Magnesium metabolism in ruminant animals and its relationship to other inorganic elements

The present work provides information about magnesium metabolism in ruminants. It includes information about some relationships between magnesium and other nutrients, such as minerals (calcium, phosphorus, sodium and potassium) and the macronutrients (protein and energy). The importance of magnesium in the diet of animals has been known for more than half a century and due to the many different biochemical reaction where this element plays an important role it has been thought that during the evolution process magnesium must have been the first element to be incorporated in the primitive cell. Magnesium is a cofactor in various reactions related to carbohydrate lipid and protein metabolism. In addition, it participates in various other reactions and processes, including oxidative phosphorylation and transphosphorylation reactions, hibernation and inhibition of thyroid hormone transport, cell adhesion, and exhibits some function as an anti-stress, anti-oxidant, anti-inflammatory, anti-hypoxic and anti-pyretic agent. Magnesium is found in nature in different forms and it may represent about 2.5% of the earth. It comprises around 0.05% of the animal organism. Legumes and grasses have different content of magnesium and its bioavailability in the plant varies through out the year. Genetic factors has great influence in the mineral content in the plant and promising efforts are being made for increasing the magnesium content of several grass species. Within the plant it is found preferably in leaves and being highly available in the chlorophyll. Absorption of ingested magnesium in the ruminant occurs preferably within the rumen through an active process. The lesser absorption occurring post-ruminally is of greater importance in young than in older animals. As such, incidence of hypomagnesaemia should be expected to be greater in the latter animals. Sodium, vitamin D, high energy content of diet and probably saponins have a positive effect on the absorption within the gut and re-absorption within the renal tubules. Factors affecting the bioavailability of intested magnesium may cause mild (hypomagnesaemia) or severe (grass tetany) magnesium deficiency.