Search

High stocking density is a stress factor that potentially affects physiological and immune responses. In this study, the effects of medlar (Mespilus germanica) extract (ME) supplementation on growth performance, antioxidant, immune status, and stress responses in rainbow trout (Oncorhynchus mykiss) were studied. Six hundred fish (40.19 ± 1.09 g; average fish weight ± standard error) were distributed randomly into five experimental groups (assayed in triplicates). The experimental diets were formulated as follows: 0 (T1, control), 0.5% (T2), 1% (T3), 1.5% (T4), and 2% (T4). After 60 days feeding trial, the fish were confined, and the density increased (60 kg/m3) for further 14 days. Results showed significant increases in final weight (FW), weight gain (WG), specific growth rate, and feed intake in the T4 compared to the control (P < 0.05). The feed conversion ratio (FCR) in T4 significantly decreased compared to the control (P < 0.05). Also, the treated groups showed significant improvements in catalase (CAT), superoxide dismutase (SOD), glutathione peroxidase (GPx), lysozyme (LYZ), total immunoglobulin (total Ig), respiratory burst activity (RBA), total protein, and phagocytosis (PHA) (P < 0.05). Moreover, compared with the control group, supplementation could significantly decrease glucose (GLU) and cortisol (CORT), alanine transaminase (ALT), lactate dehydrogenase (LDH), aspartate transaminase (AST), and alkaline phosphatase (ALP) (P < 0.05). After the challenge, FW and WG in all treated challenge groups were significantly improved compared to the control group (P < 0.05). FCR showed a significant decrease in all treated challenged groups compared to the control group (P < 0.05). However, malondialdehyde, CAT, GPx, SOD, LYZ, complement activity (C3 and C4), total Ig, RBA, peroxidase, and PHA in challenged treated groups were significantly increased compared to the control group (P < 0.05). All treated challenged groups showed lower ALT, LDH, AST, ALP, GLU, and CORT levels than the control group (P < 0.05). The experiment herein successfully demonstrated that dietary ME stimulated fish growth, antioxidant status, and immune responses in crowding conditions and can be recommended as beneficial feed additives for rainbow trout. [ABSTRACT FROM AUTHOR]

This experiment investigated the effects of Astragalus membranaceus polysaccharides (AMP) on growth, physiological and biochemical parameters, and the expression of lipid metabolism-related genes in spotted sea bass, Lateolabrax maculatus. A total of 450 spotted sea bass (10.44 ± 0.09 g) were divided into six groups and were given diets with different levels of AMP (0, 0.2, 0.4, 0.6, 0.8, and 1.0 g/kg) for 28 days, respectively. Results indicated that dietary intake of AMP significantly improved fish weight gain, specific growth rate, feed conversion, and trypsin activity. Meanwhile, fish fed with AMP manifested significantly higher serum total antioxidant capacity and activity of hepatic superoxide dismutase, catalase, and lysozyme. Lower triglyceride and total cholesterol were noted in fish fed with AMP (P < 0.05). Moreover, hepatic ACC1 and ACC2 were downregulated by dietary intake of AMP, and PPAR-α, CPT1, and HSL were upregulated accordingly (P < 0.05). Parameters with significant difference were analyzed by quadratic regression analysis, and results showed that 0.6881 g/kg of AMP is the optimal dosage for spotted sea bass in size (10.44 ± 0.09 g). In conclusion, dietary intake of AMP can improve the growth, physiological status, and lipid metabolism of spotted sea bass, thereby indicating its promise as a potential dietary supplement. [ABSTRACT FROM AUTHOR]

