In the only study on the L-Met (+Cys) requirement for turbot, the total dietary requirement for Met + Cys was estimated for the RG at 2.00% DM in diet (3.31% in CP) (Ma et al., 2013; Table 7). This determined value is clearly higher compared to the lower critical concentration in this study, where the RG was determined at 1.25% in diet DM
(±0.02 s.e.) (2.26% in CP ± 0.04 s.e.) (Table 3.2). Similar differences can be observed for the RFI when comparing the recommendations of Ma et al. (2013) (Table 7) with lower critical concentration for the RFI (Table 3.2). The relatively strong difference to our findings might be caused by the different regression analyses applied. In the current
study a segmental linear regression analysis approach was used to identify the lower as well the upper critical concentration of Met+Cys. Whereas Ma et al. (2013) determined the maximum point of response via second-order polynomial regression analysis,which does not necessarily reflect optimum supply representing the beginning of the plateau phase.