Absorption Of Methionine Research Articles

Assessing seromuscular layer and serosa removal on intestinal permeability measurements in weaned piglet everted sac segments.

The integrity of the intestinal barrier is crucial for regulating the passage of pathogens and toxins, while facilitating nutrient absorption. The everted gut sac technique, an ex-vivo technique, can be used to study interventions on barrier function. This cost-effective approach utilizes relatively large gut segments to study specific intestinal regions. Typically, intact (non-stripped) intestinal segments are used, but their use may underestimate permeability due to the medial positioning of blood vessels relative to the seromuscular layer and serosa. However, removing these layers risks physical damage, resulting in an overestimation of intestinal permeability. Therefore, we investigated the impact of stripping jejunal segments on permeability to fluorescein isothiocyanate-dextran (FITC, 4kDa) and tetramethylrhodamine isothiocyanate-dextran (TRITC, 40kDa), and on the absorption of glucose, lysine, and methionine in jejunal segments from 80 piglets at 8 d postweaning. Piglets were subjected to either high or low sanitary housing conditions and diets provoking intestinal protein fermentation or not, expected to influence intestinal permeability. Stripping of the seromuscular layer and serosa increased the passage of 4kDa FITC-dextran (stripped vs. non-stripped; 1.1 vs. 0.9 pmol/cm2/min, P < 0.001), glucose (40.0 vs. 19.1 pmol/cm2/min, P < 0.001), lysine (2.5 vs. 2.0 nmol/cm2/min, P < 0.001), and methionine (4.1 vs. 2.7 pmol/cm2/min, P < 0.001). As permeability increased, the differences in methionine passage between stripped and non-stripped intestinal segments also increased (slope = 1.30, P = 0.009). The coefficients of variation were comparable between stripped and non-stripped intestines (over all treatments, stripped vs. non-stripped 38% vs. 40%). Stripping, by isolating mucosal processes without introducing additional variation, is thus recommended for studies on intestinal permeability or absorption.

Absorption of methionine sources in animals-is there more to know?

This literature review evaluates the absorption of methionine (Met) sources such as 2-hydroxy-4-methylthiobutyric acid (HMTBa), its calcium salts (HMTBa-Ca), and DL-methionine (DL-Met) by focusing on the state of knowledge regarding the absorption mechanism, experimental methodology, and factors affecting their absorption. The 2 Met sources differ in mechanism and site of absorption due to differences in their chemical characteristics and enzymatic conversion. This review addresses diffusion- and transport-mediated absorption systems for amino acids and carboxylic compounds, best elucidated by invitro, exvivo, and invivo experimental models. Opportunities and limitations in the use of radioisotopes to depict absorption sites as well as host and microbial metabolism are described. Physiological and environmental conditions that lead to changes in gut absorptive capacity and the impact of Met source absorption are also evaluated. This review concludes that any comparison between HMTBa and DL-Met should consider their different behaviors during the absorption phase. Hence, the chemical characteristics of these 2 molecules entail different absorption sites and mechanisms, from passive absorption in the case of HMTBa and HMTBa-Ca to active transporters for DL-Met, HMTBa, and HMTBa-Ca. In addition, the different conversion modes of these 2 molecules further differentiate their absorption modes. Considering these important differences, it is easier to understand the apparent divergence between the conclusions of existing publications. When comparing these 2 molecules, it is recommended to properly adapt to the conditions under which the absorption of Met sources is evaluated.

Methionine in Poultry Nutrition: A Review

Methionine is an essential amino acid which is commonly used as a supplement in poultry diets. Multiple systems are involved in the absorption and transportation of liquid and powder Methionine in the segment of the jejunum. Methionine supplementation in a low-protein diet alleviates the negative effects of heat stress and improves the performance of chickens. The supplementation of the synthetic Methionine improves the amino acid balance and consequently promotes growth performance by enhancing quantity and quality of egg production, feed efficiency, and protein synthesis, as well as decreasing fat synthesis in poultry breeds (Broiler Chicken, Laying hen, Turkey, Duck, Guinea fowl, Quail breeder, and Gees). Methionine supplementation also improves the immune response through the direct effects on protein synthesis and breakdown and indirect effects on the derivatives of Methionine. The variables, such as growing period, type of production, sex, and breed, influence the Methionine requirement. Moreover, the Methionine requirement expressed as a percentage of diet declines during the starter and grower phases.

