A determination of the quantitative requirements for docosahexaenoic acid for juvenile barramundi (Lates calcarifer)

A series of diets with varying docosahexaenoic acid (DHA; 22:6n‐3) inclusion levels (1 g kg^?1 3 g kg^?1, 6 g kg^?1, 10 g kg^?1, 15 g kg^?1 and 18 g kg^?1) were fed to juvenile barramundi (Lates calcarifer) for 6 weeks. Two additional diets examined the addition of arachidonic acid (ARA; 20:4n‐6) or eicosapentaenoic acid (EPA; 20:5n‐3) to the diets at 10 g kg^?1 when DHA was also included at 10 g kg^?1. Fish were fed the diets on a pair‐fed feeding regime to eliminate feed intake variability. Fish were weighed, and blood and tissue samples were collected after 6 weeks. Behavioural parameters were also assessed. Improvement in growth was seen with increasing inclusion of DHA up to a maximum at 10 g kg^?1 inclusion, albeit the response was minor. However, the addition of ARA to the diet reduced the growth response, while the addition of EPA improved the growth response. An improvement in feeding behaviour was also seen with increasing DHA up to a peak at 10 g kg^?1, while those animals fed diets low in DHA showed increasingly cryptic behaviour. With the increasing inclusion of DHA, a range of pathologies were observed, but the addition of an EPA component to the diet limited these pathologies, while the addition of ARA made little improvement and in some cases exacerbated the pathologies.     

Effect of dietary arachidonic acid levels on growth performance,hepatic fatty acid profile,intermediary metabolism and antioxidant responses for juvenile Synechogobius hasta

An 8‐week feeding experiment was conducted to determine the effect of dietary arachidonic acid (ARA) levels on growth performance, hepatic intermediary metabolism and antioxidant responses for juvenile Synechogobius hasta. Five isonitrogenous and isolipidic diets were formulated with arachidonic oil (containing 400 g ARA kg^?1) at inclusion levels of 0, 2, 4, 8 and 16 g kg^?1 to replace corn oil. Dietary ARA levels were 0.6, 8.6, 16.7, 32.7 and 64.8 g kg^?1 total fatty acids (FAs), respectively. Fish fed the 8.6–32.7 g ARA kg^?1 total FAs showed the highest weight gain, specific growth rate (SGR) and feed intake. By contrast, feed conversion ratio was the lowest for fish fed the 8.6–32.7 g ARA kg^?1 total FAs. Increasing ARA and total n‐6 fatty acid contents and declining linoleic acid content in liver were observed in fish fed the diet containing increasing dietary ARA levels. As a consequence, ∑n‐6/∑n‐3 ratios increased with increasing dietary ARA levels. Dietary ARA levels significantly influenced several enzymatic activities involved in hepatic intermediary metabolism, such as succinate dehydrogenase, lactate dehydrogenase, lipoprotein lipase and hepatic lipase. Superoxide dismutase activity increased with increasing dietary ARA levels. Glutathione peroxidase and catalase activities and malondialdehyde levels in liver tended to increase with increasing dietary ARA levels from 0.6 to 32.7 g ARA kg^?1 total FAs then declined when dietary ARA levels further increased to 64.8 g ARA kg^?1 total FAs. Broken‐line regression analysis of SGR against dietary ARA level indicated that optimal dietary ARA requirement for juvenile S. hasta was 10.74 g kg^?1 total FAs.     

Effects of dietary highly unsaturated fatty acids and astaxanthin on the fecundity and lipid content of pond-reared Penaeus monodon (Fabricius) broodstock

