Methionine Requirement Research Articles

Interactive effects of water salinity and dietary methionine levels on growth performance, whole-body composition, plasma parameters, and expression of major nutrient metabolism genes in juvenile genetically improved farmed Tilapia (Oreochromis niloticus)

Salinity is an important factor in the water environment, and salinity can cause changes in fish metabolism, which may be further reflected by changes in feed nutrient requirements. Methionine is one of the key components of feed nutrition. However, the methionine nutritional requirements and metabolism of Genetically Improved Farmed Tilapia (GIFT, Oreochromis niloticus) at different salinities are still unknown. The GIFT is a euryhaline fish, and a 60-day experimental trial was conducted to examine the interactive effects of salinity and dietary methionine levels (DMLs) on the growth performance and physiological responses of GIFT. A 6 × 2 factorial design was used to formulate six isonitrogenous and isoenergetic diets with six DMLs (0.38%, 0.53%, 0.76%, 0.92%, 1.12%, 1.30%) and two salinity levels (freshwater, 0 ppt; brackish water, 8 ppt). The results showed that DML significantly affected the growth performance and feed utilization of GIFT (4.25 ± 0.01 g), and the optimum growth performance and feed utilization efficiency were observed in freshwater and brackish water group at 0.76% and 0.92% DMLs, respectively. However, there was no significant difference in growth performance and feed utilization between the freshwater and brackish water cultures. In addition, there was a significant interaction between salinity and DMLs. Based on the SGR and FCR, the quadratic regression analysis showed that the optimal methionine requirements of juvenile GIFT were 0.75%, 0.77% (freshwater) and 0.79%, 0.82% (brackish water), respectively. In brackish water culture, GIFT showed higher levels of protein and lipid anabolism metabolism-related genes, while in freshwater culture, it showed higher mRNA levels of glucose metabolism and fatty β-oxidation genes. At both salinities, the appropriate level of methionine promoted protein synthesis and the pentose phosphate pathway of GIFT. Interestingly, in brackish water culture, high levels of glycolysis-, glycogen synthesis- and lipid synthesis metabolism-related genes were observed under excessive DML, while in freshwater culture, similar phenomena were observed when DML was relatively deficient. In conclusion, protein metabolism may be closely related to the adaptation of GIFT to salinity and the methionine requirement of juvenile GIFT cultured in brackish water (0.79–0.82%) was higher than that cultured in freshwater (0.75–0.77%), which may provide a theoretical foundation for the exploitation of formulated feed for GIFT cultured in brackish water.

اثر سطوح مختلف متیونین جیره در دوره رشد بر عملکرد، خصوصیات لاشه، بازده انرژی و پروتئین، ترکیب عضله سینه و برخی فراسنجه ‏های خونی بلدرچین ژاپنی

This research aimed to investigate the effect of different dietary methionine levels on performance, carcass characteristics, energy and protein efficiencies, breast muscle nutrients, and some blood indices in Japanese quails during 11-24 days of age. This experiment was conducted in a completely randomized design during 14 days with 490 quail chicks in seven treatments and five replicates each (14 chicks in each replicate). The experimental diets were the NRC requirement of methionine for quail (0.5 percent), three methionine levels of 7.5, 15, and 22.5 percent lower than that of NRC requirement level (0.4625, 0.425, and 0.3875%, respectively), and three levels higher than that of NRC requirement level (0.5375, 0.575 and 0.6125%, respectively). The results showed that consumption of 0.575% methionine level caused the highest weight gain and lowest feed conversion ratio (linear and quadratic responses). The breast protein content was linearly increased by increasing the methionine level to 0.5%. Consumption of 0.6125% methionine (the highest methionine level) caused the highest relative thigh weight (linear and quadratic responses). The best energy and protein efficiencies were indicated by consumption of 0.575% methionine (linear and quadratic responses). The methionine requirement for optimal weight gain, feed conversion ratio, and energy and protein efficiencies were 0.569, 0.578, 0.54, and 0.35% according to the quadratic broken line. In total, the level of 0.569% was determined for methionine requirement based on the cumulative response of weight gain, feed conversion ratio, and energy and protein efficiencies.

