Identifying the Cause of Death and Factors Associated with Hogs that Perish in Transit
Project 12-019 and 13-006 - Researcher: Kathy Zurbrigg
Researcher: Kathy Zurbrigg, OMAFRA, University of Guelph
Project funded in 2012 and 2013 and completed in 2016
THESIS: Cardiac weights and lesions as risk factors of in-transit losses of market-weight pigs in Ontario
Summary: The actual cause of in-transit losses of swine is complex as they are likely the result of a combination of risk factors and situations the pigs may have been exposed to. The commonly cited risks of high temperature and stocking density are part of the problem but do not fully explain all transport losses. For this project, University of Guelph PHD student Kathy Zurbrigg wanted to investigate if individual pig factors such as health could explain why so few pigs die during transport when in general many of the pigs shipped in a day are exposed to the same conditions. Working with a large abattoir in Ontario, the researcher sent the in-transit loss (ITL) carcasses to the Animal Health Laboratory, University of Guelph for a post-mortem examination by a pathologist. The examination of 85 market hogs demonstrated the most common findings to be congestion and fluid in the lungs and cardiac abnormalities. These findings indicated acute heart failure as the cause of death in the ITL hogs examined and further examinations focused only on cardiac health.
Examination of the hearts of over 150 hogs that died during transport demonstrated thickened heart walls and enlarged heart chambers in these pigs as compared to the 350 hearts examined from the processing line (hogs that did not die during transport). The cardiac lesions of thickening and enlargement were supported by the observations of increased heart weights in the hogs that died during transport. While measures of cardiac function were not measured in this study, it is possible that pigs with cardiac lesions or increased heart weights are unable to respond to the increased cardiac exertion required during sorting, loading and transport to the abattoir which results in transport mortalities due to heart failure. This is would be similar to the reduced tolerance for exercise and heat that humans with heart dysfunction show, as both situations increase the work load on the heart. Further research is needed to determine what initiates cardiac lesions in pigs and to measure cardiac function in pigs with lesions. A preliminary genetic analyses indicated that the cause of lesions is likely multifactorial. A complete examination of the heart including total and sectioned cardiac weights and ratios should be a key component of a post-mortem examination when determining the cause of death in ITLs.