Dietary Methionine Requirement Research Articles

Dietary Methionine Enhances Portal Appearance of Guanidinoacetate and Synthesis of Creatine in Yucatan Miniature Piglets

BackgroundCreatine plays a significant role in energy metabolism and positively impacts anaerobic energy capacity, muscle mass, and physical performance. Endogenous creatine synthesis requires guanidinoacetic acid (GAA) and methionine. GAA can be an alternative to creatine supplements and has been tested as a beneficial feed additive in the animal industry. When pigs are fed GAA with excess methionine, creatine is synthesized without feedback regulation. In contrast, when dietary methionine is limited, creatine synthesis is limited, yet, GAA does not accumulate in plasma, urine, or liver. ObjectiveWe hypothesized that portal GAA appearance requires adequate dietary methionine. MethodsYucatan miniature piglets (17–21 d old; n = 20) were given a 4 h duodenal infusion of complete elemental diets with supplemental GAA plus 1 of 4 methionine concentrations representing either 20%, 80%, 140%, or 200% of the dietary methionine requirement. Arterial and portal blood metabolites were measured along with blood flow to determine mass balance across the gut. [3H-methyl] methionine was infused to measure the methionine incorporation rate into creatine. ResultsGAA balance across the gut was highest in the 200% methionine group, indicating excess dietary methionine enhanced GAA absorption. Creatine synthesis in the liver and jejunum was higher with higher concentrations of methionine, emphasizing that the transmethylation of GAA to creatine depends on sufficient dietary methionine. Hepatic GAA concentration was higher in the 20% methionine group, suggesting low dietary methionine limited GAA conversion to creatine, which led to GAA accumulation in the liver. ConclusionsGAA absorption and conversion to creatine require a sufficient amount of methionine, and the supplementation strategies should accommodate this interaction.

Methionine deficiency affects myogenesis and muscle macronutrient metabolism in juvenile turbot Scophthalmus maximus

The study was aimed to explore the impacts of dietary methionine availability on muscle growth and macronutrient metabolism in turbot. Based the optimal dietary methionine requirement, three isonitrogenous and isolipidic diets with different methionine levels (0.91%, 1.90%, and 2.90%) were formulated. 270 fish (average weight 7.40 ± 0.01 g) were distributed into 9 fiberglass tanks and fed for 10 weeks. Results showed that methionine deprivation significantly depressed fish growth and reduced the crude protein content in the whole body and muscle. Methionine deprivation inhibited the expression of myogenic differentiation antigen D (myoD), myogenin and myosin light chain (mlc) while induced myostatin expression. Methionine deficiency inhibited the mechanistic target of rapamycin (mTOR) pathway and activated the autophagy-lysosomal and ubiquitin–proteasome systems. The AMP-activated protein kinase (AMPK) was activated and uncoupling protein 1 (ucp1) was up-regulated when dietary methionine was deficient. Meanwhile, methionine deficiency reduced total free amino acid content, promoted the catabolism of amino acid, and improved the flux of tricarboxylic acid cycle (acetyl-CoA, fumarate, malate, and oxoglutarate). Methionine deficiency depressed the glycolysis and lipogenesis processes, while elevated fatty acid β-oxidation, which shifted the fuel utilization in muscle. Excess methionine intake did not further modulate the cell signaling and metabolism in muscle. Our results provide new clues on the involvement of dietary methionine on muscle growth and metabolic responses in teleost.

Reevaluation of the dietary methionine requirement of gilthead seabream (Sparus aurata) juveniles: A comparison of the efficiency of hydroxy methionine with DL-methionine as a dietary methionine source

