Davidson-York D, Galey F D, Blanchard P, Gardner I A
California Department of Food and Agriculture, Sacramento 95814, USA.
J Vet Diagn Invest. 1999 Jul;11(4):352-7. doi: 10.1177/104063879901100410.
In May 1996, 150 grower pigs in 5 California counties were exposed to selenium-contaminated feed distributed by a single feed company. Feed samples from 20 herds had a mean selenium concentration of 121.7 ppm dry weight (range, 22.1-531 ppm). In San Luis Obispo County, 52 pigs in 24 herds were exposed to the feed, and 8 pigs died with signs of paralysis. Bilateral symmetrical poliomyelomalacia involving the ventral horns of the cervical and lumbar intumescence was evident on histologic examination of spinal cord from affected pigs. Of 44 surviving exposed pigs, 33 (75%) exhibited signs of selenosis, including anorexia, alopecia, and hoof lesions. Thirty-nine of 44 pigs (88.6%) had elevated (>1 ppm) blood selenium concentrations. Surviving exposed pigs were changed to a standard commercial ration containing approximately 0.5 ppm (dry weight) selenium. Blood selenium concentrations were determined weekly for 46 days following removal of the contaminated feed and were compared with values of 20 control pigs fed a standard commercial ration. Mean (+/-SD) blood selenium concentrations of exposed pigs were 3.2 +/- 2.6 ppm at the initial sampling and 0.4 +/- 0.1 ppm after 46 days. Mean blood selenium concentrations of < or = 0.3 ppm for control pigs at all samplings were significantly lower (P < 0.001) than concentrations for exposed pigs. Muscle and liver samples of 22 of the 44 exposed pigs were collected at slaughter approximately 72 days after withdrawal of the selenium-contaminated feed. Muscle samples had a mean selenium concentration of 0.36 ppm (wet weight). Liver samples had a mean selenium concentration of 1.26 ppm (wet weight). One liver sample had a selenium value in the toxic range for pigs (3.3 ppm wet weight; reference range, 0.4-1.2 ppm). A 1-compartment pharmacokinetic model of selenium elimination in exposed pigs was generated, and the geometric mean blood selenium elimination half-life was estimated to be 12 days. The 60-day withdrawal time recommended by the Food Animal Residue Avoidance Database was considered sufficient to allow safe human consumption of tissues from exposed pigs.
1996年5月，加利福尼亚州5个县的150头生长猪食用了由一家饲料公司分发的受硒污染饲料。来自20个猪群的饲料样本干重中硒的平均浓度为121.7 ppm（范围为22.1 - 531 ppm）。在圣路易斯奥比斯波县，24个猪群中的52头猪食用了这种饲料，8头猪死于麻痹症状。对患病猪脊髓进行组织学检查时，可见双侧对称性脊髓灰质软化，累及颈膨大及腰膨大的腹角。在44头存活的接触饲料猪中，33头（75%）出现了硒中毒症状，包括厌食、脱毛和蹄部病变。44头猪中有39头（88.6%）血硒浓度升高（>1 ppm）。存活的接触饲料猪改喂含硒量约为0.5 ppm（干重）的标准商业日粮。在去除受污染饲料后的46天内，每周测定一次血硒浓度，并与20头喂标准商业日粮的对照猪的值进行比较。接触饲料猪在初次采样时血硒平均浓度（±标准差）为3.2±2.6 ppm，46天后为0.4±0.1 ppm。所有采样时对照猪血硒平均浓度≤0.3 ppm，显著低于（P<0.001）接触饲料猪的浓度。在停用受硒污染饲料约72天后宰杀44头接触饲料猪中的22头，采集肌肉和肝脏样本。肌肉样本硒平均浓度为0.36 ppm（湿重）。肝脏样本硒平均浓度为1.26 ppm（湿重）。一个肝脏样本的硒含量处于猪的中毒范围内（3.3 ppm湿重；参考范围为0.4 - 1.2 ppm）。建立了接触饲料猪体内硒消除的一室药代动力学模型，估计几何平均血硒消除半衰期为12天。《食用动物残留避免数据库》推荐的60天停药期被认为足以保证人类安全食用接触饲料猪的组织。
