Digestibility of nutrients and energy in ingredients for bullfrogs during different phases of development

The ability of frogs to digest dietary nutrients changes with growth, with the animals becoming more or less demanding. The objective of this study was to determine the apparent digestibility coefficients of protein, energy and ether extract of 14 ingredients used in bullfrog diets (spray‐dried blood meal, hydrolysed feather meal, poultry by‐product meal, red blood cell concentrate, tilapia by‐product meal, sardine fishmeal, salmon fishmeal, meat and bone meal, corn gluten meal, soybean meal, corn, wheat bran, soy protein concentrate and soybean oil). A total of 2,325 bullfrogs (Lithobates catesbeianus) in different phases of development were used: early phase (mean weight of 30–50 g), growth phase (80–110 g) and finishing phase (150–200 g). Faeces were collected using the method of dissection. Marked differences in digestibility of the ingredients were observed between the different phases of frog development. Among the ingredients studied, salmon fishmeal and corn gluten meal showed good utilization of the protein (78.9% and 86.7%, respectively) and energy fraction (89.4% and 83.3%, respectively). The salmon fishmeal, poultry by‐product meal, sardine fishmeal, soy protein concentrate, wheat bran and soybean oil exhibited good ether extract utilization (81.2%–92.8%), recommending their use in bullfrog diets.     

Apparent digestibility of animal,plant and microbial ingredients for Pacific white shrimp Litopenaeus vannamei

A digestibility trial was conducted to determine apparent digestibility coefficients of dry matter, protein, energy and amino acids of animal, plant and microbial ingredients for Pacific white shrimp, Litopenaeus vannamei. The tested ingredients included traditional soybean meal (TSBM), PepsoyGen soybean meal (PSBM), NutriVance soybean meal (NSBM), fish meal (FM), poultry meal (PM), squid hydrolysis (SQH), scallop hydrolysis (SCH), flash dried yeast (FDY), two batches of Ulva meal (UMF and UMS) and bacteria biomass (BB). A basal diet was formulated and produced along with the experimental diets which included 300 g/kg of each ingredient and 700 g/kg of the basal diet. Juvenile shrimp (initial mean weight: 12 g, six shrimp/tank, n = 3) were stocked in a recirculation system. Apparent dry matter, protein and energy digestibility coefficients ranged from ?40.11% to 78.51%, 15.17% to 97.03% and 13.33% to 82.56% among different protein sources, respectively. In general, protein and energy digestibilities in soy sources (77.6% to 97.03% and 62.77% to 82.56%, respectively) are higher than the tested animal protein (51.39% to 71.41% and 45.29% to 69.77%, respectively) and single‐cell protein sources (15.17% to 53.47% and 13.33% to 40.39%, respectively). Among the three soybean sources, TSBM showed highest protein and energy digestibility. Apparent individual amino acid digestibility coefficients were also variable among different types of ingredients, and there was a reasonable correspondence to protein digestibility. The most digestible feed ingredients for Pacific white shrimp in this study were conventional soybean meal (SBM) and NutriVance soybean meal (NSBM), which indicated that these ingredients are good protein and amino acid sources for Pacific white shrimp. Resultant digestibility data may provide useful information to commercial shrimp feed industry.     

Apparent digestibility coefficients of animal and plant feed ingredients for juvenile Pseudobagrus ussuriensis

