Evaluation of Methionine Supplements and Their Use in Grain‐based Feeds for Litopenaeus vannamei

The use of dietary supplements in commercial shrimp production feeds is increasing because of the need to reduce marine meal (e.g., fish meal) content. Our study evaluated leaching and apparent digestibility of artificial methionine supplements and their use in determining appropriate feeding levels of methionine in practical fish meal replacement diets fed to Litopenaeus vannamei. Three forms of methionine were evaluated: dl ‐methionine HCl, various mineral chelates of methionine, and a short‐chain synthetic methionine polymer. Results showed a significant increase (P < 0.05) in leaching loss of methionine from feeds with decreasing salinity and that leaching was significantly higher for dl ‐methionine than other forms in all salinity treatments. No significant difference was shown in apparent digestibility of methionine among digestibility diets, with the exception of diets supplemented with dl ‐methionine HCl. In two 6‐wk clear‐water growth trials, no significant difference in weight gain was shown by shrimp fed diets containing more than 0.4% methionine (1.14%, as percent of protein). This suggests that an appropriate feed level of methionine for practical plant protein‐based feeds is less than 0.4% of the diet. Results also indicated that mineral‐chelated and polymerized forms of methionine are appropriate for supplementation of plant protein‐based feeds.     

Effects of dietary dl‐methionyl‐dl‐methionine (Met‐Met) on growth performance,body composition and haematological parameters of white shrimp (Litopenaeus vannamei) fed with plant protein–based diets

A 10‐week feeding trial was conducted to evaluate the effects of supplementing different levels of dl ‐methionyl‐dl ‐methionine (AQUAVI^® Met‐Met) in plant protein–based diets on Litopenaeus vannamei. The positive control (PC) and negative control (NC) diets were designed with 20% and 8% fishmeal respectively, and other six diets were formulated with graded levels of Met‐Met from 0.05% to 0.30% with a 0.05% increment on the basis of NC diet (MM 0.05–MM 0.3). Six replicates were randomly assigned to each diet with 50 shrimp each having initial weight of 0.98 ± 0.02 g. The variation of FM concentration from 20% to 8% and supplemented with graded levels of Met‐Met did not affect the survival rate, feed conversion ratio, protein efficiency ratio, whole body and muscle proximate compositions (p > 0.05). However, diets with ≤0.20% Met‐Met supplementation resulted in significantly increased weight gain and specific growth rate, after which both parameters reached plateau. Shrimp fed the NC diet showed significantly lower total essential amino acid (EAA) content in muscle (p < 0.05). Supplementation of Met‐Met significantly improved apparent digestibility coefficients of dry matter, crude protein, lipid, phosphorus and EAAs (p < 0.05). Based on broken‐line analysis, the methionine requirement for white shrimp was estimated to be 0.87% when using Met‐Met as methionine source.     

Comparative study on the utilization of crystalline methionine and methionine hydroxy analogue calcium by Pacific white shrimp (Litopenaeus vannamei Boone)

The objective of this study was to compare the supplemental effects of crystalline DL‐methionine (DL‐Met) and methionine hydroxy analogue calcium (MHA‐Ca) on growth performance of Pacific white shrimp. Eight isoproteinic (355.3 ± 2.0 g/kg diet) and isolipidic (70.0 ± 2.2 g/kg diet) diets were prepared as positive diet (20% fish meal), negative diet (15% fish meal) and DL‐Met, MHA‐Ca‐supplemented diets with the supplementation of 0.03%, 0.06%, 0.09% DL‐Met and 0.04%, 0.07%, 0.1% MHA‐Ca in negative diet respectively. Pacific white shrimp (0.92 ± 0.03 g) were fed one of the eight diets for 49 days. The results showed that dietary DL‐Met did not affect weight gain (WG) and feed conversion ratio (FCR) (p > 0.05), but the supplementation of 0.1% MHA‐Ca significantly increased WG, protein and lipid retention, and reduced FCR (p < 0.05) when compared to the negative group, and reached the similar levels as the positive control. The total free amino acids (TFAA) in haemolymph of MHA‐Ca groups and PC, NC group peaked at the 3rd hr after feeding, but the peaking time of DL‐Met groups was advanced to the 2nd hr. Activities of aspartate aminotransferase (AST) and alanine aminotransferase (ALT) in haemolymph of all MHA‐Ca groups peaked at the 2nd hr, but DL‐Met groups peaked at the 1st hr after feeding. The above results indicated that the supplementation of 0.1% MHA‐Ca in a low fish meal diet could improve the growth performance and feed utilization of Pacific white shrimp, but dietary DL‐Met did not significantly affect the growth.     