Assessment of vegan complete diets for dogs and cats available in Germany

Nutritional assessment of commercial vegan complete diets for adult cats and dogs and the evaluation of the products' legal labelling. Four complete vegan diets for adult cats and dogs available on the German market were analyzed concerning their nutrient and mineral content. The required amount of food was determined by calculation and compared to the manufacturers' feeding recommendation. Data labelling was assessed for its accordance with EC regulation 767/2009. The supply of taurine and vitamins was evaluated for its adequacy by use of the nutritional additive data on the product label. In most cases, the labelled data complied with the regulatory framework. The manufacturers' feeding recommendation differed significantly from the calculated feed quantity in 2 out of 4 feeds. The recommendations resulted in a coverage of 64 to 121 % of the total energy requirement, more frequently leading to an underestimation of the required feed amount. The supply of minerals exceeded the recommended allowance by 5.2- to 8.2-fold in the adult dog and by 9.0- and 11.4-fold in the adult cat. In 1 out of 4 diets, the European Pet Food Industry Federation guidelines were undercut for crude protein, crude fat and phosphorus. Zinc and copper contents were in excess and/or insufficient. A shortfall in National Research Council (NRC) recommendations was present for zinc content in one diet. Most products met the recommended supply of essential amino acids; 2 products only met the minimum requirements for methionine and cystine but not the recommended provision. The added taurine met the recommended intake in one commercial diet for cats. Requirements for vitamin intake were fulfilled by the nutritional additives in 3 products. None of the products fulfilled the energy and nutrient requirements for a complete diet for adult dogs and cats without limitations. Therefore, deficiencies in the supply of individual nutrients cannot be ruled out under long-term feeding of the examined vegan diets.

Addition of dietary methionine but not dietary taurine or methyl donors/receivers to a grain-free diet increases postprandial homocysteine concentrations in adult dogs.

Grain-based ingredients are replaced in part by pulse ingredients in grain-free pet foods. Pulse ingredients are lower in methionine and cysteine, amino acid (AA) precursors to taurine synthesis in dogs. Although recent work has investigated plasma and whole blood taurine concentrations when feeding grain-free diets, supplementation of a grain-free diet with various nutrients involved in the biosynthesis of taurine has not been evaluated. This study aimed to investigate the effects of supplementing a complete grain-free dry dog food with either methionine (MET), taurine (TAU), or methyl donors (choline) and methyl receivers (creatine and carnitine; CCC) on postprandial AA concentrations. Eight healthy Beagle dogs were fed one of the three treatments or the control grain-free diet (CON) for 7 d in a 4 × 4 Latin square design. On day 7, cephalic catheters were placed and one fasted sample (0 min) and a series of nine post-meal blood samples were collected at 15, 30, 60, 90, 120, 180, 240, 300, and 360 min. Data were analyzed as repeated measures using the PROC GLIMMIX function in SAS (Version 9.4). Dogs fed MET had greater plasma and whole blood methionine concentrations from 30 to 360 min after a meal (P < 0.0001) and greater plasma homocysteine concentrations from 60 to 360 min after a meal (P < 0.0001) compared with dogs fed CON, TAU, and CCC. Dogs fed TAU had greater plasma taurine concentrations over time compared with dogs fed CON (P = 0.02) but were not different than dogs fed MET and CCC (P > 0.05). In addition, most AAs remained significantly elevated at 6 h post-meal compared with fasted samples across all treatments. Supplementation of creatine, carnitine, and choline in grain-free diets may play a role in sparing the methionine requirement without increasing homocysteine concentrations. Supplementing these nutrients could also aid in the treatment of disease that causes metabolic or oxidative stress, including cardiac disease in dogs, but future research is required.

