Behaviour is the primary indicator of stray voltage. In fact, the first symptoms manifested by dairy cows are for example, nervousness, changing in milking characteristics, prolonged milking process, kicking, chronic mastitis, poor breeding success, high number of somatic cells and reduced water intake. The symptoms manifested in pigs are aggressiveness, nervousness, cannibalism and reduced water intake. Other factors can contribute to undesirable behaviour, however, in case of doubt, an analysis of the presence of stray voltage is preferable. In addition, it is important to realize that sources of stray voltage can be either inside or outside of the building.