Pre-sorting and pen size effects on the stress responses at loading and unloading and transport losses in market weight pigs

The management and facility design strategies of pre-sorting prior to loading and grow to finish pen size were studied to determine their individual effects on stress responses at loading and unloading and transport losses in market weight pigs. Each trial was conducted on three commercial wean to finish sites in the Midwest. Pre-sorting market weight pigs prior to loading reduced (P < 0.01) the incidence of open mouth breathing (OMB) and skin discoloration (SD) at loading, however; there were no differences (P < 0.05) between pre-sorted and not pre-sorted pigs for the incidence of muscle tremors (MT) at loading, OMB, SD, or MT at unloading, or any transport loss measures at the harvest facility. Pigs raised in small pens throughout the grow to finish period had reduced (P < 0.01) incidences of OMB and SD at loading compared to pigs raised in large pens. At unloading, however; pigs from large pens had a lower incidence (P < 0.01) of SD and no differences (P < 0.05) existed between treatments for OMB or MT. Finally, there were no differences (P < 0.05) between pen size treatments for any transport loss measures at the harvest facility.