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Dietary availability of magnesium hydroxide powder in sheep and in vivo and in vitro assessments of granular calcined magnesites of different origin

Published online by Cambridge University Press:  05 November 2021

R.G. Hemingway ,
E.R. Parker  and
N.S. Ritchie
R.G. Hemingway
Affiliation:
Glasgow University Veterinary School, Bearsden, Glasgow G61 1QH, United Kingdom
E.R. Parker
Affiliation:
Glasgow University Veterinary School, Bearsden, Glasgow G61 1QH, United Kingdom
N.S. Ritchie
Affiliation:
Glasgow University Veterinary School, Bearsden, Glasgow G61 1QH, United Kingdom
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Extract

The standard recommendation for grazing cows to be given 60g calcined magnesite (c. 30 g Mg /day) seems large relative to the ARC (1980) dietary Mg allowance (0.17 coefficient of Mg absorption in the whole diet) of 32.6 g for 30 kg/day milk yield. ARC (1980) estimated the coefficient of absorption of calcined magnesite could be 0.05-0.10 and indicated that supplementary magnesium sources should be readily soluble in rumen liquor. Both temperature of calcination and particle size markedly influence rumen solubility and apparent Mg availability of calcined magnesite (Adam et al. 1996). Magnesium hydroxide powder (H, 404 g Mg/kg) is very finely divided (970 g/kg < 20 μm of which 870 g/kg is < 6um and with 200 g/kg < l μm diameter and is manufactured on a large scale (Redland Minerals, Hartlepool TS24 0BY). ‘Granular’ calcined magnesites are screened to < c. 2000μm diam.

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Information
Proceedings of the British Society of Animal Science , Volume 1997 , 1997 , pp. 155
Copyright
Copyright © British Society of Animal Science 1997

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References

Agricultural Research Council. 1980. The Nutrient Requirements of Ruminant Livestock. Slough: Commonwealth Agricultural Bureaux.Google Scholar
Adam, C.L., Hemingway, R.G. and Ritchie, N.S. 1996. Influences of manufacturing conditions on the bioavailability of magnesium in calcined magnesites measured in vivo and in vitro . Journal of Agricultural Science, Cambridge 127: 377–385.CrossRefGoogle Scholar