Longer transport times could reduce pig stress
The life of a hog on the journey to a processing plant can be stressful. Like in humans, effects of stress can damage the health of pigs. To better understand what causes stress in pigs, scientists at the University of Illinois recently conducted a study focusing on the effects of floor space during transport, the length of the journey and the stress levels of hogs. The researchers found that pig producers may be able to reduce animal stress by giving pigs time to recover from stress between loading and unloading of transport trailers. This information could help improve pig well-being and decrease economic losses for pig producers.
During the study, a team of processing plant workers and researchers from the University of Illinois recorded numbers of hogs that could not walk or showed other signs of stress as the hogs were unloaded from trailers. They collected data from 17,652 pigs in 160 trailer loads.
Results indicated that short transport times may not give pigs long enough to recover from loading stress before unloading stress begins. Stressed hogs may experience skin discoloration, body weight loss and muscle tremors. Signs of stress also include loud vocalizing and even open mouth breathing. This study found that frequency of skin discoloration increased for hogs with short journeys (less than 40 minutes) than hogs with longer journeys (40 minutes to 3 hours). The scientists found that 2.07% of pigs had skin discoloration after short journeys, compared with 1.29% of pigs after longer journeys. This indicated that hogs were more stressed on shorter trips.
Decreased floor spaced for hogs, combined with short journey times could also add to stress. In the study, pigs with less than 0.489 meters square of floor space showed increased open-mouthed breathing. Even with a more generous .520 meters square of floor space, open-mouthed breathing was much more common after short journeys. After short journeys 0.63% of pigs were breathing with open mouths, compared to only 0.18% after longer journeys. Though they also recorded the number of pigs with muscle tremors, the scientists did not record a significant impact of journey time or floor space on tremors.
Overall, the researcher identified 0.24% of the 17,652 pigs as ‘transport losses.’ That was the average of 0.29% lost pigs during short journeys and 0.20% lost during the longer journeys. Transport losses were defined as pigs that became nonambulatory (not able to walk) or died during transport. The loss of 0.24% of pigs was actually an extremely low number of transport losses, and it surprised the researchers.
“Results of this study with respect to the effects of floor space on total transport losses were unexpected and not in line with other studies carried out in the system used for the current experiment,” said Dr. Mike Ellis, professor of animal sciences at the University of Illinois at Urbana-Champaign and co-author of the study.
While this result was unexpected, it is encouraging news for pig producers. The researchers found that it is possible to transport hogs under commercial conditions with very few losses. To further improve animal well-being, producers could give pigs time to get over stress by extending loading and unloading times. Ellis and his colleagues also suggested that future researchers study specific reasons for stress.
The study was titled “Effects of floor space during transport and journey time on indicators of stress and transport losses of market-weight pigs.” It can be read in full at http://journalofanimalscience.org/
ASAS Scientific Communications Associate
MadelineMS@asas.org / 217-689-2435