Evaluation of the Absorption of Methionine Carried by Mineral Clays and Zeolites in Porcine Ex Vivo Permeability Models

Supplemental dietary amino acids (AAs) need to be provided in a form that prevents their degradation along the gastrointestinal tract to guarantee their high bioavailability and bioactivity. In this study, methionine (Met) protected via organo-clay intercalation (natural carriers) has been developed as a sustainable alternative to polymeric coating. Specifically, two different bentonite-zeolite-based mineral clays were tested, Adsorbene (ADS) and BioKi (BIO). Briefly, 1 g of the carrier (ADS or BIO) was contacted with 50 mL of an aqueous solution at a pH of 3.0, 5.8, and 8.9. Solid-liquid separation was conducted. The released Met in the liquid phase was analysed by Chemical Oxygen Demand, while residual Met in the solid phase was analysed by Fourier Transform Infra-Red (FT-IR) spectroscopy. The effect of Met-ADS complex on cell viability was tested on IPEC-J2 cells incubated 3 h with Met-ADS 2.5 mM. Jejunum segments obtained by entire male pigs (Swiss Large White, body weight 100 ± 5 kg) were used as ex vivo models to compare the absorption of 2.5 mM Met released by ADS with 2.5 mM free Met and its influence on epithelial integrity in perfusion Ussing chambers. The carriers released a very low amount of Met and Met-BIO interaction was stronger than Met-ADS. The maximum release of Met was at pH 3, with 3% and 6% of Met release from Met-BIO and Met-ADS, respectively. Cell viability experiments revealed that Met-ADS did not alter cell metabolic activity. No differences in Met absorption and intestinal epithelial integrity were observed ex vivo between free Met and Met-ADS. This study provided new insights into the release of Met from natural clays such as ADS and BIO, the safety of its use in the porcine intestine and the ability of ADS-released Met to absorb to the same extent as the free Met in porcine jejunum.

Putative imbalanced amino acid metabolism in rainbow trout long term fed a plant-based diet as revealed by 1H-NMR metabolomics.

The long-term effect of a plant (P)-based diet was assessed by proton nuclear magnetic resonance (1H-NMR) metabolomics in rainbow trout fed a marine fish meal (FM)-fish oil (FO) diet (M), a P-based diet and a control commercial-like diet (C) starting with the first feeding. Growth performances were not heavily altered by long-term feeding on the P-based diet. An 1H-NMR metabolomic analysis of the feed revealed significantly different soluble chemical compound profiles between the diets. A set of soluble chemical compounds was found to be specific either to the P-based diet or to the M diet. Pterin, a biomarker of plant feedstuffs, was identified both in the P-based diet and in the plasma of fish fed the P-based diet. 1H-NMR metabolomic analysis on fish plasma and liver and muscle tissues at 6 and 48 h post feeding revealed significantly different profiles between the P-based diet and the M diet, while the C diet showed intermediate results. A higher amino acid content was found in the plasma of fish fed the P-based diet compared with the M diet after 48 h, suggesting either a delayed delivery of the amino acids or a lower amino acid utilisation in the P-based diet. This was associated with an accumulation of essential amino acids and the depletion of glutamine in the muscle, together with an accumulation of choline in the liver. Combined with an anticipated absorption of methionine and lysine supplemented in free form, the present results suggest an imbalanced essential amino acid supply for protein metabolism in the muscle and for specific functions of the liver.

