g tryptophan, 5.8 g histidine, 15.7 g valine, 13.6 g leucine and 13.7 g isoleucine/kg dry matter were required. Maintenance requirements, estimated from exponential functions for protein deposition, were [in mg/(100 g BW.d)]: lysine, 1.93; tryptophan, 1.05; histidine, 1.07; valine, 2.92; leucine, 8.26 and isoleucine, 0.91. This corresponds to 4% of the requirement for protein deposition for lysine and isoleucine but 32% for leucine, with the other amino acids being intermediate. Therefore, different dietary amino acid requirement patterns were derived from protein deposition data depending on the chosen level of performance.