A study was conducted to determine apparent digestibility coefficients (ADCs) of dry matter (DM), crude protein (CP), lipid, gross energy, phosphorus and amino acids (AAs) from Peruvian fish meal (PFM), native fish meal (NFM), meat bone meal (MBM), dried daphnia meal (DDM), soybean meal (SBM), full‐fat soybean (FSBM), cottonseed meals (CSM), rapeseed meal (RSM) and corn gluten meal (CGM) for Pseudobagrus ussuriensis (7.8 ± 0.06 g). Test diets were formulated to contain a 70:30 mixture of reference diet to test ingredient with chromic oxide (5 g kg^–1) serving as the inert marker. ADCs of DM ranged from 49.94% (CGM) to 87.11% (PFM), the highest ADCs of DM were observed in PFM and the lowest was found in CGM. ADCs of CP in the test ingredients ranged from 74.92% (CGM) to 93.41% (SBM). ADCs of crude lipid ranged from 51.80% (CGM) to 94.07% (PFM) for fish. ADCs of energy ranged from 56.42% (CGM) to 90.09% (PFM). ADCs of phosphorus ranged from 21.81% (CSM) to 65.70% (PFM). AA availability for the test ingredients followed a similar pattern to ADCs of CP, in which values for PFM, NFM and MBM were generally higher (p < .05) than those of other protein ingredients. Among all plant meals, the AA availability values in SBM were higher (p < .05) than those in CGM, CSM and RSM. The availability of most AAs in CGM was the lowest (p < .05) among all tested ingredients. In conclusion, PFM and NFM are good sources of available protein and AAs. When fishmeal supply is limited, MBM and DDM are substitutes for fishmeal reduction in P. ussuriensis diets; at the same time, SBM and FSBM are also very acceptable protein feedstuffs. However, CSM, RSM and CGM could not be used at high levels in P. ussuriensis diets because of their inferior digestibilities.     

Apparent digestibility of protein, energy, and amino acids in some selected feed ingredients for pacu Piaractus mesopotamicus

The apparent digestibility coefficients (ADCs) of amino acids (AA), protein, and energy in six feed ingredients (Brazilian fish meal, soybean meal, corn gluten meal, alcoholic yeast, corn, and wheat bran) we evaluated for pacu juveniles. In general, all ingredients showed high digestibility values for all AA, and differences among ADCs of individual amino acid were detected ( P  < 0.01). Corn gluten, soybean, and fish meals had the highest ADCs of AA. The ADCs of protein in fish meal, yeast, and corn gluten meal should not be used as AA digestibility indicators, because those showed differences up to 6.7% between the ADCs of protein and AA. All ingredients had lower ADCs of energy than corn gluten meal ( P  < 0.01). Lysine was the first limiting amino acid in fish meal, corn gluten meal, wheat bran, and corn, and the second limiting amino acid in soybean meal, as methionine was the first limiting amino acid in soybean meal and yeast. However, the soybean meal was the best quality protein source, as it had the highest digestible essential amino acid index. This demonstrated that digestible amino acid values can be used to formulate practical diets for pacu, preventing potential deficiencies or excess that might cause environmental and economic losses.     

In vitro protein digestibility of different grow‐out stages of spotted rose snapper (Lutjanus guttatus,Steindachner, 1869)

The aim of this study was to compare in vitro protein digestibility between two groups of fish, at early (21 g) and late stages (400 g) of spotted rose snapper Lutjanus guttatus, to evaluate the degree of hydrolysis (DH) and total amino acid release (TAAR) using crude extracts from stomach, pyloric caeca and intestine of 13 protein ingredients including marine, animal and plant meals. Degree of hydrolysis and TAAR were measured by a pH‐Stat method, and the PAGE‐Zymogram was also used as complementary technique. Differences in DH were found between both grow‐out stages mainly in the alkaline hydrolysis phase. Fish and squid meals (marine sources) had the highest DH and TAAR, followed by porcine meat and poultry meal by‐products from recycling sources, and soybean and canola meals (plant sources), which represent better protein sources for use in practical diets. Stomach zymograms showed two pepsin isoforms in both grow‐out stages. Pyloric caeca and intestine zymograms showed five bands with proteolytic activity in the early grow‐out stage, whereas four additional bands were found in late grow‐out stage. Alkaline proteases were identified as serine and metalloproteases. Thus, L. guttatus presents an ontogenetically differentiated digestive enzyme pattern that modifies the DH and TAAR of different protein sources.     

