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1.
A 9‐week feeding trial was conducted to investigate the dietary methionine requirement of juvenile Megalobrama amblycephala at a constant dietary cystine level. Six semipurified diets were formulated to contain graded dietary methionine levels from 3.9 to 15.4 g kg?1 in about 2.5 g kg?1 increments in the presence of 2.2 g kg?1 cystine. Results showed that specific growth rate (SGR) and protein efficiency ratio (PER) significantly increased with increasing dietary methionine levels from 3.9 to 12.4 g kg?1 and thereafter kept stable. Maximum protein productive value (PPV), nitrogen retention efficiency (NRE) and liver weight were observed in 8.5 g methionine kg?1 diet. Protein contents in whole fish body were positively correlated with dietary methionine level, while lipid contents were negatively correlated with it. Morphological index and hepatic glutamate‐pyruvate transaminase (GPT) activities were independent of dietary methionine levels. However, dietary methionine supplementation significantly improved haematological parameters, plasma methionine and total essential amino acid contents and hepatic glutamate‐oxaloacetate transaminase (GOT) activities. Analysis of dose response using broken‐line regression on the basis of SGR and PPV versus dietary methionine level estimated the optimum dietary methionine requirements of juvenile M. amblycephala to be between 8.5 and 8.4 g kg?1 of diet (25.0 and 24.7 g kg?1 of protein) in the presence of 2.2 g kg?1 cystine, respectively. Hence, the corresponding total sulphur amino acids requirements of this species were calculated to be 10.7 and 10.6 g kg?1 of diet (31.5 and 31.2 g kg?1 of dietary protein).  相似文献   

2.
An 8‐week feeding trial was conducted to determine the optimum dietary methionine (Met) requirement of juvenile Pseudobagrus ussuriensis with an initial average weight of 0.60 g reared in indoor flow‐through and aerated aquaria. Six isonitrogenous (430 g kg?1 protein) and isolipidic (50 g kg?1 lipid) test diets were formulated to contain graded levels of crystalline L‐methionine (4.9, 9.0, 11.8, 14.2, 18.1 and 20.8 g kg?1 dry diets, respectively) at a constant dietary cystine level of 2.5 g kg?1 dry diets. Equal amino acid nitrogen was maintained by replacing methionine with non‐essential amino acid mixture. Fish were randomly allotted to 18 aquaria (1.0 × 0.5 × 0.8 m) with 50 fish to each glass aquarium. Fish were fed twice daily (08:00 and 16:00) to apparent satiation. No significant difference was observed in survival of fish (84.67–91.33%). Specific growth rate (SGR), weight gain (WG), feed conversion ratio (FCR), protein productive value (PPV) and protein efficiency ratio (PER) were significantly affected by different dietary methionine levels (P < 0.05). WG, SGR PPV and PER increased, while FCR decreased with increasing dietary methionine level from 4.9 to 11.8 g kg?1 (P < 0.05). However, with further increase from 11.8 to 20.8 g kg?1, WG, SGR PPV and PER significantly decreased, FCR increased (P < 0.05). The whole body and muscle composition were affected by different dietary methionine levels (P < 0.05). Condition factor (CF) increased with increasing dietary methionine levels up to 11.8 g kg?1 (P < 0.05) and after 11.8 g kg?1 methionine diet, but not significant, declines were observed (P > 0.05). Hepatosomatic index (HSI) of the 4.9, 9.0, 11.8 and 14.2 g kg?1 Met diets was significantly higher than that of fish fed diets 18.1 and 20.8 g kg?1 Met diets (P < 0.05). Viscerosomatic index (VSI) of the 4.9, 9.0 and 11.8 g kg?1 Met diets was significantly higher than that of fish fed diets 14.2, 18.1 and 20.8 g kg?1 Met diets (P < 0.05). Quadratic regression analysis of WG and PER against dietary methionine levels indicated that the optimal dietary methionine requirement for maximum growth and feed utilization of juvenile Pseudobagrus ussuriensis was 14.3 and 14.1 g kg?1 dry diet (35.3 and 34.8 g kg?1 dietary protein), respectively, in the presence of 2.5 g kg?1 dry diets cystine.  相似文献   