Butylated hydroxytoluene (BHT) is a commonly used antioxidant added to animal/fish feed to limit lipid autoxidation and peroxidation. Although there have been reviews and reports of BHT toxicity in animals, limited information is available with respect to the toxic effects and accumulation of BHT due to oral exposure in aquaculture species. Therefore, 120 days of feeding trial was conducted to evaluate the effects of dietary BHT on the marine fish olive flounder Paralichthys olivaceus. Graded levels of BHT were added to the basal diet in increments of 0, 10, 20, 40, 80, and 160 mg BHT/kg, corresponding to 0 (BHT0), 11 (BHT11), 19 (BHT19), 35 (BHT35), 85 (BHT85), and 121 (BHT121) mg BHT/kg diets, respectively. Fish with an average weight of 77.5 ± 0.3 g (mean ± SD) were fed one of the six experimental diets in triplicate groups. Growth performance, feed utilization, and survival rate were not significantly affected by the dietary BHT levels among all experimental groups, whereas BHT concentration in the muscle tissue was found to increase in a dose-dependent manner up to 60 days of the experimental period. Thereafter, BHT accumulation in muscle tissue showed a declining trend among all treatment groups. Furthermore, the whole-body proximate composition, nonspecific immune responses, and hematological parameters (except triglycerides) were not significantly influenced by the dietary levels of BHT. Blood triglyceride content was significantly higher in fish fed the BHT-free diet compared to all other treatment groups. Thus, this study demonstrates that dietary BHT (up to 121 mg/kg) is a safe and effective antioxidant without exhibiting any adverse effects on the growth performance, body composition, and immune responses in the marine fish olive flounder, P. olivaceus. [ABSTRACT FROM AUTHOR]

Macroalgae have been recently described as a potential ingredient for aquafeeds, exerting several physiological benefits. Grass carp (Ctenopharyngodon idella) is a freshwater species, which has been the major fish species produced in the world in the last years. In order to determine the potential use of macroalgal wracks in fish feeding, C. idella juveniles were fed with an extruded commercial diet (CD) or the CD supplemented with 7% of a wind dried-powder (1 mm) from either a multispecific macroalgal wrack (CD + MU7) or a monospecific macroalgal wrack (CD + MO7) obtained from Gran Canaria island (Spain) coasts. After 100 days of feeding, survival, fish weight, and body indexes were determined, and muscle, liver, and digestive tract samples were collected. The total antioxidant capacity of macroalgal wracks was analyzed by assesing the antioxidant defense response and digestive enzymes activity in fish. Finally, muscle proximate composition, lipid classes (LC), and fatty acid (FA) profiles were also studied. Our results suggest that dietary inclusion of macroalgal wracks does not have negative effects on growth, proximate, and lipid composition, antioxidative status, or digestive capacity of C. idella. In fact, both macroalgal wracks caused a general lower fat deposition, and the multispecific wrack enhanced catalase activity in the liver. [ABSTRACT FROM AUTHOR]

A digestibility trial was conducted with African catfish hybrid juveniles in order to determine the apparent digestibility coefficients (ADCs) of different nutrients. The experimental diets contained defatted black soldier fly (BSL), yellow mealworm (MW), or fully fat blue bottle fly (BBF) meals, in a 70 : 30 ratio between the control diet and the tested insect meals. The indirect method for the digestibility study was performed using 0.1% yttrium oxide as an inert marker. Fish juveniles of 217.4 ± 9.5 g initial weight were distributed in 1 m3 tanks (75 fish/tank) of a recirculating aquaculture system (RAS), in triplicates, and fed until satiation for 18 days. The average final weight of the fish was 346 ± 35.8 g. The ADCs of the dry matter, protein, lipid, chitin, ash, phosphorus, amino acids, fatty acids, and gross energy for the test ingredients and diets were calculated. A six-month storage test was carried out to evaluate the shelf life of the experimental diets, while the peroxidation and microbiological status of the diets were also assessed. The ADC values of the test diets differed significantly (p < 0.001) compared to those of the control for most of the nutrients. Altogether, the BSL diet was significantly more digestible for protein, fat, ash, and phosphorus than the control diet but less digestible for essential amino acids. Significant differences were found between the ADCs of the different insect meals evaluated (p < 0.001) for practically all nutritional fractions analyzed. The African catfish hybrids were able to digest BSL and BBF more efficiently than MW, and the calculated ADC values agreed with those of other fish species. The lower ADCs of the tested MW meal correlated (p < 0.05) with the markedly higher acid detergent fiber (ADF) levels present in the MW meal and MW diet. Microbiological evaluation of the feeds revealed that mesophilic aerobic bacteria in the BSL feed were 2–3 orders of magnitude more abundant than those in the other diets and their numbers significantly increased during storage. Overall, BSL and BBF proved to be potential feed ingredients for African catfish juveniles and the shelf life of the produced diets with 30% inclusion of insect meal retained the required quality during a six-month period of storage. [ABSTRACT FROM AUTHOR]

