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Metabolism of the lactating cow: II. Digestive elements of a mechanistic model

Published online by Cambridge University Press:  01 June 2009

R. Lee Baldwin ,
John H. M. Thornley  and
David E. Beever
R. Lee Baldwin
Affiliation:
Department of Animal Science, University of California, Davis, CA 95616, USA
John H. M. Thornley
Affiliation:
Animal and Grassland Research Institute, Hurley, Maidenhead SL6 5LR, UK
David E. Beever
Affiliation:
Animal and Grassland Research Institute, Hurley, Maidenhead SL6 5LR, UK
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Summary

The structure and characteristics of a model suitable for estimating digestion within the rumen and rates and patterns of nutrient entry in lactating cows are presented. The model consists of 12 state variables comprising a large particle pool, small particle pools representing insoluble dietary nutrients, soluble pools representing soluble dietary nutrients, and fermentation intermediates and end products. The model was constructed assuming continuous feeding, using Michaelis–Menten or mass action kinetics. The computer program was written in ACSL to run on a VAX computer. A fourth-order Runge–Kutta procedure was used for numerical integration.

Sensitivity and behavioural analysis demonstrated that overall stability and sensitivity of the model to individual parameters was generally satisfactory, but the need to improve the description and parameterization of aspects such as particle size in relation to availability, rate and affinity constants for amino acid degradation and rate constants for particle outflow from the rumen was established. Adjustments of the model to examine discontinuous feeding regimes were undertaken and initial results with respect to changes in fermentation rates, rumen acetate levels and microbial metabolism were considered realistic.

Comparisons with experimental data were considered satisfactory on forage-based and medium concentrate-containing diets, but with diets comprising 90% cereal, some inconsistencies, especially with respect to predictions of volatile fatty acid production rates, were observed. Reasons for this are put forward and suggestions for improvements in the model are discussed.

Type
Original Articles
Information
Journal of Dairy Research , Volume 54 , Issue 1 , February 1987 , pp. 107 - 131
Copyright
Copyright © Proprietors of Journal of Dairy Research 1987

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References

REFERENCES

Advanced Continuous Simulation Language (ASCL) 1981 User Guide/Reference Manual, 3rd edn. Concord, MA: Mitchell and Gauthier AssociatesGoogle Scholar
Baldwin, R. L. & Denham, S. C. 1979 Quantitative and dynamic aspects of nitrogen metabolism in the rumen: a modelling analysis. Journal of Animal Science 49 1631–1639CrossRefGoogle Scholar
Baldwin, R. L., France, J., Beever, D. E., Gill, M. & Thornley, J. H. M. 1987 b Metabolism of the lactating cow III. Properties of mechanistic models suitable for evaluation of energetic relationships and factors involved in the partition of nutrients. Journal of Dairy Research 54 133–145CrossRefGoogle ScholarPubMed
Baldwin, R. L., France, J. & Gill, M. 1987 a Metabolism of the lactating cow. I. Animal elements of a mechanistic model. Journal of Dairy Research 54 77–105CrossRefGoogle ScholarPubMed
Baldwin, R. L., Koong, L. J. &, Ulyatt, M. J. 1977 A dynamic model of ruminant digestion for evaluation of factors affecting nutritive value. Agricultural Systems 2 255–288CrossRefGoogle Scholar
Baldwin, R. L., Smith, N. E., Taylor, J. & Sharp, M. 1980 Manipulating metabolic parameters to improve growth rate and milk secretion. Journal of Animal Science 51 1416–1428CrossRefGoogle ScholarPubMed
Bauman, D. E., Eisemann, J. H. & Currie, W. B. 1982 Hormonal effects on partitioning of nutrients for tissue growth: role of growth hormone and prolactin. Federation Proceedings 41 2538–2544Google Scholar
Beever, D. E., Black, J. L. & Faichney, G. J. 1981 Simulation of the effects of rumen function on the flow of nutrients from the stomach of sheep. Part 2. Assessment of computer predictions. Agricultural Systems 6 221–241CrossRefGoogle Scholar
Beever, D. E., Coehlo Da Silva, J. F. & Armstrong, D. G. 1970 The effect of processing maize on its digestion in sheep. Proceedings of the Nutrition Society 29 43A–44AGoogle Scholar
Black, J. L., Beever, D. E., Faichney, G. J., Howarth, B. R. & Graham, N. McC. 1981 Simulation of the effects of rumen function on the flow of nutrients from the stomach of sheep. Part 1. Description of a computer model. Agricultural Systems 6 195–219CrossRefGoogle Scholar
Church, D. C. 1976 Digestive physiology and nutrition of ruminants. Vol. 1, Chapter 5. Corvallis, OR: O & B Books, Inc.Google Scholar
Cottrill, B. R., Beever, D. E., Austin, A. R. & Osbourn, D. F. 1982 The effect of protein- and non-protein-nitrogen supplements to maize silage on total amino acid supply in young cattle. British Journal of Nutrition 48 527–541Google Scholar
France, J., Thornley, J. H. M. & Beever, D. E. 1982 A mathematical model of the rumen. Journal of Agricultural Science 99 343–353Google Scholar
Harrison, D. G., Beever, D. E., Thomson, D. J. & Osbourn, D. F. 1975 Manipulation of rumen fermentation in sheep by increasing the rate of flow of water from the rumen. Journal of Agricultural Science 85 93–101CrossRefGoogle Scholar
Murphy, M. R. 1980 Modelling analyses of ruminant digestive function. Ph.D. thesis, University of California, DavisGoogle Scholar
Murphy, M. R., Baldwin, R. L. & Koong, L. J. 1982 Estimation of stoichiometric parameters for rumen fermentation of roughage and concentrate diets. Journal of Animal Science 55 411–421CrossRefGoogle ScholarPubMed
Murphy, M. R., Baldwin, R. L., Ulyatt, M. J. & Koong, L. J. 1983 A quantitative analysis of rumination patterns. Journal of Animal Science 56 1236–1240CrossRefGoogle ScholarPubMed
Osbourn, D. F., Terry, R. A., Spooner, M. C. & Tetlow, R. M. 1981 Use of processing to explore the factors affecting the digestion of forage cell walls. Animal Feed Science and Technology 6 387–403Google Scholar
Prior, R. L. & Smith, S. B. 1982 Hormonal effects on partitioning ofnutrients for tissue growth: role of insulin. Federation Proceedings 41 2545–2549Google Scholar
Reichl, J. R. & Baldwin, R. L. 1975 Rumen modelling: rumen input-output balance models. Journal of Dairy Science 58 879–890CrossRefGoogle ScholarPubMed
Russell, J. B. & Baldwin, R. L. 1979 Comparisons of maintenance energy expenditures and growth yields among several rumen bacteria grown on continuous culture. Applied and Environmental Microbiology 37 537–543CrossRefGoogle ScholarPubMed
Smith, N. E. 1970 Modelling studies of ruminant metabolism. Ph.D. thesis, University of California, DavisGoogle Scholar
Sutton, J. D. 1985 Digestion and absorption of energy substrates in the lactating cow. Journal of Dairy Science 68 3376–3393CrossRefGoogle Scholar