Characterization of methionine uptake and clearance in the hemolymph of Pacific white shrimp Litopenaeus vannamei

A series of feeding trials were conducted to investigate the absorption rate of amino acids and compare the absorption of different methionine (Met) sources in the hemolymph of Pacific White shrimp, Litopenaeus vannamei. In trial 1, a basal diet was supplemented with three alpha amino acids including DL-Met, lysine and arginine and the beta amino acid taurine. Shrimp were fed with test diets for 30 mins and then the leftover feeds were withdrawn. The hemolymph samples were taken every 30 mins over 5 h after feeding to determine amino acid (AA) concentrations in the hemolymph. Results indicated that total AA, Met and Lys were near their peak after feeding 30 mins and the level declined within 60 mins to near fasting levels. No secondary peaks were observed for any AA. The diet supplemented with AA exhibited higher peaks than the basal diet. The second and third trials focused on the identification of different patterns that would indicate asynchronous absorption and comparison of the absorption of different Met sources. Four experimental diets were produced, including a basal diet (soy protein-based), a DL-Met-supplemented, a dipeptide Met (Met-Met)-supplemented, and a high fishmeal diet (high-Met intact protein) in trial 2. Fasted shrimp were offered diets for 15 mins and then the leftover feeds were removed. The hemolymph samples were taken every 15 mins over a 1 h period after feeding. The results generally confirmed the fast absorption and clearance of AA in shrimp and indicated that the diets containing different Met sources resulted in higher Met levels in the hemolymph as compared to the basal diet. To better define the absorption process and confirm if there may be a synchronous peak during absorption, the third trial simply looked at the uptake of AA over a 1 h period with basal diet and dipeptide Met diet. The shrimp were offered diets for a total of 60 mins during this timeframe intermittent samples were taken at 0, 5, 10, 15, 20, 30, and 60 mins. Results demonstrated the pattern for AA uptake is similar with a clear upswing in AA levels in 10–15 mins after the initiation of feeding. Based on both absorption and clearance patterns of the amino acids, we demonstrated that there were no indications of asynchronous absorption of supplemented amino acids; hence, supplemented amino acids are available for metabolism. In addition, the data also demonstrated higher peak of Met over time in the hemolymph of L. vannamei with the Met-Met supplemented diet versus the DL-Met supplemented diet.

Studies on absorption of nutrients using intestinal sacs of rats fed on different diets

Absorption of glucose, sucrose, glutamic acid and methionine was studied using the intestinal everted sac technique. Rats were fed with potato tubers of Kufri Ashoka, Kufri Chipsona-1 and Kufri Chipsona-2 in combination with casein in 1:1 ratio and casein as a control at eight per cent, protein level. Absorption of sucrose, glucose, glutamic acid and methionine was monitored spectrophotometrically and of glucose, sucrose and glutamic acid by 14C radio assay using scintillation counting. In general, glutamic acid showed higher absorption values than glucose, sucrose and methionine by both the techniques. Rats fed on casein diet exhibited maximum absorption of glutamic acid and methionine. Incorporation of 10 ?mole of lithium decreased considerably the absorption of glucose, sucrose, glutamic acid and methionine. Absorption of nutrients differed between casein and casein-potato tubers diets.

Measurement of the S-adenosyl methionine (SAMe) content in a range of commercial veterinary SAMe supplements.

To measure the percentage of the stated amount of S-adenosyl methionine present in a range of commercially available S-adenosyl methionine supplements for veterinary use. Sixty-four samples of products containing S-adenosyl methionine marketed to support liver function were obtained from five manufacturers via three commercial wholesalers. The amount of S-adenosyl methionine in each product was measured using high-pressure liquid chromatography. There were greater than threefold variation in the percentage of measured S-adenosyl methionine compared to the stated amount on the packaging which was significantly (P < 0 · 001) related to the product group being measured. Differences in received dose of S-adenosyl methionine between different products were marked and this could have a profound influence on studies that evaluate any variation in absorption of S-adenosyl methionine between different product formulations, the effectiveness of S-adenosyl methionine-based products in clinical cases or when translating the results of studies that have used a specific S-adenosyl methionine product to those produced by a different manufacturer.

