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Trace element supplementation to the freshwater environment can influence the plankton density and species diversity, contributing to the nutrition of aquaculture species, especially during the juvenile stage. An experiment was conducted under laboratory conditions to evaluate the effects of supplementing different mixtures of manganese, silica and phosphorus on the plankton density and species diversity and their impact on cultured juvenile marron (Cherax cainii, Austin and Ryan, 2002). Manganese, silica and phosphorus in concentrations of 0.0024, 0.41, 0.05 mg*L-1; 0.0041, 0.82, 0.12 mg*L-1; and 0.0058, 1.26, 0.25 mg*L-1 respectively termed as low, medium and high were supplemented to tank water containing a phytoplankton density of 3.77 ± 0.16 × 106 cells*L-1 and 292.9 ± 17.6 individuals*L-1 of zooplankton, and plankton growth was observed every 24 h for 6 days. Afterwards, a 3-month trial was conducted studying the effects of these trace element concentrations and resulting plankton densities on marron growth, survival, moulting, gut microbiota and health indices. Silica supplementation at high concentration increased the diatom abundance, silica and phosphorus supplementation at higher concentration that resulted in a significant increase in plankton density and species diversity, leading to improved marron health indices than the control and the tanks receiving a low concentration. Marron-specific growth rate, weight gain and dissolved copper concentration in haemolymph were significantly higher in tanks with higher supplementation and higher plankton density. Marron survival, moult interval and total haemocyte count were not affected by the supplementation. Marron gut microbiota at higher trace element concentration supplementation showed a significant increase in abundance of phosphate solubilizing bacteria.

Feeding freshwater crayfish species with different diets not only affects the water quality but also induces the abundance of various microbial communities in their digestive tracts. In this context, very limited research has been undertaken to understand the impacts of various protein incorporated aqua-diets on the characteristics of water and its microbial communities. In this study, we have critically analysed the water quality parameters including pH, dissolved oxygen, nitrate, nitrite, ammonia and phosphorus, as well as bacterial communities under marron (Cherax cainii) aquaculture, fed fishmeal (FM) and poultry by-product meal (PBM)-based diets for 60 days. The results unveiled that over the time, feeding has significant impacts on organic waste accumulation, especially ammonia, nitrate, nitrite and phosphate, while no effects were observed on pH and dissolved oxygen. Analysis of 16S rRNA sequence data of water sample indicated significant (P

In intensive farming systems, fish are held at high densities, which may increase stress, leading to susceptibility to diseases that result in economic losses. Therefore, effective feeding practices incorporating health‐promoting compounds such as proteins, hydrolysates and bioactive peptides that can stimulate the defence mechanisms of fish and achieve better growth are some of the priorities for sustainable aquaculture development. Globally, the fish processing industries generate and discard a large volume of waste every year, estimated at up to 60% of the harvested biomass. This waste can be converted to value‐added products such as fish protein hydrolysate (FPH) with the addition of various proteolytic enzymes. FPH from fish processing waste including skin, heads, muscle, viscera, liver and bones is a good source of protein, amino acids, peptides and antioxidants and has been found to possess desirable functional and bioactive peptides. A moderate inclusion of FPH in aquafeeds has the potential to improve growth, feed utilization, immune functions and disease resistance of fish. Production of FPH, targeted to more precise molecular weight ranges, has superior functionalities that are in high demand. With interest in FPH as an aquafeed supplement, this review aimed to summarize the source, production processes and functional properties of FPH and the reported impact of FPH in aquafeed supplement on fish growth, survival, feed utilization, immune response and disease resistance. Possible limitations of using FPH and future research potential as an opportunity for the use of processing fish waste are also discussed.

The present study investigated the supplemental effects of tuna hydrolysate (TH) in poultry by-product meal (PBM) and dietary fishmeal (FM) diets on antioxidant enzymatic activities, gut microbial communities and expression of cytokine genes in the distal intestine of juvenile barramundi, Lates calcarifer. Fish were fed with fermented (FPBM + TH) as well as non-fermented PBM (PBM + TH) and FM (FMBD + TH) diets with 10% TH supplementation for 10 weeks. A basal diet prepared without TH supplementation served as control. The results showed that the activity of glutathione peroxidase was significantly higher in FPBM + TH than the control, while the malondialdehyde and catalase activities were unchanged. FPBM + TH diet significantly (P 0.05) upregulated the pro-inflammatory cytokines including IL-1β and TNF-α while considerable downregulation (P 0.05) was observed in the mRNA expression levels of anti-inflammatory cytokine, IL-10 in the distal intestine of fish. The 16SrRNA analysis using V3-V4 region evidenced the ability of FPBM + TH to modulate the distal intestinal gut microbiome, augmenting the richness of Firmicutes and Fusobacteriaat at phylum level and Bacillus, Lactococcus and Cetobacterium at genus level. All these results have shown that fermented PBM with TH supplementation could improve the antioxidant capacity and inflammatory responses of juvenile barramundi while influencing the microbial communities at both phylum and genera levels.

This study investigated the effects of replacement of fishmeal (FM) with poultry by-product (PBM) protein, supplemented with black soldier fly, Hermetia illucens (HI) larvae on growth, histomormhology, immunity and resistance to Vibrio harveyi in juvenile barramundi. Two hundred and twenty five barramundi averaging 3.51 ± 0.03 g were randomly allocated into three groups and fed isonitrogenous and isocalorific diets containing different levels of PBM supplemented with HI as follows: Control (FM based diet), 45PBM + HI (45% PBM supplemented with 10% HI), and 90PBM + HI (90% PBM supplemented with 10% HI) for 6 weeks. Results showed that dietary inclusion of 45PBM + HI significantly improved the growth performance than control whereas growth inhibition occurred in the 90PBM + HI. The 45PBM + HI groups demonstrated significant increases in histometric measurements (villus and enterocyte width, and microvilli height) and acidic mucins. The impaired growth in 90PBM + HI groups was further associated with multifocal necrosis in the liver, an upregulation of the stress related genes (HSP70 and HSP90) and increase in the levels of liver enzymes. When 45PBM + HI was fed, survival against V. harveyi increased significantly and also an increase in serum immunity and immune-related genes in the head kidney was observed after infection.

A feeding trial was conducted to test the effects of partial replacement of fishmeal (FM) protein and fish oil (FO) with partially defatted black soldier fly, Hermetia illucens insect protein, and oil, respectively, on growth performance, immune response, gut and skin barrier status, and flesh quality in juvenile barramundi. Four isonitrogenous and isocaloric diets used in the study were a control diet based on FM, 30% FM replaced with H. illucens protein (HiP), 30% FO replaced with H. illucens oil (HiO), and both 30% FM and 30% FO replaced with H. illucens protein and oil (HiPO). Diets were fed twice a day to satiety in triplicated groups of barramundi with an initial body weight of 1.74 ± 0.15 g per fish. At the end of the trial, growth and feed utilization indices were found insignificant (p &gt, 0.05) between the test diets and control. A significant increase in bactericidal activity was observed in fish fed the HiP diet while serum lysozyme activity was unchanged. Stress-related heat shock proteins (HSP70 and HSP90) did not differ significantly among the test diets while immune-relevant genes (IL-1β and IL-10) were significantly upregulated in HiP and HiOP groups. The number of mucin cells were increased in the gut and skin of HiP and HiOP fed fish when compared to the control diet. The total fatty acid compositions (∑SFA, ∑MUFA, ∑PUFA, ∑n-3, and ∑n-6) in the muscles of barramundi were not significantly influenced with H. illucens protein and oil diets when compared to the control.

