Krill Meal Research Articles

Extraction of high‐quality Antarctic krill (Euphausia Superba) oil using low‐temperature continuous phase‐transition extraction equipment

AbstractThe aim of this study was to explore a processing method for efficient extraction of high‐quality krill oil (KO) using a low‐temperature continuous phase‐transition extraction equipment (LCPE). The efficiency of lipid extraction and quality of KO and defatted krill meal (DKM) by LCPE were compared with those of supercritical CO2 and n‐hexane extraction. Results showed that compared to other methods, extraction using LCPE had the highest lipid yield (21.72 ± 0.34%), bioactive substances, and dimethyl sulfide (3.12 ± 0.09 mg/kg), the lowest oxidative deterioration. Moreover, compared to other methods, DKM extracted by LCPE had the lowest fat (<2%), the highest protein (>60%), and the best oxidative stability. These benefits would ensure easier transportation and better long‐term storage, allowing for its application on distant‐ocean fishing vessels. Therefore, LCPE is a method that allows for efficient extraction of high‐quality KO.

Impact of Krill Meal on Enhancing Skin Mucosal Health and Reducing Sea Lice in Atlantic Salmon

The salmon industry’s challenges with skin health and sea lice emphasize the necessity for fish-sensitive measures like functional nutrition to boost skin health and fish welfare. The present study investigated the efficacy of krill meal (KM) for skin mucosal health and sea lice in Atlantic salmon (170 g). Following an 8-week feeding period, in duplicate tanks, on test diets (8% KM, 12% KM, and the control group), fish underwent a 2-week sea lice challenge, reaching 350 g. The 8% KM diet group had thicker skin epithelium (72.3 µ) compared to the 12% KM (51.3 µ) and the control groups (43.8 µ) after 8 weeks. Additionally, skin mucosal health parameters—cell size (208 µ2), cell density (25.2%), and defense activity (1.19)—were significantly enhanced with 8% KM compared to the 12% KM (cell size: 162.3 µ2, cell density: 17%, defense activity: 1.04) and the control group (cell size: 173.5 µ2, cell density: 16.4%, defense activity: 0.93). Furthermore, fish fed with 8% KM significantly showed the lowest sea lice, along with reduced cell size while maintaining a high abundance of skin mucous cells, suggesting efficient turnover of the skin mucosal layer to remove sea lice effectively. This study highlights the potential of KM as part of a functional nutrition strategy to enhance skin mucosal health and mitigate sea lice challenges.

Effects of boiling, centrifuging and drying methods on bioactive compounds in Antarctic krill meal

SummaryBoiling, centrifuging and various drying techniques (vacuum freeze‐drying (VFD), vacuum drying (VD), hot‐air drying (HAD) and microwave drying (MWD)) were assessed for their impact on bioactive compounds in Antarctic krill meal. A comparison between the raw and boiling groups revealed a significant degradation and isomerisation of astaxanthin, accompanied by a 1.25‐fold and 1.32‐fold increase in saturated (SFAs) and monounsaturated fatty acids (MUFAs), respectively. Drying was the primary factor responsible for the reduction in phospholipids, α‐tocopherol and polyunsaturated fatty acid (PUFAs), in combination with the increase in thiobarbituric acid‐reactive substances. For different drying methods, it was found that HAD induced severe lipid oxidation. In contrast, the VFD, VD and MWD improved lipid quality, reducing thiobarbituric acid‐reactive substances (TBARS) by 13–22% and increasing phospholipids by 1.08–1.11 times compared to HAD. VD preserved higher levels of bioactive compounds. PLS‐DA analysis identified 13‐cis‐astaxanthin, α‐tocopherol and eleven fatty acids as key indicators for Antarctic krill meal.

