Fessler A J, Moller G, Talcott P A, Exon J H
University of Idaho, Department of Food Science and Toxicology, University of Idaho, Moscow, ID 83844-2201, USA.
Vet Hum Toxicol. 2003 Dec;45(6):294-8.
Phosphate mining operations in southeastern Idaho have exposed selenium (Se) that was originally sequestered in the subsurface. Sheep grazing in these areas have died as a result of high Se concentrations in forage and water. This study was designed to monitor the health status of sheep grazing in a natural environment with known elevated levels of Se. A total of 72 Columbia x Suffolk sheep were divided into 3 treatment groups that included control (Con), low selenium (LoSe) and high selenium (HiSe). The baseline phase of the study was conducted in an area with normal background Se levels in forage and water, and was grazed for 3 w by all sheep groups. The sheep then were moved onto reclaimed mine areas to begin the 4-w exposure phase. This was followed by a 2-w depuration phase where sheep again received normal Se levels in forage and water. The Con group was held on areas with normal Se levels of forage (< 0.32 ppm Se dw) and water (< 1.70 ppb Se). The LoSe group was held in an area of elevated forage Se (< 13.0 ppm Se dw) and normal Se levels in their water (< 1.70 ppb Se) during the exposure phase. The HiSe group was held on mining areas with elevated Se forage (< 49.0 ppm Se dw) and drinking water (340 to 415 ppb Se). Whole blood and serum levels in the HiSe group peaked at 1.32 and 0.99 ppm mean Se, respectively. The LoSe group had mean whole blood and serum Se levels of 0.75 ppm on day 42 and 0.32 ppm on day 35 respectively. The Con group maintained low Se levels in both whole blood and serum that ranged from 0.05 to 0.14 ppm and 0.06 to 0.13 ppm respectively. The Se exposure in the HiSe group was estimated 0.26 mg Se/kg body weight/d. One sheep in the HiSe group died and was diagnosed with Se toxicosis based on clinical signs, histopathology and tissue Se levels. Se in liver (3.90 ppm), kidney (1.90 ppm) and skeletal muscle (0.70 ppm) were indicative of high to toxic Se exposure. Two other sheep necropsied after the exposure phase also had Se concentrations in liver, kidney and skeletal muscle representative of high or toxic Se exposure (5.50, 3.50 and 1.10 ppm Se), but these sheep had no gross or histopathological signs of illness. More research is needed on the toxicology of Se in sheep grazing natural settings.
爱达荷州东南部的磷酸盐矿开采活动使原本被封存在地下的硒暴露了出来。在这些地区放牧的绵羊因饲料和水中的高硒浓度而死亡。本研究旨在监测在已知硒含量升高的自然环境中放牧的绵羊的健康状况。总共72只哥伦比亚×萨福克绵羊被分为3个处理组，包括对照组（Con）、低硒组（LoSe）和高硒组（HiSe）。研究的基线阶段在饲料和水中硒含量处于正常背景水平的地区进行，所有绵羊组在该地区放牧3周。然后绵羊被转移到复垦矿区开始为期4周的暴露阶段。随后是为期2周的净化阶段，在此期间绵羊再次摄入饲料和水中硒含量正常的食物和水。对照组被安置在饲料硒含量正常（<0.32 ppm硒干重）和水硒含量正常（<1.70 ppb硒）的地区。低硒组在暴露阶段被安置在饲料硒含量升高（<13.0 ppm硒干重）且水硒含量正常（<1.70 ppb硒）的地区。高硒组被安置在饲料硒含量升高（<49.0 ppm硒干重）和饮用水硒含量升高（340至415 ppb硒）的矿区。高硒组的全血和血清硒水平峰值分别为平均1.32 ppm和0.99 ppm。低硒组在第42天的全血和血清硒平均水平分别为0.75 ppm，在第35天为0.32 ppm。对照组的全血和血清硒水平均维持在较低水平，分别为0.05至0.14 ppm和0.06至0.13 ppm。高硒组的硒暴露量估计为0.26 mg硒/千克体重/天。高硒组中有一只绵羊死亡，根据临床症状、组织病理学和组织硒水平诊断为硒中毒。肝脏（3.90 ppm）、肾脏（1.90 ppm）和骨骼肌（0.70 ppm）中的硒表明硒暴露量高至中毒水平。另外两只在暴露阶段后进行尸检的绵羊，其肝脏、肾脏和骨骼肌中的硒浓度也代表了高或中毒水平的硒暴露（5.50、3.50和1.10 ppm硒），但这些绵羊没有明显的疾病体征或组织病理学症状。对于在自然环境中放牧的绵羊，还需要对硒的毒理学进行更多研究。