The effects of feeding different levels of poultry by-product meal (PBM) replacing fishmeal (FM) protein, supplemented with tuna hydrolysate (TH) and Hermetia illucens (HI) larvae, on the growth, fillet quality, histological traits, immune status, oxidative biomarker levels and gut microbiota of juvenile barramundi, Lates calcarifer were investigated for six weeks. Barramundi were fed four isonitrogenous and isolipidic diets in which a FM based diet was used as the Control diet (Diet1) and compared with other non-FM diets containing 80%, 85% and 90% PBM along with the concurrent supplementation of 5% and/or 10% TH and HI larvae meal. These treatment diets were designated as 80PBM10TH+10HI (Diet2), 85PBM5TH+10HI (Diet3) and 90PBM5TH+5HI (Diet4). The growth and condition factor of fish fed 80PBM10TH+10HI and 85PBM5TH+10HI were significantly higher than the Control. Total saturated, monounsaturated and polyunsaturated fatty acid retention in the fish muscle increased in fish fed PBM-based diets, supplemented with TH and HI larvae meal, with no adverse effect on post-harvest characteristics such as texture and colour of fish fillets. Improvement in serum total bilirubin and total protein content was found in all fish fed TH and HI larvae supplemented PBM. Similarly, immune response showed a significant increase in fish fed non-FM test diets than the Control. In the distal intestine, supplementation of any quantities of TH and HI larvae to PBM led to an increase in the microvilli density and neutral mucins while the number of goblet cells in the skin were unchanged. Liver, kidney, and spleen histology demonstrated a normal structure with no obvious changes in response to all test diets. Bacterial diversity increased in fish fed Diets 2 and 3 with a high abundance of Proteobacteria in Diets 1 and 4 and Firmicutes in Diets 2 and 3. The fish on test diets showed a lower abundance of genus Vibrio. Fish fed TH and HI larvae supplemented PBM diets showed lower infection rate to V. harveyi than the Control. Collectively, concurrent supplementation of TH and HI larvae could improve the quality of PBM diets with positive effects on growth, fillet quality, intestinal health, immunity, and disease resistance.

A feeding trial was carried out to evaluate the effects of substitution of fishmeal (FM) by dietary poultry by-product meal, fermented by Lactobacillus casei and Saccharomyces cerevisiae on growth, intestinal health, microbial composition, immune related cytokines and disease resistance of freshwater crayfish, marron (Cherax cainii) against Vibrio mimicus. Two isonitrogenous and isocaloric diets were formulated by replacing FM protein with fermented poultry by-product meal (FPBM) protein at 0% (Control) and 75% (FPBM), and fed marron for 70 days. The results indicated no significant difference (P > 0.05) in final body weights between two groups of marron, whilst intestinal microvilli number per fold was increased in marron fed FPBM than the control. The 16S rRNA sequences revealed an increased number of Lactobacillus and Streptococcus, and decreased number of Aeromonas at genus level in the distal intestine of marron fed FPBM. Marron fed FPBM showed up-regulated expression of IL-8, IL-10, and IL-17F genes in the distal intestine. Significantly (P < 0.05) increased lysozyme and phagocytic activity, and higher survival was found in marron fed FPBM following a bacterial challenge with Vibrio mimicus. Therefore, it is concluded that FPBM is beneficial to marron in terms of microbial community, immune-related cytokines and disease resistance against V. mimicus.

Peanut (Arachis hypogaea) is mainly grown for oil extraction and the remaining oil-free seed referred as peanut meal (PM) leaves with high protein content which can be a possible substitute for fishmeal in aqua-diets. This study evaluates the suitability of three types of processed peanut seeds, namely untreated PM (UPM), fermented PM (FPM), and germinated PM (GPM) from peanut seeds to replace fishmeal in barramundi (Lates calcarifer) diets cultured under a commercial production environment. Nine formulated diets having 3 inclusion levels from the 3 different peanuts (15%, 30% and 60% fishmeal replacement) were evaluated against a control without PM. The performance of various types and levels of PMs was assessed by examining the growth, gut and liver condition and survival of fish after eight weeks of feeding the test diets. The immunological responses of juvenile barramundi were assessed by exposing the fish to the hypoxic conditions for 4 hours. The results showed that fermentation and germination significantly (P

This study was conducted to investigate the combined effects of probiotic yeast, Saccharomyces cerevisiae, and lactic acid bacteria, Lactobacillus casei on the growth performance, biochemical response, cytokine gene expression, gut histomorphology and microbial composition of juvenile barramundi, Lates calcarifer. Barramundi juveniles with an initial mean weight of 12.17 ± 0.15 g were randomly allocated into 8 tanks (300L) at a density of 20 fish per tank and fed either a basal diet (control), or the same basal diet supplemented with 1% of S. cerevisiae and 1% of L. casei, collectively termed ‘probiotic’, for 56 days in quadruplicate. Results indicate that dietary probiotic supplementation produced significant (P

The study examined the effects of supplemental organic selenium (Se) extracted from selenoyeast on the growth performance, glutathione peroxidase (GPx) activity, biochemical status and liver histochemistry of juvenile cobia Rachycentron canadum. Six experimental diets were prepared supplemented with Se with total concentration of 1.52 (Se-1.52), 1.93 (Se-1.93), 2.29 (Se-2.29), 2.71 (Se-2.71) and 3.14 (Se-3.14) mg/kg of total Se in the diets and a fishmeal-based control diet without Se supplementation containing 1.15 (Se-1.15) mg/kg of Se was used as control. Experimental diets were fed to the fish of six treatment groups in triplicate twice daily for 8 weeks. Juvenile cobia fed dietary Se of 1.93, 2.29 and 2.71 mg/kg showed increased final body weight (FBW), specific growth rate (SGR) and feed intake (FI) than the fish fed the control diet. Se accumulations in the muscle and liver tissue displayed a positive linear relationship with dietary Se levels. Se deficiency was apparent in fish fed the control diet and displayed reduced growth and feed efficiency. Red blood cell (RBC) counts were significantly (P

This study tested the effects of temperature and pH on water quality and the growth of Sargassum linearifolium and S. podacanthum in potassium-fortified Inland Saline Water (ISW) of Western Australia (WA), at two levels of pH (low pH range of 5.5-6.5 and ambient pH 7.0-8.2) and two levels of temperature (high temperature 26-27°C and ambient room temperature of 20-22°C) in triplicate for 42 days. The pH of ISW in WA varies from 3.9 to 9.1, whereas the temperature is from 6.1-28.1°C. The results showed that the high temperature initiated the mortalities of the both Sargassum species from the first 14 days of culture period. The high temperature also resulted in a reduction of dried weight and ash content of these two species of Sargassum by the end of the trial. S. linearifolium temperature tolerant threshold was larger than S. podacanthum. Since the day 14, the S. linearifolium biomass and specific growth rate were higher than S. podacanthum at both temperature levels under ambient pH. Higher crude protein in S. linearifolium than S. podacanthum was also recorded at high temperature. Ambient pH and ambient temperature resulted in higher biomass and higher specific growth rate than low pH and high temperature in both species, which is recommended for Sargassum spp. growth.

