SOIL-PLANT-ANIMAL AXIS IN GRASS TETANY

The etilogies, diagnosis and prevention of grass tetany are reviewed in the present paper. Grass tetany is observed in cattle mainly in Spring and generally when grass growth is rapid after a period of cold rainy weather. It is characterized by a reduction of magnesium concentration in blood plasma. There are many causes consisting in a lack of supply, utilization or transfer of magnesium, different causes being involved simultaneously to induce grass tetany. A daily supply of magnesium in the diet is necessary in order to maintain magnesium homeostasia in the animal, grass composition being a factor of importance in appearence of grass tetany. The soil-plant-animal axis has to be taken into account since grass composition is depending both from the plant and the soil in which it is growing. The management of pasture is also determinant on grass composition. At the animal level, it is possible to explain the conditions of grass tetany from the mecanisms of magnesium absorption and its metabolism. In order to prevent grass tetany the causes which could induce the decrease of plasma magnesium have to be considered as a whole, both at the soil-plant-animal axis and the management of the animal at grass. An adequate use of fertilizer according to yield and soil composition allows the production of grass in which the chemical composition is in accordance with good supply and good assimilation. It is also possible to offer a magnesium supply to the animals in order to increase magnesium in the diet. Finally, it is suggested to supply feedstuffs high in energy and salt.