Two experiments (E) were conducted, using 204 Large White piglets (E1: from 7.23 to 12.32 kg; and E2: from 12.64 to 23.81 kg). A randomized block design was used, with four levels of threonine in the ration (E1: 0.80; 087; 0.93 e 0.99%; e E2: 0.69; 0.74; 0.80 e 0.85 %); eight (E1) and nine (E2) replicates for daily intake (DI), daily weight gain (DWG), adjusted daily weight gain (ADWG) and feed conversion (FC) and five replicates for plasma urea (U). No treatment differences (P>0.10) were observed for either DI or DWG. Quadratic effects of threonine were observed on ADWG in E1 (P=0.086) and E2 (P=0.052), on FC in E2 (P=0.035) and on U in E1 (P=0.002); as well as a linear effect on FC in E1 (P=0.030) and on U in E2 (P=0.044). U was minimized at 0.89% threonine in E1, whereas ADWG was highest at 0.94%, in E2, 0.76% threonine maximized ADWG and minimized FC.
amino acids; piglets; plasma urea; weight gain
