The optimal digestible (d) Valine (Val) to d Lysine (Lys) ratio (dVal:dLys) in weaned piglets was determined using two different regression models. A total of 200 piglets were allotted to five feeding groups and fed a corn-soybean meal based basal diet supplemented with consecutive increasing amounts of crystalline L-valine in order to reach dVal:dLys of 0.59, 0.63, 0.67, 0.71, 0.75 in the pre-starter (0-13 days) and 0.57, 0.62, 0.66, 0.70, 0.75 in the starter phase (13-43 days). In the starter phase and during the whole period, supplementing the basal diet with L-valine resulted in an improvement in body weight gain and feed intake. An exponential asymptotic (EA) and a curvilinear-plateau (CLP) regression model were fit to feed intake and body weight gain data. The estimated dVal:dLys for body weight gain was found to be 0.68 (EA, 95% of maximum response) and 0.67 (CLP) in the starter phase and 0.65 (EA, 95% of maximum response and CLP) in the total trial period. It is concluded that the supplementation of a valine-deficient basal diet for weaned piglets with L-valine improves the piglet's weight gain and feed intake and that a dVal:dLys of 0.68 is recommended to optimize body weight gain.
Keywords: curvilinear-plateau; exponential asymptotic; ideal amino acid ratios; requirements; valine; weaned piglet.