“…The discrepancies between these results may be due to the different cultivars, as discussed later, and to the different methods used. It has been speculated that the dual isotope method underestimates the IAA digestibility compared with the ileal balance method [ 35 , 36 ], but another internal comparison study does not support this systematic underestimation [ 37 ] as sometimes the dual isotope method seems to overestimate and sometimes underestimate digestibility compared with the direct method. Regarding legumes, no internal comparison exists; thus, external comparisons include the effect of the model or method and the effect of the cultivar.…”