Frequency of the malignant hyperthermia gene in the South African pig industry

Abstract

Porcine stress syndrome (PSS) is a genetic disorder caused by a recessive mutation in the halothane (HAL) gene and results in sudden death of pigs when placed under stress during transport and pre-slaughtering conditions. Animals that are affected by this mutation tend to develop pale, soft and exudative (PSE) meat, which results in an economic loss. In South Africa, the frequency of the number of carriers (Nn) and recessive (nn) pigs has increased by 21% to 30% from 2000 to 2003. This study aims to determine the prevalence of the malignant hyperthermia (MH) gene in breeding boars at nucleus or seed-stock level, and the prevalence at commercial abattoirs across the South African pig industry. Results indicate a low number of carriers (Nn = 17) and recessive (nn = 1) pigs at seed-stock level. For commercial abattoirs, 96.4% of the pigs tested did not carry the mutation. The low incidence of the MH mutation from breeding stock should eliminate a contributory factor to PSE meat in South Africa. Transport over long distances to abattoirs may ultimately have an effect on pork obtained even from non-carriers of the MH mutation. Keywords : MH gene, halothane gene, PSE meat, ryanodine receptor, seed stock herds