Dietary fishmeal substitution with Antarctic krill meal improves the growth performance, lipid metabolism, and health status of oriental river prawn (Macrobrachium nipponense)

Aims to assess the effects of dietary inclusion of Antarctic krill meal (KM), five experimental diets supplemented with graded levels of KM (0 %, FM; 5 %, KM5; 10 %, KM10; 15 %, KM15; 20 %, KM20; 0 %, 13.3 %, 26.7 %, 40.0 %, and 56.7 % replacement fishmeal levels, respectively), were prepared to feed oriental river prawn (Macrobrachium nipponense) (0.20 ± 0.01 g) for 8 weeks. The results revealed significant improvements in weight gain rate (WGR), specific growth rate (SGR), feed conversion rate (FCR), and protein efficiency ratio (PER) at the inclusion of 5 %-20 % KM (P < 0.05). In the KM10 and KM15 groups, the concentrations of hemolymph total protein (TP), albumin (ALB), triglycerides (TG), high-density lipoprotein (HDL), and hepatopancreatic glutathione (GSH) were observed to be significantly higher compared to the FM group (P < 0.05). Conversely, the contents of hepatopancreatic malondialdehyde (MDA), total nitric oxide synthase (TNOS), and inducible nitric oxide synthase (iNOS) were significantly lower in the KM10 and KM15 groups compared to the FM group (P < 0.05). The mRNA expression levels of dorsal protein (dorsal), heat shock protein 60 (hsp60), and myeloid differentiation factor 88 (myd88) in the hepatopancreas in the KM10 group exhibited the lowest level. Additionally, compared to the FM group, the expression levels of fatty acid synthase (fas) and acetyl CoA carboxylase (acc) were significantly upregulated (P < 0.05), while the acyl CoA bindingprotein (acbp), carnitine palmitoyltransferase I (cpt I), and scavenger receptor B I (sr-b I) were significantly downregulated in the KM10 group (P < 0.05). In addition, the results of histopathology sections showed that 5–15 % KM could improve the health status of hepatopancreas and was a safe alternative to fishmeal. Overall, the optimal KM inclusion level in feed was 12.96 % (substituting for 34.60 % fishmeal) based on the quadratic fitting curve calculations of WGR and SGR.

Prevention of the Quality Degradation of Antarctic Krill (Euphausia superba) Meal through Two-Stage Drying.

To achieve a krill meal of high quality, a two-stage drying involving hot-air drying and vacuum drying was investigated. Five experimental groups were established according to the different drying conditions in the second stage, including 95 °C and 101 kPa, 95 °C and 60 kPa, 75 °C and 101 kPa, 75 °C and 60 kPa, and 75 °C and 20 kPa. The results showed that reducing the drying temperature and vacuum pressure in the second stage had a significant impact on the drying characteristics, sensory quality, and bioactive compounds of krill meal. Among all five groups, the drying condition of 75 °C and 60 kPa maintained a high drying rate while preserving a phospholipid content of 30.01 mg/kg and an astaxanthin content of 37.41 mg/kg. It also effectively reduced the isomerization of astaxanthin and the oxidation of unsaturated fatty acids. These results suggested that the two-stage drying method may contribute to the production of high-quality krill meal.

The Minimum Dietary Level and Mix Ratio of Krill Meal and Fish Meal to Elicit Feed Intake and Growth Performance in Juvenile Penaeus vannamei

Shrimp feeds depend on high levels of digestible protein and essential amino acids, which can be sourced from various commercially available feed ingredients. Marine proteins can be used to partially fulfill the requirements of these and other important nutrients. Their utilization is further influenced by their palatability and growth-promoting effect. However, marine ingredients can significantly drive costs in feed formulation depending on the type and dietary inclusion level. This study aimed to determine the minimum dietary level of fish meal (FML) and krill meal (KRM) and their mix ratio to elicit feed intake and growth performance in juvenile Penaeus vannamei. Ten diets were formulated with graded FML (90, 60, 30 g kg−1) in combination with 15, 30, and 45 g kg−1 KRM and a control diet with 120 g kg−1 FML. Shrimp (1.28 ± 0.08 g body weight, BW) were stocked in seventy 1-m3 tanks (135 animals m−2), and after 88 days, their growth performance was determined. Feed preference was assessed through two-by-two comparisons in twenty 0.5 m3 tanks over four weeks. No significant differences in survival (93.9 ± 4.5%), gained yield (1235 ± 92 g m−2), and feed conversion ratio (1.47 ± 0.09) were observed. Diets with 60 g kg−1 FML led to faster growth and higher feed intake than 30, 90, and 120 g kg−1 FML. Shrimp on 30 g kg−1 FML diets had the lowest BW, especially with 30–15 (FML-KRM) and 30–30 diets. Diets with 90 g kg−1 FML outperformed 30 g kg−1 FML. The control diet delivered a higher shrimp BW than diets 30–15 and 30–30, showing similar results to other diets except 60–15. Feed preference was influenced by KRM inclusion, with 15 g kg−1 KRM resulting in higher apparent feed intake than 30 and 45 g kg−1. The findings indicate that FML can be effectively reduced by up to 75% when combined with lower levels of KRM. This corresponds with the industry’s ongoing trend to achieve greater sustainability and cost efficiency through the reduced utilization of critical resources.