Efficacy of Three Methionine Sources in Diets for Pacific White Shrimp, Litopenaeus vannamei

Abstract.— To examine the need for supplemental dietary methionine and to determine the ability of different methionine sources to meet this need for Pacific white shrimp, Litopenaeus vannamei, a growth trial was conducted. A control diet (30% crude protein) was formulated to be deficient in methionine by inclusion of high levels of dehulled, solvent‐extracted soybean meal and with no fish meal (methionine level was 0.45% of diet as fed, 1.5% of total amino acids). Three test diets were manufactured based on the control diet but supplemented with l ‐methionine, dl ‐methionine, or an analog of methionine (2‐hydroxy‐4‐methylthio butanoic acid [HMTBA], calcium salt) at the level of 0.5% as fed (equivalent to 1.5% of total amino acids). Cystine was constant among these diets at 0.5% of diet as fed. A commercial feed (30% crude protein) was included as a reference. The culture vessels were flat‐bottomed, cylindrical, black fiberglass tanks (1.5‐m diameter) initially filled with 1000 L seawater and supplied with aeration and seawater from a well at a rate of 2 L/min. At the end of the trial, all surviving shrimp were counted and weighed. The trial was run outdoors, with a mean water temperature of 25.9 C. The mean survival, final weight, growth rate, and feed efficiency of shrimp in the control group were 95.9%, 10.8 g, 0.93 g/wk, and 0.44 g/g, respectively. The mean values of all the test treatments were 96.9%, 11.6 g, 1.00 g/wk, and 0.47 g/g, respectively. The final weight and growth rate of shrimp fed the control diet were significantly lower than those of shrimp fed the methionine‐supplemented diets, indicating that this species has a requirement for dietary methionine. There were no significant differences (P > 0.05) in any of the parameters among the test treatments, indicating that l ‐methionine, dl ‐methionine, and HMTBA can be used to meet the methionine requirement of this species under these experimental conditions. It is concluded that the three sources of methionine examined in this trial, l ‐methionine, dl ‐methionine, and HMTBA, are similar in their ability to meet the methionine requirement of this species.     

Comparative study on the utilization of different methionine sources by channel catfish,Ictalurus punctatus (Rafinesque, 1818)

The study was conducted to examine the effects of different methionine (Met) sources on the growth performance of channel catfish (Ictalurus punctatus). Six diets with isonitrogen and isoenergy were formulated as positive control (PC) diet (0.57% Met), negative control (NC) diet (0.42% Met) without or with the addition of crystalline DL‐Met (CM), Met hydroxy analogue (MHA), Met hydroxy analogue calcium salt (MHA‐Ca) and microcapsulated DL‐Met (MM) to obtain the same Met level as PC diet. After 8 weeks feeding trial, channel catfish (76.0 ± 0.3 g) fed MHA‐Ca and MM diets, but not CM and MHA diets, had higher weight gain, lipid productive value, protein productive value and lower feed conversion ratio than those in NC group (P < 0.05) and showed no differences in these indicators with PC group (P > 0.05). Levels of serum total protein and total free amino acid (TFAA) of all groups peaked at the 4th h, and CM group had lower TFAA level than that in MM group at the 6th h after feeding (P < 0.05). In NC group, the activities of liver aspartate aminotransferase and alanine aminotransferase peaked at the 4 h after feeding, and the peaking time in CM group was advanced to the 2nd hour, while in MHA, MHA‐Ca and MM groups, the peaking times were delayed to the 6th hour after feeding. The above results indicated that the supplementation of MHA‐Ca, MM rather than CM, MHA in diets deficient in methionine could improve the growth of channel catfish.     

Replacement of Fish Meal with Soybean Meal,Alone or in Combination with Distiller's Dried Grains with Solubles in Practical Diets for Pacific White Shrimp,Litopenaeus vannamei,Grown in a Clear‐Water Culture System

