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This study aimed to investigate the optimal dietary vitamin B 12 requirement of fingerling blunt snout bream Megalobrama amblycephala based on the results of growth performance, intestinal digestive and absorptive capability and responses of the growth hormone (GH)-insulin-like growth factor-I (IGF-I) axis. Fish (initial body weight: 0.71 ± 0.03 g) were randomly assigned to six purified diets containing graded levels of vitamin B 12 (0, 0.028, 0.051, 0.12, 0.23 and 0.41 mg/kg) for 12 weeks. Both weight gain (WG) and specific growth rate increased significantly ( P < 0.05) as dietary vitamin B 12 levels increased from 0 to 0.051 mg/kg, then plateaued with further increasing levels. Feed conversion ratio decreased as dietary vitamin B 12 levels increased from 0 to 0.12 mg/kg, but no statistical difference was observed. Whole-body composition and intestinal brush border enzymes activities also exerted little difference within the vitamin B 12 range tested, whereas hepatic vitamin B 12 contents increased remarkably ( P < 0.01) with increasing dietary vitamin B 12 levels. Intestinal protease, amylase and lipase activities all increased significantly ( P < 0.05) as dietary vitamin B 12 levels increased from 0 to 0.12 mg/kg, but decreased remarkably ( P < 0.05) with further increasing vitamin B 12 levels. Similar results were also observed in hepatic IGF-I expressions. Furthermore, the mRNA expressions of GH in the brain decreased significantly ( P < 0.05) with increasing dietary vitamin B 12 levels. Based on the broken-line regression analysis of WG, the optimal dietary vitamin B 12 requirement of fingerling blunt snout bream was estimated to be 0.06 mg/kg. In addition, a supplementation of 0.12 mg/kg vitamin B 12 boosted intestinal digestive capability and hepatic IGF-I expression. Statement of relevance This study investigated the optimal dietary vitamin B 12 requirement of fingerling blunt snout bream based on growth performance. The underlying mechanisms were also investigated with emphasis on intestinal digestive and absorptive capability and modulation of the GH-IGF-I axis. Data obtained here might facilitate the development of low-cost formulated feed for aquatic species. [ABSTRACT FROM AUTHOR]

The serial replacement of fish meal (anchovetta) by canola meal (CM) (100, 200, 300 g kg − 1 as either solvent extracted (SE) CM or expeller extracted (EX) CM was undertaken to investigate the effects of increasing dietary CM levels on feed intake, growth, protein and energy retention, plasma biochemistry and the expression of a suite of hepatic genes in barramundi (Asian seabass; Lates calcarifer ) over an eight week feeding trial. An additional diet using lupin kernel meal (LM) to replace the fish meal was also included as a comparative reference. Eight iso-digestible nitrogenous (423 ± 29 g kg − 1 ) and iso-digestible energetic (14.6 ± 8 MJ kg − 1 DM) diets were formulated. Each diet was randomly allocated to triplicate groups of fish in seawater tanks (600 L), and each tank was stocked with 15 fish (53.4 ± 7.0 g). Fish were fed once daily (9:00–10:00) to apparent satiation, and uneaten feed was collected to determine feed consumption. The results showed that the survival, feed intake, growth, FCR, energy and protein retention of fish fed the diet containing SE CM were similar or even higher to those of fish fed the fish meal reference diet (FM) and the LM diet. Fish fed with the diet containing 300 g kg − 1 SE CM did not show any changes in biochemistry and gene expression in a suite of detoxification genes. However, the diet with 300 g kg − 1 EX CM depressed feed intake, growth performance and increased feed conversion ratio (FCR). Transcription of genes involving in fatty acid synthesis and the TCA cycle were not changed by different diets. The down regulation of gene expression in certain detoxification genes ( Lc CYP1A1 , Lc CYP3A , Lc CYP2N and Lc GST ) was observed in fish fed with the diet containing 300 g kg − 1 EX CM compared to the FM control diet and other experimental diets. In general, the SE CM can be used up to 300 g kg − 1 diet without negative performance effects or signs of clinical plasma biochemistry. By contrast the maximum acceptable level of the EX CM for barramundi was only 200 g kg − 1 . Higher inclusion level of the EX CM induced negative effects on growth performance, feed utilisation, plasma biochemistry and gene expression in relation to detoxification. Statement of relevance Previous research has demonstrated that canola meal is a potential plant protein source for fish meal replacement in diets for many fish species. The present work is designed to be the first to assess both two types of Australian canola meal in regard to different processing methods (solvent extraction and expeller extraction) in use for barramundi (Asian seabass) diets. The research not only assesses effects of canola meal on growth performance and feed utilisation but also investigate effects of canola meal use on fish health status using broad approach including plasma chemistry, histology and gene expression analysis. The present findings provide practical information for barramundi's diet formulation using canola meal as an additional plant ingredient. These also provide implications of potential health effects relating to using canola meal for barramundi. [ABSTRACT FROM AUTHOR]