Effect of Calanus finmarchicus Hydrolysate Inclusion on Diet Attractiveness for Whiteleg Shrimp (Litopenaeus vannamei)

Shrimp feed formulations have moved towards less fish meal and more of the readily available and cheaper plant proteins. To counteract the lower attractiveness and palatability of plant proteins, feeds are supplemented with ingredients known to have chemoattractive properties that will increase feed intake. This study investigated the putative chemoattractive effect of Calanus finmarchicus hydrolysate, when used as a dietary supplement in shrimp feeds. C. finmarchicus is a zooplankton species native to the northern Atlantic Ocean and is a novel and sustainable raw material for shrimp feed products. Diet attractiveness was evaluated in a 24-day feeding trial with whiteleg shrimp (Litopenaeus vannamei) by measuring the intake of 12 diets with various levels of fish meal, calanus hydrolysate, and krill (Euphausia superba) meal. Higher inclusion rates of both ingredients resulted in increased feed intake, and supplementing the high fish meal diet with calanus hydrolysate gave a statistically significant higher feed intake. Low molecular weight peptides, chemoattractive amino acids, and the water-soluble nature of the hydrolysate could explain the chemoattractive properties observed in the study.

Impact of live feed substitution with formulated diets on the development, digestive capacity, biochemical composition, and rearing water quality of European lobster (Homarus gammarus, L.) larvae

The lobster aquaculture industry, constrained by limited access to viable and cost-effective feed sources, prompted an investigation into the potential of replacing live feeds with formulated diets for Homarus gammarus larval culture, exploring alternative protein ingredients. Four diets were tested on newly-hatched H. gammarus: live Artemia nauplii (ART), an extruded control diet with krill meal and fishmeal as main protein sources (CTRL), and diets with 15% of dietary protein replaced by shrimp waste meal (SWM) or black soldier fly meal (BSF).Results revealed significant diet-induced effects on digestive enzymes in H. gammarus larvae. ART-fed lobsters exhibited increased trypsin and amylase activities but lower lipase activity than those fed extruded diets, suggesting more efficient utilization of protein and carbohydrate in ART-fed larvae, while formulated diets compensated with efficient lipid utilization. BSF and SWM diets increased exo- and endochitinase activities, likely due to chitin presence. Additionally, CTRL and BSF-fed larvae exhibited elevated body glycogen content. ART-fed larvae displayed a significantly higher ratio of low DNA to high DNA bacteria in their rearing water, indicative of lower nutrient loading. Despite these diet-induced impacts, there was no dietary effect on growth and survival during H. gammarus larval development.The study suggests successful formulated feed utilization by homarid larvae, even with alternative ingredients like BSF and SWM, offering a promising solution to reduce reliance on live feeds in lobster aquaculture. Further research is crucial to assess the long-term implications of the observed physiological responses to the different diets in later life stages.

Effects of Antarctic Krill Meal in Diet on Reproductive Performance and Embryo Quality of Eriocheir sinensis.

