Met-deficient Diet Research Articles

Effects of dietary methionine and betaine on slaughter performance, biochemical and enzymatic parameters in goose liver and hepatic composition

The effects of dietary methionine (Met) and betaine (Bet) on slaughter performance, serum biochemical parameters, and liver betaine-homocysteine methyltransferase (BHMT) were investigated in geese. Six Met-deficient diets were prepared according to a 2×3 factorial design that included two levels of Bet (0 and 600mg/kg) and three levels of Met (0, 600, and 1200mg/kg). Three hundred 21-d-old healthy male Yangzhou geese with similar body weight were randomly distributed into 6 groups with 5 replicates per treatment and 10 geese per replicate. All geese had free access to diets and water for 49 d. slaughter performance were recorded at 70 d of age. Results showed that increasing dietary levels of methionine gave a linear (P<0.05) increase in body weight and average daily gain. No significant effect of dietary Met level was found on slaughter performance (P>0.05). Geese that received 600mg/kg Bet had a higher percentage of eviscerated yield than those that did not (P<0.05). There were significant interaction effects between Met and Bet in dressing percentage, half-eviscerated yield, and eviscerated yield (P<0.05). Increasing supplemental Met led to linear increases in serum concentrations of total protein (TP), albumin (ALB), and globulin (GLOB) and hepatic crude protein levels (P<0.05). Bet supplementation also increased TP and ALB plus high- and low-density lipoprotein in serum and the mRNA level of BHMT (P<0.05) in livers. In contrast, triglyceride and homocysteine were higher in geese that did not receive additional Bet than those in the Bet supplementation group (P<0.05). The hepatic crude fat contents in the Bet supplementation group also decreased (P<0.05). Significant interactions between Met and Bet supplementation (P<0.05) were detected in several amino acids. In conclusion, optimal Met dietary supplementation could increase growth performance, serum TP, ALB, and GLOB and hepatic protein synthesis in growing goslings. Furthermore, dietary supplementation with Bet could possibly replace Met for slaughter performance through upregulation of BHMT gene expression.

Bioavailability of D-methionine relative to L-methionine for nursery pigs using the slope-ratio assay.

This experiment was conducted to determine the bioavailability of D-methionine (Met) relative to L-Met for nursery pigs using the slope-ratio assay. A total of 50 crossbred barrows with an initial BW of 13.5 kg (SD = 1.0) were used in an N balance study. A Met-deficient basal diet (BD) was formulated to contain an adequate amount of all amino acids (AA) for 10–20 kg pigs except for Met. The two reference diets were prepared by supplementing the BD with 0.4 or 0.8 g L-Met/kg at the expense of corn starch, and an equivalent concentration of D-Met was added to the BD for the two test diets. The pigs were adapted to the experimental diets for 5 d and then total but separated collection of feces and urine was conducted for 4 d according to the marker-to-marker procedure. Nitrogen intakes were similar across the treatments. Fecal N output was not affected by Met supplementation regardless of source and consequently apparent N digestibility did not change. Conversely, there was a negative linear response (P < 0.01) to Met supplementation with both Met isomers in urinary N output, which resulted in increased retained N (g/4 d) and N retention (% of intake). No quadratic response was observed in any of the N balance criteria. The estimated bioavailability of D-Met relative to L-Met from urinary N output (g/4 d) and N retention (% of intake) as dependent variables using supplemental Met intake (g/4 d) as an independent variable were 87.6% and 89.6%, respectively; however, approximately 95% of the fiducial limits for the relative bioavailability estimates included 100%. In conclusion, with an absence of statistical significance, the present study indicated that the mean relative bioequivalence of D- to L-Met was 87.6% based on urinary N output or 89.6% based on N retention.

Effect of L- or DL-methionine Supplementation on Nitrogen Retention, Serum Amino Acid Concentrations and Blood Metabolites Profile in Starter Pigs.

