Stray voltage is defined as the difference in voltage (volts) recorded between two points susceptible to be in contact with an animal, resulting in the passage of electrical current affecting its behaviour. Sources of stray voltage on a farm are vast, since the electrical equipment used has not been designed to drain electrical energy in a controlled manner. In order for an animal to react to stray voltage, the source of the voltage must generate a flow of current having an intensity superior to its tolerance threshold, that being 0.5 volts for cows and 0.25 volts for pigs.