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Overestimation of solubility when using dacron bag methodology

Published online by Cambridge University Press:  24 November 2017

J.E. Cockburn ,
M.S. Dhanoa ,
J. France  and
S. Lopez
J.E. Cockburn
Affiliation:
I.G.E.R., Plas Gogerddan, Aberystwyth, Dyfed, SY23 3EB.
M.S. Dhanoa
Affiliation:
I.G.E.R., Plas Gogerddan, Aberystwyth, Dyfed, SY23 3EB.
J. France
Affiliation:
I.G.E.R., North Wyke, Okehampton, Devon, EX20 2SB.
S. Lopez
Affiliation:
Estacion Experimental Del Zaidin, Granada, Spain.
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Extract

Dacron bag measurements (in-situ) to determine protein degradability of feedstuffs are often used as the “reference method” when comparing laboratory procedures. The model commonly adopted for interpreting data from “in-situ” dacron bag studies is that proposed by Ørskov & McDonald (1979) which is described by the asymptotic equation p = a + b (1-eα) where p is the proportion of material degraded after time t and a, b and c are constants. This model was later extended to deal with the presence of lag times and describes the instantly degradable soluble fraction (‘a’ in the above equation), and a fraction, ‘b’ which is degraded more slowly at an exponential rate V. A knowledge of the rumen fractional rate of outflow (k) for the feedstuff is also necessary to estimate effective degradability (ED). The value of ‘a’ (also referred to as the wash value) forms a major proportion of ED calculations. ED = a + (bc/(c+k)) as it is assumed to be wholly degradable.

Type
Ruminant Metabolism
Information
Proceedings of the British Society of Animal Production (1972) , Volume 1993: Winter meeting , March 1993 , pp. 188
Copyright
Copyright © The British Society of Animal Production 1993

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References

McDonald, I. (1981). A revised model for the estimation of protein degradability in the rumen. Journal of Agricultural Science. Cambridge, 96 : 251 – 252.Google Scholar
Ørskov, E.R. and McDonald, I. (1987). The estimation of protein degradability in the rumen from incubation measurements weighted according to rates of passage. Journal of Agricultural Science, Cambridge 92: 449 – 503.Google Scholar