3.
An 8‐week feeding experiment was conducted to quantify the dietary isoleucine requirement of fingerling Indian major carp, Labeo rohita (3.50 ± 0.04 cm; 0.40 ± 0.02 g) using amino acid test diets (400 g kg−1 crude protein; 17.90 kJ g−1 gross energy) containing casein, gelatin and l ‐crystalline amino acids. Six dietary treatments supplemented with graded levels of isoleucine (7.5, 10.0, 12.5, 15.0, 17.5 and 20.0 g kg−1), in gradations of 2.5 g kg−1 diet, were fed to triplicate groups of fingerlings to apparent satiation divided over two feedings at 07:00 and 17:30 h. Performance of the fish was evaluated on the basis of live weight gain, feed conversion ratio (FCR), protein efficiency ratio (PER), specific growth rate (SGR) and protein productive value (PPV). Statistical analysis of live weight gain, FCR, PER, SGR and PPV reflected significant differences among treatments. Live weight gain and conversion efficiencies were best with isoleucine at 15.0 g kg−1 of diet. Live weight gain, FCR, PER, SGR and PPV data were also analysed using second‐degree polynomial regression analysis to obtain more accurate isoleucine requirement estimate which was found to be at 15.9, 15.3, 15.2, 15.8 and 15.7 g kg−1 of dry diet, corresponding to 39.8, 38.3, 38.0, 39.5 and 39.3 g kg−1 of dietary protein respectively. Based on the quadratic regression analysis of the live weight gain, FCR, PER, SGR and PPV, the optimum level of isoleucine for fingerling L. rohita is in the range of 15.2–15.9 g kg−1 of dry diet, corresponding to 38.0–39.8 g kg−1 of dietary protein. Maximum body protein, minimum moisture and fat were noted at 15.0 g kg−1 of dietary isoleucine while the body ash remained constant among all the treatment levels. No mortality was recorded during the duration of the experiment.  相似文献   

4.
A total of 630 juvenile Chinese sucker, with an average initial weight of 1.72 ± 0.05 g, were fed seven diets for 56 days to study the effect of dietary methionine levels on growth, feed utilization, body composition and haematological parameters on juvenile Chinese sucker. Diet 1 using fish meal as the sole protein source and diets 2–7 using fish meal and fermented soybean meal as intact protein sources supplemented with crystalline amino acids contained six levels of l ‐methionine ranging from 6.4 to 18.9 g kg?1 of dry diet at a constant dietary cystine level of 3.7 g kg?1. Each diet was randomly assigned to three aquaria. Results indicated that the highest weight gain, specific growth rate (SGR), feed efficiency ratio, protein efficiency ratio and protein productive value occurred at 13.9 g methionine kg?1 diet among the methionine supplemented dietary groups, beyond which they showed declining tendency. The whole body and muscle protein contents of juvenile Chinese sucker were positively correlated with dietary methionine level, while muscle lipid content was negatively correlated with it. The total essential amino acids content of muscle was increased significantly with increasing dietary methionine level from 6.4 to 13.9 g kg?1 (P < 0.05). Apparent digestibility coefficients of dietary protein were significantly affected by dietary treatments. Serum protein, cholesterol and triacylglycerol increased with increasing dietary methionine levels, but showed a relatively lower value for fish fed the 18.9 g methionine kg?1 diet. Quadratic regression analysis of SGR against dietary methionine level indicated that optimal dietary methionine requirement for juvenile Chinese sucker was 14.1 g kg?1 of the diet in the presence of 3.7 g kg?1 cystine (corresponding to 32.0 g kg?1 of dietary protein on a dry‐weight basis).  相似文献   