Five diets that contained fresh squid meat as the basic constituent and were supplemented with different amounts of highly unsaturated fatty acids (HUFA) and astaxanthin were fed to pond‐reared Penaeus monodon broodstock. Diet A was sole squid meat. Diets B and C were supplemented with astaxanthin 50 and 100 mg kg^?1 respectively. Diets D and E were supplemented with HUFA 5 and 10 g kg^?1 and astaxanthin 50 mg kg^?1 respectively. The result showed that the group fed diet E had the best reproductive performance in all experimental groups. It had a higher proportion of spawns (71.5%), spawning rate (0.047), a shorter latency period (7.7±0.3 d), higher absolute fecundity (× 10³) (361.6±5.5) and egg production/female (× 10³) (597.0±18.0) than all the other experimental groups. The fatty acid composition in broodstock diets strongly affected the tissue and fecundity of broodstock. Good correlations between the content of 20:4n‐6 in eggs and the fecundity (r²=0.6109) and egg production (r²=0.9876) of broodstock were found. On the other hand, 22:6n‐3 and DHA/EPA ratio was negatively correlated with the fecundity of broodstock (r²=0.5362, 0.8702 respectively). The result also showed that the balance between n‐3 and n‐6 fatty acid families, total polyunsaturated fatty acids and total saturated fatty acid and 20:5n‐3 (EPA) and 22:6n‐3 (DHA) may play vital roles in maturation and reproductive performance of P. monodon broodstock.     

Effects of canola meal on physiological and biochemical parameters in rainbow trout (Oncorhynchus mykiss)

Rainbow trout (initial body weight 4.16 ± 0.25 g) were fed diets [crude protein 420 g kg^?1; gross energy 18.7 MJ kg^?1 dry matter (DM); crude fat 110 g kg^?1] containing graded levels of either a canola meal (crude protein 350 g kg^?1 DM) supplemented with DL‐methionine as partial fish meal protein. A growth trial was conducted over 16 weeks at a water temperature of 12 ± 1 °C. At the end of the growth trial, in addition to body composition analyses, plasma tri‐iodothyronine (T₃) and thyroxine (T₄), cholesterol and liver fatty acid composition were measured. Replacement of fish meal with canola meal (100–570 g kg^?1 replacement) did not affect on growth performance. At 16th week, plasma cholesterol levels were reduced in fish fed all diets in comparison with 8th week. Plasma T₄ levels were significantly higher in the canola meal‐fed fish sampled after 16 weeks, but no significant differences in T₃ levels were obtained (P > 0.05). Proximate compositions were affected by dietary treatments. The liver fatty acid composition reflected that of the diet with a higher level of polyunsaturated (n‐6) fatty acids in fish fed diet canola meal and a higher content in n‐3/n‐6 ratio in fish fed diet without canola meal. These studies show that canola meal has potential to replace substantial levels of fish meal in diets for carnivorous fish without compromising performance.     

Polka dot grouper Cromileptes altivelis fingerlings require high protein and moderate lipid diets for optimal growth and nutrient retention

An 8‐week comparative slaughter experiment was carried out to determine the effect of dietary protein and lipid on growth, apparent digestibility (AD) and nutrient retention of polka dot grouper Cromileptes altivelis. Fingerlings were fed diets that varied in crude protein (CP) at 55 g kg^?1 increments between 410 and 630 g kg^?1 dry matter (DM) and at either a moderate (150 g kg^?1 DM) or high (240 g kg^?1DM) lipid concentration. Each diet was fed to satiety twice daily to four replicate tanks (110 L) of fish. One replicate block of tanks comprised 150 fish of mean (±SD) initial weight of 9.6 ± 0.29 g, which were distributed equally to 10 tanks. The other three replicate blocks of tanks comprised 300 fish of 12.6 ± 0.45 g, which were distributed equally to 30 tanks. Tanks were provided with filtered and heated (29 ± 0.5 °C) seawater in a flow‐through system within a laboratory where photoperiod was maintained at 12 : 12 h light–dark cycle. Voluntary food intake was not significantly affected by either the CP or lipid concentration of the diet (mean ± SD of 1.93 ± 0.146 g week^?1) but there was a trend for intake to be higher on the moderate compared with the high lipid diets (mean ± SEM of 1.97 versus 1.89 ± 0.033 gweek^?1, respectively). Daily growth coefficient (DGC) and food conversion ratio (FCR) improved linearly (P < 0.01) with increasing dietary CP (from 0.94 to 1.35% day^?1 for DGC and 1.58 to 1.00 g DM g^?1 wet gain for FCR) and these responses were almost coincident for each of the lipid series. The AD of CP increased linearly with increasing dietary CP (from 46.8 to 74.1%) and was independent of dietary lipid. Apparent digestibility of energy increased curvilinearly with increasing dietary CP, with the quadratic component being more prominent for the high‐lipid series. Increasing the amount of lipid in the diet markedly increased the lipid content of the fish from an initial composition (mean ± SD) of 173 ± 7.3 g kg^?1 to a final composition (mean ± SEM) of either 217 or 250 ± 5.9 g kg^?1 for moderate and high‐lipid series, respectively. Total body lipid content tended to increase linearly with increasing dietary CP for the high‐lipid series but with an opposite effect for the moderate‐lipid series. The retention of digestible nitrogen decreased linearly with increasing dietary CP but at a steeper rate for the moderate, compared with the high, lipid series (from 62.7 to 35.7%, slope ?0.115 for moderate‐lipid and 54.6 to 41.9%, slope ?0.050 for high‐lipid). A quadratic function of dietary CP concentration best explained the retention of digestible energy with the curvilinearity being more marked for the high, compared with the moderate, lipid diet series. While there was some indication that ingested lipid spared dietary protein, the results showed a far greater propensity of polka dot grouper fingerlings to use protein as the prime dietary energy source. Diets for juvenile polka dot grouper should contain not less than 440 g digestible protein kg^?1 DM and at least 150 g lipid kg^?1 DM.     