Intestinal absorption of nutrients using rats fed different diets

Absorption of glucose, sucrose, glutamic acid, methionine, lysine and cysteine was studied using the intestinal everted sac technique. Rats were fed rice diets Basmati 370, Pusa Basmati 1 and Haryana Basmati 1 using as a casein control. Absorption of nutrients was monitored spectrophotometrically and of glucose, sucrose and glutamic acid by 14c radio assay using scintillation counting. Positive correlation coefficients between the two assay methods for glucose (r = 0.84), sucrose (r = 0.38) and glutamic acid (r = 0.80) were observed. Glucose showed higher absorption than sucrose and glutamic acid than lysine, cysteine and methionine. Absorption of glucose, sucrose and glutamic acid were higher in rats fed on Haryana Basmati 1 diet as demonstrated by both the methods. Rats on Basmati 370 diet exhibited higher methionine, lysine and cysteine absorption. Absorption of nutrients differed significantly between casein and rice.

Effect of dietary sodium on digestibility of nutrients and performance in growing rabbits.

The effects of a reduction in the sodium content from 2.6 to 1.6 g/kg DM in diets with similarelectrolyte balance on fattening performances and ileal apparent digestibility of nutrients were investigated inearly weaned rabbits. Two diets containing 17.9% DM of crude protein, with the same composition and onlydiffering in sodium chloride content (0.5 and 0.2%) were given to rabbits weaned at 25 days to measurefattening performance (46 rabbits per diet), and apparent ileal digestibility (AID, 14 rabbits per diet) of DM,crude protein (CP) and amino acids (AA). Neither AID of DM nor AID of CP, which amounted 47.4 and 60.9% asaverage respectively, were affected by the dietary sodium content. The effect of a decrease in dietary sodiumconcentration on the AID differed among amino acids, as a reduction was observed for cystine (by 11%;P&lt;0.01), methionine, arginine, tyrosine and phenylalanine (by 4.9, 5.6, 7.4 and 10.3%; respectively P&lt;0.05),glutamic acid, leucine and isoleucine (by 4.1, 6.1 and 7.1%, respectively P&lt;0.1), whereas no differences(P&gt;0.10) were detected for the other amino acids. A reduction of dietary sodium content did not affect dailyweight gain, feed intake and feed efficiency (46.7 g/d, 76.7 g/d and 0.609 as average, respectively) neitherduring the first two weeks after weaning when the experimental diets were used, nor when the wholefattening period was regarded. The results of this experiment indicate that is possible to reduce the currentdietary sodium recommendations for fattening rabbits to 1.6 g/kg DM during the first two weeks after weaning,without impairing either the fattening performances or the ileal digestibility of DM and CP. In addition, this studyindicate that the level of sodium in the diet affects the gut absorption of methionine and cystine and severalnon-essential AA.

Competition between selenomethionine and methionine absorption in the intestinal tract of green sturgeon ( Acipenser medirostris)

l-Selenomethionine (SeMet) is a dominant form of selenium (Se) found in organisms at all levels of aquatic food chains and a key source of Se bioaccumulation and ecotoxicity. In mammals, intestinal absorption of SeMet is at least partly via the Na +-dependent neutral amino acid transporter. The mechanism of SeMet absorption and competitive effects of other dietary components on SeMet absorption in fish are unknown. Thus the in vitro uptake rates of l-methionine (Met) and the competitive effect of SeMet on Met absorption, an indicator that SeMet uses the same nutrient transporter(s) for absorption, in the various regions of the green sturgeon ( Acipenser medirostris) intestine were investigated using intact tissues (a modified everted sleeve method). Intestinal tissue was incubated in Ringer's solution containing 0–10 mmol L −1 Met or SeMet ( n = 5 for each substrate's concentration and intestinal region), respectively, as well as constant tracer levels of isotope-labeled Met. The data indicate that SeMet uptake was mediated by the same transporter(s) as Met and that the absorption kinetics were similar for both substrates. When there were differences in absorption they appeared to be mostly due to higher permeability (passive uptake) of the tissue for Met than for SeMet, particularly in the pyloric caeca (PC) and distal intestine (DI). Maximum rates of absorption, on the other hand, tended to be higher for SeMet than Met in the mid intestine and DI, whereas differences in affinity for the transporters varied between these tissues but were very similar in the PC. These differences may be due to differences in regional intestinal characteristics such as amount of mucus secreted and degree of tissue contraction, and/or substrate differences regarding solubility in and movement through the mucus, influence on tissue contraction, permeability through membranes or between cells, intracellular metabolism, as well as basolateral transport. Interestingly, an increasing proximal-to-distal gradient for rates of methionine and putative SeMet absorption was observed in green sturgeon which differs from the declining gradient usually observed for substrate absorption in other fish species and mammals.

