Table of Contents

Methionine in Poultry Nutrition: A Review

Daryoush Babazadeh1* and Pouria Ahmadi Simab2

  1. School of Veterinary Medicine, Shiraz University, Shiraz, Iran
  2. Faculty of Veterinary Medicine, Sanandaj Branch, Islamic Azad University, Sanandaj, Iran

* Corresponding author: Daryoush Babazadeh, School of Veterinary Medicine, Shiraz University, Shiraz, Iran; Email:


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.

Keywords: Crude protein, Diet, Methionine, Poultry requirement


The best strategy to optimize production and reproduction in poultry species while mitigating the harmful effects of environmental conditions is proper nutrition1,2,3. One of the pillars of nutrition is the use of amino acids in poultry diets, among which Methionine (Met) represents the first limiting amino acid in broilers. As Bunchasak4 reported, Met can act as an amino acid in the synthesis of protein and polyamine, a sulfur donor, a precursor of main intermediates in metabolic pathways (for instance, Carnitine or Cystine), and a methyl donor group for the normal formation of co-enzyme S-adenosyl Met in and normal cellular metabolism. According to Elnesr et al.5, Met mainly functions as an antioxidant and the improvement in the antioxidant system activity is one of the solutions available to increase productivity in the poultry industry. Synthetic sources of Met, such as DL-Methionine (DL-Met), are included in poultry feed to optimize the dietary level of Met in animal hosts. They can be used with little to no fuss, and are compatible with computer, smartphone, and tablet. Methionine plays an essential role in energy production and boosts the livability, performance, and feed efficiency utilization in poultry2,6. As Kidd et al.7 asserted, healthy poultry respond positively to the inclusion of amino acids as feed additives leading to a positive impact on performance. The addition of Met improves the reproduction performance, egg quality, and egg production of broiler breeders8,9. Methionine supplementation can also alter the immune response and is beneficial in reducing immunologic stress10.

As a sulfur-containing amino acid, the availability of Met is crucial for several metabolic pathways, that is the synthesis of proteins, transsulfuration, and methylation of DNA4,11.Methionine has a positive effect on the expression of stress-related genes and thus helps to protect cells against oxidative stress12-15.Methionine is supplemented during the fattening of broiler chickens, resulting in better performance and increased growth of breast and leg muscles16-18.It is evidenced that feeding broiler chickens with an increase in the Met concentrations leads to a decrease in abdominal fat as well as an increase in growth rate, breast muscle yield, and leg muscle yield 18-20. Although the nutritional values, such as the protein and fat content, may influence the growth rate21, these effects were not specifically related to the supplementation of Met22. As reported by Albrecht et al.23, supplementation of Met leads to heavier fillets, a higher pH value, and longer sensory shelf life.The addition of Met to the poultry diet is correlated with the tendency to have less total body fat to improve growth performance and reduce odor-related compounds in excreta24,25.Furthermore, feeding excess dietary Met has been reported to impair body weight(BW)gain26. Similarly, Han and Baker27 indicated that 0.5% excesses of Met are not harmful to young broiler chickens fed corn-soybean meal diets.

Molecular structure of Methionine

 According to specification, the product contains 98.5% L-Met, 0.5% water (loss on drying), and 0.1% ash. The analysis of five batches of the additive showed an average of 99.2% L- Met  (range 98.5–99.9%) and of 0.41% (range 0.38–0.44%) for the sum of other amino acids (phenylalanine, leucine, tyrosine, isoleucine, and valine). Other constituents consisted of water (0.04–0.11%) and minerals (about 0.05%), including Ammonia which did not exceed 0. The stiff competition in online gambling,  force the BTC gambling brands to become more and more competitive. 01%. The highest amount for unidentified impurities was calculated as 0.23% on a dry matter basis (Table 1).