Juvenile tench ( Tinca tinca L.) response to practical diets with different replacement levels of fish meal by pea protein concentrate supplemented with methionine

The effects of methionine supplementation in diets with different replacement levels of fish meal (FM) by pea protein concentrate (PPC) on survival, growth performance and body composition of juvenile tench (0.39 g of initial weight) were studied in a 90-day experiment. Six practical diets (50% crude protein) differing in replacement level of FM by PPC were tested: 0% (control diet), 35%,45%, 60%, 75% or 85%, corresponding to 0, 285, 366, 487, 608 and 685.4 g PPC kg−1 diet respectively. To provide the same amount as in control diet, methionine was included from the 45% substitution level. Survival rates were high, between 93.7% and 100%, without differences among treatments. Juveniles fed 75% and 85% of replacement diets showed lower (p < 0.05) weight and specific growth rate, which cannot be attributed to methionine deficiency. In all treatments, percentages of fish with externally visible deformities were low (under 0.1%). The increase in PPC diet content resulted in a significant reduction of lipid content in whole-body juvenile. Minimum methionine requirements for juvenile tench could be estimated in 10 g kg−1 diet and supplementation over this amount would be not necessary. Juvenile tench exhibited a high tolerance to PPC dietary content, up to 487 g kg−1, without affecting growth performance, which make possible to consider this vegetal source of protein as a suitable substitute to FM.

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.

Choline and methionine supplementation in layer hens fed flaxseed: effects on hen production performance, egg fatty acid composition, tocopherol content, and oxidative stability

Choline is an essential nutrient in laying hen diets and is needed for the formation of phosphatidylcholine (PC), that serves as a rich source of long chain (≥20 C) n-3 fatty acids (FA) in eggs. Methionine (Met) is the first limiting amino acid in layer hen diets and serves as a lipotropic agent with antioxidant properties. The objectives of the current study is based on the hypothesis that choline and Met supplementation will enhance egg PC and n-3 FA status, lipid stability, and production indices in layer hens fed flaxseed. Ninety-six, 40-wk-old laying hens (W-36 White Leghorns) were randomly allocated to 4 treatment groups, with 6 replicates containing four hens per cage. Hens were fed corn-soybean meal-based diet containing 0% flaxseed (Control), 15/100 g flaxseed (Flax), Flax+50% more methionine requirement for W-36 White Leghorns (Flax+Met), or Flax+0.15g/100g choline chloride (Cho) (Flax+Cho). All experimental diets were isocaloric and isonitrogenous and fed for a period of 120 d. Egg production and egg mass (g/hen/d) was higher for Flax+Met and Flax+Cho when compared to Flax and Control (P < 0.05). Egg weight was greater (P < 0.05) among hens fed the Control and Flax+Cho diets compared to Flax diet. Feeding flaxseed to hens led to over 6-fold increase in total n-3 FA. Choline supplementation increased egg α-tocopherol content (P < 0.05) while reducing lipid oxidation products measured as thiobarituric acid reactive substances in egg yolk (P < 0.05). Neither Met nor Cho had any impact on docosahexaenoic (22:6 n-3) acid concentration in eggs from hens fed flaxseed. However, addition of Met and Cho to layer diets increased docosapentaenoic acid (22:5 n-3) levels in eggs from hens fed flaxseed (P < 0.05). The PC content was lower in Control and Flax+Met (P < 0.05) when compared to Flax+Cho group. No difference was found in total lipid or phosphatidylethanolamine content of eggs (P > 0.05). The results from the current study suggest that n-3 FA content of egg yolk can be greatly increased by feeding flaxseed but reduced egg production. However, dietary Met and Cho can improve production performance in hens fed flaxseed-containing diets. Addition of Cho to flaxseed increased in egg weight, yolk α-tocopherol levels, PC content and oxidative stability of eggs when compared to hens fed flaxseed. Met and choline could be used in flaxseed (>15%) to increase egg production and egg mas.