Apparent digestibility coefficient of poultry by‐product meal (PBM) in diets of Penaeus monodon (Fabricius) and Litopenaeus vannamei (Boone), and replacement of fishmeal with PBM in diets of P. monodon

Nutrient apparent digestibility coefficients (ADCs) of pet food grade poultry by‐product meal (PBM) were determined for black tiger prawn, Penaeus monodon and Pacific white shrimp, Litopenaeus vannamei by the indirect method (reference diet and test diet at 7:3 ratio). Subsequently, an 8‐week growth trial was conducted to evaluate the effects of substitution of fishmeal (FM) with PBM in diets of P. monodon (initial weight = 0.21 ± 0.01 g). In the growth trial, six isonitrogenous and isoenergetic diets PBM0, PBM25, PBM50, PBM75, PBM100 and PBMA100, containing a gradient of PBM 0, 88.7, 177.4, 266, 354.7 and 354 g kg^?1 to replace 0, 92.5, 185, 277.5, 370 and 370 g kg^?1 FM were fed to four replicate groups respectively. The diet PBMA100 was supplemented with DL‐Met to be similar to PBM0. The results showed that both P. monodon and L. vannamei had relatively high ADC of crude protein (77.6% and 84.2% respectively) and gross energy (72.8% and 84.0% respectively) for PBM. Litopenaeus vannamei showed significantly higher digestion ability for PBM than P. monodon (P < 0.05). In growth trial, no significant difference in growth performance was observed among shrimp fed the experimental diets. DL‐Met supplementation did not improve the growth of P. monodon. PBM is a suitable protein ingredient for P. monodon feeds and can be used up to 354.7 g kg^?1 to totally replaced FM.     

Response of the tropical spiny lobster Panulirus ornatus to protein content of pelleted feed and to a diet of mussel flesh

In an 8‐week growth experiment, juvenile spiny lobsters (Panulirus ornatus) grew best on a feed containing at least 610 g kg^?1 crude protein on a dry matter basis (DM) and a digestible protein to digestible energy ratio of 29.8 mg kJ^?1. The study entailed a six treatment by four replicate randomized block experiment with 222 wild‐caught P. ornatus of mean initial weight (±SD) of 2.5 ± 0.19 g. The lobsters were fed one of five isolipidic feeds (approximately 130 g kg^?1 DM) in which the crude protein was serially incremented between 330 and 610 g kg^?1 DM, or a reference diet comprising the flesh of frozen green‐lip mussels. Lobsters fed the pelleted feeds had high survival (79 ± 4.5%) and responded to increasing dietary crude protein content with progressively higher growth rates, with the daily growth coefficient improving from 0.72% day^?1 with 330 g kg^?1 crude protein to 1.38% day^?1 with 610 g kg^?1 crude protein. Both growth rate and survival were low with the mussel diet (0.80% day^?1and 41 ± 4.5%, respectively). These results demonstrate that tropical spiny lobsters grow well when fed high‐protein, high lipid, pelleted feeds, but feeding on a sole diet of freshly thawed green‐lip mussels was unsatisfactory.     