Potassium-fortified inland saline water (K+ISW) has shown potential for growing marine species, including seaweed species. The response of a brown seaweed species, Sargassum podacanthum, to nitrogen and phosphorus enrichments were evaluated by culturing the species for 84 days in K+ISW and comparing it with Ocean Water (OW). The culture media was enriched weekly with ammonium chloride and sodium dihydrogen phosphate, with ammonium and phosphate ratios of 10:1 at five different concentrations 80:8, 120:12, 160:16, 200:20 and 240:24 μM. The culture medium with no enrichment was used as a control. The water quality and biomass of S. podacanthum were measured fortnightly. The S. podacanthum biomass increase significantly with different concentrations of the nutrient supplementations. The standing biomass and Specific Growth Rate (SGR) of S. podacanthum were similar in OW and K+ISW in the absence of any nutrient supplementation and at the supplement concentration of ammonium and phosphate 160:16 μM. However, from day 42 onwards, at the ratios of 80:8, 120:12, 200:20 and 240:24, S. podacanthum cultured in OW grew significantly faster than in K+ISW. In K+ISW, optimal growth of S. podacanthum was observed at the 160:16 and the increase in biomass was significantly higher than the initial biomass until day 70, whereas at the other four nutrient supplement concentrations, the S. podacanthum biomass remained unchanged during the entire culture period. The nitrite, total Kjeldahl nitrogen and phosphate concentrations in water were found to be significantly (p

Poultry by-product meal (PBM) as a replacement for fish meal (FM), an expensive and unsustainable protein aquafeed ingredient, has been tested on different aquaculture fish species. However, the complete replacement of FM with a mixture of PBM and Hermetia illucens (HI) larvae in barramundi culture has not been previously investigated. In this study, results are presented on growth performance, fillet fatty acid composition, serum metabolites, skin mucosal barriers, hepatic steatosis, antioxidant activity, and immunity of juvenile barramundi, Lates calcarifer fed either a FM-based diet (0PBM-0HI) or two test diets in which total FM protein was replaced by a mixture of 70% PBM and 30% full-fat (FHI) and defatted HI larvae (DHI) meal (designated as 70PBM-30FHI and 70PBM-30DHI). After 56 days of feeding, the results showed that the growth was affected when fish were fed 70PBM-30DHI with a higher feed conversion ratio (FCR) with respect to 0PBM-0HI and 70PBM-30FHI diets. There was no variation in growth performance, feed utilization, and FCR between 0PBM-0HI and 70PBM-30FHI. The retention of total saturated and monounsaturated fatty acids increased in the fillet of juveniles fed 70PBM-30FHI and 70PBM-30DHI while total retention of polyunsaturated (PUFA), n-3 PUFA, and n-6 PUFA decreased than the control. Serum alanine transaminase (ALT) increased in fish fed 70PBM-30DHI whereas haptoglobin upsurged in 70PBM-30FHI compared to 0PBM-0HI. There were no significant effects in the serum immune response between dietary treatments whilst serum and liver CAT activity were negatively impacted by 70PBM-30DHI. The 70PBM-30DHI induced hepatic steatosis whilst 0PBM-0HI and 70PBM-30FHI showed no obvious change in the liver. Skin mucosal barriers were impacted by 70PBM-30DHI whilst 70PBM-30FHI fed fish showed a similar response to 0PBM-0HI. The fish fed on 70PBM-30DHI showed a higher proportion of infection rate with Vibrio harveyi than 70PBM-30FHI but showed no variation with the control-fed fish. In summary, FHI larvae meal could be a good complementary protein source, particularly when replacing FM completely with insect-based proteins.

Growing aquatic species in inland saline water (ISW) is one way to reduce the adverse impact of ISW to agriculture farms. This 84-day laboratory-trial was conducted to study the growth of Sargassum linearifolium cultured in ocean water (OW), ISW, ISW fortified with potassium equivalent to 100% (ISW100), 66% (ISW66) and 33% (ISW33) of potassium in OW at 35 g/L. The biomass and cumulative specific growth rate (SGR) of S. linearifolium increased significantly (p

The study used the mixed probiotics of Bacillus amyloliquefaciens 54A and B. pumilus 47B isolated from striped catfish ( Pangasianodon hypophthalmus ) intestine aiming to stimulate growth performance, innate immunity, stress tolerance of striped catfish. The average weight gain (AWG), specific growth rate (SGR), and feed conversion ratio (FCR) were analyzed after fish were fed the mixture of probiotics ( B. amyloliquefaciens 54A and B. pumilus 47B) at concentrations of 1 × 10 8 , 3 × 10 8 , and 5 × 10 8 CFU g −1 feed for 90 days. Immunity parameters, survival rate of fish challenged with Edwardsiella ictaluri and ammonia tolerance were also investigated. The amounts of B. amyloliquefaciens and B. pumilus were counted and identified by specific primer pairs of Ba1-F/Ba1-R, and 16-F/Bpu-R to confirm the presence of probiotics in fish intestine. The AWG (476.6 ± 7.81 g fish −1 ) of fish fed probiotics at 5 × 10 8 CFU g −1 was significant higher than the control (390 ± 25.7 g fish −1 ) after 90 days of feeding, but there was no significant ( P > 0.05) effect of probiotics on FCR and SGR. Fish fed diet containing probiotics at 5 × 10 8 CFU g −1 also expressed resistance to E. ictaluri infection and higher immune parameters such as phagocytic activity, respiratory bursts, and lysozyme activity than the control. Stress response with ammonia showed significantly lower mortality rate (25%, 20% and 27%) of fish fed probiotics at all three levels of 1, 3 and 5 × 10 8 CFU g −1 than the fish fed control diet (75%). The study also demonstrated that the probiotics survived in the intestine of striped catfish after 90 days of feeding. Therefore, the dietary supplementation of a mixture of B. amyloliquefaciens and B. pumilus at 5 × 10 8 CFU g −1 can be used to improve the health and growth rate of striped catfish.

A 10-week feeding trial was conducted to evaluate the necessity of supplementing selenium (Se) in a low-protein basal diet for Australian snapper Pagrus auratus , a slower-growing fish species. Dietary Se supplementation was tested against commercial barramundi diet, most commonly fed to Australian snapper. Se-yeast was added to a reconstituted commercial diet and to a formulated basal diet at 0, 0.8 and 1.0 mg/kg Se to form six isoenergetic test diets to evaluate the effects of diet types, dietary Se supplementation and their interaction on the growth, feed utilisation, body composition and liver morphology of juvenile Australian snapper. These Se supplementation levels resulted in total dietary Se levels of 0.92, 1.68, 1.76, 1.67, 2.59 and 2.77 mg/kg, respectively. Each test diet was fed to triplicate groups of Australian snapper in a flow-through seawater system. There were no significant interaction between diet types and Se supplementation on all tested parameters of the snapper. Regardless of the diet types, snapper fed 1.0 mg/kg Se-supplemented diet attained significantly lower growth rate than the fish fed diets supplemented with 0 and 0.8 mg/kg of Se. Feed conversion ratio was significantly increased in snapper fed diets supplemented with 1.0 mg/kg Se. There were no effects of both diet types and Se supplementation on the proximate composition of the muscle and whole-body except the reduced moisture and gross energy levels in the whole-body of snapper fed 1.0 mg/kg Se-supplemented diet. The Se contents in the muscle and liver tissues showed positive linear relationships with dietary Se levels. Fish fed diet supplemented with 1.0 mg/kg Se showed increased hepatic lipid compared with the fish fed 0 and 0.8 mg/kg Se-supplemented diets. Histopathological alterations were observed in liver tissues of snapper fed the basal diet containing 2.77 mg/kg Se. The results concluded that the protein and Se requirements of Australian snapper are low and can be met by lower protein ingredients with the endogenous Se. Further, the dietary Se threshold level in Australian snapper fed a basal diet was 2.77 mg/kg, whereas this level was only 1.76 mg/kg in the reconstituted commercial diet.

The aim of this study was to investigate the interactive effects of temperature and dietary selenium concentrations on antioxidant capacity, muscle histochemistry and the growth, of juvenile yellowtail kingfish ( Seriola lalandi ). The yellowtail kingfish were exposed to two temperatures (21 °C or 26 °C) and three selenium levels (0.0, 2.0 or 4.0 mg Se kg −1 of feed) for 30 days. Final weight and specific growth rate (SGR) were significantly affected by water temperature (ρ −1 or 4.0 mg Se kg −1 showed no significant difference (ρ > 0.05). Se concentration in the muscles of juvenile yellowtail kingfish fed Se-supplemented diets was higher than that of the yellowtail kingfish that were fed the control diet. A histopathological test confirmed that 20.3% of fish muscles exhibited lesions, which occurred in the absence of dietary Se. The outcome of the present study helps in understanding the interactive effects of dietary Se concentrations and the temperature in the farming of yellowtail kingfish.

