Porcine Stress Syndrome By Rushda Khan

Introduction Malignant hyperthermia Hypermetabolic syndrome Pig highly susceptible to stress Pietrain, Poland China, Duroc, Large White Consequences for meat quality

Across species summary Humans, pigs, cats, dogs and horses. Dramatic rise in body temperature Various symptoms Volatile anaesthetics

Species summary and History Transport or social stress Hot weather PSE meat Humans: Unexplained anaesthetic deaths First case in Australia in 1962 in humans

Clinical summary Muscular stiffness Tachycardia and tachypnea Cardiotoxic serum potassium levels Blanching and erythema Elevated core body temperature

Generalized oedema and frothy exudates from trachea

Red skin (rash) Modern hybrid pigs Show lesions of erythema when restrained. Could die if not released quickly Associated with stress susceptibility and PSS

Back Muscle Necrosis Special manifestation in animals > 50 kg’s. Curvature of the body towards affected side

Pathology summary Ryanodine receptor floods myoplasm of skeletal muscle with calcium Muscle contracture and hypermetabolism ATP depleted Increased aerobic and anaerobic metabolism Co2 and lactic acid produced Rhabdomyolysis Death occurs due to an increase in serum potassium Cardiac dysrhythmia and arrest

Prevalence and Inheritance Greater than 90 % Higher in lean, heavily muscled breeds Mortality around 3.2 % Autosomal recessive gene with variable penetrance Mutation in ryanodine receptor

Molecular genetics At least 70 mutations in ryanodine receptor have been described Long arm of 19th chromosome (19q13.1) MH1 and 2 N-terminus MH3 C-terminus

Genotype test and control Use of halothane DNA based assays Select against trait Economic consequences Some breeds extinct Good animal husbandry and management practices

Treatment Dantrolene sodium Fluid therapy Management of acidosis Oxygen enrichment Treatment of cardiac dysrhythmias Unexplained anaesthetic or transport deaths

Consequences for meat quality Unusually high rate of PM glycolysis PSE meat (Pale, soft, exudative) Poor quality

References The Encyclopaedia of Animal Science The Merck Veterinary Manual (9th edition) Pig Production A Colour Atlas on Diseases and Disorders of the Pig