The prevalence of extreme, short-term temperature spikes in coastal regions during summer months is predicted to increase with ongoing climate change. In tropical systems, these changes are predicted to increase the metabolic demand of coral reef fish larvae while also altering the plankton communities upon which the larvae feed during their pelagic phase. The consequences of these predictions remain speculative in the absence of empirical data on the interactive effects of warm temperatures on the metabolism, postprandial processes and growth responses of coral reef fish larvae. Here, we tested the effect of increased temperature on the metabolism, postprandial performance and fine-scale growth patterns of a coral reef fish (Amphiprion percula) in the latter half of its ~11-d larval phase. First, we measured the length and weight of fed versus fasted larvae (N = 340; mean body mass 4.1±0.05 mg) across fine temporal scales at a typical current summer temperature (28.5°C) and a temperature that is likely be encountered during warm summer periods later this century (31.5°C). Second, we measured routine metabolic rate (Mo2 routine) and the energetics of the postprandial processes (i.e., digestion, absorption and assimilation of a meal; termed specific dynamic action (SDA)) at both temperatures. Larvae fed voraciously when provided with food for a 12-hour period and displayed a temperature-independent increase in mass of 40.1% (28.5°C) and 42.6% (31.5°C), which was largely associated with the mass of prey in the gut. A subsequent 12-h fasting period revealed that the larvae had grown 21.2±4.8% (28.5°C) and 22.8±8.8% (31.5°C) in mass and 10.3±2.0% (28.5°C) and 7.8±2.6% (31.5°C) in length compared with pre-feeding values (no significant temperature effect). Mo2 routine was 55±16% higher at 31.5°C and peak Mo2 during the postprandial period was 28±11% higher at 31.5°C, yet elevated temperature had no significant effect on SDA (0.51±0.06 J at 28.5°C vs. 0.53±0.07 J at 31.5°C), SDA duration (6.0±0.6 h vs. 6.5±0.5 h), or the percent of total meal energy used for SDA (SDA coefficient: 10.1±1.3% vs. 13.0±1.7%). Our findings of higher Mo2 routine but similar SDA coefficient at high temperature provide the first empirical evidence that coral reef fish larvae may have to secure more food to attain similar growth rates during warm summer periods, and perhaps with chronically warmer conditions associated with climate change. [ABSTRACT FROM AUTHOR]