Supplementation with 2‐hydroxy‐4‐(methylthio)butanoic acid (HMTBa) in low fish meal diets for the white shrimp,Litopenaeus vannamei

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? Met_Ca (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%.     

Interactions between dietary docosahexaenoic acid and other long-chain polyunsaturated fatty acids on performance and fatty acid retention in post-smolt Atlantic salmon (Salmo salar)

A study with varying dietary inclusion levels (1, 5, 10, 15 and 20 g kg^?1) of docosahexaenoic acid (DHA; 22:6n-3) was conducted with post-smolt (111 ± 2.6 g; mean ± S.) Atlantic salmon (Salmo salar) over a 9-week period. In addition to the series of DHA inclusion levels, the study included further diets that had DHA at 10 g kg^?1 in combination with either eicosapentaenoic acid (EPA; 20:5n-3) or arachidonic acid (ARA; 20:4n-6), both also included at 10 g kg^?1. An additional treatment with both EPA and DHA included at 5 g kg^?1 (total of 10 g kg^?1 long-chain polyunsaturated fatty acids, LC-PUFA) was also included. After a 9-week feeding period, fish were weighed, and carcass, blood and tissue samples collected. A minor improvement in growth was seen with increasing inclusion of DHA. However, the addition of EPA further improved growth response while addition of ARA had no effect on growth. As with most lipid studies, the fatty acid composition of the whole body lipids generally reflected that of the diets. However, there were notable exceptions to this, and these implicate some interactions among the different LC-PUFA in terms of the fatty acid biochemistry in this species. At very low inclusion levels, DHA retention was substantially higher (~250 %) than that at all other inclusion levels (31–58 %). The inclusion of EPA in the diet also had a positive effect on the retention efficiency of DHA. However, EPA retention was highly variable and at low DHA inclusion levels there was a net loss of EPA as this fatty acid was most likely elongated to produce DHA, consistent with increased DHA retention with additional EPA in the diet. Retention of DPA (22:5n-3) was high at low levels of DHA, but diminished with increasing DHA inclusion, similar to that seen with DHA retention. The addition of EPA to the diet resulted in a substantial increase in the efficiency of DPA retention; the inclusion of ARA had the opposite effect. Retention of ARA was unaffected by DHA inclusion, but the addition of either EPA or ARA to the diet resulted in a substantial reduction in the efficiency of ARA retention. No effects of dietary treatment were noted on the retention of either linolenic (18:3n-3) or linoleic (18:2n-6) acids. When the total n-3 LC-PUFA content of the diet was the same but consisted of either DHA alone or as a combination of EPA plus DHA, the performance effects were similar.     

A study of the arachidonic acid requirements of the giant tiger prawn, Penaues monodon

