Rumen dilution rate

The production rate of VFAs in the rumen can be measured by infusion of isotopically labelled forms of the acids into the rumen via a cannula and by recording their dilution by newly formed VFA. If only one VFA is infused, production of the others can be estimated from their relative proportions in rumen liquor. However, infusion of all three major acids provides more reliable estimates because it allows for differences between them in rates of production and/or absorption. 

The value for r may be determined by treatment of the protein with dichromate. The treatment renders the protein completely indigestible, there is no loss of chromium from the protein subsequent to treatment, and particle size distribution is not affected. The rate of dilution of chromium in samples of rumen contents taken over a period of time (see Chapter 8) can therefore provide an estimate of the rate of passage of the protein from the rumen. 

The large size of the rumen affects response to oral toxicants. Initial exposure may result in dilution of toxicants arKi slowing of the rate of absorption. 

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