The present feeding trial examined the effect of synbiotic use of Bacillus mycoides and organic selenium (OS) as Sel-Plex on marron immunity, growth and survival. The marron were cultured in recirculated tanks and fed test diets consisting of a basal diet; basal diet supplemented with B. mycoides (108 CFU g−1 of feed); basal diet supplemented with OS (Sel-Plex) (0.2 g kg−1 of feed) and basal diet supplemented with synbiotic (B. mycoides at 108 CFU g−1 and OS 0.2 g kg−1 feed) diet, in triplicate. The effect of the prebiotic OS (Sel-Plex) on the growth rate of B. mycoides was also studied in vitro. The results suggested that synbiotic use of B. mycoides and OS significantly improved some immune parameters of marron, particularly the glutathione peroxidase, and to some extent total haemocyte counts. However, the synbiotic feed did not synergistically improve marron growth, in fact the use of B. mycoides-supplemented diet alone demonstrated significantly higher growth in marron compared with the growth of marron fed on other test diets. Supplementation of the basal diet with host origin B. mycoides significantly increased the intestinal bacterial population (3.399 ± 825 CFU g−1 of gut) in marron compared with other diets. Organic selenium as Sel-Plex in Trypticase Soya Broth also confirmed that OS did not increase the amount of growth of B. mycoides and resulted in a lower intestinal bacterial population in the synbiotic diet-fed marron. In conclusion, synbiotic of OS and B. mycoides may improve a particular immune parameters of marron and to a lesser extent their growth.

Soybean meal (SBM) has been commonly utilised as a substitute for fishmeal (FM) in the diets of several fish species. However, little is known regarding their effects on trace element availability and thus their importance to fish. The present study employed two feeding trials to evaluate the implications of dietary selenium (Se) on the growth, accumulation, antioxidant, and histopathological responses of juvenile barramundi (Lates calcarifer). In the first trial, each of three basal diets containing 0, 15 and 43 % SBM as replacements for 0, 25 and 75 % of FM protein on an isoproteic and isocalorific basis were either supplemented or not supplemented with 2 mg kg-1 organic Se (OS). In the second trial, the potential effect of OS supplementation in a high SBM diet was investigated in a feeding trial with five experimental diets: 75 % SBM protein as replacement of FM was supplemented with 2, 3, 4, 5 or 7 mg OS kg-1. Growth was independently influenced by the SBM level and the OS supplementation level but not by their interaction. Glutathione peroxidase (GPx) activity, haematocrit, Se accumulation and muscle tissue integrity were significantly enhanced in fish fed on OS-supplemented diets. Furthermore, when high SBM was included in diets, elevated Se tended to lower the barramundi's performance. These findings suggest that dietary supplementation of OS at 2-3 g kg-1 diet is necessary when high plant protein ingredients are incorporated in the diet, in order to maintain better growth and to afford protection against oxidative stress.

Very limited information is available on the relationship between dietary selenium (Se) and plant protein (PP) sources in carnivorous marine aquaculture species. Therefore, this study employed a 2 × 3 experimental layout to investigate the effects of lupin meal (LM) protein inclusion levels (0, 25 and 75%) and organic selenium (OS) levels (0 or 2 g kg− 1) on the growth, physiology and histopathology of juvenile barramundi (Lates calcarifer). The experimental diets (LM0, LM0 + OS, LM25, LM25 + OS, LM75 and LM75 + OS) were formulated on an isonitrogenous (48.8% crude protein) and isocalorific (20.6 MJ kg− 1 gross energy) basis. In the 60-day feeding experiment, final weight (FW), specific growth rate (SGR) and weight gain (WG) were improved by the supplementation of Se in LM-based diets. Fish fed diets containing Se had higher FW, SGR and WG compared with those fed diets lacking Se supplementation (P Statement of relevance While plant-based feed sources such as lupin meal have the potential to reduce the reliance on unsustainable wild fishmeal in aquaculture, such products may reduce the feed availability of selenium, an essential element for aquatic animals. We believe that the findings of this study are relevant to the general field of commercial aquaculture.

Sustainable aquaculture, from both ecological and economic perspectives, demands a substantial reduction of the amount of fishmeal used in aqua feed. Instead, plant-derived protein feed stuff, which provide a nutritious diet offer a promising alternative for inclusion in aqua feed. In this study, the effects of organic selenium supplementation in low and high soybean meal-based practical diets for yellowtail kingfish (Seriola lalandi) were evaluated over a 60-day feeding experiment. The juvenile yellowtail kingfish (initial weight 5.02 ± 0.04 g fish −1 ) were fed five iso-nitrogenous and iso-caloric diets containing 49% crude protein and 22 MJ kg −1 gross energy. The control diet(C) includes 46% fishmeal, whereas the other diets used soybean meal to replace 25% and 75% of the fishmeal protein, both without and with organic selenium supplementation (SBM 25 , SBM 25+Se , SBM 75 , and SBM 75+Se ). Fish were fed ad libitum two times a day at 09:00 and 15:00 hours. No differences were observed in feed intake among dietary treatment groups (P > 0.05). Organic selenium-supplemented diets improved final weight; however, final weight was significantly reduced when fish were fed high soybean meal diets (P < 0.05). Organic selenium supplementation had a significant effect on specific growth rate at low soybean meal diets, but did not affect specific growth rate when fish were fed high soybean meal diets. Selenium accumulation in fish fillet was strongly correlated with selenium concentration in the diets. While fish fed the SBM 25+Se diets had significantly higher glutathione peroxidase activity than those fed other diets, the lowest glutathione peroxidase activity was found in fish fed SBM 75 diets. Histologically, selenium-deficient diets induced myopathy and alterations in tissue structure were most prevalent in fish fed the SBM 75 diet. The findings of this study indicate that, with Se supplementation, soybean meal could supply 25% of the protein in yellowtail kingfish diets.

Seven isonitrogenous (47.0% crude protein), isolipidic (14.0% crude lipid) and isocaloric (22.0 MJ Kg−1 gross energy) diets were formulated and tested in a feeding trial to evaluate the efficacy of raw and enzyme-treated alga, Spirulina platensis (SP) to replace fishmeal (FM) on growth, digestibility, biochemical response and health status of juvenile barramundi, Lates calcarifer. The control diet had fishmeal as the main protein source and was progressively substituted with raw (RSP) or enzyme-treated SP (ESP) protein at 10%, 20%, and 40% of FM. Diets were fed in triplicated groups of barramundi with an initial body weight of 9.20 ± 0.3 g/fish, thrice a day for 8 weeks. The results showed that the weight gain (WG) and feed conversion ratio (FCR) were not negatively affected by the replacement of dietary ESP, while dietary 40% RSP level of FM significantly reduced (P .05) reduction of intestinal fold height, microvillus height, and thickness of muscular wall were recorded in fish fed RSP20, RSP40, and ESP40 diets than the control. The histopathological alterations in liver and muscle appeared in fish fed both ESP and RSP diets at 40% replacement of FM. Except for the fish fed 10% of RSP diet, all other fish, the exposure to transportation stress increased the plasma glucose levels although the plasma cortisol levels were not changed in various feeding levels. Overall, this study demonstrates that up to 20% RSP or 40% ESP unaffected the growth performance of juvenile barramundi while replacement of 40% FM with SP either raw or enzyme-treated impacted the health status in terms of the liver, muscle and intestinal morphology of fish.