Feed management practices significantly impact the production performance of tilapia (Oreochromis species) culture economically; hence, adopting appropriate feed management strategies is vital to maximize returns. The advancement in aquaculture has also allowed an advancement in the development formulated feeds to supplement or replace natural feeds. Farmers are now able to prepare their own fish feeds from locally available ingredients. Hence, feed ingredient evaluation is crucial for better development of appropriate diets for different aquaculture species as well as nutritional research. Therefore, this review used secondary data to evaluate the different strategies employed for better utilization of nutrients in feed by providing a discussion of functional feed additives used in aquafeeds such as the addition of enzymes, pre/probiotics, feeding stimulants, and use of hormones. Supplementation of diet with xynalase and phytase enzymes (P < 0.001) and probiotics (P < 0.05) improved growth (g/d) and FCR when applied individually. The combination of enzymes and probiotics showed an interaction effect (P < 0.05) on growth and FCR. A detailed discussion of feed ingredient processing strategies like fermentation, heat treatment, germination, and other biological methods meant to improve the nutritional quality of the feed and minimize antinutritional factors is provided. Furthermore, information on how genetic selection is being used to enhance feed utilization in tilapia fish is provided. The food conversion efficiency was found to be significantly higher (P < 0.05) in transgenic tilapia compared to the nontransgenic red tilapia fish with average weight ± SD of 384 ± 158 g and 314 ± 101 for transgenic fish and red tilapia, respectively, after 275 days of culture. The review further outlines the feed formulation challenges, and research gaps in tilapia nutrition. It was noted that proper feeding management strategies are very critical for the sustainability of tilapia aquaculture. In conclusion, dietary sources for tilapia are slowly shifting to plant-based products. However, these come with a lot of antinutritional factors and digestibility problems; hence, the right feeding strategies have to be employed to enable efficient nutrient utilization. The review discovered that there are a lot of strategies which employed research gaps in tilapia nutrition, especially on nutrient utilization of feed and feed formulation. [ABSTRACT FROM AUTHOR]

This study evaluates the potential to replace fish meal with gamma‐ray (γ) irradiated soybean meal (SM) in the diet of largemouth bass (Micropterus salmoides) and the role of brewer's yeast (Saccharomyces cerevisiae) supplementation in fish meal replacement. The reference diet (490 g kg−1 crude protein, 90 g kg−1 lipid and 400 g kg−1 fish meal) was formulated into six isoproteic and isolipidic experimental diets. In the first three diets (S20, S40 and S60), 20%, 40% and 60% of fish meal in the reference diet was replaced with γ‐irradiated SM, respectively. The brewer's yeast was then supplemented to diets S20, S40 and S60 at 10 g kg−1 to form other three diets (SY20, SY40 and SY60). The feeding trial lasted 8 weeks. Fish weight gain was not affected by the level of fish meal replacement, yeast supplementation and their interactions. Fish meal replacement and yeast supplementation significantly affected feed intake, feed conversion ratio (FCR), retention efficiencies of nitrogen (NRE) and phosphorus (NRE), nitrogen waste, phosphorus waste and the ratio of fish meal consumption to fish production (RCP). The hepatosomatic index and body contents of moisture and lipid were dependent on the level of fish meal replacement. The contents of protein, ash and phosphorus in the whole body depended on fish meal replacement and the interaction between fish meal replacement and yeast supplementation. No significant difference was found in weight gain between fish fed the reference diet and six experimental diets. Feed intake and FCR were lower in fish fed the reference diet than those fed diets S20, S40, S60, SY20 and SY60. However, feed intake, FCR, NRE and nitrogen waste in fish fed diet SY40 did not differ from those fed the reference diet. The RCP declined with the decrease of dietary fish meal. This study indicates that the γ‐irradiated SM is a promising ingredient as a fish meal substitute. Fish meal can be reduced to 160 g kg−1 with γ‐irradiated SM as the substitute in the largemouth bass diet. The supplementation of S. cerevisiae at 10 g kg−1 did not show a positive role for the reduction of fish meal in the largemouth bass diet. [ABSTRACT FROM AUTHOR]

