Grass Tetany: An Hypothesis Concerning its Relationship with Ammonium Nutrition of Spring Grasses

Abstract

An hypothesis suggests that grass tetany is caused by the peculiar growing conditions during early spring resulting in unique compositional characteristics of spring forages. Winter leaching, low soil temperatures, and application of ammonium containing fertilizers make the ammonium ion the principal source of nitrogen available to the plant during this period. Absorption of ammonium by the plant results in greatly reduced uptake of magnesium and calcium with little effect on potassium and produces high amide concentration in the plant with depletion of carbohydrates. These factors combine in the animal to create a high concentration in the rumen of free ammonia and an increased pH, depletion of the remaining carbohydrate, and a further reduction in the availability of the already low magnesium and calcium. When these factors are expressed, they result in low magnesium in blood serum and interact to produce hypomagnesemic tetany in the animal.