The present study investigates if the total replacement of dietary fishmeal (FM) with poultry by-product meal (PBM), supplemented with methionine influences the muscle fatty acids composition, normal gut morphology, histological traits of the liver, muscle, and gill, liver enzymes, immune and antioxidant response, and stress-related gene in juvenile barramundi, Lates calcarifer in relation to growth and feed utilization. Barramundi (3.58±0.01g) were randomly distributed into six 300 L seawater recirculating tanks (25 fish/tank) and fed two formulated isonitrogenous and isolipidic diets for 6 weeks. The control diet had FM as the sole animal protein source, whereas other test diet had only PBM as an animal protein source. Dietary PBM affected the fish performance and feed utilization. Regarding muscle fatty acid profile, total saturated fatty acids and monounsaturated fatty acids elevated while total PUFA particularly n-3 LC-PUFA and EPA decreased in PBM fed fish than control diet fed fish. Liver, muscle, gill, and intestinal histology showed no obvious alteration in control diet fed fish, however, more lipid droplets and hepatic vacuolization in the liver, necrotic myotome in muscle, hyperplasia in secondary lamellae in gill and short and broken folds in the intestine were observed in PBM fed fish. Similar to light microscopy observation of intestinal morphology, the transmission electron microscopy (TEM) analysis revealed shorter and smaller microvilli in fish fed PBM. Histopathological alterations in the liver of PBM fed fish were further associated with the elevated levels of aspartate aminotransferase (AST) and glutamate dehydrogenase (GLDH) and the significant upregulation of stress-related genes, HSP70 and HSP90. Also, a negative influence on lysozyme activity, and antioxidant enzymatic activities were recorded in fish fed PBM. Overall, it can be concluded that a total substitution of FM protein by methionine supplemented PBM negatively influenced the growth performance, liver health, histological traits of different organs, immune and antioxidant response, and expression of stress-related genes in juvenile barramundi.

The present study compared the nutrient compositions of peanut seed (Arachis hypogaea) subjected to three processing techniques; mechanical pressing, fermentation and germination. The study also evaluated the effect of inclusion level (0%, 15 %, 30 % and 60 %) on nutrient digestibility of these meals by juvenile barramundi (Lates calcarifer) and the subsequent discharge of nutrients to the rearing water. A diet containing no peanut meal served as a reference diet. Barramundi of average weight of 31.2 ± 1.2 g were fed on 10 test diets for 4 weeks. Germination processing significantly (p < 0.05) lowered the carbohydrate and hydrolysed fat contents of peanut meal and its protein level. Fermentation and germination significantly affected the protein quality of peanut meal producing a greater proportion of short peptides (

The purpose of this study was to identify and morphologically characterize the hemocyte cell types of freshwater crayfish, Cherax cainii. In addition to morphological observations using a light microscope (LM) and electron transmission microscope (TEM), a flow cytometer (FCM) is also used. Three main types of haemocyte of C. cainii were identified by LM, TEM, and FCM. Determination of haemocyte by LM based on the number, size of cytoplasmic granules and the ratio of N:C. These cells are Hyaline (HC), Small Granule (SGC), and Large Granule (LGC) cells. Three types of haemocyte were also observed by TEM based on cell and nucleus size, granule diameter, number of cytoplasmic granules per cell and N:C. Haemocyte population was successfully detected with FCM based on forward scatter (FSC) signals, versus side scattering signals/side scatter (SSC), with plot data via scatter parameter gating. Three cluster formations were observed, which were temporarily classified as SGC, LGC, and HC regions. Morphometric analysis was performed with TEM on C. cainii haemocyte to measure various cellular features. Some morphological features vary between types of haemocyte and are also affected by temperature. Total hemocyte count (THC) and differential hemocyte count (DHC) are calculated using FCM. THC increases with higher temperatures, from 1,9 x 106 /ml at 20 °C to 4.9 x 106 /ml at 30 °C. The most abundant hemocyte at all temperatures is HC, followed by SGC and LGC.

Poultry by-product meal (PBM) has been utilised as a substitute of fishmeal (FM) in many aquaculture species. However, little information is known regarding the use of bioprocessed PBM (BPBM) in aquaculture production. This study was undertaken to investigate whether replacing FM with BPBM improved growth performance, gut morphology and fatty acid synthesis of juvenile barramundi, Lates calcarifer. The PBM was bioprocessed by baker yeast, Saccharomyces cerevisae and Lactobacillus casei. The BPBM was used to replace FM at 75% and 100% (75BPBM and 100BPBM) contrasting against unprocessed PBM (75PBM and 100PBM) at the same levels and FM based diets as the control. Juvenile barramundi with a mean initial weight of 3.78±0.16 g were stocked at a density of 20 fish per tank. After the 42 days of study, the final weight, specific growth rate and feed conversion ratios of fish fed 75PBM and 75BPBM were not significantly different from the control. However, 100% supplementation diets of 100PBM and 100BPBM resulted in reduced performance in all growth and feed variables except total feed intake and survival. The hind gut microvillus density was significantly higher (P

This study aimed to characterize the bacterial communities in rearing water treated with commercial plastic biological ball filters named as Bio-ball in marron culture for 60 days. Inclusion of Bio-ball in the aquaculture tanks showed improvement in water quality parameters and enrichment of bacterial communities in terms of operational taxonomic units. The water treated with Bio-ball showed significantly less nitrate, nitrite, ammonia, phosphorus and high dissolved oxygen concentration than untreated control group. At phylum level, Proteobacteria was dominant in both control and treated water, whereas Firmicutes was found to be significantly (P < 0·05) enriched in Bio-ball treated water. Among the classified genus, Aquabacterium and Polunucleobacter were most dominant in control and Bio-ball treated water respectively. Linear Discriminant Analysis Effect Size exhibited 31 indicator bacterial genus, 10 in control and 21 in treated condition, suggesting the enrichment of microbial lineages with addition of Bio-ball. The bacteria Haliscomenobacter, Hypnocyclicus, Pajaroellobacter and Vibrio were found to be significantly (P < 0·001) correlated with higher pH, nitrate, nitrite, phosphorus and ammonia in control tanks, whereas Corynebacterium was linked to higher temperature in treated water. Overall results suggest that Bio-ball filter media significantly improved the water quality and microbial populations in aquaculture tanks. SIGNIFICANCE AND IMPACT OF THE STUDY: The results of this study revealed the positive impacts of Bio-ball in enrichment of microbial flora associated with the degradation process of nitrogenous and organic compounds. Bio-ball also showed the capability to prevent the colonization of harmful bacteria, and favoured the growth of beneficial microbes in aquatic system. This study therefore could pave the ways of increasing the aquaculture production by improving the water quality.

Conventional aquaculture feed materials available in Australia are expensive, which has prompted the search for alternatives that would be cost-effective and locally available. The present study was undertaken in order to maximize the use of a tuna hydrolysate (TH), which was produced locally from the tuna-processing discards. The growth performance, biochemical status, antioxidant capacity and liver health of juvenile barramundi (Lates calcarifer) were assessed. Two series of isonitrogenous and isocaloric diets labelled as TH50, TH75 (non-fermented tuna hydrolysate) and FTH50, FTH75 (fermented tuna hydrolysate) were formulated to replace FM at 50% and 75%, respectively. A basal diet without the TH supplementation was used as a control. The experimental diets were fed to the triplicate groups of fish three times a day for 56 days. The results of the experiment revealed that fish fed on both fermented and non-fermented TH-containing diets significantly reduced (p 50, FTH50 and TH75 exhibited reduced (p 75 exhibited no difference with the control. The excessive inclusion of TH in the diets of TH75 and FTH75 resulted in cytoplasmic vacuolization, with an increased amount of lipid accumulation, and necrosis in the liver tissue. These results indicated that the replacement of the FM protein with TH at 50% and 75% inclusion levels negatively affected the growth performance, feed utilization, and digestibility in juvenile barramundi; and it also increased the potential risk of hepatic failure in the fish. Further investigation is, therefore, required in order to optimize the TH levels in the fish diets which would be suitable for the growth of fish, as well as for maintaining the enhanced biochemical response in juvenile barramundi.