5.
Dietary methionine requirement for juvenile rockfish, Sebastes schlegeli   总被引：4，自引：0，他引：4  
A 65‐day growth trial was conducted at 19.5 °C to determine the optimal dietary methionine for juvenile rockfish, Sebastes schlegeli. Semipurified diets were formulated to be isonitrogenous and isoenergetic. Fish meal was used as intact protein source and crystal amino acid was used as a part of dietary protein. Six experimental diets were formulated to contain 5.8, 10.8, 15.8, 20.8, 25.8 and 30.8 g kg−1 dietary methionine. The results showed that dietary methionine significantly affected specific growth rate, weight gain, food conversion ratio, protein productive value (PPV), energy retention efficiency, carcass index and body composition. No significant difference was found in hepatosomatic index. The dietary methionine requirement for maximum growth was 13.7 g kg−1 dry matter or 28.0 g kg−1 of dietary protein when cystine content was 1.2 g kg−1 dry matter.  相似文献   

6.
A feeding trial was conducted to determine the dietary methionine requirement of juvenile golden pompano (initial body weight 12.40 ± 0.02 g). Six diets were formulated with six graded levels of methionine (8.6, 9.2, 10.4, 11.5, 13.2 and 14.5 g kg−1). Each diet was randomly assigned to triplicate groups of 20 juvenile fish in seawater floating net cages (1.0 m × 1.0 m × 1.5 m). Fish were fed twice daily (08:30 and 16:30) to apparent satiation for 56 days. Weight gain (WG), specific growth rate (SGR), feed conversion ratio (FCR), feed efficiency (FE), nitrogen retention efficiency (NRE), proximate body composition, morphometry and haematology were significantly (P < 0.05) affected by the dietary methionine levels. WG, SGR and FE increased with increasing levels of methionine up to 13.2 g kg−1 diet (P < 0.05) and remained nearly the same thereafter. NRE also increased with increasing levels of methionine up to 13.2 g kg−1 diet (P < 0.05) and remained nearly the same thereafter. Linear regression analysis on WG and NRE indicated that the recommended optimum dietary methionine levels for optimal growth of juvenile pompano were 10.6 and 12.7 g kg−1 diet, respectively, corresponding to 24.6 and 29.5 g kg−1 dietary protein, respectively, so the level of dietary methionine should be between 10.6 and 12.7 g kg−1 diet, corresponding to 24.6–29.5 g kg−1 dietary protein. Additionally, the estimated requirements for the other essential amino acids were calculated from A/E ratios of whole‐body amino acid profile based on the methionine requirement determined from the present experiment.  相似文献   

7.
A feeding trial of three protein (200, 300 and 400 g kg−1) and two lipid levels (20 and 100 g kg−1) was conducted to determine the proper dietary protein and lipid levels for growth of juvenile sea cucumber Apostichopus japonicus. Dietary protein and lipid levels were adjusted by adding with different levels of soybean meal, squid liver oil and soybean oil, respectively. Three replicate groups of sea cucumbers (average weight of 1.3 g) were fed the experimental diets for 12 weeks. At the end of the feeding trial, survival was not affected by dietary protein and lipid levels (P > 0.05). Weight gain (WG) and specific growth rate (SGR) of sea cucumbers were significantly affected by dietary protein (P < 0.006) and lipid levels (P < 0.001). The highest WG and SGR were observed in sea cucumbers fed the 200 and 400 g kg−1 protein diet with 20 g kg−1 lipid (P < 0.05). WG and SGR of sea cucumbers fed the diet containing 20 g kg−1 lipid were higher than those of sea cucumbers fed the 100 g kg−1 lipid diets (P < 0.05) at each dietary protein level. Apparent digestibility coefficients of dry matter, crude protein, carbohydrate and gross energy of sea cucumbers fed the 20 g kg−1 lipid diets were significantly higher than those of the 100 g kg−1 lipid diets at 200 and 400 g kg−1 protein (P < 0.05). Moisture, crude protein, crude lipid and ash contents were not significantly different among the groups. The results of this study indicate that the diet containing 200 g kg−1 protein (170 g kg−1 digestible protein) with 20 g kg−1 lipid (13 g kg−1 digestible lipid) may be sufficient for optimum growth of juvenile sea cucumber.  相似文献   

