Review of the chemistry, metabolism, and dose response of two supplemental methionine sources and the implications in their relative bioefficacy

Rahat Mobeen
A few good articles for you to understand this issue:
1. Fang et al (2010) Brit J Nutr - Effects of DL-2-hydroxy-4-methylthiobutyrate on the first-pass intestinal metabolism of dietary methionine and its extra-intestinal availability
2. Jendza et al (2011) J Anim Sci - The site of intestinal disappearance of DL-methionine and methionine hydroxy analogue differs in pigs
3. Richards et al (2005) Poul Sci - Comparative in vitro and in vivo absorption of 2-Hydroxy-4(Methylthio) Butanoic Acid and Methionine in the broiler chicken

Roughly, sites and mechanisms of absorption are slightly different, resulting that HMTBA absorption is less influenced by other nutrients than DLM, and is absorbed before DLM in the GIT.
But check the articles and take your conclusions.

Alireza rostamkhani
The methodology used for determining the comparative Biological Value where this lower "potency" was found is wrong and it was revised by the main research group.
Please, check on "Kratzer et al (2006) Poul Sci - Appropriate statistical methods to compare dose responses of methionine sources".
EFSA will review their position in the future, since they also have used an obsolete method, based on a misconception.
If you look to the market, 75% of US feed industry use liquid HMTBA as TSAA source with efficiency.

Luiz W. O. Souza
Kinetics of Hydrolysis of Dimeric and Trimeric Methionine Hydroxy Analogue
Free Acid under Physiological Conditions of pH and Temperature
Hans G. Koban* and Edgar Koberstein
Liquid feed supplements baaed on DL-methionine hydroxy analogue free acid (DL-MHAfree acid,
~~-2-hydroxy-4-(methylthio)butyric acid) contain considerable amounts of oligomeric MHA free acids.
As a first approach to physiological decomposition the hydrolysis of dimeric and trimeric MHA free
acid in dilute hydrochloric acid solution is investigated. By use of HPLC it is possible to follow the
changes in concentration of all species. The hydrolysis reactions are found to be first order with respect
to the oligomer concentration. The rate constant increases with HC1 concentration and temperature
(activation energy for dimeric MHA free acid: 72 kJ/mol). The rate constants obtained at 37 OC in
0.1 N aqueous HC1correspond to half-lives of 1.8 and 1.6 days for dimeric and trimeric MHA free acid,
respectively. The results indicate that oligomeric MHA free acids show rather slow hydrolysis under
physiological conditions of pH and temperature.

Alireza rostamkhani

Please, see also:

1. Martin-Venegas et al (2006) Poul Sci - Oligomers Are Not the Limiting Factor in the Absorption of DL-2-Hydroxy-4-(methylthio)butanoic Acid in the Chicken Small Intestine

2. Martin-Venegas et al (2008) Poul Sci - Partial Na+ dependence of DL-2-Hydroxy-4-(Methylthio)Butanoic Acid uptake in the chicken small intestine

3. Martin-Venegas et al (2009) Am J Physiol Cell Physiol - Effect of pH on L- and D-methionine uptake across the apical membrane of Caco-2 cells

4. Martin-Venegas et al (2011) Brit J Nutr - Intestinal cell conversion of DL-2-hydroxy-(4-methylthio)butanoic acid in vitro dietary up-regulation by this methionine precursor

5. Monocarboxylate transporter 1 is up-regulated in Caco-2 cells by the methionine precursor DL-2-hydroxy-(4-methylthio)butanoic acid

Luiz W. O. Souza
We do not how much price and purity mha used feed industry us. however mha very good source of TSAA for sow and different by DLM in efficacy and recovery rate and mix ability in broiler feed.

Rahat Mobeen
The most important problem dealing with the estimation of the RBV on MHA is the inappropraite statistical approach used in most studies as Luiz noted above. Please check out "Kratzer et al (2006) Poul Sci - Appropriate statistical methods to compare dose responses of methionine sources".
In most studies, the common plateau has been fiited for both MHA and DLM, which is incorrect approach and these two sources of Met follow different pattern to reach plateau, so separate plateau should be fitted when estimating the RBV for HMA. Kratzer et al., (2006) showed that separate plateau resulted in better RBV for HMA.