The objective of this study was to evaluate inclusion of distiller's dried grains with solubles (DDGS) as partial replacement of commercial, solvent‐extracted soybean meal (SBM) in fish meal‐free diets for Pacific white shrimp, Litopenaeus vannamei. Aquaria connected to a recirculating biofiltration system were utilized to evaluate growth, survival, and feed conversion of shrimp during the 8‐wk feeding trial. Each 110‐L aquarium was stocked with 15 shrimp (mean individual weight 0.99 g) and fed one of five diets: a diet containing 20% fish meal (FM), which served as the control (Diet 1); a diet containing 0% FM and 52.5% SBM (Diet 2); and diets containing 0% FM and either 10, 20, or 30% DDGS as partial replacement of SBM (Diets 3, 4, and 5, respectively). Shrimp were fed according to a pre‐determined feeding chart five times daily (0730, 1030, 1330, 1630, and 1930 h) and there were three replicates per dietary treatment. The results from the feeding trial demonstrated that final weight, weight gain (g), and percentage weight gain were significantly higher (P < 0.05) for shrimp fed Diet 1 (10.96 g, 10.01 g, and 1051%, respectively) compared to shrimp fed diets containing DDGS; however, shrimp fed diets containing DDGS had similar (P > 0.05) final weight, weight gain (g), and percentage weight gain as shrimp fed a diet containing 0% FM and 52.5% SBM (Diet 2). Feed conversion ratio (FCR) of shrimp fed Diet 1 (2.84) was significantly lower (P < 0.05) compared to shrimp fed any other diet. Survival (%) was not different (P > 0.05) among treatments and averaged 77.3% for the study. This study demonstrated that practical shrimp diets containing no FM had an adverse impact on growth performance of white shrimp when grown in a clear‐water system and that further research is needed to refine diet formulations when culturing shrimp in these systems when attempting to feed a diet without FM.     

Suitable dietary chitosan improves the growth performance,survival and immune function of tiger shrimp,Penaeus monodon

Different levels of dietary chitosan on growth performance, survival and stress tolerance to air exposure was studied in tiger shrimp, Penaeus monodon. Shrimp (mean initial wet weight about 1.16 g) were fed with six different diets (C0, C0.05, C0.1, C0.2, C0.3 and C0.4) containing six level of chitosan (0%, 0.05%, 0.1%, 0.2%, 0.3% and 0.4% respectively) in triplicate for 60 days. Growth performance [final body wet weight (FBW); weight gain (WG); biomass gain (BG)] of shrimp fed chitosan‐containing diets were higher (P < 0.05) than that of shrimp fed the basal diet, shrimp fed C0.1 diet showed the highest value of growth performance. Survival of shrimp in C0.1 and C0.2 diet groups were higher (P < 0.05) than that of shrimp in C0, C0.05 and C0.4 diet groups but without statistical difference (P > 0.05) in shrimp fed C0.3 diet group. Whole body and muscle lipid contents decreased with increasing dietary chitosan levels. Plasma total cholesterol and triglyceride contents of shrimp fed C0 diet was significantly higher (P < 0.05) than that of shrimp fed chitosan‐containing diets. Plasma alanine aminotransferase (ALT) and aspartate aminotransferase (AST) activities of shrimp fed C0 diet were higher than those of shrimp fed chitosan‐containing diets. Digestive gland malondialdehyde (MDA) and carbonyl protein contents of shrimp fed chitosan‐containing diets were lower (P < 0.05) than that of shrimp fed C0 diet. Total haemocyte count of shrimp fed C0 diet was lower (P < 0.05) than that of shrimp fed chitosan‐containing diets. On the contrary, the haemolymph clotting time of shrimp fed C0 diet was higher (P < 0.05) than that of shrimp fed chitosan‐containing diets. In conclusion, all results suggested that dietary intake containing 0.1% and 0.2% chitosan enhanced the growth of shrimp, whereas a higher level than 0.3% and 0.4% decreased growth of shrimp. Second‐degree polynomial regression analysis of WG and BG indicated that the optimum supplement of dietary chitosan level should be 0.19–0.21%.     

Effects of dietary astaxanthin on growth,antioxidant capacity and gene expression in Pacific white shrimp Litopenaeus vannamei

Pacific white shrimp Litopenaeus vannamei (1050 individuals with initial weight of 1.01 ± 0.001 g) were fed either control diet or one of six dietary astaxanthin (AX) concentration (25, 50, 75, 100, 125 and 150 mg kg⁻¹) diets for 56 days in 35 tanks (30 shrimp per tank). After 56 days of culture, shrimp‐fed AX125 and AX150 diets had higher (P < 0.05) weight gain, specific growth rate, total antioxidant status and lower (P < 0.05) superoxide dismutase (SOD), catalase (CAT) than shrimp fed control diet. After low dissolved oxygen stress for 1 h, survival rate of shrimp fed AX75, AX100, AX125 and AX150 diets was higher (P < 0.05) than that of shrimp fed control diet. Hypoxia inducible factor‐1α (HIF‐1α), cytosolic manganese superoxide dismutase (cMnSOD) and CAT mRNA expression levels of shrimp fed seven diets were significantly down‐regulated under hypoxia than under normoxia, but their expression levels were higher under hypoxia in shrimp fed AX‐supplemented diets than in shrimp fed control diet. About 70‐kDa heat‐shock protein (Hsp70) mRNA expression level of shrimp fed seven diets was significantly up‐regulated under hypoxia than under normoxia, but its expression level was lower under hypoxia in shrimp fed AX‐supplemented diets than in shrimp fed control diet.     

