The effect of Calcination Temperature on the Bio-availability of Magnesia in Ruminant Livestock.
Calcination is the process whereby magnesite (natural magnesium carbonate MgCO3) is decomposed under heat to produce magnesium oxide (calcined magnesia / magnesite MgO).
It has been shown1 that the temperature at which the process is conducted has a profound effect upon magnesium bio-availability from the ensuing product. Magnesia samples were prepared by calcining magnesite over a range of temperatures. Availability was determined in a balanced study with sheep and by using the chromic oxide indigestible marker method, with good agreement between each.
The availability of magnesium was similar (45-47%) from products calcined at 800, 900 or 1100oC, but lower temperatures produced materials with reduced availability.
The control of temperature and calcination technology (kiln type) employed are important considerations in the production of reactive (high bio-availability) magnesia products.
Vetmag is manufactured in modern state-of-the-art, multiple hearth kilns, employing the latest in computer process control. This type of kiln allows ultimate control over calcination temperature profile (800 - 1000oC) to ensure that consistently high surface area (hence high reactivity) products are produced.
Many other commercially available calcined magnesia products (particularly those sourced from China) are produced in old shaft kilns, which are known to be more suitable for producing high temperature magnesias (such as those used for making refractory materials). But typically such products will be over-calcined and hence of lower reactivity and bio-availability.
Availability of magnesites calcined at different temperatures.
1 Wilson C.L. & Ritchie N.S. (1981) - The dietary availability of calcined magnesites to ruminants; Journal of the Science of Food and Agriculture 32:993-994
June 1996
© Copyright - freely available for reprint as long as attribution is made to Independent Veterinary Supplies Ltd (NZ) as source of material.
® Vetmag is a registered trademark to, and is manufactured by, Queensland Magnesia Pty Ltd, Australia.