A 60-day feeding trial was conducted to evaluate the impact of dietary Antarctic krill meal on the reproductive performance and embryo quality of the Chinese mitten crab, Eriocheir sinensis. Three diets were formulated, incorporating varying levels of Antarctic krill meal at 0% (Diet K0), 10% (Diet K10), and 20% (Diet K20), with a control group fed razor clam Sinonovacula constricta. Each diet was randomly assigned to three replicate tanks, each stocked with 5 males and 10 females. Male and female weights were 145.38 ± 8.01 and 102.57 ± 9.73 g, respectively. The results revealed no significant differences in weight gain rate, specific growth rate, and survival rate. However, the hepatopancreatic weight and hepatopancreas index of female crabs in each group decreased, while gonadal weight and gonadosomatic index increased significantly after 60 days, with Diet K20 showing the highest values. Egg production and fecundity of female crabs reached their peak in Diet K20, with no significant differences in reproductive indices among all groups. The phospholipid content in Diet K20 was significantly higher than in the other groups (P < 0.05). Cholesterol contents in Diet K0 and the control group were significantly higher than in Diet K10 and K20 (P < 0.05). No significant differences were observed in egg diameter, egg weight, moisture, crude protein, and crude fat between the groups. The content of C20 : 2 and C20 : 4n6 was highest in Diet K0, with a significant difference compared to Diet K10 (P < 0.05). However, no significant differences were found in the total content of saturated fatty acids, monounsaturated fatty acids, and polyunsaturated fatty acids among all groups. Based on the research findings, it is recommended that the optimal level of Antarctic krill meal in diets is 20%.

The Impact of Marine Resource-Free Diets on Quality Attributes of Atlantic Salmon

The influence of feeding Atlantic salmon for 90 days on diets that excluded fishmeal (FM) and fish oil (FO) was examined for influence on various quality traits. In addition, the effect of adding krill meal (KM; 0%, 2.5%, and 5%), as a putative feed palatant was also examined. Total replacement of FM/FO had a limited effect on production characteristics, affecting percentage yields of headed and gutted control fish and their standard length (p &lt; 0.05). Variances between dietary groups were observed for pigmentation, and plant protein-based KM-free-fed fish returned deeper hues across their belly, NQC (Norwegian Quality Cut), and back portions (p &lt; 0.03). No differences were measured for relative fin condition. δ13C and δ15N concentrations were lower and higher, respectively (p &lt; 0.05) for fish fed the FM/FO-based diet. δ13C:δ15N likewise differed between treatments with FM/FO-fed salmon expressing higher ratios. Fillet mechanical characteristics varied with fish fed on animal protein-based diets, without KM expressing higher springiness and resilience (p &lt; 0.05). Fish fed plant-based diets were generally preferred by younger taste testers. The results from this trial illustrate that FM/FO can be completely removed from salmon diets without problematic effects on quality and palatability attributes.

Effects of Dietary Fish Meal Replacement with Composite Mixture of Chicken Meal, Krill Meal, and Plant Proteins on Growth, Physiological Metabolism, and Intestinal Microbiota of Chinese Perch (Siniperca chuatsi)

This trial aimed to investigate the influence of graded replacing fish meal (D1: 0.00%, D2: 27.27%, and D3: 54.55%) with mixed protein ingredients (i.e., chicken meal, krill meal, fermented soybean meal, and soy protein concentrate) on the growth performance, muscle nutritional composition, blood biochemical indices, gut bacterial community, and transcriptome of Chinese perch. Two hundred seventy Chinese perch were divided into three groups (90 per group) and the diet lasted for 56 days. Results showed that the weight gain rate and specific growth rate were significantly lower, and the feed conversion ratio was significantly higher in the D3 group than in fish fed D1 (P&lt;0.05), with no significant differences between the D1 and D2 groups (P&gt;0.05). The muscle crude protein content was highest in the D2 group, and the crude fat content was significantly different in the order: D3 &gt; D1 &gt; D2 (P&lt;0.05). The levels of serum triglycerides (TG) and low-density lipoprotein cholesterol in the D2 group were significantly lower than those in the D1 group (P&lt;0.05), but there was no significant difference compared to the D3 group (P&gt;0.05). The microbial community structure changed significantly. Mycoplasma showed the highest abundance in the D1 and D2 groups (P&lt;0.05), and Cetobacterium peaked in D2 group, and significantly higher than that in D1 group (P&lt;0.05). Network analysis and cohesion index calculation showed that both network complexity and cohesion peaked in D2 group, and Cetobacterium was highly correlated with the cohesion index (P&lt;0.05). Further, muscle transcriptome analysis results showed that compared with the control group, differentially expressed genes were clustered (Q &lt; 0.05) in the arginine and proline metabolism pathways in D2 group. Fish in D3 group significantly (Q &lt; 0.05) affected genes involved in KEGG pathways of ribosome, circadian rhythm, thermogenesis, insulin signaling pathway, fatty acid degradation, oxidative phosphorylation, and apoptosis. In conclusion, under the experimental conditions, the replacement of 27.27% of fish meal by the compound protein did not have a negative impact on the growth performance of Chinese perch and could improve muscle quality, lipid metabolism, and the interaction of intestinal microbiota.