Barramundi (Lates calcarifer) fillets were subjected to two different ice forms (pre-freezing treatments: slurry ice [SI] and flake ice [FI]) for 0 (before freezing) and 1 h and 1, 2, 4, 8 and 16 days prior to blast freezing at −80C for 8 h. Fillets were then stored in a freezer at −20C for 20 days. Microbiological and physiochemical analysis were then carried out. Fillets that were exposed to pre-freezing treatments in FI demonstrated larger increase in total volatile base nitrogen, total viable count and pH; larger decrease in protein content; and smaller increase in moisture content compared with SI at the end of the frozen storage. Fillets exposed to pre-freezing treatments in FI are significantly (P

This study aimed to investigate if the fermentation of sweet lupin, Lupinus angustifolius , increases the inclusion level of the lupin by replacing fishmeal content in the formulated diets of juvenile barramundi. Sweet lupin kernel was fermented by Lactobacilli (3.10 8 CFU/g) for 72 h to be used to replace fishmeal at 0%, 30%, 45%, 60%, and 75% of inclusion levels. The results showed that the fermentation of lupin significantly reduced the amount of anti-nutrients and improved the amino acid profile of the lupin. The growth rates of the juvenile barramundi were not adversely affected by the different inclusion levels of fermented lupin in the diets. There was an even significant increase in the final weight and length of the barramundi fed 45% and 60% fishmeal replacement diets. The survival rates were more than 93% in all dietary treatments. Feed conversion rates (FCR) were unchanged among the diets, except significantly higher FCR shown in 75% fishmeal replacement diet. The differences of protein digestibility among diets were not significant. However, hydrolyzed fat and phosphorus in the diets significantly increased ( p Lactobacilli improved the lupin’s nutritional quality, allowing higher inclusion level in barramundi diets.

The effect of time-temperature abuse on quality and shelf life of barramundi (Lates calcarifer) fillets using microbiological and physiochemical tools was investigated. Fillets were subjected to three different pre-blast freezing (PBF) temperatures viz. 5, 0 and −20C for 0 h, 1 h, 1, 2, 4, 8 and 16 days, after which fillets were exposed to −80C for 8 h and then stored at −20C for 20 days. Color and rheological parameter values changed as PBF time period progressed at each temperature tested. There was minimal change to the microbiological and physiochemical properties of fillets stored at −20C from 0 h to 16 days. Total viable count, total volatile base nitrogen, pH, protein, color and rheological parameters of fillets that underwent PBF temperature period at 0 and 5C for 16 days deteriorated significantly compared with those treated at −20C. The shelf life of PBF barramundi fillets at 0 and 5C was 8 days. Practical Applications After slaughter, the fish are likely to be exposed to inconsistent storage conditions (temperature abuse) for a limited period during transportation and subsequent storage. This temperature abuse may accelerate quality and shelf life changes in fillets. The purpose of the present study was to investigate the effects of different pre-blast freezing temperature periods and temperatures (time-temperature index).

The growth feasibility of Lomentaria sp. in ocean water (OW) and inland saline water (ISW) at salinity 30‰ was tested in a series of four experiments. To grow Lomentaria sp., potassium chloride (KCl) was used to fortify ISW to approximately 100%, 66%, and 33% (ISW100, ISW66, and ISW33 respectively) of [K+] in OW and compared to two controls of OW and ISW. The results showed that the ISW66 medium resulted in the highest (P

Selenomethionine (SeMet) was supplemented to a fishmeal-based diet to investigate the toxic effects of excessive levels of dietary selenium (Se) in juvenile yellowtail kingfish ( Seriola lalandi ). For 10 weeks, the fish were fed one of five experimental diets; a basal diet containing 2.31 mg/kg of inherent Se or diets supplemented with SeMet to provide 4.91, 9.58, 15.43 or 20.87 mg/kg of Se. The results showed that the fish muscle proximate composition, feed conversion ratio and survival were not sensitive to dietary Se treatments; and no histopathological lesions were observed in heart and intestine tissues of the fish. The Se concentrations in liver and muscle tissues showed a strong linear positive relationship with the levels of Se in diets. Fish when fed the basal diet exhibited Se deficiency symptoms including myopathy, reduced feed intake, glutathione peroxidase activity and growth; whereas those fed the diets containing ≥ 4.91 mg Se/kg did not. While fish fed the 15.43 mg Se/kg diet did not show any toxic effects, the 20.87 mg Se/kg diet caused histopathological changes in liver and spleen as well as reduced feed intake, growth, haematocrit and hepatosomatic index, indicating Se toxicity. In conclusion, Se levels in liver and muscle tissues can be used as effective indicators of dietary Se exposure and dietary Se level between 15.43 and 20.87 mg/kg may be a threshold level in juvenile yellowtail kingfish.

Effects of dietary selenium (Se) on immune competence of yellowtail kingfish, Seriola lalandi, were investigated. The fish were fed one of the three experimental diets including a control diet without Se supplementation and two diets supplemented with Se from Se-yeast (Selplex) at 2 and 4 mg/kg. After feeding for 6 wk, the fish were challenged by injecting Vibrio anguillarum and observed for 2 wk. Dietary Se had no effect on feed intake, feed conversion ratio, and survival over the course of 6-wk feeding; however, it significantly increased weight gain and Se content in muscle. Following the bacterial infection, the immune-stimulating effects of Se were observed in antibody, lysozyme, and bactericidal responses, and there was a corresponding increase in survival and hematocrit by Se. Under infectious condition, antioxidant capacity of fish as measured in terms of resistance of red blood cells to peroxidation and glutathione peroxidase activity also increased by supplementation of Se. Liver necrosis and kidney melano-macrophages were only seen in surviving fish fed the control diet after the challenge. Furthermore, there was evidence of myopathy in fish fed the diet without Se supplementation. This study suggests that Se, supplemented at 2 or 4 mg/kg, can improve growth and health of yellowtail kingfish.

Niobium diboride (NbB 2 ) is synthesized and consolidated by the spark plasma sintering technique. Elemental reactants such as niobium (Nb) and boron (B) were subjected to two stage heat treatment, initially at 1200 °C for synthesis and followed by densification at the temperatures in the range of 1700 °C to 1900 °C. High dense NbB 2 (~ 97.7%ρ th ) is obtained at 1900 °C after 15 min holding period. Load application during heat treatment stage is found to improve the sinterability of the niobium diboride compacts. Hardness, elastic modulus and indentation fracture toughness of the high dense NbB 2 are measured as 20.25 GPa, 539 GPa and 4 MPa m 1/2 respectively.

The densification behavior of boron carbide without sintering additives is reported for temperatures in the range of 1100 °C to 1800 °C by spark plasma sintering (SPS) technique together with the sintering parameters (Holding Time and Pulsed DC). The influence of porosity on mechanical properties (hardness, fracture toughness and elastic modulus) of boron carbide prepared by SPS is measured. Pulsed DC current is found to play a dominant role in the densification of boron carbide and in achieving near theoretical density at lower sintering temperature compared to conventional sintering techniques. Hardness, fracture toughness and elastic modulus of fully dense B 4 C are measured as 37.2 GPa, 2.8 MPa.m 1/2 and 570 GPa respectively. Microstructural analysis indicates the presence of deformation twins in boron carbide grains.

Different forms of selenium (Se) were supplemented to a fishmeal-based diet to investigate the digestibility and bioavailability of Se in yellowtail kingfish (Seriola lalandi). Five groups of fish in triplicate were fed a basal diet (containing 3.31 mg/kg Se) either unsupplemented or supplemented with 2 mg/kg Se from selenite, selenocystine (SeCys), selenomethionine (SeMet) or Se-yeast for 6 weeks. The basal unsupplemented diet resulted in significantly lower weight gain, red blood cell glutathione peroxidase (GPx) and bactericidal activities than the supplemented diets. Muscle Se concentration was increased by Se supplementation from SeCys, SeMet or Se-yeast, but not selenite. There was no difference in GPx activity of fish fed with any supplemented diets. The bioavailability of Se from SeMet and Se-yeast was similar for all measurements. The most digestible sources of Se were from SeMet and Se-yeast, whereas the least was from fishmeal. Se from SeMet or Se-yeast produced more weight gain, higher Se accumulation in muscle tissues and bactericidal activity in yellowtail kingfish than Se from SeCys or selenite. This study shows that SeMet and Se-yeast are the most bioavailable sources of Se to yellowtail kingfish and are recommended to be supplemented to fishmeal-based formulated diets for yellowtail kingfish.

