Motivated by producer reports that pigs from automatic sorting systems move easier, Pennsylvania researchers wanted verification.

The University of Pennsylvania slaughter transport study, completed last summer, tracked 2,000 loads (about 350,000 pigs) to the packing plant. Pigs came from either conventional facilities with small pens of 25 head each (1,660 loads or 83%), or from automatic sorting barns with large pens of 500 pigs each (342 loads or 17%).

Kill sheets were used to determine numbers of pigs dead on arrival (DOA) and pigs that died in holding pens prior to slaughter. Results showed pigs trucked from automatic sorting facilities had a significantly lower death loss.

“Our interpretation is that pigs from large pens are more conditioned to walk and they see more pigs, making loading and trucking less stressful,” says Tom Parsons, a veterinarian and director of the University of Pennsylvania Swine Center.

Auto-sort floors utilize large pens designed with a central eating area. Access to the feeders is limited via a one-way gate that routes animals over a scale. A computer-controlled sorting gate automatically diverts animals to light or heavy sides of the barn.

“There has been emphasis on other reasons to go to this technology — economic benefits from reduced sort loss and less labor — but significantly lower death loss during transport is a welfare benefit that needed to be documented,” he adds.

If the study was to be repeated, there would be a lot fewer conventional pens, Parsons notes.

“Everyone is seeing positive effects with the (auto sort) technology. It's nearly impossible to get someone to build a conventional barn now. But there is some backlash about feed intake. Some pigs don't seem to eat like they do in a conventional barn,” he says.

Possible confounding risk factors entered into the analysis included season of shipment, producer, genetics and hauling company. Still, after accounting for these factors, there proved to be an increased risk of DOAs and deaths in the holding pens for pigs shipped from conventional systems.

In conclusion, Parsons and his colleagues, Meghann Brumsted and David Galligan, say findings from the year-long study demonstrate an obvious welfare advantage from fewer pigs dying in transport and an economic benefit simply from more live animals.