Influence of Krill Meal on the Performance of Post-Smolt Atlantic Salmon That Are Fed Plant-Based and Animal-Based Fishmeal and Fish Oil-Free Diets

The purpose of this study was to determine the influence of krill meal (KM) inclusion at various levels (0%, 2.5%, 5%) in plant-based and animal-based feeds, that were fishmeal (FM) and fish oil (FO) free, on Atlantic salmon growth. A FM/FO feed containing 0% KM was the control. Using a 2 × 3 factorial approach, diets were randomly assigned to one of 28 0.5 m3 flow-through tanks (n = 4 tanks per diet) initially stocked with 60 fish (148.4 ± 12.9 g; 23.6 ± 0.8 cm; condition factor (K) = 1.16 ± 0.08) each. Salmon were fed for 90 days using automatic feeders ad libitum. On day 45, stocking densities were reduced to 45 fish per tank by the random removal of 15 individuals to remove any potential of density affecting growth through the trial end. Water temperature, oxygen saturation, pH, and salinity throughout the trial were 11.8 °C, 103.5%, 7.38, and 32.0 g L−1, respectively. Fish fed plant-based feed without KM were lighter (p &lt; 0.05) than all other groups at day 45 and 90, but those fed a plant-based feed with KM had comparable growth and feed intake compared to that of fish fed the control diet. Irrespective of the presence of KM, animal-based feeds achieved comparable weight growth (p &gt; 0.05) to the control and 5% KM plant-based groups, with KM increasing feed intake (p &lt; 0.05). Between day 45 and 90, feed conversion ratios increased in all groups except the control and 0% KM plant-based group, while specific growth rates (SGRs) decreased for all except the 0% KM plant-based diet. Between-group differences (p &lt; 0.05) were also noted for the thermal growth coefficient. No differences were recorded in visceral or intestinal weight, and whole-body lipid levels were identical, proportional for all groups. Although differences (p &lt; 0.05) were apparent in the concentrations of individual fillet fatty acids between groups, a 75 g serving size of any treatment would be sufficient to exceed daily intake recommendations for EPA + DHA. This trial determined that benefit, in terms of feed intake and growth performance, was gained when KM was added to plant-based feeds. However, no such advantage was observed when KM was used with animal-based feeds.

Dietary ingredient composition affects faecal waste production and characteristics in yellowtail kingfish (Seriola lalandi)

