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Studies on the nutritive value of the diet selected by grazing sheep. VI. The use of tritiated water as a marker to estimate the composition of the diet from material collected by oesophageally fistulated sheep

Published online by Cambridge University Press:  02 September 2010

J. P. Langlands  and
J. E. Bowles
J. P. Langlands
Affiliation:
CSIRO, Pastoral Research Laboratory, Armidale, N.S.W., 2350, Australia
J. E. Bowles
Affiliation:
CSIRO, Pastoral Research Laboratory, Armidale, N.S.W., 2350, Australia
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Summary

Five forages were given to three oesophageally-fistulated sheep held in metabolism cages. Estimates of the N, P and K contents of the forages were derived after correcting the composition of the extrusa for salivary contamination by using tritiated water (TOH) as a marker. Estimated N and P contents of the diet were generally higher, and estimated K content was lower, than in the diet. The estimates were variable and could not be used to estimate dietary N, P or K. It is suggested that the ratio of N, P or K to TOH of the pre-feeding saliva sample may have differed from the corresponding ratio during feeding, or that TOH may have moved independently of salivary N, P or K during feeding and processing. These difficulties might be overcome by marking each dietary component with its own isotope.

Estimates of dietary composition were also derived from analyses of squeezed extrusa without correcting for residual saliva or losses in leaching. The error with which dietary N content was estimated was then sufficiently low for most practical purposes. The equation relating dietary and extrusa N contents yielded similar estimates of dietary N to an equation derived in an earlier report.

Type
Research Article
Information
Animal Production , Volume 16 , Issue 1 , February 1973 , pp. 59 - 65
Copyright
Copyright © British Society of Animal Science 1973

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References

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