This work aimed to estimate the dietary methionine (Met) requirement of gilthead seabream (Sparus aurata) juveniles using hydroxy methionine (OH-Met) as Met source and compare its efficiency with the DL-Methionine form (DL-Met). For that purpose, triplicate groups of fish with 17 g initial body weight were fed for 83 days with diets including increasing dietary Met levels (0.66, 0.80, 0.94, 1.08, 1.22, and 1.36% - sulfur-equivalent) using OH-Met as a Met source. Three other diets were also formulated with 0.94, 1.08, and 1.22% DL-Met, to compare OH-Met with DL-Met as dietary Met source. Cysteine was maintained at 0.54% in all the diets.Fish growth increased with dietary OH-Met inclusion up to 1.22% plateauing thereafter. No effect on feed intake was observed between fish fed the different dietary Met levels and sources. Feed and protein efficiencies increased with the increase in dietary Met level. Dietary Met source did not affect growth performance, feed utilization, nitrogen, and energy retention. Based on the four-parameter logistic model, the dietary Met requirement for maximum growth was estimated to be 1.05%. The lowest hepatic level of reduced glutathione (GSH), oxidized glutathione (GSSG), total glutathione (tGSH), and malondialdehyde (MDA) were observed in fish fed the OH-Met 1.36 diet, but the oxidative stress index (OSI) and GSH/GSSG ratio were not affected by the dietary OH-Met level. In the muscle, GSH, GSSG, OSI, MDA, and GSH/GSSG ratio were not affected by the OH-Met level, while tGSH linearly decreased with increasing dietary OH-Met level. Dietary Met source did not affect the liver and muscle oxidative stress-related parameters measured. Overall, it is concluded that the Met requirement for growth of gilthead seabream juveniles is satisfied with 1.05% Met in the diets (corresponding to 1.59% total sulfur amino acids, TSAA). This corresponds to a Met requirement of 2.3 g/16 g N (3.5 g/ 16 g N of TSAA). It is also concluded that OH-Met and DL-Met can be used interchangeably as dietary Met sources and that the liver and muscle antioxidant status of fish is not affected by the dietary Met sources tested.

Revaluating the dietary methionine requirements in an improved strain of nile tilapia (Oreochromis niloticus)

It has been shown with terrestrial animals that the genetic improvement increases the nutrient requirements of the animal, which becomes more efficient in using these nutrients to achieve their higher growth potential. This study was conducted to estimate the dietary methionine requirements of different generations of the Genetically Improved Farmed Tilapia (GIFT) strain of Nile tilapia at the juvenile stage (17.51 g–19.55 g initial body weight). To achieve this objective, a completely randomized 2 × 6 factorial design was applied, with the genetic background of fish (generation) as the first independent variable with two levels, the 16th and 17th generations, and the methionine content of the diet as the second independent variable, with 6 graded levels, 0.52, 0.62, 0.84, 0.94, 1.04 and 1.27% of methionine in the diets, respectively. At the end of the 42-day experiment, the interaction effect of the generation × diet was not significant (P > 0.05) for any of the response parameters studied. The genetic improvement led to 15% more growth in the 17th generation than the 16th generation of the GIFT strain of Nile tilapia, which was accompanied with better feed conversion ratio, protein productive value, and energy productive value in the former generation (P < 0.05). Whatever the generation considered, the optimum dietary methionine requirement for the growth of the improved GIFT strain of Nile tilapia was estimated in this study, using the broken-line model, between 0.75% and 0.80% of the diet (with a cysteine level of 0.50% of the diet), which is higher than 0.49% of the diet previously estimated for conventional Nile tilapia at the juvenile stage. Therefore, the genetic improvement applied to the GIFT strain of Nile tilapia likely led to a higher methionine and total sulfur amino acid requirement than the conventional strains. The results of this study support the need to update the existing nutrient requirement databases of fish, in order to ensure that diets are formulated to effectively satisfy the requirements of not only conventional, but also improved strains of fish, for the full expression of their accrued growth potential of the latter strains.

Optimal dietary methionine requirement of sub-adult turbot (Scophthalmus maximus L.): Growth performance, feed utilization and hepatic lipid metabolism

Optimal dietary methionine requirement of sub-adult turbot (Scophthalmus maximus L.): Growth performance, feed utilization and hepatic lipid metabolism

Optimal methionine supplementation improved the growth, hepatic protein synthesis and lipolysis of grass carp fry (Ctenopharyngodon idella)