Fishmeal levels can be successfully reduced in white shrimp (Litopenaeus vannamei) if supplemented with DL‐Methionine (DL‐Met) or DL‐Methionyl‐DL‐Methionine (Met‐Met)

The main objective of this study was to evaluate the effect of methionine supplementation when reducing fishmeal levels in diets for white shrimp (Litopenaeus vannamei). Tested diets consisted of a positive control with 260 g/kg fishmeal (D1), two negative controls with 100 g/kg fishmeal and no amino acid (AA) supplementation (D2) or supplemented with lysine but not methionine (D3), and four additional diets with 100g/kg fishmeal supplemented with increasing levels of DL‐Met (1.0, 2.0 or 3.0 g/kg) (D4, D5, D6) or Met‐Met (1.0 g/kg) (D7). Each diet was fed to four groups of 30 shrimp for 8 weeks at a daily rate of 70 g/kg body weight. Reduction in fishmeal from 260 g/kg down to 100 g/kg did not significantly affect survival rate, feed conversion ratio (FCR), protein efficiency ratio (PER) or protein retention efficiency (PR%) of white shrimp. However, growth performance (final body weight, FBW; weight gain, WG; specific growth rate, SGR) was reduced when dietary fishmeal level was reduced from 260 g/kg (D1) to 100 g/kg without methionine supplementation (D2). The growth performance (FBW, WG and SGR) of shrimp was significantly increased by supplementation of the 100 g/kg fishmeal diet with increasing levels of DL‐Met (p < .05). Same performance as positive control (D1) was achieved with diets containing 100 g/kg fishmeal and supplemented with 3.0 g/kg DL‐Met or 1.0 g/kg Met‐Met. The highest values of growth performance (FBW, WG and SGR) were found in shrimp fed D6 and D7 diets, which were significantly higher than those of shrimp fed D2 and D3 diets (p < .05) but without statistical differences with shrimp fed D1, D4 and D5 diets (p > .05). The highest values of whole‐body and muscle protein contents were found in shrimp fed D1 diet, which were significantly higher than those of shrimp fed all other diets (p < .05). The highest value of intestinal tract proteolytic enzyme activity was found in shrimp fed Met‐Met‐supplemented diet (D7) and followed by the positive control diet (D1) and 3 g/kg DL‐Met‐supplemented diet (D6) (p < .05). The highest values of apparent digestibility coefficients (ADCs) of dry matter and crude protein were found in Met‐Met‐supplemented diet (D7) and followed by the positive control diet (D1) (p < .05). Shrimp fed the D1 diet showed the highest value of total essential amino acid (EAA) and was significantly higher than shrimp fed D2–D3 (p < .05) but without significant difference with shrimp fed D4–D7 (p > .05). In conclusion, results showed that same performance can be achieved with diets containing 260 or 100 g/kg fishmeal supplemented with 3.0 g/kg DL‐Met or 1.0 g/kg Met‐Met. Moreover, supplementation of limiting methionine in low‐fishmeal diets seems to improve the digestive proteolytic activity, improving digestibility of dry matter and protein, and eventually to promote growth of juvenile white shrimp in fishmeal reduction diets.     

Preliminary study on effects of methionine hydroxy analog and taurine supplementation in a soy protein concentrate‐based diet on the biological performance and amino acid composition of rainbow trout [Oncorhynchus mykiss (Walbaum)]