Artificial neural networks approach for predicting methionine requirement in broiler chickens

Artificial neural networks approach for predicting methionine requirement in broiler chickens

RESPONSE TO METHIONINE SUPPLEMENTATION OF BROILER CHICKS FED PRACTICAL CORN-GROUNDNUT MEAL DIETS IN THE TROPICS

Two floor feeding trials, involving 1000 broiler chicks fed two different practical-type diets, were conducted in order to determine the methionine and total sulphur amino acid (TSAA) requirements of broiler chicks 0-6 weeks). Two protein levels (20 and 23%) each with an energy concentration of 2800 Kcal ME (kg diet and four supplemental methionine levels (0.1, 0.2, 0.3 and 0.4%) were tested. At the end of 6 - week feeding period, a common finisher ration was fed to 10 weeks of age. Under our experimental circumstances with dietshaving 23% protein and metabolizable energy of 2800 Kcal ME/kg diet and based on assumed methionine and cystine content of feeding stuff, the quantitative requirement for methionine of broiler chicks up to six weeks of age were about 0.53% diet which is equivalent to 2.3% of the dietary protein (or TSSA of 0.85 per cent diet, that is 3.7 per cent protein). Higher supplemental methionine at this protein and energy levels resulted in deterioration in liveweight gain and slight but non-significant improvement in feed/gain ratio. The rations containing 20% protein performed poorly relative to those containing 23%. Feeding of high quality common finisher rations neutralized the initial gains due to supplemental methionine within each protein levelbut did not offset the gains due to different dietary proteins.

Sulfur amino acid requirements for pullets in growth and pre-laying trials

Context To obtain a good performance of the hens in the laying phase, adequate nutrition in the growth and pre-laying phase is necessary, especially for meeting amino acid requirements that are related to development of reproductive organs (ovary and oviduct). Aims The objective of the present study was to predict the requirements for methionine (Met) plus cystine (Cys) from the growth of the body, feathers and reproductive organs of laying hens. Methods The model estimates Met+Cys requirements as the relationship between the deposition of Met+Cys into three compartments (body, feathers, and reproductive organs) and their utilisation efficiency. The efficiency of utilisation was determined by a linear regression between Met+Cys deposition and intake for pullets aged 14–28, 56–70 and 98–112 days. Protein weight and deposition in the body and feathers were determined by the comparative slaughter method. The Gompertz function was used to model body, feathers, ovary, oviduct and liver weight against age. Key results Our results showed that the inclusion of parameters descriptive of the growth of reproductive organs and the correction for feather losses in the model enabled Met+Cys requirements for growth in pre-laying trials to be predicted with a greater precision. Conclusions The model developed in this study for determining the Met+Cys requirements for Dekalb White pullets could be extended, provided the necessary adjustments are made, to other amino acids, strains and species. Implications Meeting Met+Cys requirements in the phase of maximum growth of the reproductive organs (weeks) contributes to the uniformity of the age when the pullets reach sexual maturity and, consequently, start the egg production.

Effect of replacement different methionine levels and sources with betaine on blood metabolites, breast muscle morphology and immune response in heat-stressed broiler chickens

This study was performed to evaluate the effect of replacement different methionine (Met) levels and sources (DL or L) with betaine on blood metabolites, breast muscle morphology and immune response in heat-stressed broiler chickens. A total of 1200 unsexed day-old Ross-308 chicks were raised under the same condition in the first 10 days and then reared under normal or subnormal (32 °C) ambient temperatures for the 11 to 42 days of age. The experiment was designed as a split-plot factorial arrangement with 2 (temperatures) × 2 (Met sources) × 3 (Met levels) × 2 (betaine amounts). Met level in the basal diet was 30% lower than recommendation (Low-Met) and was increased to recommendation (Rec-Met) or 30% more than it (High-Met) by supplemental DL- or L-Met. Betaine was or was not substituted at the rate of 30% of the supplemental DL- or L-Met. From 11 to 24 d of age, broilers fed high-met diets showed better FCR than those received Low- and Rec-Met diet. High-Met diet under heat stress (HS) showed highest plasma uric acid and homocysteine concentration than two other diets, under normal or HS condition. Replacing 30% of the supplemental Met with betaine showed lower plasma homocysteine concentration compared to non-supplemented betaine diets. Birds fed Low- and Rec-Met diets under normal condition showed a significant decrease in heterophil/lymphocyte ratio compared to their counterparts under HS. Birds fed L-Met supplemented diet showed a greater myofibers diameter than birds fed DL-Met diet. In general, High-Met diet decreased heterophil/lymphocyte ratio and FCR of broilers. A total of 30% of dietary supplemental Met can be replaced by betaine. Highlights Heat stress increase methionine requirements of broiler chickens. L-methionine increases breast yield in compare with DL-methionine. Betaine in animal feed can be replaced by methionine without adverse effect on broiler chickens.