Six experimental diets with graded methionine levels (0.33%, 0.55%, 0.71%, 0.87%, 1.03%, 1.20%, dry matter) were formulated to quantify the dietary methionine requirement, and assess the influence of dietary methionine levels on the metabolism of protein and lipid in Ctenopharyngodon Idella fry (initial weight 0.36 ± 0.01 g) during an 8-week feeding trial. The results showed that 1.03% dietary methionine significantly improved the growth performance, protein efficiency ratio and feed utilization, compared with 0.33% methionine. Dietary methionine supplementation slightly increased survival rate. 0.55%–0.87% methionine level increased the phosphorylated protein and mRNA levels of phosphatidylinositol 3-kinase (PI3K), target of rapamycin (TOR), eukaryotic initiation factor 4E binding protein-1 and ribosomal protein S6 kinase 1. Compared with 1.20% methionine, 0.55%–0.87% methionine levels significantly increased mRNA levels of hepatic insulin-like growth factor-1 (IGF-1), carnitine palmitoyl transferase-1, peroxisome proliferator-activated receptor α, adipose triglyceride lipase and hormone sensitive lipase. The highest mRNA levels of hepatic acetyl-CoA carboxylase, sterol regulatory element-binding protein 1, stearyl-CoA desaturase and fatty acid synthetase were observed in 0.33% methionine diet. Based on specific growth rate and feed conversion ratio, the dietary methionine requirement of grass carp fry was 1.03% of diet (2.67% of dietary protein), using the broken-line regression analysis. Suitable dietary methionine could improve the growth, feed utilization and lipolysis of fry and promote protein synthesis via the IGF-1/PI3K/TOR pathway. While methionine deficiency tended to enhance hepatic lipid synthesis.

The optimum dietary methionine requirement of juvenile humpback grouper (Cromileptes altivelis): effects on growth, micromorphology, protein and lipid metabolism.

An 8-week feeding trial was conducted to evaluate optimum dietary methionine (Met) requirement of juvenile humpback grouper (Cromileptes altivelis) and the influence of dietary methionine (Met) supplementations on growth, gut micromorphology, protein and lipid metabolism. Seven isoproteic (48.91%) and isolipidic diets (10%) were made to contain 0.70, 0.88, 1.04, 1.27 1.46, 1.61 and 1.76% of dry matter Met levels. Results showed that lower survival, weight gain (WG%), protein efficiency ratio (PER), protein productive value (PPV) but higher daily feed intake (DFI) and feed conversion ratio (FCR) were observed in the Met deficient groups (0.70 and 0.88%). Optimum dietary Met requirement for humpback grouper was found to be 1.07% through the straight-broken line analysis of WG% against Met. Fish fed Met deficient diets (0.70, 0.88%) exhibited lower mRNA levels of growth hormone (GH), growth hormone receptor (GHR), insulin-like growth factor-I (IGF-1), target of rapamycin (TOR) as well as S6 kinase 1 (S6K1) than other dietary groups. Whereas, expression of genes related to general control nonderepressible (GCN2) kinase i.e., GCN2 and C/EBPβ enhancer-binding protein β was upregulated in fish fed low Met diets (P < 0.05). The mRNA expression of hepatic fatty acid synthase (FAS) and sterol regulatory element-binding protein-1 (SREBP-1) were higher in fish fed 0.70 and 0.88% dietary Met group and the lipolytic genes, hepatic peroxisome proliferator-activated receptor α (PPARα) and carnitine palmitoyl transferase-1 (CPT-1) showed an opposite variation tendency as FAS or SREBP1. Generally, the optimum Met requirement for humpback grouper was predicted to be 1.07% of dry matter.

Optimum dietary methionine requirement of juvenile silver pompano, Trachinotus blochii (Lacepede, 1801)

In this study, we optimized the dietary methionine requirement of juvenile silver pompano (average initial weight of 5.47 g). Six isonitrogenous and isolipidic diets (420 g/kg crude protein [CP] and 60 g/kg lipid) were formulated with different concentrations of methionine (5.1, 6.9, 9.0, 10.7, 13.1, and 15.2 g/kg dry diet) and a constant level of cysteine (5.3 g/kg). Fishes were randomly stocked in a recirculatory system for a feeding trial of 90 days. After the feeding trial, significant differences (P < 0.05) were observed in growth parameters such as weight gain (WG), specific growth rate (SGR), thermal growth coefficient (TGC), and feed utilization indices, including feed conversion ratio (FCR) and protein efficiency ratio (PER), among different treatment groups. No significant differences (P> 0.05) were observed among hepatosomatic index, viscerosomatic index, muscle ratio, condition factor, serum glucose, triglycerides, and erythrocyte count. The optimization of the fitted quadratic regression for WG, SGR, TGC, FCR, and PER based on the dietary methionine level showed that the optimum methionine requirement of silver pompano in nursery phase ranged from 11.6–11.8 g/kg dry diet (27.6–28.1 g/kg dietary CP), corresponding to a dietary cysteine level of 5.3 g/kg.