A feeding trial was conducted on the effects of methionine hydroxy analog (MHA) and taurine supplementation in diets with high levels of soy protein concentrate (SPC) on the growth performance and amino acid composition of rainbow trout, Oncorhynchus mykiss (Walbaum) comparing with fish meal based diet. The control diet had 520 g kg^?1 fish meal. In the methionine deficient diets (5.1 g kg^?1), fish meal was replaced by 490 g kg^?1 of the SPC in the SPC49 diet. The SPC49 diet was supplemented with either MHA (6 g kg^?1) only or a combination of MHA and taurine (2 g kg^?1). Fish were fed isoproteic (460 g kg^?1) and isolipidic (130 g kg^?1) diets for 12 weeks. Growth performance (i.e. weight, feed conversion ratio, and thermal‐unit growth coefficient) was inferior in fish fed the SPC49 diet. MHA supplementation improved growth performance (P < 0.05). No difference was observed when taurine was added to the SPC49 and MHA diet (P > 0.05). Whole‐body taurine contents increased with taurine supplementation, whereas plasma methionine increased with MHA supplementation (P < 0.05). In conclusion, the substitution of fish meal with SPC supplemented with MHA did not negatively impact growth, and the addition of taurine did not improve growth performance in rainbow trout.     

Evaluation of skate meal and sablefish viscera meal as fish meal replacement in diets for Pacific threadfin (Polydactylus sexfilis)

The objectives of this study were to investigate the nutritional value of skate meal and sablefish viscera meal from Alaskan fishery processing and to ascertain their suitability as replacements for pollock fishmeal in diets for Pacific threadfin (Polydactylus sexfilis). Test diets were made by replacing 50% or 100% protein from fish meal in the control diet with skate or sablefish viscera meal. The test diets and a commercial feed were each assigned to four tanks with eight juvenile fish (9.7 g) per tank in an indoor flow‐through culture system. After 6 weeks, Pacific threadfin fed skate meal‐50% and ‐100% substituted diets exhibited similar weight gains (374%; 369%) and feed conversion ratios (1.29; 1.27) as those fed the control diet (345%; 1.30 respectively) (P > 0.05). In contrast, Pacific threadfin fed the sablefish viscera meal‐50% substituted diet exhibited significantly lower weight gain (112%) than fish fed the control diets (P < 0.05). The fish fed the control diet and skate meal substituted diets also achieved significantly higher (P < 0.05) weight gain than those fed the commercial feed (288%). In conclusion, skate meal can fully replace the commercial fishmeal in a Pacific threadfin diet without adversely effecting growth performance.     

Growth performance and feed utilization of Nile tilapia Oreochromis niloticus (Linnaeus, 1758) and tilapia galilae Sarotherodon galilaeus (Linnaeus, 1758) fingerlings fed plant protein-based diets

This study was designed to determine the effect of complete substitution of fish meal (FM) by three plant protein sources including extruded soybean meal (SBM), extruded full‐fat soybean (FFSB) and corn gluten meal (CGM) on growth and feed utilization of Nile tilapia Oreochromis niloticus and tilapia galilae Sarothrodon galilaeus. Four isonitrogenous of crude protein (ca. 28.0%) and isocaloric (ca. 19 MJ kg⁻¹) experimental diets were formulated. The control diet (diet 1) was prepared with FM as the main protein sources. Diets 2–4, each FM control diet, were completely substituted with SBM (diet 2), FFSB (diet 3) and CGM (diet 4). l ‐lysine and dl ‐methionine were added to plant protein diets to cover the nutritional requirements of tilapia. Each treatment was allocated to three net pens and fed for 17 weeks. Nile tilapia fed the control diet showed significantly higher (P≤0.05) values for final body weight (FBW), feed intake (FI), weight gain (WG) and specific growth rate (SGR), whereas fish fed the diet with CGM achieved the lowest values. Tilapia galilae fed SBM diet recorded the highest (P≤0.05) values for growth performance. Better feed conversion ratio (FCR) for both Oreochromis niloticus and Sarothrodon galilaeus was observed when fish were fed SBM diet, whereas the worse FCR was recorded for FFSB diet. Feed utilization parameters including protein productive value (PPV), fat retention (FR) and energy retention (ER) showed significant differences (P≤0.05) for both the species fed different dietary protein sources. The present results suggest that, for Nile tilapia, both SBM and FFSB supplemented with dl ‐methionine and l ‐lysine can completely replace dietary FM. Meanwhile, S. galilaeus fed SBM diet exhibited comparable growth and feed utilization with those fish fed a fish‐meal‐based diet.     