Metabolizable amino acids and energy requirements of Nellore and crossbred Angus × Nellore bulls fed rations of different crude protein concentrations

Growth rate of cattle depends on their genetic makeup and nutrient intake. Moreover, increased growth rate may lead to increased amino acid (AA) requirements. Therefore, we evaluated the AA content of the empty body and estimated the net AA and energy requirements of purebred and crossbred beef bulls fed rations of different dietary CP concentrations. We performed a comparative slaughter experiment with 24 Nellore and 24 Angus × Nellore (A × N) bulls (8 months; initial shrunk BW: Nellore = 208.0 ± 12.78 kg; A × N = 221.9 ± 14.16 kg). Eight bulls (four Nellore and four A × N) were designated as the reference group, eight bulls (four Nellore and four A × N) were fed to maintenance level and 32 bulls (16 Nellore and 16 A × N) were fed ad libitum. The 32 bulls fed ad libitum were distributed using a completely randomized design in a 2 × 3 factorial scheme with two genetic groups (Nellore or A × N) and three dietary CP contents (100, 120 or 140 g CP/kg DM), being four groups with five bulls and two groups with six bulls. The experimental period lasted for 224 days. There were no interactions (P ≥ 0.056) between the dietary CP contents and genetic groups for any of the response variables. The dietary CP contents did not affect (P ≥ 0.062) the AA content in the empty body (g/kg empty BW [EBW]), with exception for Tryptophan (P = 0.027, linear effect). The dietary CP contents did not affect (P ≥ 0.051) AA content in the empty body (g/100 g of CP), with exception for Alanine (P = 0.013) that responded quadratically to dietary CP increase. The equations to estimate the net Lysine (Lys) and Methionine (Met) requirements (g/100 g of CP) were: Lys = 5.1 × EBW0.0594 and Met = 1.7 × EBW0.0255. Metabolizable Lys and Met to metabolizable energy (ME) ratios decreased as bulls EBW increased. Also, the metabolizable protein to ME ratio decreased as bulls EBW increased. In conclusion, the present study provides useful information regarding net and metabolizable requirements of AA of purebred and crossbred beef bulls. In the future, after the validation of the equations, these results can be used to calculate the AA requirements for growth of purebred and crossbred beef bulls. Nevertheless, it is important to highlight that the small sample size was one limitation of this present experiment.

The sulfur amino acid requirements of juvenile Yellowtail Kingfish (Seriola lalandi)