In vivo and in vitro protein digestibility and growth performance of animal and no‐conventional plant ingredients for river prawn Macrobrachium americanum (Caridea: Palaemonidae)

The objectives of this study were to evaluate the effects of non‐traditional plant and animal protein for river prawn M. americanum on in vivo versus in vitro digestibility in addition to growth performance. In this study, ten ingredients were used: coconut meal, jackfruit meal, soybean meal, poultry by‐product meal, squid meal and fish meal. In vivo studies were conducted using the zeolite marker method, whereas in vitro digestibility was determined by the pH‐stat method using river prawn hepatopancreas enzymes. According to the findings, river prawns digest animals more efficiently than plant ingredients, with squid and fish meal showing a tendency of higher values. Fish meal (53.66%), squid meal (48.52%) and jackfruit meal (42.21%) were found to have a digestibility greater than 40% in in vivo and in vitro methods, thus suggesting that they are the best ingredients used in this study. This also validates their inclusion in practical diets. The correlation of digestibility of in vivo and in vitro was low (R² = .6749). The highest daily weight gain was recorded in the diets containing jackfruit, coconut and squid. Given that the potential of no‐conventional plant ingredients available regionally was significantly higher, this underscores the need to conduct further research to validate their inclusion in practical diets.     

中华绒螫蟹对11种饲料原料蛋白质和氨基酸的表观消化率

以氧化钇（Y2O3）作为指示剂，按照“70％基础饲料＋30％试验原料”的原则配制饲料，测定了体重（97．34±7．36）g的中华绒螯蟹对不同饲料原料蛋白质和氨基酸的表观消化率。试验选取鱼粉、血粉、肉骨粉、乌贼内脏粉、虾壳粉、啤酒酵母、豆粕、棉籽粕、菜籽粕、花生粕、玉米蛋白粉共11种商品蛋白质饲料原料。试验结果表明，中华绒螯蟹对不同饲料蛋白源的粗蛋白表观消化率为40．62％～89．75％，其中，鱼粉和血粉组的粗蛋白表观消化率分别为86．07％和89．75％，显著高于其他原料组；而菜籽粕（42．41％）和玉米蛋白粉组（40．62％）的粗蛋白消化率则明显低于其他饲料蛋白源（P〈0．05）。其他蛋白源的消化率大小顺序依次为：豆粕（77．94％）〉啤酒酵母（76．90％）〉虾壳粉（74．02％）〉肉骨粉（73．78％）〉棉籽粕（71．63％）〉花生粕（65．90％）〉乌贼内脏粉（63．51％）。在动物性蛋白源中，中华绒螯蟹对血粉和鱼粉的氨基酸消化率较高，二者的总氨基酸消化率均高于90％，试验结果还显示，蟹对乌贼内脏粉的氨基酸消化率最低，仅为63．51％；单细胞蛋白源啤酒酵母的总氨基酸消化率（86．77％）高于其他植物性蛋白源；在植物性蛋白源中，对棉籽粕的总氨基酸消化率最高（85．37％），其次是豆粕（79．41％）。本研究结果对评价不同饲料蛋白源的营养价值，以及开发中华绒螯蟹氨基酸营养平衡的人工配合饲料提供了参考和依据。     

Amino acid availability and protein digestibility of several protein sources for Nile tilapia,Oreochromis niloticus

Apparent amino acid availability coefficients and protein digestibility of four animal products [fish meal (FM), meat and bone meal (MBM), poultry by‐product and feather meal] and four plant protein‐rich products [soybean meal (SBM), cottonseed meal‐28, cottonseed meal‐38 and corn gluten meal (CGM)] were determined for Nile tilapia, Oreochromis niloticus. Ingredients were incorporated to a practical reference diet at a 7 : 3 ratio (70% of reference diet and 30% of test ingredient). Chromic oxide was used as external digestibility marker. Among animal products poultry by‐product meal (PBM; 89.7%) and FM (88.6%) presented the highest apparent protein digestibility (APD) while MBM (78.4%) and feather meal (78.5%) presented the lowest APD. Among plant protein‐rich products CGM (91.4%) and SBM (92.4%) presented the highest APD values while cottonseed meal‐28 presented the lowest APD (78.6%). Average apparent amino acid availability of feed ingredients was similar to protein digestibility with 92.3%, 89.6%, 73.4%, 80.7%, 88.9%, 84.4%, 91.2% and 79.7% values for SBM, CGM, cottonseed meal‐28 and 38, FM, MBM, PBM and feather meal respectively. These results indicate that O. niloticus is able to utilize efficiently different feedstuffs.     