This study investigated the effect of different animal-based ingredients on faecal waste production and characteristics in yellowtail kingfish (Seriola lalandi). Seven ingredients of animal origin were tested: KM – krill meal; SHM – shrimp head meal; NIM – natural ingredient meal consisting of freeze dried krill (Euphausia superba), sand eel (Ammodytes marinus), smelt (Atherina boyeri) and squid (Loligo patagonica) (all included at 25% on dry matter basis); PHA – poultry meal with high ash content; PLA – poultry meal with low ash content; HFM – hydrolysed feather meal and POM – pork meal. Ingredients were incorporated at 30% (HFM – 15% inclusion) in a basal diet, which was predominantly marine-based. Yellowtail kingfish (mean initial weight 41 g) were fed the experimental diets restrictively, in triplicate groups. Fish performance, nutrient digestibility and faecal waste production were investigated over a 35 day experimental period. In addition, faecal characteristics were visually evaluated, and faeces removal efficiency and particle size distribution (PSD) were measured. Organic matter digestibility (OM) differed between diets, hereby altering the amount of faecal waste produced (g OM/kg DM FI). Test ingredients affected faeces removal efficiency by settling (%) and the amount of non-removed faeces (g OM/kg DM FI). Effects of ingredients on faeces removal efficiency were small compared to effects on faecal waste production. SHM, inclusion resulted in an improved faeces removal efficiency, while other animal-based ingredients did not improve faeces removal efficiency. Overall, this study highlights the importance of ingredient digestibility (and thus faecal waste production) for solid waste management in yellowtail kingfish.

Post-prandial response in hepatopancreas and haemolymph of Penaeus monodon fed different diets. Omics insights into glycoconjugate metabolism, energy utilisation, chitin biosynthesis, immune function, and autophagy

Raw materials or bioactive ingredients trigger mechanisms to assimilate nutrients and activate metabolic pathways that promote growth, immune function, or energy storage. Our understanding of these processes at a molecular level remains limited in aquaculture, especially in shrimp. Here, hepatopancreas proteomics and haemolymph metabolomics were used to investigate the post-prandial response of black tiger shrimps (Penaeus monodon) fed a conventional fishmeal diet (FM); a diet supplemented with the microbial biomass Novacq™ (NV); krill meal (KM); or, fasted (FS). Using FM as a control, a 2-fold change in abundance threshold was implemented to determine the significance of proteins and metabolites. NV fed shrimp showed preference for energy derived from carbohydrates indicated by a strong signature of glycoconjugate metabolism and activation of the amino- and nucleotide sugar metabolic pathway. KM activated the glyoxylate and dicarboxylate pathway that denoted shrimp preference for lipidic energy. KM also influenced energy generation by the TCA cycle inferred from higher abundance of the metabolites succinic semialdehyde, citric acid, isocitrate, alpha ketoglutarate and ATP and downregulation of the enzyme isocitrate dehydrogenase that catalyses oxidative decarboxylation of isocitrate. FS shrimp displayed down-regulation of oxidative phosphorylation and resorted to internal lipid reserves for energy homeostasis displaying a strong signature of autophagy. Pyrimidine metabolism was the preferred energy strategy in this group. Our study also provided evidence that during fasting or consumption of specific ingredients, shrimp share common pathways to meet their energy requirements, however, the intensity at which these pathways were impacted was diet dependent.

Effects of Different Phospholipid Sources on Growth and Gill Health in Atlantic Salmon in Freshwater Pre-Transfer Phase.

Growth and histological parameters were evaluated in Atlantic salmon (74 g) that were fed alternative phospholipid (PL) sources in freshwater (FW) up to 158 g and were transferred to a common seawater (SW) tank with crowding stress after being fed the same commercial diet up to 787 g. There were six test diets in the FW phase: three diets with different doses of krill meal (4%, 8%, and 12%), a diet with soy lecithin, a diet with marine PL (from fishmeal), and a control diet. The fish were fed a common commercial feed in the SW phase. The 12% KM diet was compared against the 2.7% fluid soy lecithin and 4.2% marine PL diets, which were formulated to provide the same level of added 1.3% PL in the diet similar to base diets with 10% fishmeal in the FW period. A trend for increased weight gain with high variability was associated with an increased KM dose in the FW period but not during the whole trial, whereas the 2.7% soy lecithin diet tended to decrease growth during the whole trial. A trend for decreased hepatosomatic index (HSI) was associated with an increased KM dose during transfer but not during the whole trial. The soy lecithin and marine PL diets showed similar HSI in relation to the control diet during the whole trial. No major differences were observed in liver histology between the control, 12% KM, soy lecithin, and marine PL diets during transfer. However, a minor positive trend in gill health (lamella inflammation and hyperplasia histology scores) was associated with the 12% KM and control diets versus the soy lecithin and marine PL diets during transfer.

