Magnesium supplementation of ruminant diets

The major objectives of this thesis were to study the variation in the dietary availability of calcined magnesites to ruminants, both indoors and at grass, and to investigate different experimental methods for availability determinations. Calcined magnesite is given to ruminant animals as a preventitive measure against hypomagnesaemic tetany due to magnesium deficiency. Section I describes this and alternative methods of prevention in current use, following a description of normal magnesium physiology and metabolism in ruminants, the symptoms and incidence of hypomagnesaemic tetany, and factors involved in the development of the clinical condition. In Section II, balance trials with sheep demonstrated that the apparent availability of calcined magnesite was lower in coarse than in fine particles, and that the temperature of calcination was important in so far as "raw" or under calcined magnesite was poorly available whereas material calcined between 800- 1,10