The objective of the current study was to evaluate the effect of supplementation of either L-methionine (L-Met) or DL-methionine (DL-Met) to diets of starter pigs on nitrogen (N) balance, metabolism, and serum amino acid profile. Eighteen crossbred (Duroc×Landrace×Yorkshire) barrows weighing 15.45±0.88 kg were randomly allotted to 1 of 3 diets with 6 pigs per treatment. The diets included a basal diet (Met-deficient diet) containing 0.24% standardized ileal digestibility Met with all other essential nutrients meeting the pig’s requirements. The other two diets were produced by supplementing the basal diet with 0.12% DL-Met or L-Met. The experiment lasted for 18 days, consisting of a 13-day adaptation period to the diets followed by a 5-day experimental period. Pigs were fed ad libitum and free access to water throughout the experiment. Results showed that the supplementation of either L-Met or DL-Met improved N retention, and serum methionine concentration, and decreased N excretion compared with basal diet (p<0.01). The N retention of pigs fed diets supplemented with the same inclusion levels of DL-Met or L-Met were not different (p>0.05). In conclusion, on equimolar basis DL-Met and L-Met are equally bioavailable as Met sources for starter pigs.

Methionine deficiency leads to hepatic fat accretion via impairment of fatty acid import by carnitine palmitoyltransferase I

1. To clarify the underlying mechanism of hepatic fat accretion due to methionine (Met) deficiency in broiler chickens, the present study investigated the effect of Met deficiency on the hepatic carnitine palmitoyltransferase (CPT) system, which imports fatty acids into mitochondria.2. Fifteen-d-old male meat-type chickens were fed on either a control diet (containing 0.52 g/100 g Met) or a Met-deficient diet (containing 0.27 g Met/100 g). After a 10-d feeding period, the birds were killed by decapitation and their livers excised to determine hepatic CPT1 and CPT2 mRNA levels and for the related hepatic fatty acid-supported mitochondrial respiration to be measured.3. Met deficiency decreased body weight gain and feed efficiency and increased hepatic lipid content compared to the control group. Whereas the hepatic CPT2 mRNA level in the Met-deficient group remained unchanged compared to that of the control group, the CPT1 mRNA level was decreased in the Met-deficient group and CPT1-dependent hepatic mitochondrial respiration was impaired.4. Our results suggest that the hepatic lipid accretion that occurs in response to Met deficiency might be attributable to the impairment of CPT1-mediated fatty acid import into mitochondria.

Effects of putrescine supplementation on growth performance, blood lipids and immune response in broiler chickens fed methionine deficient diet

The polyamines including putrescine (PUT), spemidine (SPD) and spermine (SPM) have been shown to play an important role in basic cellular processes. Methionine (Met) and arginine are required for polyamine biosynthesis. This experiment was carried out to study the effects of Met deficient diet with or without supplemental PUT on the performance, blood lipids and glucose and humoral immunity in broiler chickens. A total of 192 day-old chicks were allocated into factorial arrangement (2×2) of four dietary treatments including two Met levels (Normal and Low) and two PUT levels (0 and 0.03%). Body weight and feed intake were measured weekly. At the age of 28 d, 10 birds per treatment were challenged with infectious bursal disease vaccine orally (10 dosage/bird, 2ml). Blood samples of the challenged birds were collected for antibody determination and white blood cell count. Blood cholesterol, triglyceride, glucose, hematocrit and protein of non-challenged birds were measured at the ages of 24, 33 and 40 d. Low Met decreased body weight gain, protein efficiency ratio and feed conversion ratio (P<0.05). In grower period, energy efficiency ratio was improved by PUT supplementation in the chicks fed with normal Met level. Feed conversion ratio was badly affected (P<0.05) by low Met during grower period. PUT decreased body weight gain of chickens fed low Met significantly (P<0.05), indicating the importance of adequate Met level when high dietary PUT is offered. Met deficient diet decreased plasma protein level significantly (P<0.05). Five days post challenged, PUT supplementation elevated antibody level significantly (P<0.05) in the chicks fed normal level of Met. However, Met deficient diet in challenged chicks, caused significantly (P<0.05) lower monocyte ratio. In conclusion, growth performance declined due to Met deficiency, particularly during starter period (0–21 d) and when dietary PUT was supplemented. PUT showed the potential to increase blood antibody level and better dietary energy efficiency ratio.