Effects of dietary yeast inclusion and acute stress on postprandial plasma free amino acid profiles of dorsal aorta‐cannulated rainbow trout

In a 4‐week experiment, 15 cannulated rainbow trout were fed three diets based on fish meal (FM), Saccharomyces cerevisiae yeast (SC) and Wickerhamomyces anomalus and S. cerevisiae yeast mix (WA). Fish were fed daily, and blood samples were collected on day 7 of each week at 0, 3, 6, 12 and 24 hr after feeding. In the final week, fish were exposed to a 1‐min netting stressor. All essential and non‐essential plasma amino acid levels except methionine were similar between fish fed diets FM, SC and WA. Plasma methionine and sarcosine were significantly higher in fish fed diets SC and WA, possibly due to the crystalline methionine level, form or feeding regime. Hydroxy‐proline and 3‐methyl‐histidine were higher in fish fed diet FM, which can be explained by the higher levels present in fish meal compared with yeast. In stressed fish, there were no dietary effects on plasma amino acid levels, but significant increases in taurine and cystathionine were found in stressed compared with unstressed fish. These results demonstrate that yeast‐based diets produce similar plasma amino acid profiles to fish meal and suggest that yeast may be a suitable fish meal replacement in diets for rainbow trout.     

The effect of dietary protein source (fishmeal vs. plant protein) and non‐starch polysaccharide level on fat digestibility and faecal bile acid loss in rainbow trout (Oncorhynchus mykiss)

This study investigated in rainbow trout (Oncorhynchus mykiss) if diet composition and feeding level affect faecal bile acid loss, and whether this reflects on the apparent digestibility coefficient (ADC) of fat. Six diets were formulated with either fishmeal or plant protein as main protein source. This created a contrast in the supply of bile acids, the bile acid precursor cholesterol, taurine and the taurine precursors (methionine + cysteine) involved in bile acid conjugation. For both protein sources, three diets were formulated with increasing inclusion of a non‐starch polysaccharide (NSP)‐rich ingredient mixture (0.0, 82.0 and 164.2 g/kg diet). This aimed at enhancing faecal bile acid loss. Fish were fed both restrictively (1.2% BW/day) and to satiation. A similar fat ADC was found when substituting fishmeal with a plant protein mixture, suggesting that the lower content of bile acids, cholesterol, taurine, methionine and cysteine in the plant‐based diets did not limit fat digestion. Faecal bile acid loss increased alongside dietary NSP level, however, only during satiation feeding and most strongly for fish fed the fishmeal‐based diets. Enhanced faecal bile acid loss was not caused by NSP‐bile acid binding/entrapment, but by an increase in faeces production. During satiation feeding, fat ADC negatively correlated with faecal bile acid loss. From this it is concluded that bile acid availability/synthesis can become limiting for fat digestion in rainbow trout under conditions that enhance faecal bile acid loss (i.e. dietary NSP level and feeding level).     

Harvesting,post‐harvest handling and live‐transport of freshwater prawns in the United States

Freshwater prawn Macrobrachium rosenbergii aquaculture continues to expand in the United States though is still a relatively small industry. Innovations continue to improve efforts in harvesting with novel harvest basin designs and concrete internal pond aprons. Purging and holding strategies are more defined. Some producers are now investing in water re‐use systems to extend holding times for many days, making prawns more readily available for market. The lucrative live‐market, which historically has had many challenges, seems poised for success when following new protocols which address handling and oxygen stress.     

Apparent digestibility coefficients of feed ingredients and their predictability in compound diets for gilthead seabream, Sparus aurata L.

Apparent digestibility of crude protein, amino acids, lipid, carbohydrate and energy was measured for a range of feed ingredients fed to gilthead seabream, Sparus aurata L. — fish meal, poultry meal, meat meal, blood meal, squid meal, extracted soyabean and wheat flour. Chromic oxide was used as a non-absorbed reference substance and faeces were collected by stripping. Diets compounded from mixtures of these ingredients were then used to examine the possibility of predicting the digestibility of formulated diets.
Apparent digestibility of crude protein ranged from 79% to 90%, lipids from 83% to 95% and energy from 72% to 88% in the different ingredients. Apparent digestibility of carbohydrates was lower and ranged from 49% to 77%. Apparent digestibility of amino acids was higher than that of crude protein and differences were found among digestibilities of individual amino acids.
Tests conducted using five compound diets indicated that ingredient digestibility was additive for protein, amino acids, lipids and energy, whereas the digestibility of carbohydrates in the compound feeds was slightly lower than predicted.
Diets for Sparus aurata may thus be formulated on the basis of digestibility of individual ingredients.     