The present study evaluated the effects of a commercial soy lecithin‐containing bioemulsifier Lysomax® on growth performance, feed utilization, haematology, immune response and gut histology of adult Nile tilapia (Oreochromis niloticus) fed soybean meal‐based diets, containing plant oil as a lipid source. This emulsifier was incorporated into four isonitrogenous (30% cp), isocaloric (17.5 MJ/kg) test diets, at 0 (control), 0.3, 0.6 and 0.9 g/kg feed. The diets were fed to triplicate groups of adult Nile tilapia, reared in a closed recirculating indoor system, at a daily rate of 3% of fish live weight, twice a day for 60 days. Growth rates, feed utilization efficiency, digestive enzymes activities, blood parameters, liver function enzymes and immunological responses were all boosted (p <.05) with increasing supplemental Lysomax up to 0.3 g/kg diet, followed by a significant retardation (p <.05) at 0.6 and 0.9 levels. Muscle n‐6 and n‐3 polyunsaturated fatty acids (PUFA) and n3/n6 ratio were also increased with increasing Lysomax up to 0.3 level and then levelled off with further increase in dietary Lysomax. The highest length and width of the intestinal microvilli and goblet cell counts were also found in the fish fed on 0.3 g Lysomax/kg diet. However, the quadratic regression analyses of the obtained results indicated that the maximum performance occurred at about 0.45 g/kg of dietary Lysomax. These results suggest that lecithin‐containing bioemulsifier Lysomax® can play a significant role in feed digestion and absorption and improving fish performance and innate immune response. About 0.45 g/kg diet would be sufficient for best performance and health status of farmed Nile tilapia. [ABSTRACT FROM AUTHOR]

This study was conducted to evaluate the effects of dietary sodium diformate (NaDF) on growth performance, gut microflora, digestive enzyme activities and immune response parameters of Asian sea bass (Lates calcarifer) juveniles. Fish with initial weight of 12.5 ± 0.4 g were fed with five experimental diets contained 0.0 (control), 5, 10.0, 15.0 and 20 g NaDF kg−1 in triplicate for 6 weeks. Fish fed diet containing 5 g NaDF kg−1 had significantly the highest final body weight and feed intake among different treatments. The gut total viable bacterial counts gradually decreased with increasing dietary NaDF level. Specific activity of chymotrypsin improved in fish fed diets administered with NaDF compared to the control group. Fish fed 5 g NaDF kg−1 diet showed the highest serum lysozyme level among different treatments. The serum classical pathway activity of complement showed higher level in fish fed diets contained 5 and 10 g NaDF kg−1 than other groups. According to break‐point regression method analysis, the optimum inclusion of dietary NaDF in L. calcarifer juveniles was estimated between 4.6 and 5.1 g/kg, when specific growth rate and feed conversion ratio were plotted against dietary NaDF levels. [ABSTRACT FROM AUTHOR]

Two insect meal ( IM) products were tested as ingredient in diets for Atlantic salmon weighing ~250 g. The modern control diet contained 200 g kg−1 fish meal ( FM100), which was stepwise replaced by insect meal A ( IM A) as a 25% ( A25), 50% ( A50) or 100% ( A100) FM replacement or insect meal B ( IM B) as a 25% ( B25) or 100% ( B100) FM replacement. Selected nutrient parameters and contaminants were measured in the diets. After 15 weeks, fish length and weight were recorded and visceral and hepatic indices calculated. Fatty acid and amino acid digestibility was calculated. Morphology of the liver, kidney, mid- and hind intestine was evaluated. Finally, a sensory testing of the fillets was conducted. A25, A50 and A100 performed equally well as the FM100 diet. The feed intake decreased moderately with increasing IM A inclusion; however, food conversion ratio decreased, resulting in an equal net growth of the fish. Histology did not show any differences between any of the dietary groups, and sensory testing of fillets from FM100, A100 and B25 did not reveal any significant differences in odour, flavour/taste or texture between groups. IM A was suitable to replace up to 100% of dietary FM, whilst IM B did not perform equally well. [ABSTRACT FROM AUTHOR]

An 8-week feeding trial was conducted to determine the optimal dietary arginine requirement for juvenile swimming crab Portunus trituberculatus. Six isonitrogenous and isolipidic experimental diets were formulated to contain graded arginine levels which ranged from 15.9 to 33.0 g kg−1. Each diet was randomly assigned to triplicate groups of 60 juvenile swimming crabs (4.72 ± 0.12 g). The results indicated that dietary arginine had significant effects on weight gain ( WG), specific growth rate ( SGR), protein productive value, feed efficiency and protein efficiency ratio. Weight gain and SGR significantly increased with the dietary arginine increasing from 15.9 to 27.4 g kg−1, while with the further increasing from 27.4 to 33.0 g kg−1, WG and SGR did not increase significantly. Maximum arginine, proline and total essential amino acid contents in muscle were observed in 27.4 g kg−1 group diet. The swimming crab fed the diet with lower dietary arginine level showed higher AST and lower ALT in the serum. Crab fed with the lower dietary arginine level had significantly lower ALT in the serum than the other groups. Haemolymph indexes were significantly affected by the dietary arginine level except for the cholesterol concentration, and the highest values were all found in 27.4 g kg−1 group diet. The two slope broken-line model using SGR showed that the optimal dietary arginine requirement was 27.7 g kg−1 of the dry matter (56.0 g kg−1 dietary protein) for juvenile swimming crab. [ABSTRACT FROM AUTHOR]

