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LETTERS TO THE EDITOR |
Degussa Corporation, Kennesaw, Georgia 30144
1 Corresponding author: dirk.hoehler{at}degussa.com
Recently, Yi et al. (2007) published a paper in Poultry Science with the objective to compare the biological availability of Mintrex with free DL-2-hydroxy-4-(methylthio)butanoic acid (DL-HMTBA). The conclusion was that "HMTBA from Mintrex was fully available as a Met source." This conclusion cannot be drawn from this study and therefore is misleading. Based on the approach and methodology of the paper, one can only conclude that availability of DL-HMTBA from Mintrex (DL-HMTBA Ca salt) and from free DL-HMTBA is similar, not that DL-HMTBA from Mintrex is fully available as a Met source.
DL-Methionine (DLM) and DL-HMTBA are commonly used as supplemental Met sources in poultry and swine diets. Over the last few years, there has been a considerable amount of research published mainly with broiler chicks (Thomas et al., 1991; Van Weerden et al., 1992; Esteve-Garcia and Austic, 1993; Huyghebaert, 1993; Rostagno and Barbosa, 1995; Schutte and De Jong, 1996; Esteve-Garcia and Llaurado, 1997; Wallis, 1999; Lemme et al., 2002; Vieira et al., 2004; Hoehler et al., 2005), resulting in a nutritional effectiveness of DL-HMTBA that is significantly lower than that of DLM. Also recently, researchers in the Netherlands (Jansman et al., 2003) conducted an independent, extensive literature study and evaluation of numerous previous papers on this topic and, based on regression analysis, reported that the average bioefficacy of liquid DL-HMTBA compared to DLM was 68% on a weight basis or 77% on an equimolar basis in broilers. These figures are based on weight gain and feed conversion of a total of 18 broiler trials.
Physiological reasons for this difference have also been investigated (Maenz and Engele-Schaan, 1996a,b; Drew et al., 2003).
Thus, the only valid conclusion based on the findings of Yi et al. (2007) is that the availability of DL-HMTBA from Mintrex and from free DL-HMTBA is similar. One cannot conclude that DL-HMTBA from Mintrex is fully available as a Met source. Valid results about the biological effectiveness of Mintrex (DL-HMTBA Ca salt) as a Met source can only be obtained from studies in which Mintrex is compared to L-Met or DLM.
Received for publication May 11, 2007. Accepted for publication May 11, 2007.
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REFERENCES |
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Hoehler, D., A. Lemme, S. K. Jensen, and S. L. Vieira. 2005. Relative effectiveness of methionine sources in diets for broiler chickens. J. Appl. Poult. Res. 14:679–693.
Huyghebaert, G. 1993. Comparison of DL-methionine and methionine hydroxy analog-free acid in broilers by using multi-exponential regression models. Br. Poult. Sci. 34:351–359.[Web of Science]
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Rostagno, H. S., and W. A. Barbosa. 1995. Biological efficacy and absorption of DL-methionine hydroxy analog free acid compared to DL-methionine in chickens as affected by heat stress. Br. Poult. Sci. 36:303–312.[Web of Science][Medline]
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Van Weerden, E. J., J. B. Schutte, and H. L. Bertram. 1992. Utilization of the polymers of methionine hydroxy analogue free acid (MHA-FA) in broiler chicks. Arch. Gefluegelkd. 56:63–68.
Vieira, S., D. Hoehler, A. Lemme, S. Pophal, A. Ebert, and G. Eichner. 2004. Comparison of methionine sources based on an equimolar trial design with broiler chickens in Brazil. J. Anim. Sci. 82 (Suppl. 1):430–431.
Wallis, I. R. 1999. Dietary supplements of methionine increase breast meat yield and decrease abdominal fat in growing broiler chickens. Aust. J. Exp. Agric. 39:131–141.
Yi, G. F., C. A. Atwell, J. A. Hume, J. J. Dibner, C. D. Knight, and J. D. Richards. 2007. Determining the methionine activity of mintrex organic trace minerals in broiler chickens by using radiolabel tracing or growth assay. Poult. Sci. 86:877–887.
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