Six dietary treatments were prepared in a 3 × 2 factorial design (unsupplemented or supplemented with Se at 1 or 2 mg kg-1 × supplemented with vitamin E at 40 or 180 mg kg-1) and fed to yellowtail kingfish (Seriola lalandi) for 6 weeks to evaluate the effects of dietary Se and vitamin E on growth performance, immune and antioxidant responses and to investigate the potential interaction between these two micronutrients in this species. The results have revealed significantly interactive effects with positive physiological responses. Se significantly increased weight gain of fish fed diets low in vitamin E, but not high in vitamin E, whereas serum lysozyme activity was significantly improved by Se in diets high in vitamin E, but not low in vitamin E. Moreover, there was evidence of myopathy in fish deficient in both Se and vitamin E, but not single deficiency. There was no significant effect of dietary Se, vitamin E or their interaction on survival, antibody titre, feed intake, feed conversion ratio and fillet proximate composition; however, fillet Se and vitamin E were significantly responsive to dietary Se and vitamin E, respectively, and higher dietary Se intakes produced significantly higher red blood cell glutathione peroxidase activity.

A 90-day feeding trial was conducted to determine the effects of dietary organic selenium (OS) supplementation on immune responses, total selenium accumulation in various tissues and the digestive system health of marron Cherax cainii. A group of marron (initial weight 3.65 � 0.05 g) were fed 0.2 g kg � 1 of Sel-Plex as a source of OS and were compared to a control group of marron that were not fed OS. After 90 days of feeding OS, total haemocyte counts (THC) and the percentages of granular and semigranular cells in marron were significantly higher than in marron fed a control diet. However, dietary OS did not affect the proportion of hyaline cells. The marron fed OS had significantly lower bacteraemia and longer neutral red retention times than the control group. Total selenium levels in the haemolymph, hepatopancreas and muscle tissues of the OS-fed marron group were significantly higher (P < 0.05) than in control diet group. The highest total soluble selenium levels were found in the muscle tissues of OS-fed marron on the final day of the feeding trial. Amylase and protease activity, soluble protein, and numbers of microvilli were significantly higher (P < 0.05) in marron fed OS. These findings demonstrate the benefits of including 0.2 g kg � 1 OS in marron diet to enhance immune parameters, increase total selenium accumulation in muscle and improve marron digestive system health.

This study was conducted to compare the effects of dietary supplementation of selenium (Se, both inorganic and organic) and mannan oligosaccharide (MOS) on the growth, immune function, and antioxidant enzyme activities in the haemolymph of the marron Cherax cainii (Austin, 2002); 0.4 mg kg−1 of sodium selenate, 0.2 g kg−1 Sel-Plex®, or 0.4 % Bio-MOS® was added to the basal diet as sources of inorganic selenium (IS), organic selenium (OS), and MOS, respectively. After 90 days, marron fed all 3 supplemented test diets had significantly higher final weight, specific growth rate (SGR), survival, total haemocyte count (THC), percentage of hyaline cells, glutathione-S-transferase (GST), and glutathione peroxidase (GPx) activities than marron fed without any supplements. The marron fed OS showed significantly higher THC and percentage of hyaline cells than those fed IS and MOS. Marron fed MOS showed the highest final weight, SGR, and percentage of granular cells; however, there was no significant difference in the neutral red time retention between marron fed IS and OS, whereas marron fed OS resulted in the highest GPx activity and total Se levels in the haemolymph but the lowest lipid peroxidase activity; therefore, it is suggested that dietary supplementation with any source of Se and MOS is beneficial to improving growth, survival, and antioxidant activity.

This paper presents the experimental results on synthesis of boron carbide from its elements. Boron to carbon ratio of 4:1 and a synthesis temperature of 1850°C was found optimum to obtain stoichiometric B4C. Higher boron in charge resulted in the formation of boron rich phase B8C along with B4C but was not effective in eliminating free carbon in the product. Effect of hot pressing parameters on densification of boron carbide was investigated and the optimum operating parameters to obtain B4C pellets with a density of ≥95% TD were identified. Mechanical and thermal properties were characterized and compared with literature values.

The effects of dietary selenium (Se) and vitamin E and their interaction in the nutrition of yellowtail kingfish, Seriola lalandi, were investigated. Six dietary treatments were prepared in a 3 × 2 factorial arrangement (not supplemented or supplemented with Se at 1 or 2 mg kg−1 × supplemented with vitamin E at 40 or 180 mg kg−1). A group of fish in triplicate were fed one of the six experimental diets for 6 weeks, and their growth performance, haematological and immune responses were measured. The results revealed positively interactive effects between dietary Se and vitamin E in yellowtail kingfish. Se significantly increased weight gain of fish fed diets low in vitamin E, but not high in vitamin E. Simultaneous supplementation of both micronutrients resulted in significant increase in serum bactericidal activity. There was no significant effect of Se or vitamin E on survival, feed intake, feed conversion ratio, haematocrit, white blood cell counts and fillet proximate composition. However, Se and vitamin E contents in fillets were significantly responsive to dietary Se and vitamin E, respectively. The supplemental level of Se at 2 mg kg−1 significantly increased red blood cell counts and haemoglobin concentrations, while lysozyme activity in skin mucus was significantly stimulated by vitamin E. The findings of Se and vitamin E supplementation in this study can be applied to improve growth and health indices of yellowtail kingfish.

The dietary selenium (Se) requirement of yellowtail kingfish (Seriola lalandi) in normal and infected conditions was investigated. The fish were fed one of five experimental diets; a control un-supplemented diet (3.35 mg/kg Se) or diets supplemented with Se to provide 4.86, 5.38, 5.85 or 6.38 mg/kg Se. After feeding for 6 weeks, the fish were challenged by Vibrio anguillarum immersion and then observed for 4 weeks. Supplementation of Se had no effect on feed intake, feed conversion ratio and survival over 6 weeks of feeding; however, it significantly increased growth and Se content in muscle tissues. The optimal Se level for maximal growth of yellowtail kingfish estimated by second order regression was 5.56 mg/kg. Following the bacterial challenge, the immune-stimulating effects of Se were demonstrated in lysozyme and bactericidal activities, and there was a corresponding increase in survival and antibody response by supplementation of Se at ≥2 mg/kg (measured Se of ≥5.38 mg/kg). Under normal and infectious conditions, antioxidant capacity of fish measured as glutathione peroxidase activity increased by supplementation of Se. During post-challenge period, haematocrits were higher in the fish fed Se supplemented diets than the fish fed the control diet, while more macrophage aggregates were seen in the control group than in the others. Furthermore, there was evidence of myopathy in fish fed the diet without Se supplementation. Therefore, the results indicated that the optimal dietary Se requirement of yellowtail kingfish is 5.56 mg/kg.

Solvent-extracted soybean meal (SBM) was fermented using baker's yeast Saccharomyces cerevisae at 30 °C for 5 days. Four isonitrogenous and isocaloric diets containing 75% SBM protein, either fermented or non-fermented (SBM and FSBM), and supplemented or not with organic Se (OS) (SBMOS and FSBMOS), were fed to triplicate groups of juvenile barramundi (Lates calcarifer) (initial weight of 5 g) for 75 days. A fishmeal (FM)-based diet formulated for juvenile barramundi was used as a reference diet. The growth of fish was significantly affected by either the interaction of SBM type or by the OS level. In fish fed diets supplemented with OS (SBMOS and FSBMOS), final weight (FW), specific growth rate (SGR) and weight gain (WG) were higher in fish fed the fermented SBM (FSBMOS) than in those fed the non-fermented SBM (SBMOS). The apparent digestibility coefficient (ADC) of protein was higher in the fish fed the fermented SBM, either supplemented or unsupplemented with OS. However, there were no significant differences in the ADC of dry matter (DM) and lipids among the tested diets and in comparison to the reference diet. The haematocrit and leucocrit of fish fed the FSBMOS diet were lower than those of fish fed the FM diet. Furthermore, glutathione peroxidase (GPx) activity was significantly influenced by OS supplementation in the experimental diets; GPx activity was greater in the fish fed diets supplemented with OS. Creatinine kinase (CK) of all groups of fish was higher than the CK of those fed the reference diet. These results suggest that with a proper nutritional level, OS supplementation may act as an important factor in enzymatic GPx activity and in the haematology and blood biochemistry status of juvenile barramundi fed fermented SBM-based diets, encouraging improvement of the overall growth performance.

