With respect to DL-Met, total and digestible Met are identical as DL-Met is 100% digestible. In addition, as DL-Met can also serve as a cysteine (Cys) precursor, the same is true for Cys and Met+Cys, respectively. Indeed, on a weight basis, one gram of methionine would release less than one gram of Cys, since the molecular weight of Cys is 121 g while that of methionine is 150g. However, this is seldom considered in the practical application of least cost formulation.

With respect to methionine hydroxy analogue (MHA), the answer is a bit more difficult, as its digestibility is not 100%. Moreover, a couple of studies have suggested that a certain portion of the hydroxy analogue is degraded by gut microbes, which is then not available to the animal as a methionine precursor but also disappears from the digesta. The latter would distort the calculation of digestibility and thus overestimate the digestibility coefficient. In any case, the nutritional value of hydroxy analogue is about 65%. In practical terms this means that both total and digestible Met would have a value of 643.5 g/kg product (which is 65% of 990 g DL-Met). Indeed, the same applies for Cys and Met+Cys. Amino acids (AA) also have an energy value. While not often pronounced, the relative bioefficacy (BE) also applies to energy as it is based on empirical research. Therefore, the energy value (e.g. AME) for hydroxy analogue is 65% as high as that of DL-Met. There have been publications claiming that the energy value of hydroxy analogue is even higher than that of DL-Met. This is based on biochemical calculations only and assumes complete oxidation of the molecule (which is indeed the principle for energy systems), but which totally overlooks (and thus misleads) that supplemental AA fill a gap and thus will be utilized as amino acids (e.g. as building blocks) and not as an energy source.
 

This question has several aspects.

• Different broiler strains: As demonstrated in the webinar we performed a meta-analysis of 76 data sets, where 65 units of DL-Met were tested against 100% methionine hydroxy analogue. While this meta-analysis clearly validated the application of the BE65% concept, this method also allows for the creation of subgroups. In the webinar, we showed the distinction of different general Met+Cys levels (below, at, and above requirement). However, we could also build subgroups for Ross 308 and Cobb 500. The result was no difference at all between genetics in terms of bioefficacy of methionine sources.
• Genetic progress over time: The topic of the bioefficacy of methionine sources is in fact rather old. The recommendation for 65% BE was established already in the late 1990s and performance tests have been conducted ever since - always with the same outcome, always successful. Therefore, genetic progress has no impact on bioefficacy of Met products.
• What about other species? The BE65% concept is successfully applicable, meaning no performance loss but considerable economic savings with DL-Met, in all monogastric species including broilers, laying hens, turkeys, growing swine, reproducing swine and poultry, all aqua fish and crustacean species. Thus the concept is universally applicable for all species.

No, because the current production of L-methionine does not automatically have a lower carbon footprint than the current production of DL-methionine, it depends on the process. According to our understanding, the production of L-methionine partly consumes the same fossil raw materials as DL-methionine.

Moreover, the carbon source (e.g. from sugar or corn) used in the fermentation process also contributes significantly to the overall carbon footprint of L-methionine.

The most important future levers to reduce the carbon footprint of all commercially available methionine sources (DL-methionine, L-methionine and methionine hydroxy analog) are the following:

• Sourcing of green energy, such as green electricity and green steam.
• Sourcing of low-carbon footprint raw materials.
• Backward integration of key raw materials, process improvements and higher productivity.  
• NextGen Technologies targeting electrification, process intensification and circular production (such as the avoidance of by-products, as well as recycling)
• The highest methionine purity combined with highest relative bioavailability among the commercial methionine source. And as the purity content and the relative bioavailability of both products is 99% and 100%, respectively there is also no measurable difference between the carbon footprint of L-Met and DL-Met in this regard.

Both DL-methionine and methionine hydroxy analog (MHA) products support the microbial population and rumen function and can therefore help to mitigate milk fat depression.

DL-methionine (MetAMINO®) is used by the rumen microbes and supports rumen function. Evonik offers a rumen-protected DL-methionine, called Mepron®. Mepron®, the concentrated, rumen-stable methionine source for dairy cows, is the key to achieving the correct amino acid balance in dairy rations. More information can be found in the MetAMINO® ATLAS 2.0 and on our Mepron® product page.

Under regular feeding conditions and supplementation rates, free amino acids like methionine are completely used by the rumen microbes and therefore need to be rumen protected like Mepron®.

Yes, both editions can be downloaded at Evonik’s microsite: metamino.evonik.com. The download center of the first edition is positioned below the 2nd edition.