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A source of error in the estimation of the organic matter content of samples containing calcium carbonate

Published online by Cambridge University Press:  27 March 2009

F. D. DeB. Hovell  and
E. R. Ørskov
F. D. DeB. Hovell
Affiliation:
Rowett Research Institute, Bucksburn, Aberdeen, AB1 9SB
E. R. Ørskov
Affiliation:
Rowett Research Institute, Bucksburn, Aberdeen, AB1 9SB
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Extract

The conventional method for the determination of the organic matter content of diets and faeces is by ashing the sample at 550 °C (A.O.A.C, 1965)

Organic matter (O.M.) = dry matter (D.M.)–ash.

If the sample contains calcium carbonate, then some of this carbonate will be converted to oxide (Vogel, 1951) and the weight of carbon dioxide evolved will be calculated as organic matter. The amount of carbonate converted will be dependent upon the temperature at which the sample is ashed and the duration of the ashing process. We have found (Ørskov, Hovell & Allen, 1966; Hovell & Greenhalgh, 1972) that when calcium salts of volatile fatty acids are included in diets given to sheep, most of the calcium is excreted in the faeces as carbonate, and since apparent digestibility is the difference between the amounts of nutrient ingested and excreted, the estimation of the apparent digestibility of organic matter will be in error if no correction is made for the high calcium carbonate content of the faeces. For example, a diet which contained 9·2% of calcium acetate had a true organic matterapparent digestibility of 86·8%. Had no correction been made this would have been estimated as 84·9%.

Type
Short Note
Information
The Journal of Agricultural Science , Volume 79 , Issue 3 , December 1972 , pp. 541 - 542
Copyright
Copyright © Cambridge University Press 1972

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References

REFERENCES

Association of Official Agricultural Chemists (1965). Official Methods of Analysis. Tenth, Ed, A.O.A.C., Washington, D.C.Google Scholar
Hovell, F. D. DeB. & Greenhalgh, J. F. D. (1972). Unpublished observations.Google Scholar
Ørskov, E. R., Hovell, F. D. DeB. & Allen, D. M. (1966). Utilization of salts of volatile fatty acids by growing sheep. 2. Effect of stage of maturity and hormone implantation on the utilization of volatile fatty acid salts as sources of energy for growth and fattening. Br. J. Nutr. 20, 307–15.CrossRefGoogle ScholarPubMed
Vogel, A. I. (1951). A text-book of Quantitative Inorganic Analysis, theory and practice. Second Edn, p. 413. London, New York, Toronto: Longman's Green and Co..Google Scholar