The geometric framework: An in vivo approach

The science of nutrition is complex and multifactorial. To render accessible this multidimensional discipline, one-factor-at-a-time experimental approaches are useful. For example, when Met requirements for broilers are investigated, it is common for a Met-deficient diet to be offered to broilers of a specific age, and phenotypic responses to supplemental Met measured. Though these experimental approaches are clearly useful, they are usually focused in scope and do not allow panoptic interpretation across environmental-, bird-, and diet-related factors. An alternative experimental approach has been recently described and is called geometric framework. This framework uses Euclidean geometric vocabulary to describe nutrients, ingredients, animals, and environmental conditions as coordinates in multidimensional space. The current review briefly describes the foundational premises of the geometric framework and how it may be applied to explore the complex and multifactorial interactions that exist in broiler nutrition to derive nutritional tautology.

Pathology of Bursae of Fabricius in Methionine-Deficient Broiler Chickens

The purpose of this 42-day study was to investigate the effects of methionine (Met) deficiency on immune function by determining the relative weight, morphological and ultrastructural changes of bursae of Fabricius, cell cycle, and apoptosis of bursa cells. One hundred and twenty one-day-old avian broilers were randomly divided into two groups and fed on a control diet (starter diet, Met 0.50%; grower diet, Met 0.40%) and Met-deficient diet (starter diet, Met 0.26%; grower diet, Met 0.28%) for six weeks. The relative weight of bursae was decreased with Met deficiency when compared to that of the control group. Lesions were also observed in the Met-deficient group. Histopathologically, the numbers of lymphocytes in the follicles were decreased. Ultrastructurally, the mitochondria of lymphocytes were swollen in the Met-deficient group. As measured by flow cytometry, bursal cells in the G0G1 phase were significantly higher (P < 0.01), and bursal cells in the S, G2M phases and proliferating index were obviously lower (P < 0.01) with Met deficiency than in the control group. Moreover, the percentage of apoptotic cells in the bursae were significantly increased in Met-deficient birds (P < 0.01). It was concluded that Met deficiency restrained the development of the bursae of Fabricius and affected the humoral immunity of the chickens.

Effects of metabolizable protein supply and amino acid supplementation on nitrogen utilization, milk production, and ammonia emissions from manure in dairy cows

Two experiments were conducted with the objective of investigating the effects of rumen-protected methionine (RPMet) supplementation of metabolizable protein (MP)-deficient or MP-adequate but Met-deficient diets on dairy cow performance. Experiment (Exp.) 1 utilized 36 Holstein dairy cows blocked in 12 blocks of 3 cows each. Cows within block were assigned to one of the following dietary treatments: (1) MP-adequate diet [AMP; positive MP balance according to the National Research Council (2001) dairy model]; (2) an MP-deficient diet supplemented with 100g of rumen-protected Lys (RPLys)/cow per day (DMPL); and (3) DMPL supplemented with 24g of RPMet/cow per day (DMPLM). Experiment 2 utilized 120 Holstein cows assigned to 6 pens of 20 cows each. Pens (3 per treatment) were assigned to one of the following dietary treatments: (1) AMP diet supplemented with 76g of RPLys/cow per day (AMPL); and (2) AMPL (74g of RPLys/cow per day) supplemented with 24g of RPMet/cow per day (AMPLM). Each experiment lasted for 10wk (2-wk adaptation and 8-wk experimental periods) following a 2-wk covariate period (i.e., a total of 12wk). In Exp. 1, the MP-deficient diets decreased apparent total-tract nutrient digestibility but had no statistical effect on dry matter intake (DMI), milk yield, or milk fat percentage and yield. Compared with AMP, DMPL decreased milk protein content; both DMPL and DMPLM diets decreased milk protein yield. Urinary N losses and milk urea-N concentration were decreased by the MP-deficient diets compared with AMP. The ammonia emitting potential of manure from the MP-deficient diets was decreased by about 37% compared with that of AMP manure. Plasma Lys and Met concentrations were not affected by treatment, but concentrations of His, Thr, and Val were lower for the MP-deficient diets compared with AMP. In Exp. 2, the AMPLM diet had lower milk yield than AMPL due to numerically lower DMI; no other effects were observed in Exp. 2. In conclusion, feeding MP-deficient diets supplemented with RPLys and RPMet did not statistically decrease milk yield in dairy cows in Exp. 1. However, without RPMet supplementation, milk protein content was decreased compared with the MP-adequate diet. Other amino acids, possibly His, may limit milk production in MP-deficient, corn or corn silage-based diets. A summary of 97 individual cow data from trials in which MP-deficient diets were fed suggested the National Research Council (2001) model under-predicts milk yield in cows fed MP-deficient diets (MP balance of –20 to –666g/d) in a linear manner: milk yield under-prediction [National Research Council (2001) MP-allowable milk yield, kg/d – actual milk yield, kg/d] = 0.0991 (±0.0905) + 0.0230 (±0.0003) × MP balance, g/d (R2=0.99).