Modelling Methionine Requirements of Fast- and Slow-Growing Chinese Yellow-Feathered Chickens during the Starter Phase.

Simple SummaryIn poultry production, consuming diets with low or excessive methionine levels leads to negative effects on growth performance. The requirements of methionine may differ among the fast and slow-growing breeds; therefore, the optimal dietary methionine level should be estimated for each. In this study, six dietary methionine levels were evaluated to estimate the optimal level for fast and slow-growing yellow feathered chicken breeds. The quadratic polynomial and exponential asymptotic regression showed that the optimal methionine requirements for maximal growth performance were 0.50% and 0.53% in the fast-growing breed, and 0.48% and 0.52% in the slow growing breed.Two experiments were carried out to investigate the dietary methionine requirement for fast and slow-growing Chinese yellow-feathered breeds during the starter phase, based on growth variables and regression models. In Experiment 1, a total of 2880 one-day-old Lingnan chicks (fast growing breed) were used to test the methionine requirement from 1 to 21 days of age for males and females separately. Of each gender, 1440 birds were allocated into 6 dietary methionine levels (0.28%, 0.32%, 0.37%, 0.43%, 0.50% and 0.63%), each with 6 pen replicates of 40 chicks. Experiment 2 had the same design with Guangxi chicks (slow growing breed) from 1 to 30 d of age. Results indicated that significant nonlinear or quadratic responses to increasing dietary methionine levels were observed in body weight, daily gain, feed intake and feed conversion ratio of both breeds. In summary, the quadratic polynomial regression showed that the optimal methionine requirements for maximal growth performance of Lingnan chickens were 0.52–0.58% in males, 0.51% in females, and 0.53% in mixed genders. The corresponding values for Guangxi breed were 0.53% in males by quadratic polynomial regression and 0.43% in females, and 0.48% to 0.49% in mixed sexes by exponential asymptotic models.

Short-term determination and long-term evaluation of the dietary methionine requirement in adult dogs.

Methionine, an essential sulphur-containing amino acid (SAA), plays an integral role in many metabolic processes. Evidence for the methionine requirements of adult dogs is limited, and we employed the indicator amino acid oxidation (IAAO) method to estimate dietary methionine requirements in Labrador retrievers (n 21). Using semi-purified diets, the mean requirement was 0·55 (95 % CI 0·41, 0·71) g/4184 kJ. In a subsequent parallel design study, three groups of adult Labrador retrievers (n 52) were fed semi-purified diets with 0·55 g/4184 kJ (test diet 1), 0·71 g/4184 kJ (test diet 2) or 1·37 g/4184 kJ (control diet) of methionine for 32 weeks to assess the long-term consequences of feeding. The total SAA content (2·68 g/4184 kJ) was maintained through dietary supplementation of cystine. Plasma methionine did not decrease in test group and increased significantly on test diet 1 in weeks 8 and 16 compared with control. Reducing dietary methionine did not have a significant effect on whole blood, plasma or urinary taurine or plasma N-terminal pro B-type natriuretic peptide. Significant effects in both test diets were observed for cholesterol, betaine and dimethylglycine. In conclusion, feeding methionine at the IAAO-estimated mean was sufficient to maintain plasma methionine over 32 weeks when total SAA was maintained. However, choline oxidation may have increased to support plasma methionine and have additional consequences for lipid metabolism. While the IAAO can be employed to assess essential amino acid requirements, such as methionine in the dog using semi-purified diets, further work is required to establish safe levels for commercial diet formats.

Dietary methionine spares the requirement for taurine in juvenile Yellowtail Kingfish (Seriola lalandi)

