“…Methionine (Met) is considered as the second or third limiting amino acid in diet for modern nursery pigs ( Gaines et al, 2005 ), and it plays several roles such as an initiating amino acid in protein synthesis and as the principal biological methylating agent in the body ( Bunchasak, 2014 ). Commercially, both in powder DL-methionine (DL-Met, 99% powder) and its analogue liquid DL-methionine hydroxy analog free acid (DL-MHA, 88% aqueous solution) are supplemented in diets or drinking water for improving growth responses ( Kaewtapee et al, 2010 ; Krutthai et al, 2015 ). Although the composition or material used in diets such as practical, semi-purified, or purified diets influence the bioefficacy of DL-MHA compared to DL-Met ( Bunchasak, 2014 ), a smaller effect of DL-MHA and DL-Met can be seen when a practical diet formulated based on corn-soybean or broken rice-soybean is used ( Bunchasak, 2014 ; Krutthai et al, 2015 ).…”