To determine the threshold voltage at which lambs start to express avoidance behavior and to test if the contextual conditions (1 or two feeders) influence the determination of the threshold voltage inducing avoidance behavior.
Six month-old female lambs were divided into two groups. The first group (n=13) had one feeder, while the second group (n=13) had two feeders. A voltage was then applied during a 2-min test to either the only feeder available (group 1) or to the first of the two feeders in which the lamb started to eat (group 2). The lambs of the first group had to stop eating to avoid the voltage, whereas the lambs of the second group were allowed to switch to the non-electrified feeder to carry on eating without any stray voltage. The voltage was increased every day in 0.5 V steps (0-8 V).
Exposure duration: continuous for 2 min/day for 16 days
|Exposure duration||continuous for 2 min/day for 16 days|
|Setup||lamb starting from a 1.5 m x 1.0 m starting cage into a 4.0 m x 1.5 m raceway whose sidewalls consisted of wood; a 1.2 m x 1.4 m copper plate, insulated from the ground, placed at the end of the raceway; one or two metal feeders, insulated from the other metalic equipment, positioned on the copper plate; for the tests with one feeder the voltage was applied to this feeder, for the tests with two feeders the voltage was applied only to one of them|
|cf. remarks||-||-||-||-||U = 0 - 8 V rms increased in 0.5 V steps|
No voltage effect was observed for the heart rate during the entire test.
In both groups, more urinations were recorded during the 5.5 to 8 V period compared with the 0.5 to 2.5 V period. Additionally, more lambs of the first group urinated during the whole experiment compared with lambs of the second group.
For voltages higher than 4.5 V, lambs of the second group spent less time eating and ate less in the electrified feeder compared with the non-electrified feeder, and their latency to switch to the non-electrified feeder was shorter than in voltages below 4.5 V. In addition, in the second group, a transient modification of behavior was observed at 1.5 V: the latency to change to the non-electrified feeder decreased and the lambs spent more time eating in the non-electrified feeder compared with voltages below 1.5 V. For the lambs of the first group, a decrease in the quantity of feed eaten was found for voltages higher than 5 V, although the time spent eating in the electrified feeder was not modified.
The authors conclude that the contextual conditions in which animals are exposed to stray voltage influence their subsequent reactions: a clear behavioral reaction threshold is easier to detect in choice than in no-choice conditions.