Selenosis in the Soil, Plant and Human Continuum-A Review

Chronic Selenium toxicity is a leading cause of hair, hoof, bone and reproductive disorders in animals. It occurs due to consumption of water or vegetation (fodder) growing on seleniferous soils (soils >0.5 mg Se/kg) leading to cycling of selenium in soil-plant-animal-human cycle continuum. The minimum nutritional requirement of animals is above 0.05–0.10 mg Se/kg in dry forage feed, below which deficiency disorders arise, levels ranging from 0.1–1.0 mg/kg feed offers protection and exposure to still higher levels ranging from 2–5 mg Se/kg feed results in toxic effects. Selenium poisoning results in loss of body condition and hair, necrosis of tail tip, reluctance to move, stiff gait, hoof over growth followed by cracks gradually leading to detachment from main hoof, abnormalities of horn growth and shedding of horn corium, some may show loss of hair from swish of tail and bilateral cataract. Selenium toxicosis in human population showed loss of hair from body particularly head, malformation of fingers as well as toe nails, occasional severe headaches and nausea and general malaise. In some humans, finger nails detached completely with blood oozing from finger tips. Various farmer friendly technologies for minimizing movement of Selenium through soil-plant-human/animal system have been devised such as feeding of cereals, oat, maize, sorghum, bajra, guinea grass and senji and avoidance of first two cuts of lucerne and berseem as well as phosphatic fertilizers. Application of Gypsum (sulphur) and feeding of arsenic salts, pentasulphate salt mixture and high protein diet have also proved to be useful antidote of Selenium toxicosis.