A commercial diet (C) (48% protein and 20% lipids) and a high-digestible carbohydrate diet (CH) (37% protein, 12.5% lipids and 40% high-digestible carbohydrates) were used to feed sea bream juveniles for an 8-week period. In the commercial diet, more than 60% of ingredients were of plant origin from various sources, whereas the only component of plant origin in the CH diet was wheat. To determine the best time to administer carbohydrates and the possible protein-sparing effect, three different dietary regimes were established: C, CH-M and CH-A, and the corresponding diet was fed to sea bream in the morning (1.6% of bw) and in the afternoon (1% of bw), calculating quantities according to the amount of feed that fish ate during the acclimatization period. After the growth trial, specific growth rate (SGR), relative intestinal length, intestinal pH content, gastric and pancreatic digestive enzyme activities and nutrient absorption capacities were studied 5 h post-feeding after each meal (morning and afternoon). The acid protease activity measured was anticipatory and was higher when the next meal would have more protein. No differences in relative intestinal length or feed buffering capacity were found. The smaller ration given to sea bream in the afternoon led to a lower pancreatic release of alkaline protease and α-amylase and an up-regulation of D-Glc and L-Ala absorption capacity. A higher transit rate was measured when sea bream were fed the CH diet. When high-digestible carbohydrates were administered in the morning and the commercial diet in the afternoon, we observed a better assimilation of both diets due to compensatory mechanisms such as an increase in L-Lys, D-Glc and L-Ala absorption capacity after the morning feed, and a higher pancreatic release of alkaline protease and amylase after the afternoon feed. In contrast, when high-digestible carbohydrates were given in the afternoon, only a significant up-regulation of the capacity to absorb L-Lys was detected. Thus, the inclusion of high-digestible carbohydrates in the diet improved digestion and absorption processes when administered in the morning, leading to a protein-sparing effect that yielded growth comparable to that of fish fed an exclusively commercial diet. [ABSTRACT FROM AUTHOR]

Modern feeds for industrial salmon farming are presently formulated to fulfill specific digestible protein (DP, grams per kg feed, hereafter called units) and digestible energy (DE, Mega Joule (MJ) per kg feed) specifications. In the present study, 299 feed samples and accompanying fecal samples were obtained from 43 different farming sites for Atlantic salmon along the coast of Norway between October 2010 and February 2013. Apparent digestibility coefficients for protein and fat were calculated from protein and fat in feed and fecal matter, using analyzed crude fiber contents as a digestibility marker. Overall mean apparent protein and fat digestibilities were 87.1% (±4.9; overall mean±S.D.) and 92.5% (±3.7), respectively. Linear mixed models with rearing site as random effect were applied to evaluate factors that influenced the apparent digestibility of protein and fat, feeding intensity and energy intake. Apparent digestibility of fat tended to increase over the study period, and both feed type and feed manufacturing company, and water temperature influenced the digestibility significantly. Digestible energy content (DE, MJ/kg) was significantly negatively associated with feeding intensity, but not with total digestible energy intake. Variation at site level was significant in all analyses, and was moderate for the digestibility analyses and high regarding feeding intensity and energy intake. Digestibility assessments were used to assess accuracy, precision and agreement between optimized and realized digestible protein (DP, %) and DE level of feeds, using the mean difference between the two sets of observations and a fixed contribution of dietary energy from starch. Overall mean difference between realized and optimized DP and DE was −0.28units and −0.56MJ/kg, respectively, and there were significant differences between feed manufacturing companies. The results indicated that field digestibility assessments can be used to validate nutritional and economical value of feeds in commercial salmon farming. [ABSTRACT FROM AUTHOR]

Abstract: The effects of dietary probiotics on growth performance, health status of the digestive system and on the blood parameters of juvenile rainbow trout (Oncorhynchus mykiss, Walbaum) were investigated. Compared to the controls, diets supplemented with Kocuria SM1 and Rhodococcus SM2 for 14days caused no significant (P>0.05) change on the growth of fish, although SM2 led to an increased specific growth rate. SM1 or SM2 started to colonize in the gut after 7days of administration reaching a maximum, i.e. ~90–100% of total bacterial population, at 14days. Yet, the probiotics disappeared from the gut once administration ceased. Structural differences were not noted in the pyloric caeca and foregut, but the overall condition of the midgut and hindgut improved in fish receiving probiotics. The profile of digestive enzymes, as determined by the use of API ZYM, and stress indicators, i.e. serum hemoglobin, urea, creatinine and glucose, was not affected by any of the experimental diets (P>0.05). [Copyright &y& Elsevier]