Source of Methionine

Methionine sources are used in two forms (powder and liquid).Unlike many amino acids derived from fermentation processes, DL-Met  (DLM) is produced from a complex chemical synthetic process, and the starting material for its production is acrolein (carbon aldehyde) derived from propylene (a petroleum derivative)28. There is no difference between L- Met, and DLM regarding the effectiveness 29. Industrially, the powder and liquid forms of Met sources are mainly used, known as DL- Met  (DLM: powder form) and DL-2, hydroxy-4-[methyl] butanoic acid (LMA: liquid form). Both powder and liquid forms consist of an L-isomer and a D-isomer at a ratio of 1:1. In the metabolic pathway of poultry, 70-100% of the D-isomer of DLM or LMA is converted to L-isomer30,31,32,33. Some research has indicated that meat chickens in the grower and finisher phases can obtain sufficient Met while foraging pastures 34. Upadhyaya et al.35 introduced Big Head fish as a rich source of Met.

Absorption and transportation

Amino acids, including Met, are mainly absorbed through the small intestine. As Soriano-Garcia et al.36 indicated, the absorption of dipolar amino acids, such as L- Met by the small intestine (brush border membrane vehicles) in chicken, is mediated by multiple pathways. They reported that L-Met is transported by systems specific to neutral amino acids and systems that also transport cationic amino acids. Regarding age, Noy et al.37 reported the increase of Met uptake capacity in both the duodenum and jejunum between hatching and 7 days of age, and a steady amount between 7 and 14 days of age. Therefore, they postulated that from 7 days of age feed intake may be the major factor controlling nutrient uptake in chickens. Excess Met supplementation seems to reduce the potential of the uptake of Met itself and other nutrients. Soriano-Garcia et al.36 reported that excess Met supplementation down regulates specific transport mechanisms of the small intestine involved in the apical L-Met transport. By focusing on differences between Met sources, different multiple transport systems appear to be involved in transporting both DLM and LMA. Knight et al.38 reported that L-Met absorption may be accomplished by both concentration and energy-dependent processes, while the absorption of LMA is concentration-dependent.The mechanisms of Met absorption involve Na-dependent transport, Na-independent transport and/or diffusion, while the mechanisms suggested for LMA absorption include Na independent but H-dependent transport and/or diffusion38-41. Methionine can increase the digestibility of other essential amino acids and also changes the dynamics of amino acid transporters to reflect their availability42. Therefore, differences in the mechanism of transportation between the two Met sources may lead to different amounts of their transportation. Thus, the absorption and transportation of Met are complicated processes.

Interrelationship between Methionine and other nutrients

Among essential amino acids, Met seems to have many interrelationships with other nutrients (Cystine, Choline, Betain, Vitamin B6, Vitamin B12, and Folate) due to many metabolic pathways involving Met4,32,43,44. Methionine synthase is a Vitamin B12-dependent enzyme. Vitamin B12 is essential for the synthesis of myelin in nerve tissue, a function probably related to Met production from the Met synthase reaction and the subsequent formation of S-adenosyl-methionine43,44. The molar efficacies of Met, 1/2 Cystine, and Cystine are the same43.Poultry requires both Met and Cystine for protein synthesis, so the total sulfur amino acids (TSAA) requirement should be taken into account. In avian species, it is generally accepted that around 45-50% of TSAA can be supplied by Cystine. However, Cystine supplementation has a negative impact on voluntary feed intake when the diet is markedly deficient in TSAA (more than 50% of TSAA intake is provided by Cystine)29. Moreover, when the TSAA requirement is expressed as a percentage of the diet, the need for a Met plus Cystine combination is less than that for Met  alone45.

