Frantz, N.Z.Tokach, Michael D.Goodband, Robert D.Nelssen, Jim L.DeRouchey, Joel M.Dritz, Steven S.2009-10-292009-10-292009-10-29http://hdl.handle.net/2097/1969A total of 1887 pigs (PIC 337 × C22; 213 lb initial BW) were used in a 28-d growth assay to simultaneously examine both the true-ileal-digestible (TID) lysine and TID total sulfur amino acid (TSAA) requirements. The objective was to determine the appropriate TID TSAA-to-lysine ratio in finishing pigs fed Paylean® (4.5 g/ton) to maximize growth performance and carcass composition. Four TID lysine (0.66. 0.79, 0.92, and 1.05%) and four TID TSAA (0.47, 0.52, 0.57, and 0.63%) concentrations were evaluated. The highest lysine and TSAA concentrations were combined in the same diet, and there were eleven or twelve replicate pens per treatment. The lysine treatments were formulated with a minimum TID TSAA to lysine ratio of 60%, and the TSAA diets were formulated with 1.05% TID lysine. No gender × treatment or treatment × week interactions were observed (P>0.13). Increasing TID lysine increased ADG (linear, P<0.01), with the greatest response at 0.92% TID lysine, but ADG (P>0.76) was not affected by increasing TID TSAA. This resulted in a TID TSAA-to-lysine ratio of not more than 51% for optimum ADG. Increasing TID lysine did not affect ADFI (P>0.60), but ADFI decreased (linear, P<0.04) with increasing TID TSAA. Increasing dietary TID lysine improved feed efficiency (F/G) (linear, P<0.01), and increasing TID TSAA tended to improve F/G (linear, P<0.09). Although the response was linear, the greatest improvement in F/G was observed as the TID TSAA increased from 0.47% to 0.52%, resulting in an optimum TID TSAA-to-lysine ratio of 57%. Regression analysis indicates that the maximum F/G response was obtained with a TID TSAA-to-lysine ratio of 58%. Increasing TID lysine had no effect on any carcass criteria (P>0.11), but increasing TID TSAA from 0.47 to 0.52% tended to improve fat-free lean (quadratic, P<0.10). No other carcass criteria were affected by increasing TID TSAA (P>0.10). In summary, a TID TSAA-to-lysine ratio of 58% optimizes growth performance of finishing pigs fed Paylean.Finishing pigsLysineMethioninePayleanPigsSulfur amino acidsSwineConference paper