Background. Long whiskered catfish, Mystus gulio (Hamilton, 1822), enjoys a high consumer preference and market demand in many Asian countries including India. However, the growth of this fish is very slow under normal aquaculture conditions. The non-hormonal growth promoter--cholymbi--which contains minerals and the essential amino acids lysine and methionine, is widely used in livestock and poultry as a feed additive to improve growth and survival. Supplementing feed with cholymbi may increase the growth and survival of Mystus gulio. Materials and methods. A feeding trial was conducted to determine the effect of dietary cholymbi supplementation on growth, survival, and feed conversion ratio of long whiskered catfish fingerlings. Four isoproteic diets (crude protein 37%) were formulated to incorporate cholymbi at 0%, 0.25%, 0.50%, and 0.75% diet. The diets were fed to triplicate groups offish twice daily to supply 5% of the total body weight per day for 120 days. Water quality parameters were maintained within the range suitable for catfish growth. Results. Weight gain (WG), protein efficiency ratio (PER) and feed conversion ratio (FCR) were all affected by diet (P < 0.01, 0.001, and 0.001, respectively). The group fed the 0.50% cholymbi diet had the highest WG and PER and the lowest FCR, although not significantly different from the group fed the 0.25% cholymbi diet. There was no significant difference (P > 0.05) in carcass proximate composition of catfish fed diets containing these different levels of cholymbi. Gut protease, amylase, and lipase activities were stimulated by dietary inclusion of cholymbi at all levels compared to control. Conclusion. As cholymbi is a newly introduced dietary supplement for fish, more research is needed to optimize its supplementation to improve growth, PER, FCR, and survival of long whiskered catfish. Until then, a diet with 0.50% cholymbi can be recommended to improve the aquaculture production of this species. [ABSTRACT FROM AUTHOR]

Abstract: A 10-week feeding trial in seawater floating cages (1.5×1.5×2.0m) was conducted to investigate the effects of dietary canola meal (CM) levels on growth, survival, digestion and selected immune parameters of Japanese seabass (initial average weight 8.3±0.15g). Six isonitrogenous (crude protein 43%) and isoenergetic (20kJg− 1) practical diets were formulated by replacing 0 (the control), 10, 20, 30, 40, and 50% of protein from fish meal with CM. Each diet was randomly fed to triplicate groups of fish, and each cage was stocked with 20 fish. Fish were fed twice daily (06:30 and 16:30) to apparent satiation. The results showed that with increasing dietary CM levels, the survival, specific growth rate (SGR) and feed efficiency (FE) decreased. The survival was significantly lower compared to the control group (P <0.05) with a 40% substitution level. Fish fed the diet with 20% or more protein from CM had significantly lower SGR than the control group (P <0.05), but there was no significant difference in FE at this level (P >0.05). The activities of digestive enzymes and apparent digestibility coefficients of dry matter, protein, lipid and phosphorus significantly decreased with increasing dietary CM level. A similar trend was observed in the immune response where lysozyme activity significantly decreased compared with the control group when the substitution level was more than 20%. Results of the present study indicated that protein from CM could substitute less than 20% for fish meal protein without influencing the growth of Japanese seabass. The higher substitution levels of CM induced negative influences on growth, survival and serum lysozyme of Japanese seabass. [Copyright &y& Elsevier]

Abstract: Ration levels were used to determine the digestible protein (DP) and amino acids as well as digestible (DE) and metabolizable energy (ME) requirements of Atlantic salmon post-smolts for maintenance and the efficiency of utilization for gain above maintenance. The salmon (96g) were held in seawater at a temperature of 10°C and were fasted for 28days or fed incremental ration levels of a fishmeal-based diet for 51days. The composition of gain was determined by the comparative slaughter technique. The relationships between intake of digestible or metabolizable nutrients or energy and gain of those nutrients or energy were linear (R 2 ≥0.98) between zero intake and maximum voluntary intake. The DE and ME requirements for maintenance were 31.5 and 30.6kJkg−0.8 d−1, respectively, and the efficiency of utilization of DE and ME for gain were 0.80±0.01 and 0.82±0.01, respectively. The efficiency of utilization for gain of DP was 0.64±0.01 and that of the sum of digestible amino acids 0.57±0.02. The efficiency of utilization of the individual amino acids for gain varied from 0.45 for tryptophan to 0.65 for histidine. The maintenance requirement for DP was 117.5mgkg−0.7 d−1 and for digestible sum of amino acids 204.0mgkg−0.7 d−1. The maintenance requirements for the individual amino acids varied from 4.3mgkg−0.7 d−1 for methionine and tryptophan to 20.9mgkg−0.7 d−1 for leucine. The results suggest more emphasis should be directed towards determining the maintenance requirements and the efficiency of utilization for gain above maintenance for the individual amino acids and the sum of amino acids rather than for crude protein. [Copyright &y& Elsevier]