Comparison of Fish, Krill and Flaxseed as Omega-3 Sources to Increase the Omega-3 Index in Dogs

(1) Background: it is only the longer chain omega-3 polyunsaturated fatty acids (n-3 PUFAs), eicosapentaenoic acid (20:5n-3, EPA), and docosahexaenoic acid (22:6n-3, DHA) and not the shorter chain α-linolenic acid (ALA, 18:3n-3) that have been linked to health benefits. (2) Methods: 45 dogs divided into three groups were first given premium dry food for 38 days (baseline). The O3I was then used as a diagnostic tool to provide a measure of the sum of EPA + DHA in red blood cell membranes given as a percentage of all fatty acids. The dogs were subsequently fed with either krill meal (krill), fishmeal/oil (fish) or flaxseed cake (flax) included in raw food providing daily 416 mg EPA + DHA (971 mg ALA), 513 mg EPA + DHA (1027 mg ALA) and 1465 mg ALA (122 mg EPA + DHA), respectively. (3) Results: the average baseline O3I level of all dogs was low (1.36%), warranting n-3 supplementation. After four weeks, O3I levels were significantly increased in the krill (from 1.36 ± 0.44 to 2.36 ± 0.39%) and fish (from 1.35 ± 0.22 to 1.9 ± 0.35%) groups (p < 0.001). No significant modification of the O3I was detected in the flax animals. (4) Conclusions: only marine n-3 PUFAs resulted in a significantly increased O3I, with dietary krill meal providing the highest increase.

Phosphatidylcholine in Krill Meal and Krill Oil as a Source of Choline for Prevention of Intestinal Steatosis in Atlantic Salmon

Intestinal steatosis, called lipid malabsorption syndrome (LMS) in severe cases, is a common condition in farmed Atlantic salmon, associated with choline deficiency causing low lipid transport in enterocytes, excessive lipid accumulation, and increased mucosal weight. A previous dose-response study supplying a plant-based diet with choline chloride indicated that 3.4 g/kg choline prevents LMS in Atlantic salmon. However, no similar documentation exists using phosphatidylcholine (PC) as a choline source. The present study therefore aimed to determine the ability of PC from krill meal (KM) and krill oil (KO) towards reducing steatosis in Atlantic salmon. Two diets with suboptimal PC levels (1.5 and 2.6 g/kg) were tested against two control diets, a choline-deficient diet with no supplementation (0.6 g/kg), and a high choline (4.0 g/kg choline chloride) diet. After 8 weeks of freshwater feeding, growth was significantly higher in KM and KO groups, at both PC levels, in comparison to the choline-deficient group. However, growth was significantly higher only in the KM and KO diets with 2.6 g/kg of PC when compared to the positive control. This indicated that suboptimal levels of PC from KM and KO satisfied choline needs for growth. A clear dose-dependent effect on the decreasing pyloric intestine (PI) somatic index was observed for KM and KO diets, with no significant difference between KM and KO diets (2.6 g/kg choline) and high choline reference diet. Accordingly, PC from both KM and KO significantly reduced lipid accumulation in the PI and liver when added to a choline-deficient diet. However, histological and lipid analyses also indicated that the optimal dietary choline requirement for full elimination of lipid accumulation in PI is higher than 2.6 g/kg with KM and KO as supplementary sources.

Effects of composite mixture of protein sources in replacing fish meal on nutritional value and flavor quality of Pacific white shrimp (Litopenaeus vannamei)