Effect of pH on l- and d-methionine uptake across the apical membrane of Caco-2 cells

The transport systems involved in intestinal methionine (Met) absorption are described as Na(+)-dependent and Na(+)-independent mechanisms. However, since recent studies have suggested the importance of the H(+) gradient as a driving force for intestinal nutrient absorption, the aim of the present work was to test whether Met transport across the apical membrane of Caco-2 cells is affected by extracellular pH. The results show that l- and d-Met uptake was increased by lowering extracellular pH from 7.4 to 5.5, in both the presence and absence of Na(+). Cis-inhibition experiments revealed that inhibition of l-Met transport by 2-aminobicyclo[2,2,1]heptane-2-carboxylic acid (BCH) or l-lysine (l-Lys) was higher at a pH of 5.5. Moreover, the BCH-insensitive component was not affected by pH, whereas the l-Lys-insensitive component was increased by lowering extracellular pH, thus suggesting the participation of system L. The contribution of another mechanism, sensitive to both BCH and l-Lys, was also considered. The inhibition obtained with taurine (Tau) was also higher at a pH of 5.5, thus suggesting the involvement of system B(0,+) on pH-stimulated component. As for d-Met uptake, the results showed higher inhibition with l-Lys and Tau at a pH of 5.5 and no effect on the l-Lys- or Tau-insensitive component. In conclusion, Met transport across the apical membrane of Caco-2 cells is increased by low extracellular pH as the result of the stimulation of two transport systems functionally identified with systems L and B(0,+) for l-Met and with system B(0,+) for d-Met.

Apparent absorption of methionine and 2-hydroxy-4-methylthiobutanoic acid from gastrointestinal tract of conventional and gnotobiotic pigs

The effect of commensal microbiota and feeding corn or wheat/barley-based diets on the apparent gastrointestinal absorption of dl-methionine (MET) and 2-hydroxy-4-methylthiobutanoic acid (MHA-FA) was studied in conventional (n = 32) and gnotobiotic pigs (n = 24). Conventional pigs (CON) were vaginally delivered and sow-reared until weaning at 14 days of age. Gnotobiotic pigs were derived by caesarian section and reared in HEPA (high efficiency particulate air)-filtered isolator units with ad libitum access to a milk-based formula. Corn or wheat/barley-based diets were fed to all pigs from 14 to 24 days of age. At 24 days of age, after an overnight fast, pigs were fed 20 g/kg BW of experimental diet supplemented with 107 Bq of either 3H-l-MET or 3H-l-MHA-FA per kg of feed and chromic oxide (0.5% wt/wt). Pigs were killed for sample collection 3 h after consuming the meal. Residual 3H-MET and 3H-MHA-FA were estimated in gastrointestinal contents as the ratio of 3H : chromic oxide in digesta samples to the ratio of 3H : chromic oxide in feed. In CON pigs, feeding a wheat/barley-based diet increased (P < 0.05) total aerobes, whereas supplementation with MHA-FA increased (P < 0.05) total aerobes and lactobacilli populations in proximal small intestine (SI). Among the gnotobiotic pigs, bacterial contamination occurred such that eight pigs (two isolators) were monoassociated with a Gram-negative bacteria closely related to Providencia spp. and 16 pigs (four isolators) were monoassociated with Gram positive Enterococcus faecium. Species of monoassociated bacterial contaminant and diet composition did not affect residual methionine or MHA-FA in digesta. In both CON and monoassociated (MA) pigs, methionine and MHA-FA were retained in stomach (92%) but disappeared rapidly from proximal SI. Residual methionine and MHA-FA in digesta was not different in MA pigs; however, in CON pigs, less (P < 0.01) apparent residual methionine was found in digesta recovered at 25% (from cranial to caudal) and 75% of SI length compared with MHA-FA. Apparent residual methionine was 16% and 8% compared with 34% and 15% for MHA-FA, at the 25% and 75% locations, respectively. In proximal SI tissue, significantly (P < 0.05) higher radioactivity (cpm/mg wet tissue) was associated with MET pigs (8.56 ± 0.47) as compared to MHA-FA ones (5.45 ± 0.50). This study suggests that microbial metabolism of MHA-FA increases retention in small intestinal digesta relative to methionine and contributes, in part, to the lower bioefficacy of MHA-FA compared to methionine.

