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Measurement of the phosphorus content of herbage selected by grazing cattle: influence of route of isotope administration, animal live weight and dose size on specific activity of saliva

Published online by Cambridge University Press:  27 March 2009

R. W. McLean  and
D. A. Little
R. W. McLean
Affiliation:
C.S.I.R.O. Division of Tropical Crops and Pastures, Cunningham Laboratory, St Lucia, Queensland4067, Australia
D. A. Little
Affiliation:
C.S.I.R.O. Division of Tropical Crops and Pastures, Cunningham Laboratory, St Lucia, Queensland4067, Australia
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Extract

In an earlier paper (Little, McLean & Winter, 1977) we reported a technique for the measurement of the phosphorus content of the diet consumed bygrazing cattle, which recently has been used successfully to measure the dietary intake of phosphorus by sheep grazing Mitchell grass (Astrebla spp.) pastures in western Queensland (Beale & McMeniman, 1978). In this technique, phosphorus of salivary origin is distinguished from that of plant origin in samples extruded by oesophageally nstulated animals by prior labelling of salivary phosphorus with the isotope 32P following the intravenous infusion of Na2H32PO4. The difference in specific activity between saliva and extruded bolus is used as the basis of the calculation of the phosphorus content of consumed herbage. Oesophageally nstulated animals may graze experimental pastures for an hour or more while samples are collected from them. It is important to have an accurate measure of saliva speoific activity, representative of that secreted during the grazing period; therefore, application of the technique is facilitated if the rate of change in saliva specific activity during collection periods is slow and linear.

Type
Short Note
Information
The Journal of Agricultural Science , Volume 93 , Issue 3 , December 1979 , pp. 757 - 760
Copyright
Copyright © Cambridge University Press 1979

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References

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