Sorting growing-finishing pigs by weight fails to improve growth performance or weight variation

Objective: To examine the effects on growth performance when growing-finishing pigs are sorted uniformly by weight at placement. Methods: Pigs selected from a group of 384 were sorted into Heavy (37.1 +/- 1.4 kg), Medium (34.0 +/- 0.77 kg), and Light (30.2 +/- 2.0 kg) groups, or placed in an Unsorted group (33.8 +/- 3.2 kg) with a mean starting weight similar to that of the Medium pigs, but with quadruple the variation. Pigs and feeders were weighed on days 0, 7, 14, 21, 28, 56, 70, and 91 for determination of ADG, ADFI, feed efficiency, and within-pen pig weight variation. Results: From day 0 to 91, ADG of Unsorted pigs and Heavy pigs did not differ, but was greater (P