Abstract: Krill growth and physiological condition were measured during the Baseline Research on Oceanography, Krill and the Environment - West (BROKE-West) large-scale survey of the Western Indian Ocean sector (30-80 °E) of the Southern Ocean. Krill growth and condition were related to sea-surface temperature (SST) and Chlorophyll a levels. Estimates of Antarctic krill growth were obtained using the Instantaneous Growth Rate (IGR) technique, which reflects in situ growth of krill during the intermoult period prior to capture. A total of 10,362 krill were incubated in the IGR experiments conducted on board the research vessel. The average growth rate ranged between 1.8–9.6% of body length throughout the study area (n=1557). Juvenile and sub-adult krill showed higher growth rates compared to adults. Growth decreased with size for krill of all maturity classes, with the largest krill (total length >50mm) expressing negative growth. On average, mean growth was higher (6.5%) in the western section (30-55° E) of the study area compared to the east (56-80° E) (4.2%). In the western section significantly higher growth rates were recorded for krill sampled close to the ice-edge (8.4%) compared to the open ocean (4.2%), which may be due to the presence of phytoplankton blooms associated with the retreating sea ice. However, in the eastern sector higher growth rates occurred in krill from the open ocean compared to the krill caught in areas closer to the coast (5.4% and 2.6% respectively). Krill condition was measured in terms of digestive gland size as a percentage of carapace length. The size of krill digestive gland relative to carapace length ranged from 0.46 to 0.66 (n=2403). A significant positive correlation was found between growth rate and size of the digestive gland (r2=0.7), indicating that growth is related to feeding events. Both digestive gland size and krill growth significantly increased with increasing Chlorophyll a levels and declining SST. [Copyright &y& Elsevier]

Five iso-nitrogenous (300 g crude protein kg−1 diet) semi-purified diets with graded levels of carbohydrate at 220 (D-1), 260 (D-2), 300 (D-3), 340 (D-4) and 380 (D-5) g kg−1 diet were fed ad libitum to Puntius gonionotus fingerlings (average weight 0.59±0.01 g) in triplicate groups (20 fish replicate−1) for a period of 90 days to determine the effect of the dietary carbohydrate level on the growth, nutrient utilization, digestibility, gut enzyme activity and whole-body composition of fish. Fifteen flow-through cement tanks of 100 L capacity with a flow rate of 0.5 L min−1 were used for rearing the fish. The maximum weight gain, specific growth rate, protein efficiency ratio, RNA:DNA ratio, whole-body protein content, protease activity, protein and energy digestibility and minimum feed conversion ratio (FCR) were found in the D-2 group fed with 260 g carbohydrate kg−1 diet. The highest protein and energy retention was also recorded in the same group. However, from the second-order polynomial regression analysis, the maximum growth and nutrient utilization of P. gonionotus fingerlings was 291.3–298.3 g carbohydrate kg−1 diet at a dietary protein level of 300 g kg−1 with a protein/energy (P/E) ratio of 20.58 −20.75 g protein MJ−1. [ABSTRACT FROM AUTHOR]