Response of common carp (Cyprinus carpio L.) to supplemental DL-methionine and different feeding strategies

The common carp (Cyprinus carpio) is an agastric fish, meaning absorption of nutrients is highly dependent on the rate of feed passage in the gut. Two diets and 3 feeding strategies were used in a 2×3 factorial experiment, conducted to determine whether utilization of supplemental DL-methionine (DL‐Met) interacts with feeding strategies. Diets 1 and 2 contained, respectively, no Met supplementation (Met deficient diet with Met level of 0.45% Met in DM) and supplemented with DL-Met (Met balanced diet with Met level of 0.86% Met in DM). The three feeding strategies included, hand feeding twice daily to apparent satiation (feeding strategy 1), pair feeding the same amount of feed as in strategy 1 continuously by means of an automatic feeder over 2×6h periods (feeding strategy 2), and continuously feeding a fixed rate of 1.4% BW using an automatic feeder (feeding strategy 3). The fish, with a mean initial weight of 239g, were fed for 82days in a recirculation system. The results indicated that supplementation of DL-Met in the diet improved (P<0.05) final weight(483 vs. 424g), daily weight gain, feed consumption, feed efficiency (1.60 vs. 1.92g DMweight gain−1) and protein digestibility (90.7 vs. 87.9%). Supplemented DL-Met also resulted in increased carcass protein and reduced carcass fat. Plasma levels of methionine and arginine were higher with supplemented dietary DL-Met, while plasma levels of lysine and serine were lower (P<0.05). Feeding strategy also affected performance and except for feed efficiency no interactions with dietary methionine supply were detected. Compared to feeding strategy 1 feeding strategies 2 and 3 improved (P<0.05) protein digestibility, whereas only feeding strategy 3 increased organic matter digestibility. Continuous feeding (strategies 2 and 3) increased (P<0.05) final weight, daily weight gain and improved feed efficiency. The positive impact of continuous feeding (strategies 2 and 3) compared to twice daily feeding was more pronounced with Diet 1 indicating that also at low feeding frequency supplemental DL-Met is effectively utilized for growth. Feeding strategy 3 was accompanied with a lower feed consumption in comparison to feeding strategies 1 and 2. Feeding strategy did not influence the chemical composition of the carp. The study established that DL-Met can be an effective nutrient for carp, that feeding frequency impacts nutrient utilization and that this effect is not restricted to DL-Met supplemented diets.

Bioavailability of methionine hydroxy analog-calcium salt relative to dl-methionine to support nitrogen retention and growth in starter pigs

This study assessed the efficacy of a calcium salt of methionine hydroxy analog (MHA-Ca, 84%) relative to dl-methionine (dl-Met, 99%) in starter pigs. In Experiment 1 (Exp. 1, N balance trial), 42 individually housed barrows (Genesus, average initial BW 19 kg) were used in two blocks of 21 pigs each with six replicates per treatment. Within each block, pigs were randomly allotted to seven diets: a methionine (Met)-deficient basal diet or the basal diet with three added levels of dl-Met (0.02%, 0.04% and 0.06%) or MHA-Ca (0.024%, 0.048% and 0.071%) on an equimolar basis. After a 7-day adaptation period, feces and urine were collected quantitatively for 5 days. Urinary and total N outputs decreased linearly (P < 0.05) with dl-Met or MHA-Ca supplementation. Nitrogen retention, expressed as g/day and as % of intake increased linearly (P < 0.01) with dl-Met and MHA-Ca supplementations. The relative efficacy of MHA-Ca to dl-Met was estimated to be 71.2% on a product-to-product basis for N retention expressed as % of intake. In Exp. 2 (performance trial), 280, 21-day-old crossbred (Pietrain × (Landrace × Large White)) pigs (eight pigs per pen, seven pens per treatment), were allocated to five diets in a completely randomized block design after a 10-day adaptation period. The Met-deficient basal diet contained 16.5% CP and 0.21% Met. Other diets were basal diet supplemented with two graded levels of dl-Met (0.04% and 0.08%) or MHA-Ca (0.062% and 0.12%) on a product basis at a dl-Met to MHA-Ca ratio of 65 : 100 at the expense of maize. BW and feed disappearance were monitored weekly for 3 weeks to determine performance. Final BW, average daily gain and average daily feed intake increased (P < 0.05) and feed to gain ratio decreased (P < 0.05) with the addition of Met to the basal diet irrespective of the source. Overall, the N retention results of Exp. 1 showed that the average relative bioavailability of MHA-Ca to dl-Met to support N retention (% of N intake) was 71% on a product- to-product basis (85% on an equimolar basis). In Exp. 2, pig performance was not different when Met was supplemented in the Met-deficient diet at a dl-Met to MHA-Ca ratio of 65 : 100 on a product basis.