Equilibrium sorption of methionine on carboxyl cation exchangers from solutions of various acidities

The influence of the acidity of solutions of methionine on methionine interaction with KB-2 and KB-4 carboxyl cation exchangers in the protonated and deprotonated forms was studied by the calorimetric, sorption, and spectroscopic methods. It was found that nonexchange methionine absorption occurred from acid solutions, and mixed ion exchange and nonexchange sorption, from alkaline solutions. The enthalpies of sorption of methionine at various external solution pH values were determined.

Dietary amino acids fed in free form or as protein do differently affect amino acid absorption in a rat everted sac model

In the present study, the effect of free amino acid (FAA) diets on the intestinal absorption rate of methionine and leucine was studied 'ex vivo' with rats adapted for different periods of time to the diets, using the everted sac method. The adaptation period to the 21% FAA diet with an amino acid content based on casein was either, 0 (no adaptation, N-ADA), 5 (short-term adaptation, ST-ADA), or 26-33 days (long-term adaptation, LT-ADA). Within the ST-ADA and the LT-ADA groups, three different levels of methionine were included: 50%, 100% and 200% of the level normally present in casein. All diets were iso-nitrogenous and iso-caloric. After the adaptation period (0, 5, or 26-33 days), intestinal everted sacs were prepared. Methionine or leucine was added to the medium as transport substrate. The methionine absorption rate of the rats of the LT-ADA groups was higher than that of the N-ADA groups. Furthermore, adaptation to 200% dietary methionine levels caused a significantly slower leucine absorption compared to the 100%, and 50% group. Methionine absorption was similar in the 100% and 200% groups, but the absorption of methionine in the 50% group was enhanced in the distal part of the intestines. We concluded that in response diets with 21% FAAs as only amino acid source, amino acid absorption is decreased to avoid toxic effects of high levels of methionine in the circulation.