8.
A growth trial was conducted to examine the effect of dietary digestible energy (DE) content on methionine (Met) utilization and requirement in juvenile Nile tilapia (Oreochromis niloticus). Ten iso‐nitrogenous (288 g kg?1 protein) practical diets, with two DE levels (10.9 MJ kg?1; 12.4 MJ kg?1) and five methionine supplementation levels (0, 1, 2, 4 and 6 g kg?1), were hand‐fed twice daily to triplicate groups of Nile tilapia (initial body weight 8.95 ± 0.06 g) for 8 weeks. Weight gain (WG) and specific growth rate (SGR) increased significantly with increasing dietary methionine concentration at the same DE content (P < 0.001). At the same dietary methionine level, WG and SGR of fish fed high‐DE diets were significantly higher than that of fish fed low‐DE diets (P = 0.0001), although no interaction was found between dietary DE and methionine supplementation. Based on quadratic regression analysis between dietary methionine concentration and weight gain, optimal methionine requirement for maximum growth, expressed as g Met required kg?1 diet (low‐ versus high‐DE diets), increased as diet DE concentration increased (7.34 versus 9.90 g kg?1 diet, respectively; with cysteine 4.70 g kg?1 diet). The results indicated that diet DE content affects methionine utilization and requirement in juvenile Nile tilapia, fish fed high‐DE diets required more methionine for maximum growth.  相似文献   

9.
Two, 8‐week feeding trials were conducted to compare protein‐sparing capability of dietary lipid in herbivorous grass carp (Ctenopharyngodon idella) and omnivorous tilapia (Oreochomis niloticus × O. aureus). Utilizing a 2 × 3 factorial design, experimental diets containing two levels of crude protein (380 and 250 g kg−1) and three levels of lipid (0, 40 and 100 g kg−1) were formulated for use in both feeding trials. Growth performances showed better response of both fish fed 380 g kg−1 protein diet than those fed 250 g kg−1 protein diet. Despite the dietary protein level, weight gain (WG), specific growth ratio (SGR), feed conversion ratio (FCR) and protein efficiency ratio were much higher (P < 0.05) for grass carp fed 40 g kg−1 lipid diet than those fed 100 g kg−1 lipid diet; however, there were no significant differences in tilapia fed the two diets. The feed intake of grass carp fed lipid‐free diet was the lowest, but it tended to decrease with increase in dietary lipids in tilapia. Lipid retention (LR) was negatively correlated with dietary lipid concentration of both fish. Viscerosomatic index (VSI), hepatosomatic index (HSI), intraperitoneal fat ratio (IPF) and whole‐body and liver lipid content positively correlated with dietary lipid concentration of both fish. Plasma parameters and liver enzymes activities were also positively correlated with dietary lipid concentration of both fish. Liver lipid contents were higher and enzymes activities were lower in grass carp when compared with tilapia. These data suggested that there was no evidence of a protein‐sparing effect of dietary lipids in grass carp. Tilapia has relatively higher capacity to endure high dietary lipid level compared to grass carp.  相似文献   