Interactive effect of two methyl-group sources on the growth and phospholipids’ content of kuruma shrimp Marsupenaeus japonicus Bate post-larvae

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.

Effects of Selenium and Methionine Supplementation of Breeder Hen Diets on Selenium Concentration and Oxidative Stability of Lipids in the Thigh Muscles of Progeny

The effects of dietary supplementation to female chickens with selenium (Se) and methionine (Met) on the next generation were studied. Lang-shan breeding hens (450) were obtained at 52 wk of age and randomly allotted to 9 treatments; 5 replicates of each treatment were carried out. The breeders were fed a basal corn-soybean meal diet (0.13 mg Se/kg) supplemented with 0, 0.30, or 0.60 mg/kg Se from Sel-Plex and 0.32%, 0.40%, or 0.54% Met for the 30-d adapting period and 70-d experiment period. Se and glutathione (GSH) concentrations, glutathione peroxidase (GSH-Px) activity, and the oxidative stability of muscular lipids of 90-d progeny were determined by testing the TBARS values. When breeders received the highest levels of Met or Se, GSH-Px activity was decreased, the Se concentration and the oxidative stability of muscular lipids were increased with the supplementation of Se or Met. When breeder hens were given a Met-deficient diet, supplementing with Se decreased the Se deposition in progeny thigh. With regard to lipid oxidation, 0.3 mg/kg maternal dietary Se supplementation decreased the oxidative stability of muscle lipid and 0.6 mg/kg Se supplementation showed no difference from the control. When breeders were fed a Se-deficient diet, the GSH-Px activity was increased significantly and the oxidative stability of progeny muscles was decreased with the supplementation of Met. It was concluded that supplementation of the maternal diet with higher Se and Met can increase Se deposition in progeny muscle and lead to more effective protection against lipid oxidation in progeny thighs.

Cyst(e)ine imbalance and its effect on methionine precursor utilization in chicks

Five 9- or 12-d chick growth bioassays were done in batteries using 2 Met-deficient diets: a purified AA-based diet containing (by analysis, as-fed) 20.3% CP, 0.12% Met, and 0.05% cyst(e)ine; and an AA-fortified corn-peanut meal diet containing (by analysis, as-fed) 19.0% CP, 0.22% Met, and 0.23% cyst(e) ine. Feed-grade DL-Met (dl-M; 99%) was compared with feed-grade DL-OH-Met, Ca (OH-M; 84%). When the purified diet was modified to contain 0.12% Met and 0.20% or greater cyst(e)ine, slope-ratio assays involving graded dosing of DL-M (0, 404, 808, and 1,212 mg of DL-M/kg) or isosulfurous levels of OH-M resulted in linear (P < 0.01) BW gain and G:F responses. Multiple linear regression analysis (BW gain vs. supplemental sulfur intake, R(2) = 0.98) resulted in a mean bioefficacy estimate of 78.1% for OH-M vs. DL-M (equivalent to 65.6% on a supplemental compound basis). In assay 3, the purified diet was modified to be equally deficient in Met and cyst(e)ine [i.e., 0.12% Met, 0.12% cyst(e)ine]. When this diet was supplemented with either 404 mg of DL-M/kg or 476 mg of OH-M/kg, BW gain and G:F responded (P < 0.01) markedly to either compound, and differences between DL-M and OH-M were not significant (P > 0.10). Assays 4 and 5 used the corn-peanut meal basal diet containing 0.22% total Met and 0.23% total cyst(e)ine. In both assays, addition of either 465 mg of DL-M/kg or 554 mg of OH-M/kg resulted in increased (P < 0.01) BW gain and G:F, regardless of dietary cyst(e)ine concentration. In the absence of excess cyst(e)ine, BW gain responses to DL-M and OH-M were similar, but when 0.10% excess cyst(e)ine was provided as L-cystine or feather meal, DL-M responses tended to exceed those of OH-M. Moreover, this small excess of dietary cyst(e)ine, regardless of source, depressed (P < 0.01) feed intake and BW gain when added to the basal diet. Overall, these results suggest that excess dietary cyst(e)ine, when included in Met-deficient diets, has the potential to be both anorexigenic and pernicious to OH-M utilization.