The dietary methionine and cysteine requirements of Yellowtail Kingfish (YTK) are unknown. Methionine, an essential sulfur-containing amino acid, acts as a sulfur and methyl donor for key metabolites, such as cysteine and taurine. Cysteine, a conditionally essential sulfur-containing amino acid, can spare significant amounts of methionine in the total sulfur amino acid (TSAA) requirement. Both methionine and cysteine are an integral part of YTK aquafeeds, in which methionine supplementation levels are based on the requirements of the closely related Japanese Yellowtail (Seriola quinqueradiata) at approximately 11.1 g kg−1 diet. However, recent research has demonstrated better growth and feed efficiency in YTK fed diets containing more than 11 g methionine kg−1, although the precise methionine requirement and potential interactions with cysteine remain unknown. Therefore, the present study was designed to (1) elucidate the methionine requirement of YTK at low and high dietary cysteine contents and to (2) quantify cysteine's sparing capacity for methionine in the TSAA requirement. These requirements and relationships were established by feeding ten isonitrogenous and isoenergetic diets, made from common feed ingredients, to triplicate groups of 12 fish (initial 52.6 ± 1.0 g fish−1) over 54 days. The orthogonal design consisted of two levels of dietary cysteine (5.6 & 13.9 g kg−1), crossed with five levels of dietary methionine, increasing from 7.9 to 25.2 g kg−1. Non-linear regression analysis indicated an average digestible TSAA requirement of 0.70 g kgBW−1 d−1 (0.56 g Met kgBW−1 d−1 & 0.14 g Cys kgBW−1 d−1) based on feed conversion ratio, specific growth rate, and protein retention efficiency. This approximates to an average dietary sulfur amino acid specification of 24.5 g kg−1 (18.9 g Met kg−1 & 5.6 g Cys kg−1). Cysteine spared 40.4–49.2% of methionine in the TSAA requirement on an equimolar sulfur basis. Sub- and supra-optimal levels of dietary methionine and cysteine induced inferior growth and feed efficiency. Additionally, fish fed the diet lowest in dietary methionine and cysteine indicated early stages of cataract. This study provides quantitative data on the sulfur amino acid requirements of juvenile YTK and will facilitate the formulation of better diets for this species.

Quantifying methionine requirement of juvenile African catfish (Clarias gariepinus)

This study was conducted to estimate the methionine (Met) requirement of African Catfish (Clarias gariepinus). A basal diet was formulated to contain 32% crude protein, 12% lipids, and 0.44% cysteine using only protein from legume ingredients as intact protein. This diet was supplemented with graded levels of crystalline DL- methionine (0, 0.12, 0.24, 0.36, 0.48, 0.60, and 0.84%), which resulted in seven dietary methionine levels ranging from 12.2 to 36.0 g kg−1 crude protein. Triplicate groups of 40 fish (78 g) were restrictively fed one of the seven diets for six weeks. Dietary methionine level significantly affected growth rate, feed conversion ratio, retained nitrogen, methionine efficiency and body composition. All parameters were fitted to dietary digestible methionine content expressed per unit of digestible protein (dMetDP) to estimate the Met requirement using; the linear plateau model (LP), broken line model (BL), or quadratic regression model (QR). LP and BL recorded similar values for requirement estimates while QR evidently recorded a 57% higher requirement estimates across different parameters. The digestible methionine requirement of African catfish for growth (using LP) ranges between 18.7 and 21.4 g kg−1 per unit of digestible protein. This equates to a minimum dietary methionine level of 6.3 g kg−1 diet (19.2 g kg−1 Crude protein), which is lower than was has been previously reported for this species.

Minimum dietary methionine requirements in Miniature Dachshund, Beagle, and Labrador Retriever adult dogs using the indicator amino acid oxidation technique.