Apparent digestibility coefficients of fungal fermented plant proteins in two different penaeid shrimps—A comparative study

Using the 70:30 replacement method and chromium as an inert marker, the digestibility of four fermented oilseed meals/cakes (soybean meal (FSBM), groundnut oil cake (FGNC), rapeseed meal (FRSM), and sunflower oil cake (FSFC)) were determined in Penaeus monodon and Penaeus indicus. Apparent dry matter digestibility (ADMD) of fermented ingredients was ranked as FSBM > FGNC > FRSM > FSFC. The critical variations in apparent protein digestibility (APD) in P. monodon (0.816%) and P. indicus (0.608%) were lower than the ADMD. Appaprent amino acid digestibility (AAD) was >90% in FSBM for both the species and was lower for other ingredients. Protein had a higher digestibility than total amino acids and was in the range of 0.69%–2.71% in P. monodon and 0.32%–2.75% in P. indicus. A correlation between the ADC of total amino acids and protein was found to be r = 0.8229 in P. indicus and r = 0.7447 in P. monodon. Data were further subjected to two way analysis of variance for assessing the digestibility variations between the species. It was observed that P. indicus had higher values of ADMD than P. monodon in FSBM (2.97%) and FRSM (1.22%) and the reverse was true in FGNC and FSFC. The APD was high in P. indicus for FSBM, FGNC and FRSM but not for FSFC. However, significant variations could be noticed in AAD between the species.     

Measurement of digestibility in agastric fish based on stripping method – apparent nutrient,energy and amino acid digestibilities of common feed ingredients for carp diets (Cyprinus carpio)

Apparent nutrient, energy and amino acid (AA) digestibilities of wheat starch (WS), corn starch (CS), pea protein concentrate (PPC), soy protein concentrate (SPC), corn gluten meal (CGM) and soybean meal (SM) were assessed indirectly in common carp by applying the marker‐based indicator method. Each test diet consisted of 70% reference diet and 30% test ingredient. Stripping as faeces collection technique was applied to obtain faecal material two times a day for 9 weeks. Apparent digestibilities of ingredients (ADIs) for crude protein (CP) were higher in SM (79.5 ± 5.1%) and SPC (75.2 ± 4.8%) than in CGM (59.2 ± 6.6%). Regarding ADIs of individual AAs, SM and SPC always showed higher values than CGM and PPC. ADIs for crude carbohydrates in CS (90.4 ± 2.2%), WS (88.8 ± 2.0%) and CGM (82.3 ± 3.9%) exhibited higher amounts than in SM (26.3 ± 1.0%). Evaluated apparent digestibilities indicate that in particular SM and SPC are good protein and CGM, WS and CS are promising carbohydrate sources to be included in diets for common carp. A strong correlation between ADI_CP and ADI_AA was determined. Stripping used for digestibility measurement in carp was found to be a viable method as conventional passive faeces collecting techniques such as sedimentation or sieving.     

Effect of fish meal replacement with Carinata Brassica carinata in low animal protein diets of rainbow trout Oncorhynchus mykiss (Walbaum) on trypsin activity,protein and amino acid digestibility and bioavailability