10.
This study examined the effect of dietary protein and lipid levels on growth, feed utilization and body composition of Asian catfish Pangasius hypophthalmus reared in cages. Eight test diets were formulated at four protein (340, 380, 420 and 460 g kg−1 crude protein) and two lipid (50 and 90 g kg−1 crude lipid) levels. Fish (initial weight 4.7 g fish−1) were fed the test diets for 8 weeks. Final body weight, weight gain (WG), feed intake (FI), feed conversion ratio (FCR), contents of crude protein, lipid and energy in whole body were dependent on both dietary protein and lipid levels, while specific growth rate (SGR), hepatosomatic index and body moisture content were dependent on dietary lipid level. The WG and SGR increased with the increase in either dietary protein level (at the same lipid level) or lipid level (at the same protein level). The FI and FCR decreased with the increase in dietary protein level (at the same lipid level) or lipid level (at the same protein level). Protein sparing action occurred in case dietary lipid level increased. Fish fed the diet containing 453 g kg−1 crude protein and 86 g kg−1 lipid had the highest WG and SGR, but the lowest FI and FCR, among the diet treatments. There were no significant differences in the protein retention efficiency (PRE) and energy retention efficiency (ERE) among the diet treatments, although PRE and ERE were relatively high in fish fed the diet containing 453 g kg−1 crude protein and 86 g kg−1 lipid. At the end of the feeding trial, body protein content increased, while body lipid content decreased, with the increase in dietary protein content at the same lipid level. Our results suggest that dietary levels of 450 g kg−1 crude protein and 90 g kg−1 lipid are adequate to support fast growth of P. hypophthalmus reared in cages.  相似文献   

11.
A 9‐week feeding trial was conducted to estimate the dietary isoleucine requirement of juvenile blunt snout bream. Six isonitrogenous and isoenergetic experimental diets were formulated to contain graded isoleucine levels ranging from 5.3 to 20.1 g kg?1 dry diet. At the end of the experiment, weight gain (WG), specific growth rate (SGR), feed efficiency ratio (FER) and protein efficiency ratio (PER) increased with increasing dietary isoleucine level up to 11.1 g kg?1 dry diet, and dietary isoleucine level above 14.2 g kg?1 dry diet declined these performances. Dietary isoleucine levels (14.2 and 17.3 g kg?1 dry diet) significantly improved whole‐body protein content, but decreased whole‐body lipid, plasma triglyceride and cholesterol contents. Significantly lower visceral fat index (VFI) in fish fed with 14.2 g kg?1 dietary isoleucine was observed compared to those fed with deficient or excessive isoleucine. Dietary isoleucine supplementation significantly increased plasma isoleucine concentration, while plasma valine and leucine concentrations showed a reversed trend. Dietary isoleucine levels regulated the target of rapamycin (TOR) gene expression and improved plasma superoxide dismutase (SOD) activity in juvenile blunt snout bream. Based on second‐order polynomial regression model analysis of SGR and FER, the optimum dietary isoleucine requirement was estimated to be 13.8 g kg?1 dry diet (40.6 g kg?1 dietary protein) and 14.0 g kg?1 dry diet (41.2 g kg?1 dietary protein), respectively.  相似文献   

12.
An 8‐week feeding experiment was conducted to determine the quantitative l ‐lysine requirement of juvenile black sea bream Sparus macrocephalus (initial mean weight: 9.13 ± 0.09 g, SD) in eighteen 300‐L indoors flow‐through circular fibreglass tanks provided with sand‐filtered aerated seawater. The experimental diets contained six levels of l ‐lysine ranging from 20.8 to 40.5 g kg?1 dry diet at about 4 g kg?1 increments. All the experiment diets were formulated to be isoenergetic and isonitrogenous. Each diet was assigned to triplicate groups of 20 fish in a completely randomized design. Weight gain and specific growth rate (SGR) increased with increasing levels of dietary lysine up to 32.5 g kg?1 (P < 0.05) and both showed a declining tendency thereafter. Feed efficiency ratio and protein efficiency ratio was poorer for fish fed the lower lysine level diets (P < 0.05) and showed no significant differences among other treatments (P > 0.05). All groups showed high survival (above 90%) and no significant differences were observed. The whole body crude protein and crude lipid contents were significantly affected (P < 0.05) by dietary lysine level, while moisture and ash showed no significant differences. The composition of muscle and liver also presented similar change tendency. Total essential amino acid and lysine contents in muscle both obtained the highest value when fish fed 32.5 g kg?1 lysine diet (P < 0.05). Serum protein, cholesterol and free lysine concentration were affected by different dietary treatments (P < 0.05), triacylglyceride and glucose contents were more variable and could not be related to dietary lysine levels. Dietary lysine level significantly affected condition factor and intraperitoneal fat ratio of juvenile black sea bream (P < 0.05) except for hepatosomatic index. There were no significant differences in white blood cell count and red blood cell count (P > 0.05), however, haemoglobin level was significantly influenced by different diets (P < 0.05). Analysis of dose (lysine level)‐response (SGR) with second order polynomial regression suggested the dietary lysine requirement of juvenile black sea bream to be 33.2 g kg?1 dry diet or 86.4 g lysine kg?1 protein.  相似文献   