A 10-week growth trial was performed to evaluate the effects of feeding rate on growth performance, nutrient partitioning, and to determine the optimum feeding rate for young-of-the-year white sturgeon. Three tanks with 30 fish per tank each were assigned to five feeding rates, 0.4-2.0% body weight per day ( BW day−1). Weight gain significantly ( P < 0.05) increased with increasing feeding rate up to 1.2% BW day−1. Feed efficiency exhibited an inverse relationship to weight gain. Hepatosomatic and gonadal-fat-body ( GFB)-somatic indices were significantly affected by feeding rate, and the lowest values were observed at 0.4% BW day−1. The increased feeding rate significantly affected whole-body and carcass lipid and moisture contents. Protein gain in the carcass, but not in the GFB, was significantly influenced by feeding rate. Lipid gain in the carcass and GFB was also significantly affected by feeding rate. Four regression models were tested for the estimation of optimum feeding rate, including one-slope straight broken-line, two-slope straight broken-line, quadratic broken-line and quadratic models. Adjusted coefficient of correlation and corrected Akaike information criterion were used to compare model performance. The quadratic broken-line model was chosen as the best based on the criteria. The estimated optimum feeding rate for young-of-the-year white sturgeon (360 g) is 1.5% BW day−1. [ABSTRACT FROM AUTHOR]

One of the strategies used to improve fish production is lowering the feed costs and the environmental impact by reducing dietary protein content. Using the deletion method, we determined the optimal amino acid ( AA) ratio for Nile tilapia ( Oreochromis niloticus) (body weight 20 g). Eleven experimental diets and four replications, taken two at a time, distributed in a randomized block design were used. For this trial, a balanced diet ( BD) was formulated. Ten other diets were formulated by the deletion method, in which the BD diet was adjusted to result in a reduction of 45% of the test amino acid. Fish were fed three times a day for 57 days. Groups of fish at the beginning and at the end of the experiment were euthanized for further determination of the carcass nitrogen (N) composition. The optimal ratio of each AA was derived by dividing the requirement for each AA by the requirements for lysine. The essential AA ratios, expressed relative to lysine (=100), were methionine 64, threonine 93, tryptophan 24, arginine 125, histidine 34, isoleucine 57, leucine 96, valine 76 and phenylalanine 101. Our findings might be used to design strategies aimed at reducing the production costs of Oreochromis niloticus. [ABSTRACT FROM AUTHOR]

To investigate effects of iron (Fe) on growth, haematological parameters, flesh quality and antioxidant status in muscle, young grass carp ( Ctenopharyngodon idella) (292.0 ± 3.2 g) were fed graded levels of Fe (20.7, 38.4, 52.8, 79.3, 98.0 and 120.0 mg kg−1 diet) for 8 weeks. Per cent weight gain ( PWG) and feed intake were improved with Fe levels up to 52.8 mg kg−1 diet. Serum Fe, erythrocyte counts, haemoglobin (Hb), haematocrit and mean cell haemoglobin increased with optimal Fe levels (38.4-79.3 mg kg−1 diet) ( P < 0.05). The muscle protein and lipid contents were increased by dietary Fe, whereas moisture, liquid loss, shear force and hydroxyproline contents followed opposite trends. Malondialdehyde and protein carbonyl contents in muscle were the lowest in fish fed the 52.8 or 79.3 mg Fe kg−1 diet, respectively, while superoxide dismutase, catalase, glutathione- S-transferase, glutathione peroxidase and glutathione reductase activities, and glutathione content were increased by Fe levels up to 52.8-79.3 mg kg−1 diet. Results indicated that the optimal Fe improved growth, flesh quality and muscle antioxidant defence of young grass carp. Dietary Fe requirements for PWG, serum Fe and Hb of young grass carp (292-695 g) were 73.5, 72.8 and 69.0 mg kg−1 diet, respectively. [ABSTRACT FROM AUTHOR]