우모분 및 우모분 Digest 첨가가 우유 내 Taurine 함량에 미치는 영향

This study, consisting of three experiments, was conducted to determine the effects of feeding feather meal (FM), feather meal digest (FMD), L-cystine and methionine hydroxyl analogue (MHA) on taurine content of milk and milk production of Holstein dairy cows. In experiment 1, FM or FMD was supplemented at 0, 1, 3 and 5% of dry matter intake (DMI), respectively. Taurine concentration of 3% FM and 5% FMD treatment were increased by 14% and 220/0, respectively. The 5% FM treatment had a negative effect on milk yield and FM and FMD treatments had no significant or consistent effects on milk fat, protein, lactose, milk urea nitrogen (MUN) and somatic cell count (SCC). In experiment 2, Lcystine or MHA was supplemented at 0, 1, 3, and 5g or ml/d along with 5% FMD, respectively. Milk yield decreased at 3 and 5g or ml Lcystine or MHA supplementation along with 5% FMD. Fat and lactose in milk were not significantly affected by treatments. However, milk protein level increased significantly in the 5 ml HMA with 5% FMD treatment. SCC decreased significantly in 1ml MHA with 5% FMD supplemented treatment but increased in 5g Lcystine with 5% FMD and 5 ml MHA with 5% FMD treatments. Increase of milk taurine concentration of L'cystine with 5% FMD treatments was not significant but those of MHA with 5% FMD treatments were significantly higher than the control. The highest increase of milk taurine concentration was 65% shown in 1 ml MHA with 5% FMD treatment. In experiment 3, 5% FM, 5% FM+3% molasses or 5% FM+3% molasses+l ml MHA was supplemented to the based TMR diet. The molasses treatments (5% FM+3% molasses and 5% FM+3% molasses+l ml MHA) showed significantly higher milk taurine content than the 5% FM treatment. The molasses treatments significantly reduced MUN but increased SCC. It was concluded that FMD is more effective than FM in enriching taurine in milk. Maximum taurine enrichment (65%) in the milk was obtained by supplementation of 5% FMD/DM1+1 ml MHA/d/cow. Molasses supplementation to 5% FM diet increased milk taurine content. However, MHA supplementation in dairy cows increased ruminal escape, gastrointestinal absorption and response of serum methionine.

Coating crystalline methionine with tripalmitin-polyvinyl alcohol slows its absorption in the intestine of Nile tilapia, Oreochromis niloticus

Supplemental free amino acids (FAA) can be used to satisfy dietary amino acid requirements when plant products replace fish meal and other animal byproducts in formulated diets. Use of coated FAA in diets could provide benefits by slowing the rate of FAA absorption and perhaps by increasing utilization efficiency. A laboratory feeding trial was conducted to determine the effect of two coatings—tripalmitin-polyvinyl alcohol (TPA) and cellulose-acetate-phthalate (CAP)—on absorption of supplemental methionine by Nile tilapia. Forty-five adult fish (mean weight, 185 g) were stocked individually in 5-l aquaria and fed one of three, semipurified diets containing uncoated l-[ 35S]methionine (UM) or TPA- or CAP-coated methionine as 50% of the dietary sulfur amino acid requirement. Three fish were taken from each treatment 0.5, 1, 3, 6, and 12 h after force-feeding to measure relative rates of 35S uptake and the amount of 35S-activity in intestinal tissues, liver, spleen, muscle, and blood plasma. Methionine uptake was highest in the foregut area, but absorption appeared to occur throughout the length of the intestine, including the hindgut. TPA-coated methionine was absorbed more slowly than uncoated methionine and fish fed with TPA-coated methionine had significantly lower levels of 35S-activity in tissues than fish fed with UM. Activity of labeled methionine in tissues of fish fed with CAP-coated methionine usually was not significantly different from 35S-activity in fish fed with UM. The TPA coating appeared to effectively slow the absorption of free methionine in the gut of Nile tilapia, but additional work is needed to determine if TPA-coated methionine is utilized more efficiently than the uncoated amino acid.

Absorption of methionine and 2-hydroxy-4-methylthiobutoanic acid in conventional and germ-free chickens

The apparent absorption of 3H-labeled L-Met and L-2-hydroxy-4-methylthiobutoanic acid (MHA-FA) was compared in germ-free and conventional broiler chickens to determine the effect of intestinal bacteria on the absorption of Met and MHA-FA. The two diets contained 0.236% of added Met or MHA-FA. Nineteen germ-free birds were maintained in two isolators and fed diets that had been sterilized by gamma irradiation (50 kilogreys). Nineteen conventional birds were reared in batteries and received nonirradiated feed. Diets were fed ad libitum for 3 wk. On d 21 of the experiment, the birds fasted overnight and were refed the experimental diets to which 1.11 × 10(7) Bq of 1-[methyl3H]MHA-FA or 1-[methyl3H]Met/kg of feed had been added. 51CrCl3 (1.11 × 10(7) Bq/kg of feed) was added as an indigestible marker. After 3 h the birds were euthanized, and their intestinal tracts were removed and partitioned into six sections. Residual Met and MHA-FA in digesta were calculated as the ratio of 3H:51Cr in each sample divided by the ratio of 3H:51Cr in the feed. The residual MHA-FA in the distal ileum of germ-free broilers was lower than in conventional birds (4.7 and 10.2% respectively; P < 0.05). In contrast the residual Met in the distal ileum of germ-free broilers was not different than in conventional birds (3.0 and 3.7% respectively; P > 0.05). This study demonstrates that intestinal bacteria significantly reduce the apparent absorption of MHA-FA from the intestinal tract of broiler chickens.

