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 < .05) than that of Medium or Light pigs. Grouping had no effect on overall ADFI. Feed efficiency did nor differ (P=.25) for Heavy, Medium, and Unsorted pigs, but Light pigs were less efficient (P < .05) than Heavy pigs. Final body weights differed for each group (P < .05) and ranked in the following descending order: Heavy, Unsorted, Medium, and Light. Mean final weights of Unsorted pigs were greater (P < .05) than mean final weights of all sorted pigs. No differences in within-pen SD were detectable (P=.13) by the end of the study. Implications: Sorting pigs into finishing pens by weight has no effect on final variability in individual body weights. Placing pigs without sorting by weight may increase the amount of pork produced from a system and reduce turnaround time in barns.