Juvenile Litopenaeus vannamei were fed for 8 weeks with diets containing four ratios of protein to carbohydrate ( CBH) at P26 : C30, P30 : C25, P34 : C19 and P38 : C14, respectively, at 3.0 g L−1 salinity. Shrimp weight gain of P34 : C19 group was the highest and differed from the shrimp fed the P26 : C30 or P30 : C25 diet. Shrimp fed the P26 : C30 diet obtained higher survival than those fed other diets. Shrimp fed the P34 : C19 diet contained the highest body protein and lipid, which were significantly higher than those fed the P38 : C14 diet. Shrimp fed the P30 : C25 diet had the highest haemolymph glucose content, which was significantly higher than those fed the P26 : C30 or P38 : C14 diet. Shrimp muscle glycogen of the P26 : C30 group was the highest. Hepatopancreas B-cell number of shrimp fed the P26 : C30 diet was lower than those fed other diets, and the R cell number was the highest in the shrimp fed the P30 : C25 diet. This study indicates that the protein-sparing effect by CBH occurred in the P30 : C25 and P34 : C19 groups because these proteins to CBH ratios can support normal growth. Within the range of basic energy demand, the high dietary CBH to protein ratio can improve L. vannamei survival at low salinity. [ABSTRACT FROM AUTHOR]

An 8-week feeding trial was conducted to determine the effectiveness of replacing fish meal ( FM) with blends of alternative proteins in diets for white seabass ( WSB, Atractoscion nobilis) at a starting weight of 5.6 g. Five diets were formulated with 400-440g kg−1 crude protein (380g kg−1 digestible). These included a high 520g kg−1 FM control diet, a series of three diets with a sequential replacement of FM containing 410g kg−1, 510g kg−1 and 630g kg−1 of a soy-based protein blend ( SPC) and 200g kg−1, 100g kg−1 and 0g kg−1 FM, respectively and a fifth diet containing 550g kg−1 of a corn-based protein blend ( CGM) and 100g kg−1 FM. Survival was highest in the FM control group at 99% but all other performance measures (weight gain, feed conversion ratio, specific growth rate and protein retention efficiency) were worse than the other treatment groups. Weight gain reached a maximum of 595% in the SPC 200g kg−1 FM treatment group. Performance decreased as inclusion of the soy-based protein blend increased. The CGM treatment performed comparably to the SPC 100g kg−1 FM treatment among all measures, except for survival, which was higher in the CGM 100g kg−1 FM treatment. With nutrient levels and alternative protein blends used in this study, FM can be reduced to 100g kg−1 of the diet for WSB without reductions in performance. [ABSTRACT FROM AUTHOR]

Apparent digestibility coefficients ( ADCs) for dry matter, crude protein, energy and essential amino acids for five commonly used feed ingredients were determined for juvenile spotted rose snapper Lutjanus guttatus (average body weight 90.6 g). ADCs were determined using the stripping technique to collect faeces after fish were fed a reference diet and test diets composed of 700 g kg−1 reference diet and 300 g kg−1 test ingredient. Chromic oxide (Cr2O3) was used as an inert indicator. Ingredients tested included sardine fishmeal ( FM), canola meal ( CM), tuna by-products meal ( TBM), poultry by-product meal pet grade ( PBM- PG) and solvent-extracted soybean meal ( SBM). In general, all ingredients showed high digestibility values for all essential amino acids, although differences were detected among ingredients. ADC values for dry matter, protein and energy ranged 77.0-80.4%, 84.3-82.5% and 89-88.8%, respectively, for marine ingredient and land-based animal protein sources, and 75.0-74.2%, 81.5-80.9% and 87.4-86.8%, respectively, for the plant-based protein source. SBM, TBM and PBM- PG should be further evaluated in feeding trials as partial FM replacements in rose snapper L. guttatus diets. Knowledge of ADC values for these ingredients will allow feed producers to develop nutritionally balanced, low-cost feed formulations for this species. [ABSTRACT FROM AUTHOR]