Replacement of >25% of fish meal (FM) with aerobically converted carinata meal (ACCM) in low (200g/kg) animal protein (reference = 200g/kg FM) diets of rainbow trout Oncorhynchus mykiss resulted in reduced growth, partly due to reduced feed consumption and protein utilization. In this study, we determined the effect of FM replacement with ACCM on trypsin activity, apparent digestibility coefficients (ADCs) of protein, and essential amino acid (EAA) or conditionally essential amino acid (CEAA) ADCs and bioavailability. Replacement of FM did not alter protein ADCs or trypsin activity. Replacement of >25% FM reduced all EAA and CEAA ADCs except for arginine and leucine which were only reduced by 75% FM replacement. Only serum free lysine and muscle free histidine were reduced by >25% FM replacement. Muscle free lysine was only reduced by 75% FM replacement. Replacement of FM reduced EAA peak concentrations and resulted in slower release of EAAs in serum. Cumulative total EAAs in serum and muscle decreased with FM replacement. Ratios of EAAs to lysine showed that tryptophan was the most limiting EAA. However, isoleucine, leucine, methionine and phenylalanine were also inadequate for muscle synthesis for the first 9–12 hr following force‐feeding. Optimal time for protein synthesis was ≥36 hr. Although any level of FM replacement did not reduce protein ADCs and trypsin activity, replacement of ≥25% FM reduced EAA ADCs and bioavailability of lysine and histidine, which partly contributed to the observed differences in growth.     

Potential bioavailability of protein and lipids in feed ingredients for the three‐spot cichlid Amphilophus trimaculatus: An in vitro assessment

For the commercial culture of the three‐spot cichlid (Amphilophus trimaculatus), it is important to have available a set of protein and lipid ingredients suitable for feed manufacturing, which allow to optimize the culture at affordable costs. The in vitro digestibility was evaluated with pH‐stat technique, using stomach and intestine multi‐enzymatic extracts from A. trimaculatus juveniles. The digestion of protein ingredients was taken place both in acid and in alkaline conditions, quantifying the total of free amino acids at the end of the hydrolysis, whereas the digestion of lipid ingredients was taken place only in alkaline conditions. The digestive enzymes of this species showed a better affinity to raw materials of animal origin such as beef meal, fish meal and premium chicken meal, which presented better digestibility. The best lipid ingredient that could be used is the fish oil. However, it is possible to use ingredients from the plant sources, such as soy or cereals, and vegetable oils such as olive, corn or soy oil. It is necessary to complement this study in vitro with the digestibility analysis in vivo, in order to determine the inclusion percentages in feeds and costs and therefore to develop an efficient feed formulation for the aquaculture of A. trimaculatus.     

Evaluation of a novel bacterial biomass as a substitution for soybean meal in plant‐based practical diets for Pacific white shrimp Litopenaeus vannamei

Three growth trials and a digestibility trial were designed to evaluate the efficacy of a novel bacterial biomass (BB) in commercial‐type feed formulation for Pacific white shrimp, Litopenaeus vannamei. In trial 1, the basal diet was supplemented with 0, 60 and 120 g/kg BB to replace soybean meal (SBM). Significant improvement was observed in the survival when BB was incorporated in the diets. However, shrimp fed diets containing 120 g/kg BB exhibited significantly lower weight gain (WG) and higher feed conversion ratio (FCR). To confirm the results from trial 1 and explore the effects of BB supplementation at low levels, the basal diet was incorporated with 0, 10, 20, 40, 60 and 120 g/kg BB to replace SBM in trial 2. Significant reductions in WG, FCR, lipid content of whole body, protein retention efficiency and most amino acids retention efficiency were detected in shrimp fed with diet containing 120 g/kg BB. Trial 3 was designed to elucidate whether the digestible protein is the cause of reduced growth. No improvements in terms of growth performance and FCR were detected in the treatments balanced for digestible protein. Apparent digestibility coefficients of energy, protein and amino acid (AA) for BB were determined using chromic oxide as an inert marker and the 70:30 replacement technique. The energy, protein and individual amino acid digestibility coefficients of BB were significantly lower than those of fish meal (FM) and SBM that were given at the same time. Results of this study indicated that BB can be utilized up to 40 g/kg in shrimp feed without causing a decrease in growth. However, supplementations (≥60 g/kg) of BB can result in negative effects on growth response, FCR and protein as well as amino acids retention efficiency. At the lower levels of inclusion, shrimp performance was improved when BB was supplemented on a digestibility basis; however, at the higher level of inclusion, there was no improvement, indicating there may be other nutrients limiting. Based on enhanced survival in the treatment with BB supplementation in trial 1, further research regarding the immune effects of BB in practical shrimp feed will be necessary.     