13.
A 63‐day growth trial was undertaken to estimate the effects of supplemented lysine and methionine with different dietary protein levels on growth performance and feed utilization in Grass Carp (Ctenopharyngodon idella). Six plant‐based practical diets were prepared, and 32CP, 30CP and 28CP diets were formulated to contain 320 g kg?1, 300 g kg?1 and 280 g kg?1 crude protein without lysine and methionine supplementation. In the supplementary group, lysine and methionine were added to formulate 32AA, 30AA and 28AA diets with 320 g kg?1, 300 g kg?1 and 280 g kg?1 dietary crude protein, respectively, according to the whole body amino acid composition of Grass Carp. In the groups without lysine and methionine supplementation, weight gain (WG, %) and specific growth rate (SGR, % day?1) of the fish fed 32CP diet were significantly higher than that of fish fed 30CP and 28CP diets, but no significant differences were found between 30CP‐ and 28CP‐diet treatments. WG and SGR of the fish fed 32AA and 30AA diets were significantly higher than that of fish fed 28AA diets, and the performance of grass carp was also significantly improved when fed diets with lysine and methionine supplementation (P < 0.05), and the interaction between dietary protein level and amino acid supplementation was noted between WG and SGR (P < 0.05). Feed intake (FI) was significantly increased with the increase in dietary protein level and the supplementation of lysine and methionine (P < 0.05), but feed conversion ratio (FCR) showed a significant decreasing trend (P < 0.05). Two days after total ammonia nitrogen (TAN) concentration test, the values of TAN discharged by the fish 8 h after feeding were 207.1, 187.5, 170.6, 157.3, 141.3 and 128.9 mg kg?1 body weight for fish fed 32CP, 32AA, 30CP, 30AA, 28CP and 28AA diets, respectively. TAN excretion by grass carp was reduced in plant‐based practical diets with the increase in dietary protein level and the supplementation of lysine and methionine (P < 0.05). The results indicated that lysine and methionine supplementation to the plant protein sources‐based practical diets can improve growth performance and feed utilization of grass carp, and the dietary crude protein can be reduced from 320 g kg?1 to 300 g kg?1 through balancing amino acids profile. The positive effect was not observed at 280 g kg?1 crude protein level.  相似文献   

14.
A ten‐week feeding trail was conducted to investigate the effects of increasing DL‐methionine (Met) supplementation on the success of fish meal (FM) replacement with plant proteins in practical diets for juvenile gibel carp, Carassius auratus gibelio. Twelve isoenergetic diets were formulated including two 150 g kg?1 FM diets (Diet 1—positive control 1 reflecting a commercial diet and Diet 2—positive control 2 reflecting a commercial diet but with balanced essential amino acid (EAA) profile) and ten 50 g kg?1 FM diets (negative controls) supplemented with graded levels (0–3.0 g kg?1) of DL‐Met (Diets 3–12). Each diet was fed to triplicate groups of gibel carp, near satiation four times daily for 10 weeks. Diet 2 with balanced EAA profile produced better final weight, specific growth rate (SGR) and feed conversion ratio (FCR) than the negative control diet containing no supplemental Met (Diet 3), but did not significantly differ from Diet 1. However, DL‐Met supplementation (0.5–3.0 g kg?1) in the negative control diets (Diets 4–12) produced growth performances similar to those fed the positive control diets (Diets 1 and 2). Based on quadratic regression analysis, the optimal dietary Met level with 5.2 g kg?1 of dietary cysteine (Cys) was found to be 7.1 g kg?1 dry diet for SGR and FCR. The corresponding total sulphur amino acid requirements (Met + Cys) of this species were calculated to be 12.3 g kg?1 dry diet for SGR and FCR. DL‐Met supplementation in 50 g kg?1 FM diets showed a decreasing trend in plasma cholesterol contents (p < .05). No significant differences were observed in whole‐body composition, plasma protein, triglyceride and free EAA contents among dietary treatments, while plasma aspartate transaminase, albumin and ammonia contents were significantly influenced by dietary Met levels. Juvenile gibel carp grew equally well on 150 g kg?1 FM diet or 50 g kg?1 FM diets balanced for EAA profile with supplemental amino acids. The results of this study overall indicate that balancing dietary amino acid levels with DL‐Met supplementation is a key strategy in successfully reducing FM levels in the diets of gibel carp.  相似文献   