This study examined the dietary requirement of arachidonic acid (ARA) when that of linoleic acid (LOA), the natural precursor to ARA, was also satisfied with linolenic acid (LNA) and also with and without the other key dietary highly unsaturated fatty acids (HUFA). Growth by prawns fed diets supplemented with ARA was poorer than in diets where it was not present. Supplementation of ARA to diets with either optimized HUFA or just optimised poly unsaurated fatty acids (PUFA) (i.e. LOA, LNA) resulted in poorer growth. Growth was poorest by prawns (215 ± 13%) fed diets with ARA supplemented at 20% of the total fatty acids but including 7% LOA, 21% LNA and 4% of both eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). Growth was best in prawns fed diets devoid of ARA but with 7% LOA and 21% LNA (350 ± 19%). Prawns fed the reference diet (348 ± 21%) and the other diet devoid of ARA but containing about 7% LOA, 21% LNA and 4% of both EPA and DHA (345 ± 18%) had similar growth. The growth responses were not effects of altered lipid or fatty acid digestibilities. Indeed supplementation of ARA to the diet marginally improved the digestibility of the total neutral lipid in the diet and the digestibilities of some other dietary fatty acids. The amount of lipid in the digestive glands of prawns fed with the diets was reduced by the inclusion of ARA in the dietary lipids. Composition of the lipids in the digestive gland (DG) of the prawns was almost directly related to the composition of their dietary lipids. The proportion of ARA in the total fatty acids increased with level of supplementation of dietary ARA. An increased level of dietary ARA reduced the proportion of EPA, DHA in the DG lipid and also the total n‐3 and n‐6 fatty acids in the DG lipid. The results of this study support that addition of ARA to the diet of Penaues monodon when the other key essential fatty acids (EFA) have been optimized, does not improve their growth performance. It is suggested that key cause for this response may lie in the importance of the balance of the n‐3 to n‐6 fatty acids in the diet of these animals.     

Effect of lipid supplementation on reproductive performance of female channel catfish,Ictalurus punctatus,induced and strip‐spawned for hybridization

The influence of different lipid sources and n3:n6 ratios on reproductive performance of female channel catfish, Ictalurus punctatus was evaluated. A commercial catfish feed was top coated with 2% oil and offered to brood stock females fish during 70–85 days before spawning season. Four dietary treatments were formulated using the following top coating ratios: diet 1, soybean oil 9.5 g kg^?1 and linseed oil 10.5 g kg^?1; diet 2, soybean oil 17.5 g kg^?1 and linseed oil 2.5 g kg^?1; diet 3, 20.0 g kg^?1 linseed oil, and diet 4, 10.0 g kg^?1 menhaden fish oil, supplemented with 5.0 g kg^?1 arachidonic acid (ARA), and 5.0 g kg^?1 docosahexaenoic acid (DHA). Fatty acid composition of the eggs reflected the effect of dietary treatment offered during spring season. Supplementation of ARA, EPA and DHA in commercial catfish feed in the form of menhaden fish oil with purified liquid algae extracts of ARA and DHA produced from two to five times the number of fry per female body weight when compared to the effect of fed top coated with vegetable oils. Although, this effect was not statistically significant it may represent an economical improvement for the industry.     

Growth and body composition of juvenile white shrimp,Litopenaeus vannamei,fed different ratios of dietary protein to energy

A 10‐week feeding experiment was conducted to evaluate the effect of different protein to energy ratios on growth and body composition of juvenile Litopenaeus vannamei (initial average weight of 0.09 ± 0.002 g, mean ± SE). Twelve practical test diets were formulated to contain four protein levels (300, 340, 380 and 420 g kg^?1) and three lipid levels (50, 75 and 100 g kg^?1). Each diet was randomly fed to triplicate groups of 30 shrimps per tank (260 L). The water temperature was 28.5 ± 2 °C and the salinity was 28 ± 1 g L^?1 during the experimental period. The results showed that the growth was significantly (P < 0.05) affected by dietary treatments. Shrimps fed the diets containing 300 g kg^?1 protein showed the poorest growth. However, shrimp fed the 75 g kg^?1 lipid diets had only slightly higher growth than that fed 50 g kg^?1 lipid diets at the same dietary protein level, and even a little decline in growth with the further increase of dietary lipid to 100 g kg^?1. Shrimp fed the diet with 420 g kg^?1protein and 75 g kg^?1 lipid had the highest specific growth rate. However, shrimp fed the diet with 340 g kg^?1 protein and 75 g kg^?1 lipid showed comparable growth, and had the highest protein efficiency ratio, energy retention and feed efficiency ratio among dietary treatments. Triglycerides and total cholesterol in the serum of shrimp increased with increasing dietary lipid level at the same dietary protein level. Body lipid and energy increased with increasing dietary lipid level irrespective of dietary protein. Results of the present study showed that the diet containing 340 g kg^?1 protein and 75 g kg^?1 lipid with digestible protein/digestible energy of 21.1 mg kJ^?1 is optimum for L. vannamei, and the increase of dietary lipid level has not efficient protein‐sparing effect.     

