Rapid Communication: A comparison of cardiac lesions and heart weights from market pigs that did and did not die during transport to one Ontario abattoir1

Abstract

In-transit losses of market hogs represent a small proportion of all market-weight pigs shipped in a year. This suggests that individual pig factors may be a significant cause of in-transit losses along with more traditionally considered environmental and transport factors. An investigation was performed to determine whether cardiac pathology and heart weights were associated with pigs that did or did not die during transport to an abattoir. The hearts from 70 pigs that died in-transit to one Ontario abattoir and 388 pigs that arrived alive were collected and examined. Hearts from pigs that died during transport demonstrated greater frequencies of cardiac lesions (P < 0.05). These included hypertrophy of ventricle walls (Left: 97% vs. 64%; Right: 86% vs. 57%), dilation of ventricle chambers (Left: 79% vs. 0.5%; Right: 100% vs. 5%), and dilation of the pulmonary artery and aorta (59% vs. 1.5%). Total heart weight to body weight ratios were increased (3.6 vs. 3.3 g/kg) and left ventricle plus septum weight over right ventricle weight ratio was decreased in pigs that died during transport over non–in-transit loss pigs (2.5 vs. 2.8; P < 0.05). This may indicate reduced cardiac function in hogs that died during transport. Pigs with reduced cardiac function would have exercise intolerance and be more susceptible to death during transport due to the increased cardiac workload required during sorting, loading, and transport of the pigs to the abattoir. Further research to quantify cardiac function in pigs with cardiac lesions or abnormal heart weight ratios is warranted.

A high-throughput study of visceral organs in CT-scanned pigs

“…It should also be mentioned that the outer heart volume could e.g. potentially be influenced by hypertrophy of ventricular walls and dilatation of ventricular chambers, which is reported to be common in finisher pigs in Canada 6 . Whether such lesions exist among purebred nucleus pigs, is questionable, but compensatory remodelling could potentially give a deviating relationship between heart and body size.…”

“…quantifying the capacity of the heart and lungs. Previous studies 2 , 6 show that heart lesions and abnormalities, like hypertrophy of the ventricular walls are quite common in finishers and growing pigs, even in animals that seem healthy 6 . More specifically, van Essen et al 2 observed that some traits describing the circulatory capacity, like cardiac output and stroke volume in pigs did not scale proportionally with body weight (BW) according to the allometric scaling laws.…”

“…Pig breeders have selected pigs for traits like feed efficiency, backfat thickness and daily gain for several decades. It has been debated how this has affected the size of visceral organs 1 – 5 , and whether the organs have been developing accordingly, to cope with stressors and disease 6 .…”

“…However, since the circulatory and respiratory systems seem to play important roles for sudden deaths, both among finishers 6 , 12 and sows 8 , 13 , one strategy could be to develop indicator traits, e.g. quantifying the capacity of the heart and lungs.…”