15.
A 10‐week feeding trial was conducted to estimate the optimum dietary selenium (Se) requirement for juvenile cobia, Rachycentron canadum L. The basal diet was formulated to contain 50.6% crude protein from vitamin‐free casein, gelatin. A control diet (no added seleno‐dl ‐methionine) and five experimental diets containing 0.20, 0.40, 0.60, 0.80 and 1.00 mg seleno‐dl ‐methionine kg?1 were prepared. Each diet was randomly fed to triplicate groups of juvenile cobia with initial weight 6.27±0.03 g in a flow‐through system. The Se concentration in rearing water was monitored during the feeding period, and was not detectable. The dietary Se level significantly influenced the survival, specific growth rate (SGR), feed efficiency and the Se concentrations in the whole body and vertebra of cobia. The Se‐dependent glutathione peroxidase (EC 1.11.119) activity increased with an increase in the dietary Se levels (P<0.05). Hepatic glutathione reductase (EC 1.6.4.2) activity was the highest in fish fed the diet with 0.21 mg Se kg?1, and declined with an increase in the dietary Se levels. Based on broke‐line regression of SGR, the Se concentration in the whole body and vertebra, the Se requirements of juvenile cobia were 0.788, 0.811 and 0.793 mg Se kg?1 diet in the form of seleno‐dl ‐methionine respectively.  相似文献   

16.
Two growth studies (56 days) were conducted with juvenile all male Oreochromis niloticus, using six mixed diets with threonine and five mixed diets, with methionine as the first limiting amino acid (LAA), respectively. Diets were randomly assigned to four repetition tanks with 25 fish per tank. Growth results and body nutrient analyses yielded protein deposition data depending on the uptake of the LAA. For further modelling, a nonlinear N‐utilization model was utilized for assessing the dietary efficiency of threonine and methionine utilization, respectively. By use of the observed dietary AA efficiency, threonine and methionine requirement data were established, depending on the daily protein deposition. The optimal dietary AA concentrations (8.3 g kg−1 versus 9.9 g kg−1 threonine; 7.3 g kg−1 versus 8.8 g kg−1 methionine) were derived for 70% of the potential for protein deposition (NDmaxT) and predicted daily feed intake (3% versus 2.5% of BW). Observed methionine requirements are imposing for the upper limit for methionine replacement by cystine and minimal catabolism of methionine to yield cystine. Generally, the modelling provided requirement data in line with current recommendations. Variation of the dietary AA efficiency by modelling procedure ranks this factor as very important for the conclusion of amino acid requirement data.  相似文献   