Potential of meat meal to replace fish meal in extruded dry diets for barramundi, Lates calcarifer (Bloch). I. Growth performance

Juvenile barramundi (～220–280 g start weight) were fed extruded dry‐pelleted diets containing varying amounts of fish meal and meat meal in three experiments (E). E1 and E2 were each 66‐day farm studies utilizing 16 floating cages (400 fish per cage) in an aerated freshwater pond. E3 examined the same diets as fed in E2 but under controlled water temperature (28 ± 0.7 °C) and photoperiod (12:12) laboratory conditions in a 42‐day study involving 24 aquaria (eight fish per aquarium). In all studies, the same 430 g kg^?1 crude protein (CP), 15 kJ g^?1 digestible energy (DE) control (Ctl) diet (containing 35% Chilean anchovy fish meal) was compared with two high‐inclusion meat meal diets and a proprietary diet. The meat meal diets evaluated in E1 were a high‐ash (260 g kg^?1) meat meal that contained 520 g kg^?1 CP and a low‐ash (140 g kg^?1) meat meal that contained 600 g kg^?1 CP when included at either 450 or 400 g kg^?1, respectively, in combination with 100 g kg^?1 Chilean fish meal in diets that were isonitrogenous and isoenergetic with the Ctl diet. Growth rates and feed conversions were similar (P > 0.05) for all diets. In E2 and E3, the 520 g kg^?1 CP meat meal was included at 500 g kg^?1 without any marine protein source in diets formulated to provide either 15 or 16.2 kJ g^?1 DE and the same CP/DE ratio (29 mg kJ^?1) as the Ctl diet. Fish performance ranking of diets was similar in both experiments, with the 16.2 kJ g^?1 DE diet supporting better (P < 0.05) growth rates than the Ctl diet and feed conversion ratios equivalent to the Ctl diet but better (P < 0.05) than all other diets.     

Use of marine by‐product meals in diets for juvenile longfin yellowtail Seriola rivoliana

A 60‐day feeding trial to determine the nutritional value of marine by‐product meals in diets for longfin yellowtail Seriola rivoliana juveniles (48.1 ± 0.6 g initial weight) was conducted. Five diets were evaluated: a reference diet (RD; 500 g kg^?1 CP, 130 g kg^?1 L), containing 500 g kg^?1 of fish meal (FM); three experimental diets with 125 g kg^?1 of shrimp head (SM), Catarina scallop viscera (CM) or Pen shell viscera (PM) meals; and one diet (SCP) containing 125 g kg^?1 of each of the experimental meals, to partially replace FM. Survival was not significantly affected by any treatment. Individual weight gain per day was high for the PM (5.3 ± 0.51 g d^?1) and SM (4.7 ± 0.32 g d^?1) diets, being significantly higher than the RD (3.5 ± 0.23 g d^?1) and the other treatments (<1.2 g d^?1). Feed intake was high in PM and SM diets, and very low in SCP and CM diets. Biochemical and haematological parameters were similar among treatments RD, PM and SM, while fish fed CM and SCP exhibited lower levels of total protein, cholesterol, haematocrit and haemoglobin. The results indicate that SM or PM can be used to partially replace FM in diets for yellowtail juveniles.     

Dietary arginine requirement of fingerling Indian major carp, Cirrhinus mrigala (Hamilton)