An 8-week feeding trial was conducted to investigate the effects of fish meal partially or totally replaced with poultry by-product meal (PBM), antarctic krill meal (AKM), corn gluten meal (CGM), cottonseed meal (CM) and rice protein concentrate meal (RPM) on amino acids, fatty acids, nucleotides and volatile compounds of Pacific white shrimp (Litopenaeus vannamei). Results showed that shrimps fed with partial replacement of fish meal (50 %) with AKM and PBM (1:1) significantly increased the content of inosine monophosphate (IMP), the proportion of eicosapentaenoic acid (EPA), n-9 monounsaturated fatty acids (MUFAs), and significantly decreased the content of hypoxanthine (Hx), benzaldehyde, and the proportion of saturated fatty acids (SFAs). Dietary fish meal totally replaced by the whole-plant protein diet resulted in a lower value of essential amino acids to total amino acids (EAA / TAA), n-3 / n-6 PUFAs, and a lower proportion of docosahexaenoic acid (DHA), n-3 polyunsaturated fatty acid (PUFAs). Principal component analysis and hierarchical cluster analysis revealed that shrimps fed diet with fish meal partially replaced by AKM and PBM (1:1) had the most similar volatile compounds profile to the fish meal-based diet. These results indicated that the composite mixture of PBM and AKM (1:1) is an excellent substitution for fish meal in shrimp diets.

Effects of Tea Polyphenol and Its Combination with Other Antioxidants Added during the Extraction Process on Oxidative Stability of Antarctic Krill (Euphausia superba) Oil

Antarctic krill (Euphausia superba) oil contains high levels of marine omega-3 long-chain polyunsaturated fatty acids (n-3 LC-PUFA), including eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). In industrial production, krill oil is usually extracted from krill meals by using ethanol as a solvent. Water in the krill meal can be easily extracted by using ethanol as an extraction solvent. During the extraction process, the EPA and DHA are more easily oxidized and degraded when water exists in the ethanol extract of krill oil. Based on the analysis of peroxide value (POV), thiobarbituric acid-reactive substances (TBARS), fatty acid composition, and lipid class composition, the present study indicated that the composite antioxidants (TP-TPP) consist of tea polyphenol (TP) and tea polyphenol palmitate (TPP) had an excellent antioxidant effect. By contrast, adding TP-TPP into ethanol solvent during the extraction process is more effective than adding TP-TPP into krill oil after the extraction process.

Evaluation of Krill Meal in Commercial Diets for Juvenile Swimming Crab (Portunus trituberculatus).

An 8-week feeding trial was carried out to assess the effect of dietary krill meal on growth performance and expression of genes related to TOR pathway and antioxidation of swimming crab (Portunus trituberculatus). Four experimental diets (45% crude protein and 9% crude lipid) were formulated to obtain different replacements of fish meal (FM) with krill meal (KM); FM was replaced with KM at 0% (KM0), 10% (KM10), 20% (KM20), and 30% (KM30); fluorine concentration in diets were analyzed to be 27.16, 94.06, 153.81, and 265.30 mg kg-1, respectively. Each diet was randomly divided into 3 replicates; ten swimming crabs were stocked in each replicate (initial weight, 5.62 ± 0.19 g). The results indicated that crabs fed with the KM10 diet had the highest final weight, percent weight gain (PWG), and specific growth rate (SGR) among all treatments (P < 0.05). Crabs fed with the KM0 diet had the lowest activities of total antioxidant capacity (T-AOC), total superoxide dismutase (SOD), glutathione (GSH), and hydroxyl radical scavenging activity and had the highest concentration of malondialdehyde (MDA) in the hemolymph and the hepatopancreas (P < 0.05). In the hepatopancreas, the highest content of 20:5n-3 (EPA) and the lowest content of 22:6n-3 (DHA) were shown in crabs fed with the KM30 diet among all treatments (P < 0.05). With the substitution level of FM with KM gradually increasing from 0% to 30%, the color of the hepatopancreas changed from pale white to red. Expression of tor, akt, s6k1, and s6 in the hepatopancreas was significantly upregulated, while 4e-bp1, eif4e1a, eif4e2, and eif4e3 were downregulated with dietary replacement of FM with KM increasing from 0% to 30% (P < 0.05). Crabs fed with the KM20 diet had notably higher expression of cat, gpx, cMnsod, and prx than those fed with the KM0 diet (P < 0.05). Results demonstrated that 10% replacement of FM with KM can promote growth performance and antioxidant capacity and notably upregulate the mRNA levels of genes related to TOR pathway and antioxidant of swimming crab.