Waldner Cheryl, Checkley Sylvia, Blakley Barry, Pollock Colleen, Mitchell Becky
Department of Large Animal Clinical Sciences, Western College of Veterinary Medicine, Saskatoon, Saskatchewan, Canada.
J Vet Diagn Invest. 2002 Nov;14(6):481-6. doi: 10.1177/104063870201400606.
Lead poisoning is commonly diagnosed in cattle. In this study, 3 groups of cattle from different herds accidentally exposed to discarded lead batteries on pasture were intensively studied to determine the extent and severity of exposure. The losses from acute death due to lead toxicity were substantial in all the 3 study groups at 12%, 17%, and 4%. Blood samples were taken from all cattle around the time of the first diagnosis and then later in 2 of the 3 herds to monitor the change in lead concentrations over time. Asymptomatic lead toxicosis was observed in these herds. In these 3 groups, between 4% and 12% of asymptomatic cattle had blood lead concentrations consistent with acute lead poisoning (> 0.35 ppm), and between 7% and 40% of these asymptomatic animals were in the high-normal range (0.1-0.35 ppm). Because of the consistently high number of asymptomatic cattle with elevated lead levels, all cattle potentially exposed to a lead source should be tested before sale or slaughter to minimize the entry of lead into the food chain. The blood lead concentrations, which were monitored for months after the initial diagnosis, decreased slowly after the cattle were removed from the lead source. The prolonged retention of lead may be due to continued release and absorption of lead from metal particles in the reticulum or rumen. The mean reduction in the lead level was 0.046 ppm (95% CI, 0.017-0.075 ppm) every 30 days for these 2 herds. Using a single-component exponential model, the half-life of lead in the animals retested from Herds 1 and 2 was highly variable. The median half-life was 63 days (interquartile range, 34-107 days). One out of 8 pregnant heifers with high blood levels had a stillborn calf. There were no abortions or calf mortalities in this group. Blood samples were'collected from the calves around the time of birth. The concentrations of lead in the blood of the calves exposed in utero were low (0.010-0.095 ppm).
牛群中铅中毒很常见。在本研究中，对来自不同牛群、意外在牧场接触废弃铅电池的3组牛进行了深入研究，以确定接触的程度和严重程度。在所有3个研究组中，因铅中毒导致急性死亡的损失相当大，分别为12%、17%和4%。在首次诊断时从所有牛身上采集血样，随后在其中2个牛群中进行后续采样，以监测铅浓度随时间的变化。在这些牛群中观察到无症状铅中毒。在这3组中，4%至12%的无症状牛的血铅浓度与急性铅中毒一致（>0.35 ppm），这些无症状动物中有7%至40%处于高正常范围（0.1 - 0.35 ppm）。由于无症状且血铅水平升高的牛数量一直居高不下，所有可能接触铅源的牛在出售或屠宰前都应进行检测，以尽量减少铅进入食物链。在首次诊断后的数月内对血铅浓度进行监测，牛群脱离铅源后，血铅浓度下降缓慢。铅的长期留存可能是由于来自网胃或瘤胃中金属颗粒的铅持续释放和吸收。这2个牛群每30天铅水平的平均下降量为0.046 ppm（95%可信区间，0.017 - 0.075 ppm）。使用单组分指数模型，对来自第1和第2牛群重新检测的动物体内铅的半衰期变化很大。中位半衰期为63天（四分位间距，34 - 107天）。8头血铅水平高的怀孕小母牛中有1头产下死胎小牛。该组未出现流产或犊牛死亡情况。在小牛出生时采集血样。子宫内接触铅的小牛血液中的铅浓度较低（0.010 - 0.095 ppm）。
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