Small electric currents affecting farm animals and man: a review with special reference to stray voltage. II. Physiological effects and the concept of stress.

The literature on the influence of small, steady electric currents on animal health, especially cardiovascular and endocrinological functions and milk let-down, and the effects on milk production is reviewed, with special reference to the problem of stray voltage. Direct physiological effects in cows may occur above 4 mA. How the long-term effects may contrast with the acute effects is not known. Habituation may occur. The altered behaviour and physiological changes due to exposure to stray voltage may be termed a stress response. The type of stress most likely to be encountered is chronic. Whether or not stress occurs depends on the timing and context of exposure and on individual cognition. Hence stray voltage may threaten farm animal health and production wherever modern animal housing is applied.