研究のタイプ: 医学/生物学の研究 (experimental study)

[漂遊電圧閾値はヒツジでの選択試験条件下でより良く測定される] med./bio.

Stray voltage threshold is better determined under choice test conditions in sheep.

掲載誌: Animal 2011; 5 (6): 918-926

この研究は、農場で発生する迷走電圧(通常、10 V未満)がヒツジの行動に及ぼす影響を調べた。具体的には、(i)子ヒツジが回避行動を始める閾値電圧を決定すること、(ii)回避行動誘発閾値電圧は、行動に選択なしと選択ありの状況が影響を与えるか否かを、分析した。自由に餌を与えられた生後6か月の雌の子ヒツジを、長さ4mの競走路の端にある1つまたは2つの金属製給餌装置からペレットを食べるよう訓練した。次に、2分間の選択なしテスト(n = 13)または選択ありテスト(n = 13)を行った。選択なしテストでは、2つの給餌装置のどちらかを餌が出るようにし、それにのみに電圧を印加した。選択ありテストでは、2つの給餌装置のうち、子ヒツジが餌を食べ始めた装置に電圧を印加した。すなわち、選択なしテストでは、電圧を避けるために食べるのをやめなければなりないが、選択テストでは、電圧なしで食べ続けるために、もう一方の装置に移ることができた。迷走電圧AC、50 Hz)は、0から8 Vまで0.5 V刻みで、毎日印加された。その結果、電圧が4.5 Vを超えると、選択ありテストにおいて、子ヒツジの印加装置での食餌時間および食餌量は、非印加装置でのものに比べて少なくなり、非印加装置への切替えまでの潜時が短くなった;一時的な行動の変化は、1.5 Vで観察された;選択なしテストにおいては、 5 Vを超える電圧で、食餌量減少が見られたが、印加装置での食餌時間に変化はなかった;選択の余地のない子ヒツジは、排尿の発生増加という負のイベントとして迷走電流を体験するが、どんな電圧でも印加装置での食餌を続けた、と報告している。

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研究目的(著者による)

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.

詳細情報

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).

影響評価項目

ばく露

ばく露 パラメータ
ばく露1: 50 Hz
ばく露時間: continuous for 2 min/day for 16 days
  • U = 0 - 8 V rms increased in 0.5 V steps

ばく露1

主たる特性
周波数 50 Hz
タイプ
  • electric field
ばく露時間 continuous for 2 min/day for 16 days
ばく露装置
ばく露の発生源/構造
  • 詳細不明
ばく露装置の詳細 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
パラメータ
測定量 種別 Method Mass 備考
参照 - - - - U = 0 - 8 V rms increased in 0.5 V steps

ばく露を受けた生物:

方法 影響評価項目/測定パラメータ/方法

研究対象とした生物試料:
研究対象とした臓器系:
  • 感覚器
調査の時期:
  • ばく露中

研究の主なアウトカム(著者による)

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.

研究の種別:

研究助成

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