THE PORCINE STRESS SYNDROME - A REVIEW OF GENETICS, ENVIRONMENTAL-FACTORS, AND ANIMAL WELL-BEING IMPLICATIONS

The porcine stress syndrome (PSS) is of great importance to the swine industry since it affects both the producers, the packers, and the con sumers. Live animals are affected in the form of malignant hyperthermi a, and the post-slaughter carcass in the form of pale, soft, exudative (PSE) or dark, firm, dry (DFD) muscle. This article reviews the preva lence and pathogenesis of the condition, its linkage to genetic and en vironmental factors, including the well-being of market hogs on the fa rm, during transportation, and during holding at the abattoir. Genetic and environmental factors are particularly highlighted since the rece nt development of DNA probes has enabled determination of both homozyg ous (nn) and heterozygous (Nn) carriers of the stress gene. Multinatio nal surveys show that homozygous (nn) carriers are at the greatest ris k (> 90%) of developing PSE, but heterozygous (Nn) carriers are also a t a much greater risk than non-stress (NN) pigs; however, the most sta rtling finding is the high prevalence of PSE in hams and loins of non- stress (NN) pigs. These findings, and the high prevalence of DFD in so me studies, indicate a very strong impact of environmental factors on the condition (transportation, pre- and post-slaughter handling, etc.) , which might need equal or even more attention than the stress gene.