A core concept in the Cornell Net Carbohydrate and Protein System (CNCPS) (Fox et al., 2004) is the competition between rates of digestion and passage to determine rumen balance. The current status of both CNCPS 4.0 and CPM Dairy feed libraries only provide book values for rates of digestion that are treated as constants. Many of the book values of digestion rates are likely too low for high quality forages. The consequence of underestimating the rate of fiber digestion in the model is the incorporation of more concentrate into the ration leading to potential rumen imbalances. Fiber and lignin increase while digestion rates decline with forage maturity. Data presented in the current CNCPS do not reflect these differences.
Any attempt to account for nonlinearity will result in declining kd values with time, and
will result in a major adjustment in the CNCPS. Undervaluing the rate constant in high quality forages leads to increased feeding of concentrate. The nonlinearity could be resolved by curve-peeling to discern faster and slower pools or by applying higher order kinetics. The difficulty with curve-peeling to discern two or more first-order pools is that the choice of time for inflection points seems purely arbitrary, and the observed fermentation curves of digestion seem continuous. Higher order kinetic
systems would avoid this problem.
The NDF Fractional Rate Calculator is based on the work published by Van Soest et al. (2000) by providing a mechanistic approach to the problem of rate estimation of NDF digestion when the true unavailable fiber is not available.
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The current version of the Neutral Detergent Fiber kd Calculator is 1.1.2.
Previous versions can be downloaded from here.
No registration is needed. Nonetheless, you are welcome to submit your comments to improve the NDFkd Calculator by going to the CONTACT US web page.
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Dr. Luis O. Tedeschi |
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Dr. Peter J. Van Soest |
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Additional references are listed in the Publications web page.
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