Relationship between soil cobalt and vitamin B12 levels in the liver of livestock in Saudi Arabia: role of competing elements in soils

Objective: This study aimed to analyze the agricultural soils from different regions in Saudi Arabia for cobalt and related metals as Cu2+, Ni2+, Cr3+, Zn2+ and Pb2+. Materlais and methods: Liver and muscle tissues of livestock grazing on the selected areas were analyzed for the content of Co and vitamin B-12. Results: Our results indicated that the levels of Co in surface soil (0-15 cm) were higher than in sub-surface soil (> 15 cm-45 cm). In contrast, Pb and Zn were higher in sub-surface soil than in surface soil. A significant positive correlation existed between the levels of Co and vitamin B-12 in the liver of livestock. However, Co was not detected in muscle tissues while vitamin B-12 was present at very low levels in comparison with the levels found in the liver. The results indicated that Zn2+, Pb2+ compete with Co in soil, which eventually affected the levels of vitamin B-12 in liver. Conclusion: It was recommended that survey of heavy metals in grazing fields of cattle should consider inclusion of multiple elements that compete with the bioavailability of essential elements in plants and animals for the prevention of deficiency of essential elements such as Co.