Taurine, a β-sulphonic amino acid, is a growth and health promoting dietary supplement in commercial finfish aquaculture. Reported recommendations for taurine supplementation in Seriola spp. feeds broadly range from 2.6 to 10.2 g kg−1 diet. Methionine is an essential amino acid and substrate for various metabolic compounds and acts as a methyl and sulfur donor, potentially sparing taurine. Dietary methionine requirements are currently unknown for Yellowtail Kingfish (Seriola lalandi); however, recommendations for the closely related Japanese Yellowtail (Seriola quinqueradiata) indicate that 11.1 g kg−1 diet is adequate. The taurine requirement and sparing effect of methionine of juvenile Yellowtail Kingfish was quantified by conducting a feeding experiment and applying a factorial, orthogonal dose-response design. Fourteen isonitrogenous and isoenergetic diets were prepared using practical raw ingredients with either one of two levels of methionine (10.9 ± 0.2 g kg−1 or 17.2 ± 0.6 g kg−1) and either one of seven levels of taurine, increasing from 1.6 to 20.4 g kg−1, respectively. Triplicate groups of 14 fish (53.3 ± 0.4 g fish−1) were fed one of the 14 diets over seven weeks. Based on growth and feeding results, juvenile Yellowtail Kingfish do not require dietary taurine supplementations when the basal taurine diets content is at least 1.6 g taurine kg−1 at a dietary methionine content of 17.2 ± 0.6 g kg−1 diet. This demonstrates that dietary methionine has a sparing effect on taurine supplementation. Yellowtail Kingfish fed dietary methionine exceeding the current minimum industry standard (~11.1 g kg−1), grew more rapidly than those fed high dietary taurine contents at dietary methionine levels approximating that of current industry practice, indicating the indispensability of adequate methionine supply. Breakpoint analysis on the specific growth rate in Yellowtail Kingfish fed a methionine level of current industry practice, estimated a digestible taurine requirement of 1.98 g kgBW−1 d−1 at an average digestible methionine intake of 3.4 g kgBW−1 d−1 This equates to a dietary taurine content of 7.7 g kg−1 diet at a dietary methionine content of 10.9 g kg−1 diet. Our results indicate that in juvenile Yellowtail Kingfish: adequate dietary methionine spares dietary taurine supplementation; insufficient dietary methionine provokes a taurine requirement; and current industry specifications for dietary methionine for Yellowtail Kingfish aquafeed require reassessment.

The effect of dietary methionine levels on growth, feed conversion and protein retention efficiency of Nile Tilapia (Oreochromis niloticus) fingerlings

Abstract. Mohammed FA, Yousif RA, Hilal FM, Adam RA, Ahmed TK. 2020. The effect of dietary methionine levels on growth, feed conversion and protein retention efficiency of Nile Tilapia (Oreochromis niloticus) fingerlings. Nusantara Bioscience 12: 21-27. A 49 days feeding trial was conducted to evaluate growth, feed utilization and body composition of Nile tilapia Oreochromis niloticus (4.30±0.01 g), fed five isonitrogenous (32 g 100 g-1 crude protein) and isoenergetic (14.51 kJ g-1 Gross energy) practical diets and five levels of methionine supplementation (0.5, 1, 1.5, 2 and 2.5 g 100 g-1). The experimental design was completely randomized with five treatments and three replicates. Fish were stocked in triplicate groups of 20 fish held in 70 L flow-through tanks (water volume 55 L) and fed twice daily (08:00 am and 04:30 pm) to apparent satiation. When absolute weight gain (AWG; g fish-1), feed conversion ratio, protein deposition (g fish-1) and protein retention efficiency (%) data were subjected to second-degree polynomial regression analysis 95% of the plateau of the above parameters was achieved at dietary methionine concentrations between 1.4-1.5 g 100 g-1 dry diet or 0.09-0.10 g methionine kJ-1 GE. Corresponding to 4.4-4.7 g 100 g-1 of the dietary protein. Based on these results, dietary methionine requirement for Nile tilapia Oreochromis niloticus is recommended 1.4-1.5 g 100 g-1 diet.

Supplementation of diets with Brazil nut powder can meet dietary methionine requirement of organic broiler chickens

Synthetic amino acids are not permitted in organic feeds by the National Organic Standard Board (NOSB) in the USA. However, low levels of methionine (Met) are permitted, and the NOSB recommends 0.1% synthetic Met for broilers. Inadequate level of dietary methionine poses concerns pertaining to health and welfare of broilers, as these limitations lead to possible Met deficiency. This research examined the effects of complete replacement of synthetic DL-methionine (DLM) by Brazil nut powder in a 100% organic diet. Eight hundred Ross 308 chicks were hatched and randomly divided into 4 treatments with 4 replicates of 50 chicks and raised for 56 days. Treatments included birds fed a conventional diet and raised organically (Conv_Org), NOSB diet raised organically (NOSB_Org), 100% organic diet and raised organically (Org_Org), and a conventional diet raised conventionally (Conv_Conv). Body weight at 56 days were 3960, 3995, 3981, and 3676 g for Conv_Org, NOSB_Org, Org_Org, and Conv_Conv, respectively. Body weights of the Conv_Conv group were lower (P < 0.05) than the other treatments. The FCR (0–8 weeks) of Org_Org treatment was lower (P < 0.05) than the NOSB diet. The birds on the NOSB diet had increased feed intake perhaps to compensate for the deficiency in Met. The NOSB diet may not sufficiently meet the requirement of broiler chickens even when raised with access to pasture. There were no differences in carcass yield and composition in any treatment. We conclude that Brazil nut powder is a viable substitute for DLM in organically raised broilers, as there were no differences in growth and carcass yield and improved FCR when compared to current NOSB recommended diet.

