The plasma free AA dose-response technique has been proposed as the standard approach for arriving at estimates of efficacy for rumen-protected Lys supplements. Results of the first replicate of a 5 × 5 Latin square study, reported last year [J. Dairy. Sci. (97(E-Suppl. 1):763], confirmed that a positive relationship also exists between increasing amounts of absorbed Met and plasma Met and total sulfur AA (TSAA) concentrations. The objective of adding a second replicate was to complete the study, and using the combined data set, to determine if using plasma Met or TSAA concentrations (µM) is the more precise response parameter and whether expressing either as a % of total AA (TAA) or total essential AA (TEAA) would reduce the error of calculated estimates of Met-bioavailability. Experimental protocol was as previously described: namely, 5 rumen-cannulated Holstein cows (74–222 DIM) were fed a Met-deficient basal diet with identical treatments. Combined data were analyzed using PROC MIXED and PROC REG of SAS. Outlier analysis, using ± 2.0 SD away from the mean for plasma Met and TSAA concentrations, resulted in removal of all data for one cow. Plasma Met and TSAA concentrations (µM), and both expressed as %TAA and %EAA, were regressed on 0, 12, and 24 g of infused Met and 0, 15, and 30 g of fed Met. Slopes (and associated CV, %) for infused and fed Met were 1.40 and 1.04 (3.68 and 1.85) for Met, 0.067 and 0.048 (4.92 and 3.18) for Met as %TAA, and 0.152 and 0.112 (4.48 and 3.22) for Met as %TEAA. Corresponding values for total TSAA were 2.00 and 1.64 (1.58 and 2.57) for µM concentrations, 0.108 and 0.079 (2.79 and 2.48) for %TAA, and 0.234 and 0.184 (2.67 and 3.48) for %TEAA, respectively. Estimates of bioavailability (and 95% CI) of the RP-Met supplement for the 6 respective methods of expression were 74.4 (2.1), 71.6 (1.9), 73.7 (1.3), 81.8 (3.3), 72.7 (1.3) and 78.6 (2.3). We conclude the plasma free AA dose-response technique is precise, and because Met is a precursor to other sulfur AA, TSAA (µM) is the most appropriate response parameter for estimating Met bioavailability of RP-Met supplements.