REVIEW PAPER
A review of starch digestion in the lactating dairy
cow and proposals for a mechanistic model: 1.
Dietary starch characterisation and ruminal starch
digestion
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1
The University of Reading, Centre for Daily Research, Department of Agriculture,
Earley Gate, PO Box 236, Reading RG6 6AT, UK
2
WIAS Animal Nutrition, Wageningen Agricultural University,
Marijkeweg 40, PO Box 338, 6700 AH Wageningen, The Netherlands
Publication date: 1999-07-20
J. Anim. Feed Sci. 1999;8(3):291-340
KEYWORDS
ABSTRACT
The objective of this paper is to review the literature concerning starch digestion in the rumen of
the lactating dairy cow and to propose the framework for a mechanistic model representing this
process that may be used as part of a larger model of whole rumen function. The review defines
starch as it occurs in the diet of the dairy cow, followed by a detailed description of the digestion of
starch in the rumen. Emphasis is placed on the role of the microbial population in the degradation of
starch and the significance of both amylolytic bacteria and protozoa. During the investigation, use is
made of data gathered from both in vivo, in vitro and in situ studies concerning mainly lactating
dairy cows. Regression relationships are presented to describe the significance of dietary starch
intake, starch source and processing method on digestion characteristics. The quantity of rumen
escape starch is increased at high starch intakes. Maize and sorghum starches tend to be more slowly
degraded within the rumen than other cereals and they also benefit to a greater extent from physical
and chemical processing techniques designed to increase ruminal and total tract starch digestion.
Other factors influencing the nature of starch digestion are also presented in order to allow the
interpretation of experimental data and hence the development of a conceptual model of starch
digestion. The review subsequently examines starch digestion in the rumen as it is represented in
extant models of ruminant digestion. The essential elements of a rumen model that would accurately
account for the fate of dietary starch within the rumen are identified. Finally, a scheme representing
starch digestion in the dairy cow that may be incorporated into a model of whole rumen function is
presented.
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