2-Keto-4-(Methylthio)Butyric Acid (Keto Analog of Methionine) Is a Safe and Efficacious Precursor of l-Methionine in Chicks ,

Relative bioefficacy and toxicity of Met precursor compounds were investigated in young chicks. The effectiveness of dl-Met and 2-keto-4-(methylthio)butyric acid (Keto-Met) to serve as l-Met precursors was quantified using Met-deficient diets of differing composition. Efficacy was based on slope-ratio and standard-curve methodology. Using l-Met as a standard Met source added to a purified diet, dl-Met and Keto-Met were assigned relative bioefficacy values of 98.5 and 92.5%, respectively, based on weight gain. Relative bioefficacy values of 98.5 and 89.3% were assigned to dl-Met and Keto-Met, respectively, when chicks were fed a Met-deficient, corn-soybean meal-peanut meal diet. Thus, both dl-Met and Keto-Met are effective Met precursor compounds in chicks. Additionally, growth-depressing effects of l-Met, dl-Met, and Keto-Met were compared using a nutritionally adequate corn-soybean meal diet supplemented with 15 or 30 g/kg of each compound. Similar reductions in weight gain, food intake, and gain:food ratio were observed for each compound. Subjective spleen color scores, indicative of splenic hemosiderosis, increased linearly (P < 0.01) with increasing intakes of each compound, suggesting a similarity in overall toxicity among these compounds. Because conversion of Keto-Met to l-Met in vivo merely requires transamination, Keto-Met may prove to be a useful supplement not only in food animal production, but also as a component of enteral and parenteral formulas for humans suffering from renal insufficiency.

Liver Choline Dehydrogenase and Kidney Betaine-Homocysteine Methyltransferase Expression Are Not Affected by Methionine or Choline Intake in Growing Rats

AbstractCholine dehydrogenase (CHDH) and betaine-homocysteine methyltransferase (BHMT) are 2 enzymes involved in choline oxidation. BHMT is expressed at high levels in rat liver and its expression is regulated by dietary Met and choline. BHMT is also found in rat kidney, albeit in substantially lower amounts, but it is not known whether kidney BHMT expression is regulated by dietary Met or choline. Similarly, CHDH activity is highest in the liver and kidney, but the regulation of its expression by diet has not been thoroughly investigated. Sprague Dawley rats (∼50 g) were fed, for 9 d in 2 × 3 factorial design (n = 8), an L-amino acid–defined diet varying in L-Met (0.125, 0.3, or 0.8%) and choline (0 or 25 mmol/kg diet). Liver and kidney BHMT and CHDH were assessed using enzymatic, Western blot, and real-time PCR analyses. Liver samples were also fixed for histological analysis. Liver BHMT activity was 1.3-fold higher in rats fed the Met deficient diet containing choline, which was reflected in corresponding increases in mRNA content and immunodetectable protein. Independent of dietary choline, supplemental Met increased hepatic BHMT activity ∼30%. Kidney BHMT and liver CHDH expression were refractory to these diets. Some degree of fatty liver developed in all rats fed a choline-devoid diet, indicating that supplemental Met cannot completely compensate for the lack of dietary choline in growing rats.