Dietary arginine requirement of fingerling Indian major carp, Cirrhinus mrigala (4.20 ± 0.05 cm; 0.60 ± 0.02 g) was determined by conducting a 8‐week feeding trial with casein–gelatine‐based diets (400 g kg^?1 crude protein; 17.90 kJ g^?1, gross energy), containing crystalline amino acids with graded levels of l ‐arginine (10, 12.5, 15, 17.5, 20 and 22.5 g kg^?1, dry diet). Fish were randomly stocked, in triplicate groups, in 55‐L indoor polyvinyl flow through circular tanks and fed experimental diets at 5% of their body weight divided into two feedings at 08.00 and 16.00 hours. Live weight gain (321%) and feed conversion ratio (FCR 1.40) were significantly (P < 0.05) higher in fish fed diet containing 17.5 g kg^?1dietary arginine compared with other diets. Second‐degree polynomial regression analysis of live weight gain, FCR and protein efficiency ratio data indicated requirements for dietary arginine at 18.7, 18.4 and 18.3 g kg^?1 of the dry diet, respectively. Maximum carcass protein, and minimum moisture and fat contents were noticed at the requirement level. Carcass ash content remained insignificantly different among the treatments except at 17.5 g kg^?1 dietary arginine showing significantly higher ash content. Based on the above results, it is recommended that the diet for fingerling C. mrigala should contain arginine at 18.4 g kg^?1, dry diet, corresponding to 46 g kg^?1 dietary protein for optimum growth and efficient feed utilization.     

Effects of dietary fatty acids on the production and quality of eggs and larvae of Atlantic cod (Gadus morhua L.)

Cultivated Atlantic cod (Gadus morhua) entering their first year of gamete maturation were fed diets with different levels of arachidonic acid (ARA) and eicosapentaenoic acid (EPA) for 6.5 months prior to commencement of spawning. Gravid females were stripped three times: at the beginning, peak and end of spawning. Lipid composition and egg and larval quality of 34 family crosses were investigated. Results indicated that ARA uptake into eggs from broodstock diet was highly efficient achieving proportions of ARA up to 84% higher in eggs than in the diet. EPA was 42–76% higher, and DHA was 155–173% higher in eggs than in diets. Cod fed the diet with the lowest EPA/ARA ratio had the greatest egg production. Eggs from fish on a diet with high ARA level had significantly higher fertilization and hatching success than those fed low levels of ARA. This diet produced on average 71 viable eggs g^?1 female compared with 32.5 and 4 eggs in diet B and C, respectively. Furthermore, larval survival until 8 days posthatch was higher in diets with lower ARA levels. The combined results showed that ARA dietary supplementation and low EPA/ARA ratio yielded a greater number of viable larvae kg^?1 female.     

Total aromatic amino acid requirement of juvenile grass carp (Ctenopharyngodon idella)

This experiment was conducted to investigate total aromatic amino acid requirement of juvenile grass carp Ctenopharyngodon idella. Six isonitrogenous and isoenergetic semipurified diets containing casein and gelatin with graded level of phenylalanine (7.8, 11.1, 14.4, 17.6, 21.7, 24.9 g kg^?1 DM) were formulated. Each diet was randomly assigned to triplicate group of 30 fish (3.58 ± 0.002 g, mean ± SEM) each tank for 8 weeks. The highest weight gain (WG, %), final body weight (g) and specific growth rate were recorded when phenylalanine level was 17.6 g kg^?1 of the diet. Fish muscle protein content, protein efficiency ratio (PER), feed conversion ratio and alanine aminotransferase were significantly affected by dietary phenylalanine level. The polynomial regression calculated using WG and PER indicated that the optimal dietary total aromatic amino acid (phenylalanine + tyrosine) requirement for juvenile grass carp was 24.4 g kg^?1 of the diet, corresponding to 65.9 g kg^?1 of dietary protein.     

