Chemical properties and distribution

The liver, bones, pancreas and kidney maintain relatively high levels of manganese, the muscles very little, the skeleton accounts for approx 25% of total body manganese.

Metabolism

Absorption is equally effective throughout small intestine, yet as a guide horses naturally can have poor absorption ability with regards to manganese, high dietary concentrations of calcium, phosphorous and iron reduce manganese availability within the system. (Hidiroglou, 1979)

Physiological functions

• Enzyme activity – manganese functions as an enzyme activator and as a constituent of metalloenzymes
• Manganese containing enzymes include arginase, pyruvate carboxylase and manganese-superoxide dismutase
• Biotin dependant enzymes such as pyruvate carboxylase continue to fix CO2 during manganese deficiency because magnesium substitutes

Bone growth: manganese deficient bones are considerably shortened and thickened, manganese is essential for the development of the organic matrix of bone which is composed largely of mucopolysaccharides.

There is a metabolic association between manganese and choline (e.g, both prevent perosis). Manganese is involved in the biosynthesis of choline, both nutrients affect membrane integrity.

Carbohydrate metabolism – with manganese glucose utilisation is impaired.

• Abnormalities in the pancreas, manganese may be involved in insulin formation or activity
• Biosynthesis of glycoprotein is impaired in manganese deficiency
• Prothrombin, a glycoprotein, synthesis is controlled by vitamin K and manganese
• A deficiency of manganese can reduce the vitamin K-induced clotting response (Dosey, 1974)

Cell function and structure

In deficiency: abnormalities in cell function and ultrastructure, particularly the mitochondria, various tissues reveal alterations in cell membrane integrity.

Immune function: manganese plays a major role in immunological function, manganese interacts with neutrophils and macrophages. Brain function is also affected by manganese.

Deficiency

In horses deficiency symptoms not available or unknown. Also bear in mind when supplementing with manganese, some forms are more readily absorbed and utilised by the system.