Effect of Cobalt in Plants on Animals

Cobalt uptake by plants allows its access to animals. Kosla (29) demonstrated the effect of irrigation of meadows with the water of the river Ner in Poland on the levels of iron, manganese, and cobalt in the soil and vegetation. Experiments were also carried out on young bulls (Bos taurus L.) fed with the hay grown on these meadows. The levels of iron and cobalt were determined in the blood plasma, and manganese level in the hair of the bulls. The irrigation caused an increase of the cobalt content in the soil, but had no effect on cobalt content in the plants or in the blood plasma of the bulls. Webb et al. (30) stated that animals may act as bioindicators for the pollution of soil, air, and water. To monitor changes over time, a baseline status should be established for a particular species in a particular area. The concentration of minerals in soil is a poor indicator of mineral accumulation by plants and availability to animals.

The chemical composition of the body tissue, particularly the liver, is a better reflection of the dietary status of domestic and wild animals. Normal values for copper, manganese, and cobalt in the liver have been established for cattle, but not for African buffalo. As part of the bovine-tuberculosis (BTB) monitoring program in the KNP in South Africa, 660 buffalo were culled. Livers were randomly sampled in buffered formalin for mineral analysis. The highest concentrations of copper in livers were measured in the northern and central parts of the KNP, which is downwind of mining and refining activities. Manganese, cobalt, and selenium levels in the liver samples indicated neither excess nor deficiency although there were some significant area, age, and gender differences. It was felt that these data could serve as a baseline reference for monitoring variations in the level and extent of mineral pollution on natural pastures close to mines and refineries. Cobalt is routinely added to cattle feed, and deficiency diseases are known. Of interest also are the possible effects of minor and trace elements in Indian herbal and medicinal preparations (64).