Effect of choline and methionine as methyl group donors on juvenile kuruma shrimp, Marsupenaeus japonicus Bate

Choline and methionine are considered as methyl-group donors; therefore, their interaction may affect the growth of the aquatic animal. Thus, a 42-day feeding trial was conducted as a 2 × 3 factorial design to evaluate the effect and interaction of two methyl-group donors, choline chloride (CC) and methionine (Met), on juvenile kuruma shrimp of initial size 0.91 ± 0.04 g (mean ± S.D.). Six test-diets were formulated to contain 3 levels of CC (0%, 0.06% and 0.12%) and 2 levels of Met (0% and 1.5%). Soybean protein isolate (SPI) was utilized as the main source of protein because of its limited Met content. A significant ( P < 0.05) interaction was determined between CC and Met on survival (%S), percent weight gain (%WG), specific growth rate (SGR% day − 1 ), feed efficiency ratio (FER), protein efficiency ratio (PER) and both choline and Met content of the whole body of the juvenile Marsupenaeus japonicus. The shrimp group with neither supplemental CC nor Met showed lower ( P < 0.05) values of the above-mentioned parameters than other shrimp groups fed with 0.06% and 0.12% supplemented CC with or without Met supplementation. The present study showed that supplementation of 0.12% CC in the diets could compensate kuruma shrimp juveniles with the needed methyl-group when fed Met-deficient diets. Also, the supplementation of Met was needed in the case of rearing kuruma shrimp juveniles on choline-deficient diets to compensate methyl group deficiency.

Evidence of a dietary selection for methionine by the piglet1

The objective of the current study was to investigate if there is a preference of piglets for diets varying in Met content and whether these preferences change with time. For this purpose, a feeding trial was carried out over a period of 6 wk. Piglets (equal numbers of males and females) with an initial BW of 7.2 +/- 0.1 kg were randomly subdivided into 4 groups of 12 pigs each. Two reference groups were fed either 0.19% Met (low-Met group) or 0.26% Met (high-Met group) diets. Two other groups had the choice between 2 diets containing 0.19 or 0.23% Met (Met-choice 1 group), or 0.19 or 0.26% Met (Met-choice 2 group). Compared with the low-Met group (397 g), daily feed intake was increased by 43%, 60%, and 82% (P < 0.05) in the Met-choice 1, Met-choice 2, and the high-Met group, respectively. Piglets on the Met-choice 1 and Met-choice 2 groups, respectively, selected 72 and 80% of the higher Met diet. In the first week, piglets on both Met-choice groups selected the diets at random, but they increased their preference for the diets higher in Met up to 81 and 89%, respectively, in the last experimental week. For the total experiment, mean Met contents of total diets were 0.22 and 0.25% in the Met-choice 1 and Met-choice 2 groups, respectively. Average daily gain of 195 g in the low-Met group was more than doubled (P < 0.05) in the high-Met group. Daily gains of 306 and 366 g in the Met-choice 1 and 2 groups, respectively, were (P < 0.05) improved compared with the low-Met group but lower (P < 0.05) than in the high-Met group. Plasma Met concentration of 46.3 micromol/mL in the Met-choice 2 group was greater than in the low-Met or the Met-choice 1 groups (25.3 and 32.8 micromol/mL, respectively) but lower (P < 0.05) compared with the high-Met group (59.6 micromol/mL). Conversely, the sum of essential AA showed a greater (P < 0.05) concentration in plasma from pigs on the low-Met and Met-choice 1 groups than in plasma from pigs on Met-choice 2 group and the high-Met group. In conclusion, the present data demonstrate that piglets are able to discriminate among diets of varying Met content. When given a choice, they prefer a diet better balanced for Met to a Met-deficient diet. As a result of the altered feeding pattern, piglets are able to partly redress the depressed performance and altered plasma AA pattern resulting from the ingestion of the diet more limiting in Met concentration.

Influence of Dietary Sodium Level on Utilization of Methionine from DL-Methionine and Liquid Methionine-Hydroxy Analogue

A study was conducted to determine if dietary Na levels influenced the utilization of 2 different sources of supplemental Met in diets for male broilers. A Met-deficient diet (0.33% Met by analysis) based on grain sorghum and soybean meal was fortified with either DL-methionine (DL-Met) or the liquid form of 2-hydroxy-4-methylbutanoic acid (HMB) to provide supplemental levels of Met ranging from 0.0 to 0.28% in increments of 0.04%. Using sodium bicarbonate as a variable, dietary Na levels were 0.15, 0.20, and 0.25% with a constant Cl level of 0.20%. The experimental treatments consisted of a 2 × 3 × 8 factorial arrangement with 2 Met sources (DL-Met and HMB), 3 Na levels (0.15, 0.20, and 0.25%), and 8 levels of supplemental Met (0, 0.04, 0.08, 0.12, 0.16, 0.20, 0.24, and 0.28%) for a total of 48 treatments. Each treatment was fed to 6 replicate pens of 5 male broilers from 1 to 21 d of age.There was no significant effect of Met source on BW, feed conversion, or mortality. Both Met level and Na level significantly affected these factors, with a significant interaction between Met level and Na level for both BW and feed conversion. Feeding the higher levels of Na at lower levels of Met supplementation had adverse effects on both BW and feed conversion, independent of source of supplemental Met. Results of this study indicated that in practical diets using equivalent levels of fortification, no significant differences were detectable in the utilization of the 2 sources of Met.

