Meet swine sulfur amino acids requirements correctly using a modern, a more sustainable and a healthier source:


L-Methionine By Dr. Behnam Saremi, Head of Technical Center, CJ Europe GmbH


Methionine (Met) is an essential amino acid in pigs. It is considered as the second limiting amino acid in the typical swine diets. Thus, supplementing Met to feed in order to balance sulfur amino acids (SAA) has a long history in swine nutrition. Methionine deficiency not only has negative effects on performance of pigs but also reduces redox potential value of tissues dramatically (Bauchart-Thevret et al. 2009). Methionine deficiency reduces protein and DNA synthesis in most of the important organs (gut, liver, spleen and stomach) (Bauchart-Thevret et al. 2009). Ingested Met starts to be metabolized right in the intestine: gut utilizes 20% of ingested Met (called first pass metabolism), 49% of ingested Met will be used for methylation (transmethylation) and 32% of the ingested Met will be transformed to cysteine (transsulfuration) in the whole body (Riedijk et al. 2007).


Bioavailability of Methionine sources Methionine can be provided via raw materials or by adding supplemental Met to the feed. The first Met sources which became commercially available were DL-Met and its liquid hydroxy analogue (DL-HMTBA) which is available in two forms: liquid fatty acid (MHA-FA) or powder calcium salt (MHA-Ca). These Met sources are produced from nonrenewable resources through chemical synthesis. Because L-Met is the natural form of Met (the only form which the animal can utilize directly), D-Met and DL-HMTBA need to be transformed to L-Met by


the animal itself which costs energy, enzyme activities, amino acids (for amination of Keto-Methionine) and cellular capacities (Figure 1). Since 2015, L-Met has also been commercially available (in high


volumes) which is produced from renewable resources. Crystalline L-Met provides the opportunity to relieve farm animals from the extra unnecessary job of converting the D isomer and the precursors to L-Met. End-users are always confronted with the question of relative


bioavailability (RBA) of Met sources because of commercial and nutritional interests. There is a huge controversy in literature about RBA of Met sources. One needs to look at the whole picture to be able to decide about the correct effectiveness of Met sources. Professor Baker is the major cited scientist when it comes to RBA of Met sources (Katz and Baker, 1975). “L-Met is a better source of sulfur amino acids than D-methionine” Baker wrote (Baker, 1994). Nevertheless, in a more recent publication, Baker thinks that the RBA is a matter of species (Baker 2006). For example, RBA of D-Met is 90% in chicks, but 100% in pigs although RBA of DL-HMTBA is 80% in both species (Table 1). Running RBA trials has been revolutionized over the years and nowadays looks quite different. For example, the basis for pig RBA values in Table 1 is an experiment where two doses (0.025% and 0.050%) of either L-Met or DL-Met is compared with one single dose (0.057%) of DL-HTMBA (Chun and Baker, 1992). No surprise that no difference between Met sources could be detected. It is already known that at least a basal diet (containing no supplementary Met source) which is deficient in Met plus Cys and 4 graded levels of each source of Met are needed in order to be able to run a proper estimation of bioavailability.


Table 1. Relative utilization of methionine isomers and the OH analogue (1)


(Baker, 2006)


Amino acid Rat Mouse Pig 100 90 95


L-Met D-Met


DL-Met DL-HMTBA 70


Figure 1. Metabolism of different dietary methionine (Met) sources. Met isomer D-Met and Met precursor DL-2-hydroxy-4-(methylthio) butanoic acid (DL-HMTBA) must be converted to L-Met for utilization. Different enzymes and cofactors play roles in this process (adapted from Zhang et al. 2018).


PAGE 48 SEPTEMBER/OCTOBER 2019 FEED COMPOUNDER


100 75 88 70


100 100 100 80


Chick Dog Human 100 90 95 80


100


100(2) 100 NA


100 30(3) 65


NA


DL-HMTBA, hydroxy analogue of methionine: NA, data unclear or not available. (1)


Values are expressed as percentages of the growth efficacy


(molar or isosulphurous basis) of the L-isomer, which in all cases is presumed to represent 100% oral utilization. (2)


Efficacy of D-Met is also almost 100% in growing kittens. (3) Efficacy is also about 30% in non-human primates.


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