The halothane test: a practical method of eliminating porcine stress syndrome.

Pigs that are genetically liable to porcine stress syndrome can be detected around seven weeks old by their reaction to breathing halothane. Selection trials showed that the most probable form of inheritance for the halothane reaction was a single recessive gene. This halothane gene was also found to have good and bad effects on other economically important production traits, for example, improved carcase quality but reduced reproductive performance. The highest frequencies of the halothane gene were found in the pietrain and landrace breeds.