Dietary methionine and lysine requirement of snakehead (Channa striata) fingerlings

Dietary methionine and lysine requirement of snakehead (Channa striata) fingerlings

Determination of methionine requirement of juvenile silver catfish (Rhamdia quelen) and its effects on growth performance, plasma and hepatic metabolites at a constant cystine level

This study was performed to determine the dietary methionine requirements and its effects on growth performance, plasma and hepatic metabolites for juvenile silver catfish. The fish (initial weight = 3.26 ± 0.3 g) were distributed in 24 experimental units (35 fish each). Six diets were formulated with increasing levels of methionine (09, 16, 23, 30, 37 and 44 g/kg protein diet). Each diet was distributed randomly to the groups, with four replicates fed twice daily to apparent satiation for 15 weeks. Methionine levels influenced in body composition (moisture and ash), and submit effect on liver metabolism and plasma. The relative weight gain (RWG) and specific growth rate (SGR) increased with highest levels of methionine to 30 g/kg protein in the diet, thereafter maintaining a nearly constant level of 1.9 g/kg cystine in the protein diet. The protein retention coefficient (PRC) also increased with increasing levels of up to 23 g/kg protein diet, thereafter maintaining a constant level of 1.9 g/kg cystine protein diet until beginning to decrease at a level of 44 g/kg protein diet. In conclusion, methionine is an essential amino acid for the growth of juvenile silver catfish and exhibits an efficient capacity when provided as a synthetic amino acid. Based on the RWG and SGR data, the methionine requirement of juvenile silver catfish was estimated at 34.42 and 35.85 g/kg of the CP or 12.74 g/kg and 13.26 g/kg of the diet respectively.

Evaluation of dietary methionine requirement of male Korean native ducks for 3weeks post-hatching.

A total of 336 1-day-old male Korean native ducks (KND) were used in a completely randomized design with seven dietary methionine levels (0.30-0.90% with 0.1% increment) to determine the methionine requirement of male Korean native ducks for 3weeks after hatching. Each dietary treatment had six replicates with eight ducklings per pen. One duckling from each pen (n=6) was sacrificed to weigh empty body and drumsticks at the end of the experiment. Final body weight and weight gain of 3weeks old KND were increased with increasing dietary methionine levels up to 0.4%, and then decreased (P<0.05) with a further increasing dietary methionine level. In contrast, feed conversion ratio of the KND decreased up to 0.4% and increased (P<0.05) with the increasing dietary methionine level. Both empty body weight and proportions of empty body weight were linearly increased (P<0.05) while the dietary methionine level elevated up to 0.4%. Estimated dietary methionine requirement for maximum body weights, daily gain and minimum feed conversion ratio were 0.36, 0.39 and 0.40%, respectively, when it was fitted into linear- and quadratic-plateau models.