      Since TSAA act as a sulfur donor, sulfur supplementation influences the sparing effect between Met and Cystine. It seems that when sulfur sources are added to the diet, the sparing effect between Cystine and Met or the TSAA requirement is reduced. Sasse and Baker46 found that when TSAA was at or near adequacy, the optimal percentage from Cystine was 48.4% in the presence of dietary K2SO4 and 52.6% in its absence. However, optimal performance occurred when TSAA was set at a deficient level, Cystine furnished 41.3%  and K2SO4 of the TSAA need, respectively, in the presence and absence of K2SO4, respectively. Using practical broiler finisher diets, three trials were carried out to determine the extent to which synthetic Met can be replaced by sodium sulphate. The results revealed that weight gain and the feed conversion ratio both increased with incremental increases in sodium sulphate in diets containing sub-optimal concentrations of TSAA47. Cystine can spare with Met in increasing the absorption of essential minerals, such as zinc48. Lysine and Met as two essential precursors of L-carnitine can play important roles in lipid and energy metabolism in poultry. L-carnitine is a natural, Vitamin-like substance that acts in the cells as a receptor molecule for activated fatty acid. Its major metabolic role appears to be the transport of long-chain fatty acids into the mitochondria for B-oxidation. As they say the more, the merrier so if you can win a welcome bonus which is in hundreds of dollars, then it becomes exciting. A shortage of this substance results mainly in impaired energy metabolism and membrane function. In this regard, some studies have indicated that carnitine supplementation of diets can be used to augment carnitine supply for use in metabolism, thereby facilitating fatty acid oxidation and reducing the amount of long-chain fatty acids available for storage in adipose tissue.

Protein level in the diet
Addition of synthetic amino acids like lysine and Met at high levels to the poultry diet can stimulate insulin secretion from the pancreas by being aggregated in plasma which in turn releases amino acids and fatty acids from the bodily saved sources leading to protein synthesis. The optimal level of Met in the diet seems to depend on the protein concentration in the diet. Vieira et al.49 indicated that the optimum dietary TSAA level depends on the dietary protein level. The TSAA requirement does not change with age when it is expressed in terms of dietary protein50. In addition, a broiler chicken’s requirement for TSAA increases with increasing dietary protein concentrations ranging from 19. Today 28  states have legal tribal casinos. 7 to 25.9%51,52. Therefore, several investigators have suggested that the Met concentration in chicken diets should be around 2.5 to 4% of the protein concentration51,53,54. Although an increase in the dietary Met requirement is often found with elevated protein concentrations, the capacity to use Met for protein. gain is also reduced55. Sterling et al.56 intensively reviewed the ratio of protein, including amino acids, and found that the amino acid requirements expressed as a percentage of diet tended to decline as protein content increased. In laying hens, when the ratio of protein:Met was kept constant, Met supplementation to a high protein level
(18% Crude Protein) decrease egg production, while supplementation to lower protein levels (14 and16% Crude Protein ) improved the production performance57. Jankowsk et al.58 reported that higher dietary Met levels (45 vs. 30% of Lys content) increase the final BW of turkeys and cause a beneficial increase in plasma albumin concentration. In addition, Elsharkawy et al.59 reported that supplementation of 0.1% Met to rooster diets can improve carcass characteristics and meat quality of progeny. Similarly, Liu et al.60 indicated that supplementation of maternal diet with 0.1% coated Met had a positive effect on growth performance and carcass traits of offspring. According to Rehman et al.61, in case DL-Met and L-Met are included in feed at a standard level, they are equally effective as a source of Met for the broiler chickens. These results may suggest that increasing the Cystine content by increasing dietary protein concentration reduces the Met requirement. In addition to keno, specialty games  include bingo, a Soduko-based game and an array of scratch cards to choose from.

Methionine and heat stress


High environmental temperature decreases the feed intake to maintain homeothermy62 and degrade subsequent live weight gain, digestibility, egg production, egg quality, and feed efficiency63,64. Diets with an amino acid imbalance or Met deficiency normally increase heat production65 and induce a more negative effect of heat stress when the environmental temperature is high64. As balancing the amino acid composition in the diet with Met supplementation improves production performance through pathways of polyamine metabolism62, glutathionine (derived from Met ) may reduce damage from oxidative stress.


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