Refined understanding of sulphur amino acid nutrition in hybrid striped bass, Morone chrysops♀×M. saxatilis♂

Previous studies have indicated that the level of total sulphur amino acids (TSAA) (methionine+cystine) is most limiting in practical diet formulations for hybrid striped bass (HSB), especially if animal feedstuffs are replaced with plant feedstuffs. Reduction in costly animal feedstuffs such as fish meal, while maintaining adequate dietary levels of TSAA, may enhance the cost effectiveness of production. Therefore, this study investigated three different aspects of sulphur amino acid nutrition of HSB including: (1) the efficacy of crystalline methionine hydroxy analogue (MHA) and liquid MHA (Alimet?) relative to l‐ methionine in meeting the requirement for TSAA; (2) the cystine‐sparing value for methionine; and (3) the influence of various sulphur amino acid supplements on ammonia excretion. During three separate feeding trials (2, 6 and 10 weeks in duration), juvenile HSB were fed various diets including a basal diet deficient in TSAA (0.33% or 0.51% of diet), and experimental diets supplemented on an equal‐sulphur basis with different levels of either l‐ methionine, Alimet? or crystalline MHA. Diets containing TSAA at 1% of diet and different ratios of cystine to methionine (60:40, 55:45, 50:50 and 45:55) were also fed to re‐evaluate the sparing effects of cystine on methionine. In trial 1, over the course of 10 weeks, Alimet? was 73% as effective in promoting weight gain as l ‐methionine at the same concentration while MHA was 83% as effective. After 6 weeks in trial 2, fish fed Alimet? at 1.25% of diet displayed similar growth performance as those fed TSAA at 1.0% of diet, while weight gain of fish fed Alimet? at 1% was only 58% of that displayed by fish fed TSAA at 1.0%. No significant differences in weight gain, feed utilization or survival were observed among fish fed diets containing various ratios of cystine to methionine, although the diet with 60:40 cystine to methionine had the lowest numerical responses. Inclusion of MHA or Alimet? did not affect TAN excretion of HSB. These findings will aid in refining diet formulations for HSB to ensure adequate sulphur amino acid nutrition.     

Effects of Varying Concentrations of l-carnitine-incorporated Diets on Growth and Body Composition of Fry of Cirrhinus mrigala (Hamilton, 1822)

Experiment was conducted to ascertain the effect of l ‐carnitine on growth and body composition of Cirrhinus mrigala fry (0.342 ± 0.03 g) using five different concentrations (0.25, 0.50, 0.75, 1, and 0%) of l ‐carnitine‐incorporated diets for 120 d. At the end of trial, weight gain, feed conversion efficiency, and protein efficiency of fishes fed with 0.25% l ‐carnitine diet were observed to be significantly higher. Poor growth was recorded in the fry fed diet with no carnitine, while intermediate growth was observed when fed with 0.50, 0.75, and 1% l ‐carnitine‐incorporated diets. The analysis of body composition of C. mrigala fry indicated that there is no significant difference (P > 0.05) in moisture, protein, and ash contents, but significant difference (P < 0.05) was found in body lipid content of fry, fed with different concentrations of l ‐carnitine. Decrease in viscerosomatic and hepatosomatic indices were observed in fishes fed with l ‐carnitine‐incorporated diets. Results of this study indicated that diet containing 0.25% l ‐carnitine can promote higher growth in C. mrigala fry.     

Effects of dietary administration of Macsumsuk® on growth and stress to low salinity and low dissolved oxygen in whiteleg shrimp,Litopenaeus vannamei (Boone, 1931) juveniles

An 8‐week study was conducted to explore the results of Macsumsuk^® as a feed additive on the stress tolerance and growth of Litopenaeus vannamei in 15 culture tanks of 36 L each. Three hundred shrimp averaging 0.1 ± 0.01 g were fed with five isonitrogenous (48.38 ± 0.38% CP) diets (in triplicate groups) containing kaolinite (Macsumsuk^®) at 0%, 0.3%, 0.6%, 1.2% and 2.4%, namely Mk₀, Mk_0.3, Mk_0.6, Mk_1.2 and Mk_2.4. Specific growth rate (SGR) and weight gain (WG) of shrimp fed diets Mk_1.2 and Mk_2.4 were significantly better than those of shrimp fed diet Mk₀ (p < .05). However, SGR and WG of shrimp fed diets Mk_0.6, Mk_1.2 and Mk_2.4 were not significantly different. Protein efficiency ratio (PER) and feed efficiency (FE) of shrimp fed diets Mk_1.2 and Mk_2.4 were significantly better than those of shrimp fed diets Mk₀, Mk₀.₃ and Mk_0.6. Furthermore, the survival of shrimp fed diet Mk_2.4 was significantly lower than that of shrimp fed diet Mk_0.6 (p < .05). Cumulative mortality of shrimp fed diet Mk_1.2 was significantly lower than that of shrimp fed diet Mk₀ at 1–1.5 hr post‐stress to low dissolved oxygen (from 6.1 mg/L to 2.9 mg/L) and 4–5 hr post‐stress to low salinity (from 32‰ to 1‰) (p < .05). The optimum dietary Macsumsuk^® level for juvenile L. vannamei was determined as 1.97% by the polynomial regression analysis of weight gain.     