17.
The feeding experiment was conducted to evaluate the replacement effect of cystine on methionine at a constant total sulphur amino acid (TSAA) level in practical diets of juvenile Nile tilapia (Oreochromis niloticus). Soybean meal, cottonseed meal and rapeseed meal were used as the main protein sources in the diets containing 16.4 MJ kg?1 gross energy and 301 g kg?1 crude protein. Crystalline DL‐methionine (Met) to L‐cystine (Cys) were supplemented to fulfil various ratios of Met to Cys (60:40, 50:50, 40:60 and 30:70, based on an equimolar sulphur basis; and the analysed ratios were 53:47, 49:51, 34:66 and 31:69). Each diet was fed to triplicate groups of Nile tilapia juveniles (10.1 g mean initial weight) in a recirculation system for 8 weeks. The results showed that the growth performance and nutrient accretion were not affected by dietary methionine:cystine ratios (P > 0.05). However, the survival rates of fish tended to decrease with the decreasing methionine: cystine ratios. The only dietary treatment to achieve 100% survival was the 53:47 methionine: cystine treatment. And methionine digestibility decreased linearly with the decreasing methionine: cystine ratios (P < 0.05). Thus, it was concluded that cystine could replace up to approximately 47% of TSAA requirement on an equimolar sulphur basis without hampering growth performance in the practical diets of juvenile Nile tilapia.  相似文献   

18.
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.  相似文献   

19.
Six micro‐bound diets were formulated to contain three levels of choline chloride (CC) (0.0, 0.6 and 1.2 g kg−1) and 2 levels of methionine (Met) (0 and 15 g kg−1). Soybean protein isolates (SPI) were used as the main protein source for its limited Met content. A significant (P < 0.05) interaction was determined between CC and Met on the survival (S %), weight gain (WG%), specific growth rate (SGR % day−1), feed efficiency ratio (FER), protein efficiency ratio (PER) and phosphatidylcholine (PC), phoshphatidylethanolamine (PE) and Met contents of the whole body of shrimp. The shrimp group did not receive either supplemental CC or Met showed lower (P < 0.05) values of the above‐mentioned parameters than other shrimp groups fed with 0.6 and 1.2 g kg−1 supplemental CC with or without Met supplementation. The present study showed that supplementation of 1.2 g kg−1 CC in the diets could compensate shrimp post‐larvae with the needed methyl group when received Met‐deficient diets. The study also assumed that the biosynthesis of PC in the shrimp’s body can be achieved by the methylation of PE through the S‐adenosylmethionine (SAM) pathway and/or through the cytosine di‐phosphoryl (CDP) choline pathway directly from dietary choline.  相似文献   

20.
An 11‐week feeding trial was conducted to evaluate the effect of dietary methionine on the growth, antioxidant status, innate immune response and disease resistance to Aeromonas hydrophila of juvenile yellow catfish. Six isonitrogenous and isolipidic practical diets were formulated to contain different graded methionine levels ranging from 6.1 to 16.4 g kg?1 of dry weight. The results indicated that growth performance and feed utilization were significantly influenced by the dietary methionine levels; fish fed the diet containing 6.1 g kg?1 methionine level had lower specific growth rate, percentage weight gain (PWG), feed efficiency and protein efficiency ratio than those fed the other diets (P < 0.05). Fish fed the diet containing 16.4 g kg?1 methionine level had lowest protein contents in whole body and muscle among all treatments. Triacylglycerols, cholesterol, aspartate aminotransferase, alanine aminotransferase and haemoglobin (Hb) in plasma or whole blood were significantly affected by dietary methionine levels. Fish fed the diet containing 6.1 g kg?1 methionine level had higher superoxide dismutase, glutathione peroxidase activities and malondialdehyde values than those fed other diets. Fish fed diets containing 9.7 and 11.8 g kg?1 methionine levels had higher lysozyme activity, total immune globulin, phagocytic activity and respiratory burst than those fed other diets. The lowest survival after A. hydrophila challenge was observed in fish fed a diet containing 6.1 g kg?1 methionine. Quadratic regression analysis of PWG against dietary methionine levels indicated that the optimal dietary methionine requirement for the maximum growth of juvenile yellow catfish was estimated to be 11.5 g kg?1 of the diet in the presence of 4.0 g kg?1 cystine (corresponding to 23.5 g kg?1 of dietary protein on a dry weight basis).  相似文献   

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