Transport losses represent a significant economic cost to the swine industry and are of major concern from an animal welfare perspective. Losses include pigs that die during the journey or are non-ambulatory on arrival at the plant. A significant proportion of non-ambulatory pigs exhibit classic symptoms of an extreme stress response (open-mouth breathing, skin discoloration, and muscle tremors); these are often referred to as “fatigued”. Previous research funded by the National Pork Board and carried out at the University of Illinois has shown that low floor space on the trailer during transport can increase transport losses. However, that research was carried out with relatively long journey times of about 3 hours. In addition, there is evidence that pigs transported for relatively short journeys (< 1 hour) are more stressed on arrival at the plant compared to those transported on longer journeys. The objective of this study was to determine the impact of floor space on the trailer during transport from the farm to the packing plant for short (< 1 hour) and long (~3 hours) journey times on stress responses and transport losses in market weight pigs.
Two treatments were evaluated, namely transport floor space and transport time. Six transport floor spaces (4.3, 4.5, 4.7, 5.0, 5.3, and 5.6 ft2/pig) were compared on both short (30 to 40 minutes) and long journeys (~3 hours). The pigs used were from wean-to-finish facilities of the same production system that were located between 20 to 30 miles from the plant. Pairs of consecutively loaded trailers were randomly allotted to transport time treatment with the trailers on the short journey time treatment traveling directly from the farm to the plant and those on the long journey time treatment traveling along a predetermined route for approximately 3 hours prior to arrival at the plant. The study was carried out at four times during the year to ensure that the typical range of weather conditions experienced in the Midwest of the US were encountered during the experiment. Pigs were monitored after unloading at the plant and the frequency of pigs exhibiting indicators of stress (open-mouth breathing, skin discoloration, and/or muscle tremors) and of transport losses (dead, non-ambulatory injured, and non-ambulatory non-injured) were recorded.
Overall, the frequency of transport losses observed in this study was extremely low (0.24% of pigs transported) and was considerably below levels observed in previous studies carried out within the production system used for the study, which have generally been within the range of 1.0 to 1.5% of pigs transported. Neither transport floor space nor journey time had any effect on total transport losses or on the incidence of dead or non-ambulatory injured pigs. The incidence of non-ambulatory non-injured pigs was greater on short than long journeys for two of the lowest three, but not for the other, floor spaces. In addition, the frequency of indicators of stress (open-mouth breathing and skin discoloration) in the pigs after unloading at the plant suggested that they were more stressed at the end of short than long journeys, particularly, at the lower floor spaces. Thus, although this study showed no treatment effects on total transport losses, the results suggest that pigs transported for short journey times at low floor spaces are more stressed after unloading at the plant and, consequently, are likely to be more at risk of becoming fatigued. Encouragingly, the results of this study also clearly demonstrate that it is possible to transport pigs from the farm to the plant with very low losses, certainly relative to what historically has been the case in the US.