Effects of dietary methionine hydroxy analogue supplement on growth,protein deposition and intestinal enzymes activities of juvenile Jian carp (Cyprinus carpio var. Jian)

A total of 900 juvenile Jian carp (Cyprinus carpio var. Jian) (8.24 ± 0.03 g) were fed practical diets containing graded levels of methionine hydroxy analogue (MHA) (0, 5.1, 7.6, 10.2, 12.7 and 15.3 g kg^?1 diet) for 60 days to investigate the effects of MHA on growth, protein deposition and intestinal enzymes activities. Per cent weight gain (PWG) significantly increased with increasing levels of MHA up to a point (P < 0.05), and thereafter declined. Feed efficiency was the highest when MHA level was at 5.1 g kg^?1 diet. Feed intake (FI) significantly enhanced with dietary MHA level up to a point (P < 0.05), beyond which it plateaued. Patterns of differences in protein production value, lipid production value, intestosomatic index, folds height, lipase, chymotrypsin, γ‐glutamyl transpeptidase, Na⁺, K⁺‐ATPase, creatinekinase, glutamate‐oxaloacetate transaminase and glutamate‐pyruvate transaminase activities were the same as that in PWG, whereas the trend of plasma ammonia content was opposite. Hepatopancreas protein content, trypsin and amylase activities followed the same trend as that of FI. The optimal supplemental level of MHA for fish meal and miscellaneous meals–based diet (6.9 g methionine kg^?1 diet) for PWG was 8.2 g kg^?1 diet by the quadratic regression analysis.     

Assessing the bioavailability of L‐methionine and a methionine hydroxy analogue (MHA‐Ca) compared to DL‐methionine in rainbow trout (Oncorhynchus mykiss)

Different synthetic forms of supplemental methionine (Met) are produced commercially by various manufacturers. Limited information exists on the bioavailability of these different forms in commercially relevant fish species. The objective of this study was to compare the relative bioavailability of L‐methionine and a methionine hydroxy analogue calcium salt (MHA‐Ca) to DL‐methionine in a commercially relevant species, rainbow trout, using a linear slope‐ratio assay. In addition, the ability of the rainbow trout to effectively convert the D‐isomer of methionine into the biologically active L‐isomer was studied by comparing the relative bioavailability of L‐methionine to DL‐methionine. Nine (9) diets were created from a methionine‐deficient basal diet which was supplemented with graded equimolar levels of methionine (0.1%, 0.2%, 0.3% of diet by weight) from either DL‐methionine, L‐methionine and methionine hydroxy analogue calcium salt (MHA‐Ca). Diets were fed in triplicate (IBW = 24.0 ± 0.6 g) for 12 weeks using a pair‐feeding protocol. The basal diet was formulated to be deficient in both methionine (0.5%) and cysteine (0.3%), whereas meeting all other known nutritional requirements of rainbow trout. MHA‐Ca was found to be less available (P < 0.05) than DL‐methionine with relative bioavailability values of 69%, 60% and 73% based upon weight gain, growth rate (TGC) and retained nitrogen values respectively. No significant differences (P > 0.05) in bioavailability were found between DL‐methionine and L‐methionine. These findings lead to the conclusion that differences in bioavailability do exist between sources of synthetic methionine, additionally findings suggest that rainbow trout are able to effectively convert the D‐isomer of methionine into the L‐isomer without significantly affecting fish performance.     

Utilization of Deoxynivalenol‐Contaminated Hard Red Winter Wheat for Shrimp Feeds1

