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Dynamics of forage ingestion, oral processing and digesta outflow from the rumen: a development in a mechanistic model of a grazing ruminant, MINDY

Published online by Cambridge University Press:  19 November 2018

P. Gregorini ,
F. D. Provenza ,
J. J. Villalba ,
P. C. Beukes  and
M. J. Forbes
P. Gregorini*
Affiliation:
Feed and Farm Systems Group, DairyNZ Ltd, Private Bag 3221, Hamilton 3240, New Zealand
F. D. Provenza
Affiliation:
Department of Wildland Resources, Utah State University, Logan 84322-5230, USA
J. J. Villalba
Affiliation:
Department of Wildland Resources, Utah State University, Logan 84322-5230, USA
P. C. Beukes
Affiliation:
Feed and Farm Systems Group, DairyNZ Ltd, Private Bag 3221, Hamilton 3240, New Zealand
M. J. Forbes
Affiliation:
Institute of Integrative and Comparative Biology, Faculty of Biological Sciences, 13 University of Leeds, LS2 9JT, UK
*
Author for correspondence: P. Gregorini, present address: Faculty of Agricultural and Life Sciences Lincoln University Lincoln 7647, Christchurch, New Zealand. E-mail: pablo.gregorini@lincoln.ac.nz
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Abstract

Detailed representation of ingesta inflow to and digesta outflow from the rumen is critical for improving the modelling of rumen function and herbage intake of grazing ruminants. The objective of the current work was to extend a mechanistic model of a grazing ruminant, MINDY, to simulate the dynamic links between ingestive and digestive processes as affected by forage and sward features (e.g. sward structure, herbage chemical composition) as well as the internal state of the animal. The work integrates existing aspects of forage ingestion, oral physiology and rumen digestion that influence ingesta characteristics and digesta outflows from the rumen, respectively. The paper describes the structure and function of the new development, assessing the new model in terms of dynamic changes of oral processing of ingesta and rumen dilution rate under different grazing contexts. MINDY reproduces characteristics of ingesta inflow to and digesta outflow from the rumen of grazing ruminants, achieving temporal patterns of occurrence within and between meals, similar to those for grazing animals reported in the literature. The model realistically simulates changes in particle size distribution of the ingestive bolus, bolus weight and rumen dilution rate in response to contrasting grazing management regimes. The new concepts encoded in MINDY capture the underlying biological mechanisms that drive the dynamic link between ingestion and digestion patterns. This development advances in the understanding and modelling of grazing and digestive behaviour patterns of free-ranging ruminants.

Keywords

digestagrazingmodellingruminants
Type
Modelling Animal Systems Research Paper
Information
The Journal of Agricultural Science , Volume 156 , Issue 8 , October 2018 , pp. 980 - 995
Copyright
Copyright © Cambridge University Press 2018 

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