Dietary requirements for leucine,isoleucine and valine (branched‐chain amino acids) by juvenile red drum Sciaenops ocellatus

The objective of this study was to determine the minimum dietary requirements of the branched‐chain amino acids (BCAAs: leucine [Leu], isoleucine [Ile] and valine [Val]) for juvenile red drum, Sciaenops ocellatus. This was accomplished by conducting three independent 49‐day feeding trials with juvenile red drum. Experimental diets were prepared by supplementing a basal diet containing 370 g/kg crude protein from red drum muscle and crystalline amino acids with incremental levels of Leu (9.0, 13.0, 17.0, 21.0, 25.0 and 29.0 g/kg of dry diet), Ile (5.0, 8.0, 11.0, 14.0, 17.0 and 20.0 g/kg of dry diet) and Val (6.8, 8.0, 9.2, 10.4, 11.6, 12.8 and 14.0 g/kg of dry diet). Fish were fed to apparent satiation twice daily in each trial, after which growth performance parameters were calculated and body composition and concentrations of BCAAs in plasma were analysed. Incremental levels of dietary Leu, Ile and Val significantly affected weight gain, feed efficiency and protein retention. Analyses of the weight gain data using a broken‐line regression model estimated the minimum Leu, Ile and Val requirements for maximum growth of juvenile red drum to be 15.7 ± 1.7 g/kg (±95% confidence interval), 11.1 ± 2.3 g/kg and 12.4 ± 0.6 g/kg of dry diet, respectively.     

Effect of dietary protein and lipid levels on gonadal development of female redclaw crayfish Cherax quadricarinatus

The effect of two crude dietary protein (26% and 32% P) and two lipid levels (4.7% and 12% L) on gonadal development of female redclaw crayfish Cherax quadricarinatus was determined. The gonadosomatic index (GSI), hepatosomatic index (HSI), biochemical composition of gonad and hepatopancreas, oocyte diameter and frequency of the developmental stage of oocytes were analysed. The GSI was significantly less using 26% P to 4.7% L. A significant interaction between P and L content was found for GSI. A significantly higher HSI value was obtained when L was 12%. P content in the hepatopancreas was significantly higher using 32% P and 4.7% L. The maximum L content in the hepatopancreas was obtained from the 32% P and 12% L diet. A significant interaction between P and L content was found for L content in the hepatopancreas. A higher frequency of post‐vitellogenic oocytes was obtained with diets containing 32% P. There was an interaction between dietary P and L level causing lipid accumulation in the hepatopancreas and changes in GSI. For an optimum 32% P, excess dietary lipid is bioaccumulated in the hepatopancreas, indicating that there is excess available energy. When the P and L levels are restricted, there is a limited gonad development, thus affecting overall reproduction in female C. quadricarinatus.     

Effects of dietary n‐3 to n‐6 fatty acid ratios on spawning performance and larval quality in tongue sole Cynoglossus semilaevis

This study investigated the effect of n‐3 to n‐6 fatty acid ratios in broodstock diets on reproduction performance, fatty acid composition of eggs and gonads of tongue sole Cynoglossus semilaevis. Broodstock were fed five isonitrogenous and isoenergetic diets for 60 days. The supplemented lipids were prepared by a combination of fish oil and soybean oil inclusion FO (fish oil); FSO1 (fish oil: soybean oil = 7:1); FSO2 (fish oil: soybean oil = 2.2:1); FSO3 (fish oil: soybean oil = 1:1); FSO4 (fish oil: soybean oil = 1:4.3) as lipid sources with different n‐3 to n‐6 fatty acid ratios 10.40, 5.21, 2.81, 1.71 and 0.87. Results showed that relative fecundity, fertilization rate and survival rate of larvae at 7 days posthatching were all higher in broodstock fed FSO1 and FSO2 diet and significantly (P < 0.05) decreased in groups fed FSO3 and FSO4 diets. The best result in starvation tolerance test was obtained in FSO2 diet. The present study suggests that n‐3 and n‐6 PUFA ratio in broodstock diet has a considerable effect on spawning performance, egg and larval quality for C. semilaevis.