The objective of this study was to determine the minimum requirement (MR) for methionine (Met), when cyst(e)ine (Cys) is provided in excess, in adult dogs of three different breed sizes using the indicator amino acid (AA) oxidation (IAAO) technique. In total, 12 adult dogs were used: 1 neutered and 3 spayed Miniature Dachshunds (4.8 ± 0.4 kg body weight [BW], mean ± SD), 4 spayed Beagles (9.5 ± 0.7 kg BW, mean ± SD), and 4 neutered Labrador Retrievers (31.8 ± 1.7 kg BW, mean ± SD). A deficient Met basal diet with excess Cys was formulated. Dogs were fed the basal diet randomly supplemented with different Met-Alanine (Ala) solutions to achieve final Met concentrations in experimental diets of 0.21%, 0.26%, 0.31%, 0.36%, 0.41%, 0.46%, and 0.66% (as-fed basis). After 2 d of adaptation to the experimental diets, dogs underwent individual IAAO studies. During the IAAO study day, the total feed was divided into 13 equal meals; at the sixth meal, dogs were fed a bolus of l-[1-13C]-phenylalanine (Phe), and thereafter, l-[1-13C]-Phe was supplied with every meal. The total production of 13CO2 during isotopic steady state was determined by the enrichment of 13CO2 in breath samples, and the total production of CO2 measured using indirect calorimetry. The mean MR for Met and the upper 95% confidence limit (CL) were determined using a two-phase linear mixed-effects regression model. For Miniature Dachshunds, the MR for Met was between the first two dietary Met concentrations and is, therefore, between 35.7 and 44.1 mg.kg BW−1·d−1 (0.21% to 0.26%, as-fed basis; no requirement could be determined on a metabolic BW basis). For Beagles and Labrador Retrievers, the MR for Met was 57.5 and 50.4 mg.kg BW−1·d−1, 107.7 and 121.8 mg/kg BW^0.75, or 0.338 and 0.360%, respectively (as-fed basis). The upper 95% CL of Met requirements was 77.9 and 72.4 mg.kg BW−1·d−1, 147.8 and 159.6 mg/kg BW^0.75,or 0.458 and 0.517% for Beagles, and Labradors, respectively (as-fed basis). When pooling data from Beagles and Labrador Retrievers, the MR and upper 95% CL were 56.0 and 75.8 mg.kg BW−1·d−1 or 118.4 and 150.5 mg/kg BW^0.75 or 0.360% and 0.482% (as-fed basis). In conclusion, the MR and the upper 95% CL for Met are different for Dachshunds when compared with Beagles and Labrador Retrievers. Using this low-protein diet, the estimated upper 95% CL Met requirement for Beagles and Labrador is higher than those recommended in the National Research Council (NRC), but NRC is similar to the estimated upper 95% CL for Dachshunds.

Characterization of Met25 as a color associated genetic marker in Yarrowia lipolytica

Yarrowia lipolytica offers an ideal host for biosynthesis of high value natural products and oleochemicals through metabolic engineering despite being restricted to a limited number of selective markers, and counter-selection achieved primarily with URA3. In this work, we investigate MET25, a locus encoding sulfide housekeeping gene within the cell, to be exploited as a standard genetic marker. Divalent lead supplemented in media induces lead sulfide (PbS) aggregation in MET25-deficient cells such that deficient cells grow brown/black, and cells with functional copies of MET25 grow white. Loss of MET25 did not induce strict auxotrophic requirements for methionine in Y. lipolytica, indicating MET25 deficiency could be rescued by alternative pathways. Plasmid and chromosomal-based complementation of MET25 in the met25 deficient cells on a double layer agar plate with nutrient gradients demonstrates delayed phenotype (white morphology) restoration, indicating post-transcriptional feedback regulation of methionine biosynthesis in this yeast. MET25 deficient Y. lipolytica could be used as an efficient whole-cell lead sensor with detection limit as low as 10 ​ppm of lead in drinking water. We further tested whether MET25 deficiency can be exploited to confer resistance to methyl-mercury through chemical neutralization and detoxification. Kinetic growth curves of wild type and MET25-deficient cells were obtained under varying concentrations of methylmercury and cellular toxicity to methyl mercury was calculated from the Hill equation. Our results indicate that methylmecury may not be used as the counter-selectable marker due to insignificant changes of growth fitness. This work demonstrates the utility of using MET25 as a sensitive lead sensor and the challenges of using MET25 as a counter-selectable genetic marker, as well as the complex regulation of methionine biosynthesis in Y. lipolyitca, which may shed lights for us to develop valuable biotechnological applications centering around the sulfur house-keeping metabolism of the nonconventional yeast.

Lipid metabolism in juveniles of Yellowtail,Seriola dorsalis,fed different levels of dietary methionine containing a low level of cholesterol: Implication in feed formulation

The involvement of dietary methionine in the lipid metabolism of Seriola dorsalis, at different levels of dietary methionine (Met), and low content of cholesterol was investigated. Four diets containing different Met levels and a low amount of cholesterol (0.23 g/kg diet) were prepared. One hundred and eighty juveniles (16.2 ± 1.5 g) were randomly distributed into each 12 500-L ponds. After 60 days, the growth in weight (%) significantly increased following the Met supplementation, whereas SGR of all the experimental treatments was higher than the Basal Diet. The expression of the insulin-like growth factor (IGF-1) increased significantly (0.2-fold) and was complemented by significant changes in Mat, BHMT and HMG-CoA, for fish that were in the low and higher Met levels. The cholesterol content in the whole body and liver increased following methionine supplementation, similarly to that observed for crude lipids, in particular in the whole body and liver tissues. However, the relative amount of most fatty acids remained unchanged. Only the oleic acid increased at a higher amount of Met. Therefore, once the dietary requirement of methionine is met, the methionine is used to synthesize cholesterol. It is recommended to supply a higher amount of methionine to spare energy for growth.

