The threshold for even one animal can change over time. Research was concerned with the determination of the lower threshold for a livestock population. The pathway for current through an animal with the least resistance is from the mouth to all hooves. Due to this pathway being the most sensitive for the animal, much of the research has focused on current or voltages at feeders and waterers. This is especially true for long term studies.
Perception involves an animal's initial awareness of current.
Animals cannot tell us when they first perceive current, therefore, researchers can only look for initial changes in normal behavior. Behavior change will normally involve some type of avoidance by the animal. When exposed to the electrical current, an animal may position or move itself so that it is no longer a part of the electrical circuit. All of these changes can also be associated with normal behavior, making the interpretation of behavior difficult at times. A production loss occurs if water or feed consumption is reduced for a sustained period of time.