Broiler trial in the Netherlands confirms 2018 EFSA scientific opinion on methionine sources while validating the experimental approach

Dears Mr. Naranjo and Mr. Lemme, as you well mention in your study, the diets tested are deficient on Methionine (Met) and Methionine+Cystine, therefore not representative of the commercial conditions. It has already been demonstrated that along with the most rapid increase in plasma there is a more rapid feed intake with DL-Met over HMTBa (referred as MHA-FA in your study) at low levels of Met supplementation, such as the deficient diets you are showing in this design/model. In contrast, as level of Met supplementation increases, feed intake for HMTBa supplemented diets reaches that of DL-Met diets when both are supplemented at requirements and HMTBa even overtakes DL-Met, as described in the work of Gonzalez-Esquerra et al. (2007). In a similar way, Knight et al. (2006) using paired-feeding studies demonstrated that differences in performance between HMTBa and DL-Met were due to differences in intake and not inefficiency of conversion of HMTBa to L-Met. These studies have been done using 100% equivalence between the 2 on an equimolar basis. Equimolar means equal supplementation of molecules (1 gram of HMTBa results in 1 gram of DL-Met. MetAMINO equals 1.125 grams of Alimet for equal supplementation, as MetAMINO has 99% DL-Met and Alimet 88% HMTBa). Any feeding study that compares doses on an equal product basis instead of an equimolar basis is also statistically incorrect. That is because the initial assumption in an experiment is that two materials are EQUAL and the objective of the experiment is to determine if a statistically significant difference can be detected. If you start an experiment with DIFFERENT levels of supplementation for the two molecules being compared, lack of a significant difference becomes a conclusion that they are different, a major deviation from acceptable statistical experimental design and analysis. BOTTOMLINE: you can never prove that two things are the SAME, only that they are DIFFERENT or that you cannot prove that they are DIFFERENT, i.e. no significant difference. In your study, taking the data from Table 3, granting 100% efficacy of conversion to L-Met to both active substances (DL-Met and HMTBa), and plotting body weight, feed conversion and feed intake against the active substance, it again demonstrates and confirms what has been described in the works of Knight et al. (2006) and Gonzalez-Esquerra et al. (2007). It is a good exercise to do, as you clearly see the link between active substance intake and response in performance, expressed here as body weight and feed conversion, so nothing to do with conversion efficiency. Since HMTBa and DL-Met are different compounds, therefore showing differences in absorption and metabolism as it has widely been described in the scientific literature, there is not a unique bioequivalence factor, but it is mainly related to feed ingestion (thus active substance ingested), as explained above. Finally, I would just like to add that looking at the data from Agristats in US, mentioning for more than 700 billion broilers per year (representing more than 95% of broilers produced in that area), it is impossible that when splitting the data according to the methionine source used, animals supplemented with HMTBa are performing similar or even better than those supplemented with DL-Met while they are giving full credit to HMTBa conversion to L-Met in the animal (100% on equimolar basis meaning 88% for Alimet –liquid form- or 84% for MHA –powder form). References: Gonzalez-Esquerra R., Vázquez-Añón M., Hampton T., York T., Feine S., Wuelling C., and Knight C.D. 2007. Evidence of a different dose response in turkeys when fed 2-hydroxy-4(methylthio) butanoic acid versus DL-methionine. Poult. Sci., 86:517-524. Knight C.D., Dibner J.J., Gonzalez-Esquerra R., and Vázquez-Añón M. 2006. Differences in broiler growth rates when methionine (Met) sources are fed in deficiency or excess are equalized when feed consumption is equalized. Poult. Sci., 85 (Suppl. 1):P191 (Abstract).