The reason that
each feed component must has its own Kd value is due to the fact that the
rumen operates as a continuous culture system and there is a competition
between degradation and passage rates from the rumen.
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If the Kd and Kp
are the same, 50% of the feed is ruminally degraded and 50% passes, but the
ratio of Kd to Kp can be significantly different.
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The graph at the
right shows the relationship between Kd and ruminal degradation at 2
different passage rates. Please note that ruminal degradations can vary from
virtually zero to nearly 100%.