Feed rate is one of the important variables considered for the improvement in production of prawns. The effects of four feeding rates on growth, water quality and the nutrient budget of Penaeus latisulcatus were investigated for 98 days. The specific growth rate (SGR) at 3.0% feed rate was significantly higher than at all higher feed rates, and there was no significant difference in SGR between 4.5%, 6% and 7.5%. Total ammonia nitrogen concentrations in all treatments remained low in the safe range for prawn culture. Dissolved inorganic nitrogen and nitrate nitrogen were significantly higher (P < 0.05) in prawn tanks received feed rates of 6.0% and 7.5%. Total phosphorus and the soluble reactive phosphorus linearly increased with the progression of the trial and feeding rates. Nutrient conversion rates were significantly higher (P < 0.05) in prawns receiving the feeding rate of 3.0% than feeding rates of 6.0% and 7.5%. The lowest food conversion ratio was recorded at feeding rates of 3% and 4.5%. Nutrient budget showed that 6.01–15.99% nitrogen and 4.53–9.29% phosphorus of the nutrient inputs were retained in the prawn biomass. The results indicated that the growth and nutrient conversion rate may not increase with the increase above 3.0% of biomass per day.

Gracilaria is the most importance source of raw material for the extraction of the polysaccharide agar. Despite its worldwide importance, few papers have addressed the effect of different life stages on the biomass and agar production. Gracilaria cliftonii Withell, Millar & Kraft (1994) has been identified as a potential species for aquaculture due to its high agar yield (> 60%). However, information related to seasonal variations in biomass and abundance of the species has not yet been determined. The present study reports the seasonality of biomass, abundance, occurrence and plant length variations of different life stages from G. cliftonii from Western Australia. The biomass and abundance of tetrasporophyte and carposporophyte stages of G. cliftonii in autumn was significantly higher (p < 0.05) than other seasons, while the biomass of the vegetative stage was significantly higher in spring and summer. Biomass and abundance were found to be dependent on nitrate and nitrite concentration, while male biomass was dependant (p < 0.05) on rainfall and osmolality. The present study provided new information on the phenology of Gracilaria from a different location of the world and demonstrates that variations in biomass, abundance and plant length of G. cliftonii are influenced by environmental parameters.

Integrating recirculating aquaculture systems with seaweeds is one of the strategies that can minimise wastes and risk of disease outbreaks. This study investigated the effect of integrating green seaweed ( Ulva lactuca ) with western king prawns ( Penaeus latisulcatus ) at varying stocking densities on the water quality, nutrient conversion rates and nutrient budget under closed recirculating culture system. The experiment was conducted using fifteen indoor tank recirculating systems and tested four different stocking ratios of prawns and seaweed with a control having prawns only. The four stocking ratios of seaweed and prawn biomass were 2, 4, 8 and 16 per tank. The mean concentrations of total ammonia nitrogen (TAN), NO 3 − –N and PO 4 3− –P in the prawn and seaweed tanks were significantly lower (P U. lactuca was highly efficient in removing the inorganic nutrients from the culture systems with TAN removal rate of 59–81% and PO 4 3− –P removal rate of 50–55%. Integrating seaweed with prawns did not significantly alter the specific growth rate (SGR) and survival rate of the prawns (P > 0.05). Ratio of C:P in seaweed tissues decreased with increasing seaweed stocking densities while C:N ratio showed an adverse trend. The nutrient conversion rate into total biomass (prawns plus seaweed) in the integrated systems was significantly higher at the highest seaweed stocking density (2.00 kg m − 2 ). Nutrient budget revealed that seaweed retained about 6.5–29.7% nitrogen and 1.6–13.5% phosphorus inputs while values for prawns were 28.0–31.9% and 13.5–14.6%, respectively. Seaweed also removed dissolved inorganic nitrogen effectively in the closed recirculating aquaculture system.

The efficacy of dietary supplementation of mannan oligosaccharide (MOS) (Bio-Mos®, Aqua Grade; Alltech, Lexington, KY, USA) was evaluated on survival, growth, physiological and immunological parameters of marron, Cherax tenuimanus. Marron were fed six different isonitrogenous and isocalorific diets supplemented with 0, 0.05, 0.1, 0.2, 0.4, and 0.8% of MOS for a duration of 112 d and examined for survival and growth every 28 d. Physiological and immunological indicators were measured every 56 d. After 112 d, survival was the highest when marron were fed 0.2 and 0.4% MOS supplemented diets. Wet tail muscle index (TMIwet) and dry tail muscle index (TMIdry) of marron fed MOS supplemented diets were significantly higher (P < 0.05) than marron fed diet without MOS. Osmoregulatory capacity was highest in marron fed 0.4% MOS. Marron fed MOS supplemented diets had lower (P < 0.05) bacteraemia than marron fed diet without MOS. Hemolymph clotting time was the lowest and granular cells were the highest in marron fed 0.2 and 0.4% MOS. The results suggest that feeding 0.2–0.4% MOS in the diet increases the health status of marron.

This paper presents the results of experimental investigations carried out on the synthesis of pure ZrB2 by boron carbide reduction of ZrO2 and densification with the addition of HfB2 and TiSi2. Process parameters and charge composition were optimized to obtain pure ZrB2 powder. Monolithic ZrB2 was hot pressed to full density and characterized. Effects of HfB2 and TiSi2 addition on densification and properties of ZrB2 composites were studied. Four compositions namely monolithic ZrB2, ZrB2 + 10% TiSi2, ZrB2 + 10% TiSi2 + 10% HfB2 and ZrB2 + 10% TiSi2 + 20% HfB2 were prepared by hot pressing. Near theoretical density (99.8%) was obtained in the case of monolithic ZrB2 by hot pressing at 1850 °C and 35 MPa. Addition of 10 wt.% TiSi2 resulted in an equally high density of 98.9% at a lower temperature (1650 °C) and pressure (20 MPa). Similar densities were obtained for ZrB2 + HfB2 mixtures also with TiSi2 under similar conditions. The hardness of monolithic ZrB2 was measured as 23.95 GPa which decreased to 19.45 GPa on addition of 10% TiSi2. With the addition of 10% HfB2 to this composition, the hardness increased to 23.08 GPa, close to that of monolithic ZrB2. Increase of HfB2 content to 20% did not change the hardness value. Fracture toughness of monolithic sample was measured as 3.31 MPa m1/2, which increased to 6.36 MPa m1/2 on addition of 10% TiSi2. With 10% HfB2 addition the value of KIC was measured as 6.44 MPa m1/2, which further improved to 6.59 MPa m1/2 with higher addition of HfB2 (20%). Fracture surface of the dense bodies was examined by scanning electron microscope. Intergranular fracture was found to be a predominant mode in all the samples. Crack propagation in composites has shown considerable deflection indicating high fracture toughness. An oxidation study of ZrB2 composites was carried out at 900 °C in air for 64 h. Specific weight gain vs time plot was obtained and the oxidized surface was examined by XRD and SEM. ZrB2 composites have shown a much better resistance to oxidation as compared to monolithic ZrB2. A protective glassy layer was seen on the oxidized surfaces of the composites.