Effects of Intestinal Modification by Antibiotics and Antibacterials on Utilization of Methionine Sources by Broiler Chickens

A study was conducted to determine if the response to different sources of Met was influenced by the presence or absence of antibiotics and antibacterials that might alter intestinal microflora. A Met-deficient diet (0.33% by analysis), based on corn and soybean meal, was fed with or without a mixture providing 200 g/ton of bacitracin methylene disalicylate, 200 g/ton of chlortetracycline, 100 g/ton of penicillin, and 100 g/ton of sulfaquinoxaline. Diets were fortified with DL-Met or the liquid form of 2-hydroxy-4-methylbutanoic acid (HMB) to provide supplemental levels of Met ranging from 0.0 to 0.20% in increments of 0.04%, based on 99% activity for DLDL-Met and 88% activity for HMB. The experimental treatments consisted of a 2 × 2 × 6 factorial arrangement of treatments with 2 diet types (medicated and unmedicated), 2 Met sources (DL-Met and HMB) at 6 levels of supplementation for a total of 24 dietary treatments. Each of these was fed to 6 replicate pens of 5 male chicks from 0 to 21 d, stratified across tiers in the battery.Feeding the medicated diets resulted in a significant reduction in intestinal bacterial as measured by total aerobic plate count of ileal contents, with significant improvements in BW and feed conversion. However, there were no significant interactions between the medications and the response to the 2 sources of Met. There was no difference in BW or feed conversion related to the 2 different sources of Met when fed to provide equimolar amounts of Met activity. Chicks responded to increasing levels of Met, but there was no interaction between source and level of Met for BW or feed conversion. Peak response appeared to occur at approximately 0.08% supplemental (0.41% total) Met, somewhat below current NRC recommendations. It does not appear that a difference in antibiotic content of test diets is responsible for the discrepancy in reported responses to the 2 sources of Met.

Effects of methionine deficiencies on plasma levels of thyroid hormones, insulin-like growth factors-I and -II, liver and body weights, and feed intake in growing chickens

We showed previously that Met deficiency at 0.25% of the diet causes elevations in plasma triiodothyronine (T3) in broilers. In the present study, plasma levels of thyroid hormones as well as insulin-like growth factors (IGF)-I and -II were measured in chicks fed 3 deficient levels of total Met. Control (0.5%) and Met-deficient diets (0.4, 0.3, and 0.2%) were fed to male broilers from 8 to 22 d of age. Additional groups of control chicks were pair-fed with the Met-deficient ones. Chicks receiving 0.4% Met increased feed intake by 10% with no significant change in body weight. The more severe Met deficiencies of 0.3 and 0.2% caused graded reductions in feed intake and weight gain. However, corresponding pair-fed control chicks were significantly heavier. These changes suggest more marked alterations in metabolic processes with 0.3 and 0.2% Met than with 0.4% Met. Liver weights were heavier in chicks fed 0.3 and 0.2% Met but not 0.4%. Plasma T3 was higher in all deficient chicks compared with the free-fed control, which was significant only with 0.3% Met. However, with 0.3 and 0.2% Met, plasma T3 was significantly elevated compared to pair-fed controls. Plasma thyroxine (T4) was lower in all deficient groups, which was significant only with 0.2% Met, whereas no significant differences occurred between deficient chicks and their pair-fed controls. Plasma IGF-I levels were not significantly different, but they were consistently lower in deficient chicks and deserve further study. Plasma IGF-II was significantly less in chicks fed 0.2% Met compared to pair-fed controls suggesting that Met deficiency interferes with IGF-II metabolism. We concluded that a deficit of dietary Met altered plasma T3 and IGF-II levels, but the effect was dependent on the degree of deficiency.