Wheat is used in shrimp feed as protein and energy sources, as well as a nutritive binder that promotes water stability. However, wheat may be contaminated with deoxynivalenol (DON or vomitoxin) when wet weather conditions prevail during the growing season. Deoxynivalenol‐contaminated wheat was added to shrimp diet to obtain DON levels of 0.2, 0.5, and 1.0 ppm. Pelleted diets were fed 3 times daily until satiation to Pacific white shrimp Liropenaeus vanna‐mei. Biological performance (live weight, weekly growth increment, feed conversion ratio, and survival) was determined biweekly for 16 wk. Histological characteristics of shrimp were determined on samples obtained after 8 and 16 wk of growth. The DON levels in ground wheat, feed mash, pellets, and freeze‐dried shrimp were determined using thin layer and high performance liquid chromatography. Deoxynivalenol levels of 0.2, 0.5, and 1.0 ppm in the diet significantly reduced shrimp body weight and/or growth rate. However, the effects of 0.2 and 0.5 ppm DON were manifested at later stages of shrimp growth, and 0.2 ppm DON significantly affected only growth rate and not body weight (P > 0.05). Feed conversion ratio and survival of shrimp fed diets containing 0.2, 0.5, and 1.0 ppm DON were not significantly different from those of shrimp fed the control diet (0.0 ppm DON). After 16 wk of growth, no DON was detected in freeze‐dried shrimp, and no consistent difference was observed in the histological organ profiles of shrimp fed diets containing various levels of DON. Because low levels of DON in the diet can significantly reduce body weight and growth rate of shrimp, feed ingredients should be monitored for DON.     

Effect of dietary l‐methionine concentrations on growth performance,serum immune and antioxidative responses of juvenile Nile tilapia,Oreochromis niloticus

An 8‐week feeding trial was conducted to determine the effect of dietary l ‐methionine supplementation on growth performance, serum immune and antioxidative responses of juvenile Nile tilapia Oreochromis niloticus. Six iso‐nitrogenous (282 g kg^?1 crude protein) diets were formulated to contain graded levels of methionine (0.32%, 0.54%, 0.75%, 0.93%, 1.14% and 1.33% of dry weight) at a constant dietary cysteine level of 0.83 g kg^?1. Each diet was randomly assigned to triplicate groups of 25 juvenile fish (2.3 ± 0.0 g), which were fed three times daily (8:30, 12:30 and 17:00 hours). The results showed that growth performance and feed utilization significantly improved when dietary methionine levels increased (P < 0.05). Using quadratic regression analysis of weight gain against dietary methionine levels indicated that, the optimal dietary methionine requirement for maximum growth of juvenile tilapia was 9.12 g kg^?1 of the dry diet in the presence of 0.83 g kg^?1 cystine. In addition, maximum C4 content and lysozyme activity were observed in fish fed 7.50 g kg^?1 methionine diet; maximum C3 content and superoxide dismutase activity were obtained in fish fed 9.30 g kg^?1 dietary methionine level. While there was no significant difference in serum glutathione peroxidase activity among all methionine supplemented treatments (P > 0.05). Methionine supplementation decreased malondialdehyde content in serum significantly (P < 0.05) when compared with the control diet, while there was no significant difference among supplemented treatments. These data suggested that l ‐methionine affected antioxidant status and promoted serum immune response in juvenile Nile tilapia, and at non‐stressed status, the requirement of dietary methionine in maintaining normal immunity and physiology is lower than that for maximum growth.     

Fungus,Aspergillus niger,fermented groundnut oil cake as a fishmeal alternative in the diet of Penaeus vannamei

Commercial de‐fatted groundnut oil cake (GNC) fermented with the fungus Aspergillus niger was evaluated as a fishmeal alternative in the diet of Penaeus vannamei. A 45‐day growth trail was performed using nine iso‐nitrogenous and iso‐lipidic diets. Untreated/fermented GNC was included at the rate of 0 (control), 25, 50, 75 and 100 g/kg by replacing fishmeal (w/w). Each diet was randomly assigned to triplicate group of 20 shrimps (initial weight of 3.09 ± 0.03 g). Results revealed that shrimp fed with diets having untreated GNC up to 50 g/kg has no significant difference in growth, whereas the inclusion level was enhanced to 100 g/kg with fermented GNC with no deleterious effect. The negative linear trend was found for SGR with increasing the inclusion of both untreated and fermented GNC. The feed and protein efficiency measures, viz. feed conversion ratio, protein efficiency ratio and apparent protein utilization, were better in shrimps fed with diets having fermented GNC than those fed the respective level of untreated GNC. The broken‐line analysis indicated that the inclusion of 72.5 g/kg fermented GNC showed the best FCR. No significant difference was observed in survival (86.67%–96.67%) between the dietary treatments. There was a significant difference in ether extract of shrimp between the treatments, whereas other parameters were not affected. Haemolymph indices showed a significant difference in total protein, glucose, cholesterol and triglycerides between control and test diets. The results conclude fermented GNC, which can be better than untreated one in the diet of shrimp.