Toxicity of Organic Mercury in Sheep and Hens

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Abstract
When during a year of poor crops, farmers in Iraq tested the toxicity of seed grain treated with methyl mercury (MeHg) fungicide by feeding it to hens, they observed no ill effect. Believing the seed grain to be safe, they consumed it with catastrophic results. The present study was undertaken to compare the toxicity of MeHg in hens with its effects in sheep. New Hampshire hens were fed MeHg-treated grain (8. 5 ppm Hg) for 50 days; then MeHg was withdrawn for 50 days. Lactating and nonlactating ewes were fed the same grain for 65 days, followed by a recovery period of 75 days. Total Hg in blood, plasma, and tissues was determined by flameless atomic absorption spectrophotometry. Hens showed no sign of illness except a 25% decrease of egg laying, which could not reliably be attributed to MeHg. Sheep suffered from exfoliative dermatitis and gingival bleeding, but no overt neurologic signs. The effective biologic half-time (BHT) was 36 days in hens and 29 days in sheep. Significant amounts of Hg appeared in eggs and in milk. Hg levels in the blood and tissues of lactating sheep were significantly lower than in nonlactating animals. This study showed that hens can tolerate exposure to MeHg better than sheep and humans. Eggs and milk appear to be a significant route for the elimination of a body burden of MeHg.