A 60-day feeding trial was carried out with juvenile Jian carp ( Cyprinus carpio var. Jian) to study the effects of myo-inositol (MI) on the growth, digestive enzyme and intestinal microbial population. Diets with seven levels of inositol (163.5, 232.7, 384.2, 535.8, 687.3, 838.8 and 990.3 mg MI kg−1 diet) were fed to Jian carp (initial weight 22.28±0.07 g). Per cent weight gain (PWG) was improved with increasing inositol levels up to 535.8 mg MI kg−1 diet ( P<0.05), and plateaued ( P>0.05). The protein production value, lipid production value and ash production value were increased with increasing dietary inositol levels up to 384.2, 838.8 and 838.8 mg MI kg−1 diet respectively ( P<0.05). Although intestinal protein content and trypsin activity were not affected by inositol levels ( P>0.05), chymotrypsin, lipase and amylase activities in intestine were the lowest for fish fed the MI-unsupplemented diet ( P<0.05). Alkaline phosphatase, Na+, K+-ATPase, γ-glutamyl transpeptidase and creatinkinase activities in the intestine were increased with an increase in the inositol levels up to 384.2–687.3 mg MI kg−1 diet ( P<0.05). Intestinal Aeromonas hydrophila and Escherichia coli decreased with an increase in the levels of dietary inositol up to 232.7 and 687.3 mg MI kg−1 diet respectively ( P<0.05), while Lactobacillus in the intestine increased with an increase in inositol levels up to 990.3 mg MI kg−1 diet ( P<0.05). In conclusion, inositol improved growth, digestive capacity and intestinal microbial population of juvenile Jian carp, and the dietary inositol requirement for PWG of juvenile Jian carp is 518.0 mg MI kg−1 diet. [ABSTRACT FROM AUTHOR]

Hierarchies readily appear when rearing flounders through metamorphosis in space-limited conditions. In this experiment, subordinate fish were stressed, as suggested by their elevated cortisol level compared to dominant fish. Subordinate fish, although of smaller size than the dominant fish, showed no suppressed digestive capacity. By separating the two hierarchical groups into different tanks at low density, the cortisol level of the subordinate fish substantially decreased. The removal of the stressor also resulted in an increase in digestive function and improved coloration. Also, compensatory growth in length but not in weight was observed in the subordinate group, suggesting that the subordinate fish devoted their energy to increase their length. These results imply that the climax of flounder metamorphosis (i.e. the settlement stage) is a highly sensitive period, where social interactions may induce high levels of stress. However, Japanese flounder early juveniles prove to have a high recovery capacity from stress and show to allocate energy preferentially to growth in length. This seems to be an adaptation to diminish the probability of death by predation. [ABSTRACT FROM AUTHOR]

Hepatocytes in primary culture from fed and 2 month fasted Arctic charr Salvelinus alpinus were exposed to physiological doses of either cortisol, salmon growth hormone (GH), salmon insulin-like growth factor-I (IGF-I) or a combination of salmon GH and salmon IGF-I. Fasting significantly lowered medium glucose levels compared to the fed fish, but had no significant effects on hepatocyte glycogen content or on the activities of enzymes involved in the intermediary metabolism. Cortisol treatment had no effect on hepatocyte glycogen content or on the enzyme activities investigated, but resulted in a significant increase in medium glucose concentration in hepatocytes isolated from fasted, but not fed fish. GH and IGF-I treatments, both singly and in combination, significantly increased the glycogen content of hepatocytes isolated from fed fish, with less pronounced effects on hepatocytes isolated from fasted fish. The combination of GH and IGF-I significantly increased lactate dehydrogenase activity regardless of the feeding state and significantly reduced the phosphenolpyruvate carboxykinase activity and medium glucose concentration in hepatocytes isolated from fed fish. Further, GH and IGF-I significantly increased the activities of alanine aminotransferase and aspartate aminotransferase in hepatocytes isolated from fasted fish, but not fed fish. There were no effects of GH, IGF-I, or their combination, on glucose 6-phosphate dehydrogenase or 3-hydroxyacyl-CoA dehydrogenase activities. The results demonstrated that nutritional status of the animal modulates hepatocyte responsiveness to metabolic hormones, and suggested a role for GH and IGF-I in hepatic glycogen conservation. [ABSTRACT FROM AUTHOR]