Issues with a meta-analysis assessing the efficacy of different sources of methionine supplementation

Meta-Analyses of Methionine Source Concept Validation Trials in Broilers

“…Batonon-Alavo and Rouffineau suggested that Met source comparison trials should be run at commercial level (see previous paragraph [32]) but compared DL-Met and MHA-FA trial data only below the requirement in another study while excluding all data above the requirement [25]. In that meta-analysis, the growth responses were regressed against methionine intake above basal diets (as well as Met+Cys levels above basal diet, which does not make sense in a Met source comparison [26]), but they did not share information as to what methionine value they assigned to MHA-FA. Therefore, the final conclusion that the slopes for the two products did not differ is questionable because a certain (high?)…”

“…The similar outcome for both subgroups in the current meta-analysis is, thus, not surprising. above basal diet, which does not make sense in a Met source comparison [26]), but they did not share information as to what methionine value they assigned to MHA-FA. Therefore, the final conclusion that the slopes for the two products did not differ is questionable because a certain (high?)…”

“…After an unconventional processing of data, a meta-analysis using the slope-ratio comparison concluded that the efficiency of MHA-FA would not differ from that of DL-Met [25]. The authors of that paper could only partly justify doubts on reliability and scientific adequacy regarding data treatment and the selection of the finally used publications [26,27]. Kratzer, who co-authored [23], and Littell, who originally described the slope-ratio and multi-exponential approach [21], referred to the abovementioned study by Jansman et al [15] and concluded that response curves to MHA-FA and DL-Met would differ in their asymptote, and therefore, the conclusion of lower bioefficacy of MHA-FA compared to DL-Met would be invalid [28].…”