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.

Digestible methionine+cystine levels for white-egg layers aged one to six weeks

The aim of this study was was to determine the nutritional requirements of digestible methionine+cystine (M+C) for white-egg layers aged one to six weeks. A completely randomized design with five methionine+cystine levels, six replicates, and 30 birds per experimental unit was adopted. Dietary treatments consisted of five diets supplemented with DL-Methionine with resulted in five levels of digestible methionine + cystine, 80% (0.516%), 90% (0.578%), 100% (0.640%), 110% (0.702%), and 120% (0.764%), based on Brazilian tables of nutritional requirements. Performance, serological blood, and histological data were evaluated. Feed intake, feed conversion, hepatic glycogen deposition, enzymatic activity of alanine aminotransferase and gamma-glutamyl transferase, and serum creatinine and albumin levels had showed a quadratic response to the levels of digestible M+C, with the respective requirements: 89.78% (0.575%), 114.33% (0.732%), 86.50% (0.554%), 100% (0.640%), 100.40% (0.643%), 104.30% (0.668%), and 111.88% (0.716%). Increasing levels of methionine+cystine elevated the relative liver weight and the deposition of hepatic glycogen, in addition to promote higher growth in pullets, with better body weight and body weight gain and feed conversion ratio. Our findings suggest that 0.732% digestible methionine+cystine is recommended, which corresponds to an intake of 151.20 mg/bird/d and a Met+Cys:Lys ratio 83%, for light pullets from one to six weeks.

Effects of a high-protein corn product compared with soy and canola protein sources on nutrient digestibility and production responses in mid-lactation dairy cows

An experiment was conducted to assess the effects of a novel and proprietary high-protein corn product [56% crude protein (CP)] relative to other common sources of protein on the lactation performance of dairy cows. Twenty-four Holstein cows (620 ± 47.7 kg of body weight, 111 ± 34 d in milk, 2.28 ± 0.46 lactations; mean ± standard deviation) were randomly assigned to treatment sequence in a replicated 4 × 4 Latin square design balanced for carryover effects. Cows were individually fed 1 of 4 diets with a different protein concentrate source during each 28-d period, including soybean meal (SBM), high-protein corn product (HPCP), soybean meal with rumen-bypass soy protein (SBMBP), and canola meal with rumen-bypass soy protein (CANBP). Diets were formulated for equal concentrations of CP and balanced to meet predicted lysine and methionine requirements. The SBM diet was formulated to provide 5.7% rumen-undegradable protein (RUP), whereas SBMBP and CANBP diets were formulated for 6.8% RUP to match HPCP. Data were analyzed using mixed models with the fixed effects of treatment, period, square, the interactions of treatment and period and of treatment and square, and the random effect of cow. The CANBP diet increased dry matter intake (DMI) compared with SBM and HPCP. Treatment affected milk yield, as SBMBP and CANBP increased yield compared with SBM, but HPCP decreased milk yield compared with all treatments. The HPCP diet reduced CP intake as a percent of total DMI and increased the CP content of orts, indicative of selection against HPCP. The HPCP diet also decreased apparent total-tract and CP digestibility, leading to less urine nitrogen excretion and greater fecal nitrogen output. The SBMBP and CANBP diets performed similarly in nearly every variable measured, except that SBMBP increased milk urea nitrogen. In conclusion, the HPCP diet reduced yield of milk and milk components, likely because of reduced apparent total-tract dry matter and CP digestibility.