Research conducted at five university farms shows that sorting off lightweight finishing pigs and relocating them to another pen does not improve grow/finish performance.

A total of 900 crossbred pigs were housed at research centers at the universities of Nebraska, Illinois, Minnesota and Michigan State and Iowa State universities.

Twelve replicates were used to evaluate the effect of remixing the lightest 25% of pigs per pen.

Three treatments included 15 pigs/pen from 58 lb. to slaughter; 20 pigs/pen to 154 lb. and then 15/pigs/pen to slaughter; and the 15 pig/pen remixed pens, where five lightest pigs/pen were removed at 154 lb. and housed to slaughter.

Four typical meal-form, phase diets were fed. Lysine was standardized to the Nebraska. South Dakota Nutrition Guide levels.

Researchers found no difference in average daily gain, average daily feed intake and feed to gain ratio in the grower stage.

There was no significant effect on ADG, ADFI and F:G between the sorted and unsorted pens, according to Nebraska swine specialist Mike Brumm, who reported the findings at the Midwest Animal Science meetings.

"Pulling the light pigs and putting them with similar pigs doesn’t improve the days to emptying the barn and overall pig performance," Brumm concludes. "It is not worth the effort to leave pens empty to put light pigs into as they grow."

The researchers are now experimenting with pulling the five heaviest pigs from pens and remixing them as a way to improve population performance.

Researchers: Mike Brumm, University of Nebraska; Mike Ellis, University of Illinois; Dale Rozeboom, Michigan State University; and Dean Zimmerman, Iowa State University. For more information, contact Brumm at (402) 584-2261 or e-mail

Kansas Researchers Agree – Sorting Finishers Doesn’t Improve Performance

Kansas State University researchers found similar results from their study of sorting to improve overall pig performance.

Two trials each used 192 PIC crossbred barrows and gilts weighing 75 lb. and 14 weeks of age to determine the effects of sorting on growth performance and weight variation.

The pigs were divided by sex and ancestry into one of four groups: heavy sorted (82 lb. ± 3 lb.); medium sorted (75 lb. -± 1.75 lb.); light sorted (66 lb. ± 4.4 lb.); and unsorted (74.36 lb. ± 7 lb.). There were 12 pigs/pen and eight pens/group.

Pigs were fed nutritionally adequate grain-sorghum-soybean meal-based diets in three phases.

Overall, ADG of the unsorted and heavy sorted pigs was similar, but greater than the medium or light sorted pigs. ADFI was unaffected by grouping. All groupings were different in final weight and ranked in the following order: heavy sorted (271.48 lb. ± 16.28 lb.); unsorted (263.78 lb. ± 19.14 lb); medium sorted (259.16 lb ± 16.72 lb.); and light sorted 249.04 lb. ± 20.46 lb.).

The final weight of the unsorted pigs was heavier than the average weight of all sorted pigs. Differences in body weight variation were not detectable by the end of the study.

The researchers conclude that the increase in pig weight from not sorting was due to the growth performance of the medium weight pigs in the unsorted pens. Those medium weight pigs grew faster than medium weight pigs penned uniformly by weight.

Therefore, sorting pigs by weight does not improve growth performance or reduce weight variation, and not sorting pigs may actually increase throughput (amount of pork produced) in a production system.

Researchers: P. R. O’Quinn, Steve Dritz, Robert Goodband, Mike Tokach, J.C. Swanson, Jim Nelssen and R.E. Musser. Contact Dritz at (785) 532-1231 or email