Quantitative l-lysine requirement of juvenile grouper Epinephelus coioides

An 8‐week feeding trial was conducted to determine the quantitative lysine requirement of juvenile grouper Epinephelus coioides (initial mean weight: 15.84 ± 0.23 g, mean ± SD) in eighteen 500‐L indoors flow‐through circular fibreglass tanks provided with sand‐filtered aerated seawater by feeding diets containing six levels of l ‐lysine ranging from 19.2 to 39.5 g kg^?1 dry diet in 4 g kg^?1 increments. The diets, in which 250 g crude protein kg^?1 diet came from fish meal and soybean protein concentrate, and 230 g kg^?1 from crystalline amino acids, were formulated to simulate the amino acid profile of 480 g kg^?1 whole chicken egg protein except for lysine. Each diet was assigned to three tanks in a completely randomized design. Grouper were fed to apparent satiation twice daily during the week and once daily on weekends. Weight gain and specific growth rate increased with increasing levels of dietary lysine up to 27.2 g kg^?1 (P < 0.05) and remained nearly the same thereafter (P > 0.05). Feed efficiency was the poorest for fish fed the lowest lysine diet (P < 0.05) and showed no significant differences among other treatments (P > 0.05). Survival could not be related to dietary treatments. Body composition remained relatively constant except for lipid contents in muscle and liver. Total essential amino acid contents in liver increased with dietary lysine level although there was a slight decline for fish fed the highest lysine level of diet. Plasma protein content increased with increasing dietary lysine level (P < 0.05), but cholesterol, triacylglycerol and glucose contents were more variable and could not be related to dietary treatments. Dietary lysine level significantly influenced morphometrical parameters (condition factor, hepatosomatic index and intraperitoneal fat ratio) of juvenile grouper (P > 0.05). Broken‐line analysis of weight gain indicated the dietary lysine requirement of juvenile grouper to be 28.3 g kg^?1 diet or 55.6 g kg^?1 dietary protein.     

Effects of dietary mannan oligosaccharide on growth,survival, physiological,immunological and gut morphological conditions of black tiger prawn (Penaeus monodon Fabricius 1798)

The aim of this experiment was to determine the effects of dietary inclusion with mannan oligosaccharide (Bio‐Mos, Alltech, Nicholasville, KY, USA) on growth, survival, physiological and immunological conditions and gut morphology of the black tiger prawn (Penaeus monodon). Five diets supplemented with MOS at 0 g kg^?1 (control diet), 1, 2, 4 and 8 g kg^?1 were fed to the prawn juveniles (0.4 ± 0.06 g, total weight) for the duration of 63 days. Growth was the highest (P < 0.05) when the prawns were fed the 1 g kg^?1 MOS included diet. Wet tail muscle index (Tw/B), dry tail muscle index (Td/B) and tail muscle protein (Tmp) were higher (P < 0.05) in the prawns fed MOS included diets MOS compared with the prawns fed the control diet. Total haemocyte counts (THCs) of the prawns fed MOS included diets were higher (P < 0.05) than THCs of the prawns fed the control diet. Epithelium layer and epidermal cell density of the gut of the prawns fed 1 g kg^?1 and 2 g kg^?1 MOS diets were better than the prawns fed the control and other MOS diets. The results imply a positive effect of dietary supplementation of 1–2 g kg^?1 MOS in the culture of black tiger prawns.     

Total sulphur amino acid requirement and cystine replacement value for fingerling rohu,Labeo rohita: effects on growth,nutrient retention and body composition

Two feeding experiments were conducted to quantify the total sulphur amino acid (TSAA) requirement and replacement value of cystine for methionine for fingerling Labeo rohita. In Experiment I, isonitrogenous (380 g kg^?1 CP) and isocaloric (17.90 kJ g^?1 GE) amino acid test diets with graded levels of methionine (4, 6, 8, 10, 12, 14 g kg^?1 dry diet) and 0.4 g kg^?1 cystine were fed to fish (4.62 ± 0.2 cm; 0.66 ± 0.1 g) and methionine requirement determined by analysing absolute weight gain (AWG) (5.48), feed conversion ratio (FCR) (1.26), protein retention efficiency (PRE%) (39%) and energy retention efficiency (ERE%) (85%) data which were best at 10 g kg^?1 methionine of dry diet. In Experiment II, six diets with different ratios of L‐cystine and L‐methionine on equimolar sulphur basis were fed to fish (4.71 ± 0.1 cm; 0.69 ± 0.2 g) under identical conditions. Maximum AWG (5.58), best FCR (1.24), PRE (41%) and ERE (86%) in fish fed Diet IV indicated cystine replacement value to be 40%. On the basis of the broken‐line and second‐degree polynomial regression analyses of results obtained in Experiments I and II, it is concluded that inclusion of TSAA in the range of 25.2–31.31 g kg^?1 of protein is optimum of which 33–39% could be spared by cystine.