The effect of burbot weight ( BW) and length ( TL) on the efficiency of weaning under controlled conditions was investigated. Growth, survival rate, cannibalism and histological analysis of digestive tract were examined. The experiment lasted 49 days (40-89 days post hatch [ DPH]). The fish ( BW 0.12 g; TL 14.1 mm) were divided into four groups: a control group ( C) exclusively fed Artemia sp. nauplii and groups F40, F47 and F54 that were weaned to dry feed on 40, 47 and 54 DPH, respectively. The highest survival rate was observed in groups C (78%) and F54 (58%). In group F54, similar TL (53.8 mm) and higher BW (1.36 g) at the end of experiment, in comparison with group C (43.9 mm, 0.84 g for TL and BW, respectively), were obtained. At the end of the experiment, the length of enterocytes in groups C and F54 was at a similar level (over 23 μm), whereas in group F47 was significantly lower (approximately 20 μm; P < 0.05). This study for the first time presents successful weaning of the burbot. The data indicate that live food should be offered until the fish reach 25 mm and 0.20 g. [ABSTRACT FROM AUTHOR]

A total of 630 juvenile Chinese sucker, with an average initial weight of 1.72 ± 0.05 g, were fed seven diets for 56 days to study the effect of dietary methionine levels on growth, feed utilization, body composition and haematological parameters on juvenile Chinese sucker. Diet 1 using fish meal as the sole protein source and diets 2-7 using fish meal and fermented soybean meal as intact protein sources supplemented with crystalline amino acids contained six levels of l-methionine ranging from 6.4 to 18.9 g kg−1 of dry diet at a constant dietary cystine level of 3.7 g kg−1. Each diet was randomly assigned to three aquaria. Results indicated that the highest weight gain, specific growth rate ( SGR), feed efficiency ratio, protein efficiency ratio and protein productive value occurred at 13.9 g methionine kg−1 diet among the methionine supplemented dietary groups, beyond which they showed declining tendency. The whole body and muscle protein contents of juvenile Chinese sucker were positively correlated with dietary methionine level, while muscle lipid content was negatively correlated with it. The total essential amino acids content of muscle was increased significantly with increasing dietary methionine level from 6.4 to 13.9 g kg−1 ( P < 0.05). Apparent digestibility coefficients of dietary protein were significantly affected by dietary treatments. Serum protein, cholesterol and triacylglycerol increased with increasing dietary methionine levels, but showed a relatively lower value for fish fed the 18.9 g methionine kg−1 diet. Quadratic regression analysis of SGR against dietary methionine level indicated that optimal dietary methionine requirement for juvenile Chinese sucker was 14.1 g kg−1 of the diet in the presence of 3.7 g kg−1 cystine (corresponding to 32.0 g kg−1 of dietary protein on a dry-weight basis). [ABSTRACT FROM AUTHOR]

Apparent digestibility coefficients ( ADCs) of dry matter, crude protein, crude lipid, gross energy, phosphorus and amino acids in Peruvian fish meal, poultry by-product meal, meat and bone meal, spray-dried blood meal, hydrolysed feather meal, corn gluten meal, soybean meal, peanut meal, cottonseed meal and rapeseed meal were determined for juvenile snakehead ( Ophiocephalus argus) with initial mean body weight of 78.1 g. A reference diet and test diets that consisted of a 70 : 30 mixture of the reference diet to test ingredient were used with 5 g kg−1 Cr2O3 as an external indicator. Fish meal, poultry by-product meal and corn gluten meal had higher ADCs of dry matter, crude protein, and gross energy among ingredients tested. Dry matter ADCs ranged 61.9-81.5% for animal ingredients and corn gluten meal and ranged 52.2-68.0% for soybean meal, peanut meal, cottonseed meal and rapeseed meal. Energy ADCs of ingredients followed similar trends to differences in dry matter digestibility. Protein ADCs of animal and plant ingredients ranged 73.6-92.8% and 75.3-85.6%, respectively. Amino acid ADCs generally reflected protein digestibility. Lipid ADCs were relatively high for the ingredients tested. Phosphorus ADCs of animal and plant ingredients ranged 39.5-65.2% and 38.7-57.1%, respectively. [ABSTRACT FROM AUTHOR]

