The cause of death for hogs that die in transit to a packing plant is an economic and welfare concern to producers, transporters, abattoirs and consumers.
In fact, according to K. Zurbrigg of the Ontario Ministry of Agriculture and A. van Dreumel of the University of Guelph, the increase in shipping mortalities observed during the summer months in Canada and the U.S. is commonly attributed to heat exhaustion or heat stress but few studies have identified the specific cause of death for these hogs.
The objective of recent work by Zurbrigg and van Dreumel was to determine if there are underlying physiologic risk factors that predispose a market hog to death during transport to slaughter.
In an attempt to make this determination, post-mortems on 62 hogs that died in transit were completed at the abattoir or at the Animal Health Laboratory, University of Guelph. Fifty hearts were collected from hogs that did not die in transit. Each heart was examined blindly by one veterinary pathologist (TVD) grossly and histologically. Heart weights for hogs that died in transit were compared with the controls.
The researchers reported at JAM 2013 that heart failure was the cause of death for 68% (42/62) of the hogs that died during transport. Heart lesions were chronic in nature, they said.
In 21% of the hogs, the only findings on gross post-mortem examination were pulmonary congestion and edema of the lungs. In 11% of the hogs, lesions unrelated to heart failure were identified (e.g., respiratory or gastrointestinal disease, fractures). No lesions were found on the gross examination of the control hearts. Final analysis of histologic results is pending.
Compared with most other mammals, the researchers noted that a pig’s heart is small in relation to its body size. As a result, they said, hearts with compromised function have little reserve capacity to respond to challenges.
In this study, the researchers determined the majority of hogs that died in transit had a pre-existing cardiac abnormality resulting in hogs that were unable to survive standard transport practices.