Response of nitrogen metabolism in preparturient dairy cows to methionine supplementation.

Three multiparous Holstein cows (607 kg of BW) were surgically prepared with an elevated carotid artery and indwelling catheters in the hepatic, portal, and two mesenteric veins to study the effects of methionine supplementation on amino acid metabolism during the last 2 wk of pregnancy. The study began 15 d before the expected calving date. Dietary treatments were Control (1.53 Mcal NE(l)/kg, 15.6% CP, and 40% ruminally undegradable protein) and Control supplemented with 60 g/d of ruminally protected methionine (MET, supplying 39 g/d of DL-methionine and approximately 18 g/d of methionine available for intestinal absorption). Each cow received both dietary treatments in a crossover design. Cows were fed once daily. After 5 d on treatment, a blood flow marker (para-aminohippurate) was infused into a mesenteric vein, and arterial, portal, and hepatic blood samples were obtained at 0, 2, 6, 12, and 18 h after feeding. Net flux of methionine was calculated as the plasma arteriovenous difference multiplied by plasma flow. Dry matter intake (10.8 kg/d) and portal (824 L/h) and hepatic (995 L/h) plasma flows were not affected (P > .10) by treatment. Arterial plasma concentration of methionine was greater (P = .10) with MET (27.67 microM) than with Control (16.42 microM). Net portal absorption of methionine increased (P = .10) with MET (26.2 g/d) compared with Control (9.5 g/d). The net portal methionine flux was negatively correlated (r = -.59; P < .001) with arterial urea concentrations. Net flux of methionine across splanchnic tissues shifted (P = .06) from a net uptake with Control (4 g/d) to a net output with MET (11 g/d). Therefore, MET increased by 15 g/d the methionine supply to the rest of the body. The net uptake of methionine by splanchnic tissues observed with Control indicated a net mobilization of methionine by peripheral tissues. Results indicate that methionine was the limiting amino acid with Control and that MET was beneficial because it increased methionine supply to peripheral tissues and reduced arterial urea concentrations.

Ruminal escape, gastrointestinal absorption, and response of serum methionine to supplementation of liquid methionine hydroxy analog in dairy cows.

Availability of liquid methionine hydroxy analog [D,L-2-hydroxy-4-(methylthio)-butanoic acid] was evaluated in two experiments using four cannulated lactating dairy cows. The first experiment was designed as a 4 x 4 Latin square. Each cow received a pulse dose of 0, 30, 60, or 90 g of the methionine analog in the rumen each day for 10 d. Duodenal samples were collected at 16, 20, and 24 h after dosing for the last 5 d and pooled. The methionine analog was not detected in duodenal contents because it passed rapidly from the rumen relative to the sampling protocol. In the second experiment, cows were offered 90 g of the methionine analog and 600 ml of Cr-EDTA (3.5 g of Cr) mixed with ground corn for a period of 20 min after which any remains of the treatment were placed in the rumen. The concentration of the analog peaked in ruminal and duodenal fluid at 1 and 3 h, respectively. Based on the fractional rate constants for ruminal and duodenal disappearance of the methionine analog and passage of the liquid, it was determined that 50.0 +/- 2.8% of the methionine analog escaped ruminal degradation and became available for intestinal absorption (44.6 +/- 5.7%) or was absorbed from the omasum (5.4 +/- 3.3%). Serum methionine concentration peaked 6 h after analog dosing at a level that was three times the predose level, indicating that the methionine analog that escaped ruminal degradation was absorbed and metabolized to methionine.