Journal of Animal Science, Vol 74, Issue 12 3076-3081, Copyright © 1996 by American Society of Animal Science

JOURNAL ARTICLE

Modeling ruminant feed intake with protein, chemostatic, and distention feedbacks

D. S. Fisher
USDA-ARS, College of Agriculture and Life Sciences, North Carolina State University, Raleigh 27695-7620, USA.

Little progress has been made in modeling intake regulation in spite of the many mechanisms identified as important. A model with relatively simple inputs was developed that included compartments for protein, soluble carbohydrate, digestible fiber, and very slowly digesting fiber. Distention and chemostatic feedbacks were combined using a previously published equation. The ratio of current ruminal fill to a modulating parameter for ruminal fill represented distention feedback. The ratio of the current flow of available energy to a modulating parameter for chemostatic demand represented chemostatic feedback. The modulating parameter for ruminal fill was based on literature reports of ruminal contents. Intake was adjusted based on current fill and energy flow relative to modulating parameters for fill and chemostatic feedback. The effect of the digestible organic matter (DOM) to CP ratio on DOM intake was modeled to adjust rates of digestion, rates of passage, and the chemostatic feedback. The model tested an integrated concept of intake regulation with only CP, IVDMD, and NDF as inputs. In spite of relatively simple inputs, the model behavior in response to variation in protein, digestibility, and fiber was similar to observations of animal responses.

This article has been cited by other articles:

				D. S. Fisher A Review of a Few Key Factors Regulating Voluntary Feed Intake in Ruminants Crop Sci., September 1, 2002; 42(5): 1651 - 1655. [Abstract] [Full Text] [PDF]