This work evaluated the performance of Litopenaeus vannamei to low fish meal diets supplemented with 2-hydroxy-4-(methylthio)butanoic acid (HMTBa). A basal diet with 150.0 g kg−1 of anchovy fish meal was designed. Two positive control diets were formulated to reduce fish meal at 50% and 100% with 1.0 and 2.0 g kg−1 of MERA™ MetCa (calcium salt with 84% HMTBa activity), respectively. Two nearly equivalent diets acted as negative controls, without HMTBa supplementation. A total of 50 clear-water tanks of 500 L were stocked with 2.22 ± 0.19 g shrimp under 70 animals m−2. Shrimp survival (92.3 ± 5.1% and 81.4 ± 8.0%), yield (808 ± 12 and 946 ± 17 g m−2) and FCR (2.17 ± 0.19 and 3.12 ± 0.37) showed no differences among diets after 72 or 96 days, respectively. A significantly higher shrimp body weight and weekly growth were observed for those fed with the basal diet or diets supplemented with HMTBa compared with non-supplemented ones. This study has shown that L. vannamei growth, body weight, survival, yield and FCR were supported by HMTBa supplementation when 150.0 g kg−1 of fish meal was replaced by soybean meal and other ingredients, at 50% and 100%. [ABSTRACT FROM AUTHOR]

Four 1-week growth trials were conducted to determine the effects of feeding rates on the growth performances of white sturgeon ( Acipenser transmontanus) fries 6-9 weeks after initiation of feeding. Six feeding rates with four replications were used in each of the four trials, and the feeding rates were 3.0-8.0, 2.0-7.0, 1.0-6.0 and 1.0-6.0% body weight (BW) per day in 1% increment, respectively. Number of fries per replicate and their initial BW (means ± SEM) were 60, 45, 30 and 30 and 2.8 ± 0.1, 4.5 ± 0.4, 8.5 ± 0.7 and 10.0 ± 0.7 g, respectively. The fries were kept at 18-19 °C and fed a commercial salmonid feed (488 g kg−1 protein and 123 g kg−1 fat). Mortality was low and unrelated to feeding rates. Final body weights, body weight increases, specific growth rates and feed efficiency were significantly ( P < 0.05) affected by the feeding rates. Body moisture and lipid contents were significantly affected by feeding rates except body moisture content in trial II. Body protein contents were not affected by feeding rates except in trial III. Broken-line analysis on specific growth rates indicated that the optimum feeding rates were 6.5 ± 0.4, 4.8 ± 0.2, 4.2 ± 0.1 and 3.8 ± 0.2% body weight per day, respectively, for white sturgeon fries 6-9 weeks after initiation of feeding. [ABSTRACT FROM AUTHOR]

This study evaluated the effects of sparteine, a lupin alkaloid, on growth and organ histology in rainbow trout. Eight diets with increasing concentrations of sparteine (0, 50, 100, 250, 500, 1000, 2500 and 5000 mg kg−1) were fed to triplicate groups of 61-g fish for 62 days. Survival was not affected by the dietary treatments. Weight gain, feed conversion efficiency and feed intake decreased in a quadratic manner for sparteine levels above 100 mg kg−1. No effects were observed at inclusion levels ≤100 mg kg−1. Whole-body lipid and dry matter was depleted in a quadratic manner, while protein and ash were not affected. No tissue alteration attributable to sparteine alkaloid intake was found in liver, kidney, spleen or mid and distal intestines. At sparteine levels above 1000 mg kg−1 of diet, the weight of the intestines and the liver relative to body weight decreased, whereas the weight of the spleen increased. These effects were likely associated with low feed intake and starvation. These results indicate that dietary sparteine alkaloid primarily reduced palatability, but did not impair the health of the fish. The level of sparteine should be kept below 100 mg kg−1 in trout diets to ensure rapid growth. [ABSTRACT FROM AUTHOR]

The implications of temperature on bioenergetics for barramundi ( Lates calcarifer) were defined in an improved factorial model that encompassed revised parameters accounting for effects over the temperature range of 16-39 °C and size range of 10-3000 g. A revised growth function describing weight gain by barramundi as a function of fish weight and temperature was derived from farm and laboratory data and included a term for a shift in optimal temperature with fish size: Gain (g fish−1 day−1) = ( K + xT + yT 2 + zT3) * (weight) ax+ b. Maintenance energy and protein demand functions were also derived on a similar form, and all three functions combined to form the basis of a factorial model for energy and protein demand. Using this model, optimal iterative feed specifications were defined for a range of fish sizes at temperatures of 25, 30 and 35 °C. A feed demand model was also developed based on the demand for digestible energy (DE) at each of these temperatures. The model shows that at high temperatures (35 °C), there is an increase in digestible protein (DP) to DE demand, and that with increasing size, there is a decrease in the DP to DE demand. [ABSTRACT FROM AUTHOR]