Optimal dietary methionine requirement of bullfrog Rana (Lithobates) catesbeiana

A feeding experiment was conducted to determine dietary methionine requirement of bullfrog Rana (Lithobates) catesbeiana. Bullfrogs were fed six experimental diets containing 0.63%, 1.00%, 1.42%, 1.78%, 2.26% or 2.68% methionine for 8weeks. After the feeding experiments, growth performance, body composition, blood biochemistry and expression levels of hepatic genes were determined. The results showed that growth and feed utilization were significantly affected (P<0.05) by dietary methionine levels. Weight gain (WG) and protein efficiency ratio (PER) both increased with increasing level of dietary methionine from 0.63% to 1.42% and then decreased. While, the variation trend of feed conversion ratio (FCR) is just opposite with WG and PER. Crude lipid concentrations of whole body and muscle tissue were also significantly affected (P<0.05) by dietary methionine levels. However, there was no significant difference (P>0.05) in amino acid composition in muscle among methionine treatments. Triglyceride (TG) and cholesterol (CHO) levels, as well as aspartate aminotransferase (AST) and alanine aminotransferase (ALT) activities, were all significantly affected (P<0.05) by dietary methionine levels. TG and CHO levels decreased as dietary methionine increased from 0.63% to 1.78% and then increased with further increases in methionine. Serum AST and ALT activities in bullfrogs fed with 0.63% methionine diet were both significantly higher (P<0.05) than in bullfrogs fed other diets. Gene expressions in bullfrogs fed with 1.00%, 1.42% and 1.78% methionine diets was higher (P<0.05) than these of other groups. On the basis of WG and PER, the optimal level of dietary methionine for bullfrogs was estimated to be between 1.53% and 1.62% of diet using second-order polynomial regression analysis. The corresponding optimal level of total sulfur amino acids in the diet of bullfrogs is therefore between 1.79% and 1.88% of diet in the presence of 0.26% cystine. Statement of relevanceThe authors have declared that no competing interests exist.

Dietary methionine requirement of pre-adult blunt snout bream, (Megalobrama amblycephalaYih, 1955)

Summary A nine-week feeding trial was conducted to test the hypothesis that an adequate methionine diet might improve growth, feed utilization, body composition and physiology, and biochemical parameters in pre-adult blunt snout bream Megalobrama amblycephala, whereas a methionine deficiency might have adverse effects on these parameters. Six isonitrogenous and isoenergetics semi-purified diets (33.0% crude protein, 7.0% crude lipid) were formulated to contain graded methionine levels (0.39–1.54% of dry weight) at 0.25% increments replaced by equal proportions of glycine. Results show that the survival rate (SR) was not significantly affected by the dietary methionine level. Final weight (FW), feed efficiency ratios (FER), weight gain (WG), and specific growth rate (SGR) increased with increasing dietary methionine levels up to 1.00% and then showed a declining trend. Using quadratic regression analysis of FER and SGR, the dietary methionine requirement was estimated to be 0.74% (2.24% of dietary protein) and 0.76% of the diet (2.30% of dietary protein), respectively. Fish fed the 0.39% methionine diet showed significantly lower whole body protein content compared to those fed with 0.85, 1.00 and 1.24% methionine diets (P 0.05). No significant differences were found in other indexes such as the hepatosomatic index (HSI), viscerosomatic index (VSI), condition factor (CF), albumin (ALB), total protein (TP), alanine aminotransferase (ALT), and spartate transaminase (AST) (P > 0.05). Most important, the optimal dietary methionine level of pre-adult blunt snout bream should be 0.74–0.76% of the diet (2.24–2.30% of dietary protein).

Dietary methionine requirement of Jing Brown layer hens from 9 to 17weeks of age.

This study was conducted to evaluate the effect of dietary methionine (Met) supplementation in growth performance and reproductive performance of Jing Brown layer hens. A total of 375 9-week-old Jing Brown layer hens were allocated equally to five treatments consisting of 5 replicates with 15 hens. Hens were fed with a diet of corn and soya bean meal supplemented with 0.23%, 0.27%, 0.31%, 0.35% and 0.39% Met respectively. Different Met levels did not significantly affect average daily feed intake (ADFI), average daily gain (ADG) and feed/gain ratio (F/G) (p>0.05), whereas flock uniformity (FU) and jejunum index were significantly different (p<0.05), and the largest FU was observed in 0.31% Met. Dietary supplementation of Met significantly affected reproductive system development (p<0.05), and 0.27-0.31% Met obtained optimal reproductive system development. Different Met levels significantly affected serum uric acid and alkaline phosphatase. Moreover, the relatively higher reproductive hormones in serum were observed in 0.27% Met. Analysis of quadratic curve estimation of flock uniformity, the total number of follicles, the primary follicles and the secondary follicles showed that the optimal Met levels were 0.293%, 0.286%, 0.286% and 0.288%, which could be averaged to 0.288%. These results suggested that the optimal Met requirement for Jing Brown layer hens from 9 to 17weeks old is 0.29%.

The effect of dietary methionine on growth, antioxidant capacity, innate immune response and disease resistance of juvenile yellow catfish (Pelteobagrus fulvidraco)

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).