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Modelling nutrient utilization in farm animals.

Book cover for Modelling nutrient utilization in farm animals.

Description

This book presents edited and revised versions of papers presented at the Fifth International Workshop on Modelling Nutrient Utilization in Farm Animals, held at the University of Cape Town, Cape Town, South Africa, 25-28 October 1999. There are 31 chapters and 6 sections entitled ruminal metabolism, absorption and metabolism, growth and development, ruminant production in various situations, nutr...

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Chapter 1 (Page no: 11)

The role of thermodynamics in controlling rumen metabolism.

Chemical reactions are controlled either thermodynamically or kinetically. Most mechanistic biological models assume kinetic control of metabolism pathways. The profile of products formed depends on substrate concentrations and enzyme activities, which control the rates of synthesis for competing pathways. Thermodynamic control occurs when reactants are sufficiently limited relative to products for the reactions not to be able to proceed, according to the second law of thermodynamics. Under these circumstances, thermodynamics controls which pathway branches are available and the final concentration of products. This chapter investigates the possibility of thermodynamic control of ruminal fermentation. Ruminal pH is buffered by bicarbonate in a system that is near equilibrium. This is a clear example of thermodynamic control. Rates of acetate, propionate and methane synthesis also appear to be controlled by thermodynamics, but these reactions do not approach equilibrium. These reactions proceed until the change in Gibbs free energy (G) approaches a negative value, representing the inherent inefficiency of the system. A dynamic model of glucose fermentation was developed that incorporated thermodynamic limits to volatile fatty acid (VFA) and gas production. Incorporation of thermodynamic limits was achieved by including fractional rate constants for reverse reactions. These reverse rate constants were determined from published thermodynamic data for the reactants and products. This model predicted realistic steady-state concentrations of major VFA and gases. Incorporation of factors that decrease the efficiency of certain reactions (i.e. low pH or use of ionophores) would shift the fermentation in directions similar to those observed in the rumen.

Other chapters from this book

Chapter: 2 (Page no: 25) Modelling lipid metabolism in the rumen. Author(s): Dijkstra, J. Gerrits, W. J. J. Bannink, A. France, J.
Chapter: 3 (Page no: 37) Towards a more accurate representation of fermentation in mathematical models of the rumen. Author(s): Nagorcka, B. N. Gordon, G. L. R. Dynes, R. A.
Chapter: 4 (Page no: 49) Simple allometric models to predict rumen feed passage rate in domestic ruminants. Author(s): Cannas, A. Soest, P. J. van
Chapter: 5 (Page no: 63) Ruminal metabolism of buffersoluble proteins, peptides and amino acids in vitro. Author(s): Udén, P.
Chapter: 6 (Page no: 73) Models to interpret degradation profiles obtained from in vitro and in situ incubation of ruminant feeds. Author(s): López, S. France, J. Dijkstra, J. Dhanoa, M. S.
Chapter: 7 (Page no: 87) Modelling production and portal appearance of volatile fatty acids in dairy cows. Author(s): Bannink, A. Kogut, J. Dijkstra, J. France, J. Tamminga, S. Vuuren, A. M. van
Chapter: 8 (Page no: 103) Modelling energy expenditure in pigs. Author(s): Milgen, J. van Noblet, J.
Chapter: 9 (Page no: 115) Aspects of modelling kidney dynamics. Author(s): Robson, B. Vlieg, M.
Chapter: 10 (Page no: 127) Evaluation of a representation of the limiting amino acid theory for milk protein synthesis. Author(s): Hanigan, M. D. France, J. Crompton, L. A. Bequette, B. J.
Chapter: 11 (Page no: 145) Multiple-entry urea kinetic model: effects of incomplete data collection. Author(s): Zuur, G. Russell, K. Lobley, G. E.
Chapter: 12 (Page no: 163) Evaluation of a growth model of preruminant calves and modifications to simulate shortterm responses to changes in protein intake. Author(s): Gerrits, W. J. J. Togt, P. L. van der Dijkstra, J. France, J.
Chapter: 13 (Page no: 175) Simulation of the development of adipose tissue in beef cattle. Author(s): Sainz, R. D. Hasting, E.
Chapter: 14 (Page no: 183) A simple nutrient-based production model for the growing pig. Author(s): Boisen, S.
Chapter: 15 (Page no: 197) Second-generation dynamic cattle growth and composition models. Author(s): Oltjen, J. W. Pleasants, A. B. Soboleva, T. K. Oddy, V. H.
Chapter: 16 (Page no: 211) Modelling interactions between cow milk yield and growth of its suckling calf. Author(s): Blanc, F. Agabriel, J. Sabatier, P.
Chapter: 17 (Page no: 227) A mechanistic dynamic model of beef cattle growth. Author(s): Hoch, T. Agabriel, J.
Chapter: 18 (Page no: 241) Modelling nutrient utilization in growing cattle subjected to short or long periods of moderate to severe undernutrition. Author(s): Witten, G. Q. Richardson, F. D.
Chapter: 19 (Page no: 253) An integrated cattle and crop production model to develop whole-farm nutrient management plans. Author(s): Tylutki, T. P. Fox, D. G.
Chapter: 20 (Page no: 263) Modelling nutrient utilization by livestock grazing semiarid rangeland. Author(s): Richardson, F. D. Hahn, B. D. Schoeman, S. J.
Chapter: 21 (Page no: 281) Using the cornell net carbohydrate and protein system model to evaluate the effects of variation in maize silage quality on a dairy farm. Author(s): Tylutki, T. P. Fox, D. G. McMahon, M. McMahon, P.
Chapter: 22 (Page no: 289) Challenge and improvement of a model of post-absorptive metabolism in dairy cattle. Author(s): McNamara, J. P. Phillips, G. J.
Chapter: 23 (Page no: 303) A rodent model of protein turnover to determine protein synthesis, amino acid channelling and recycling rates in tissues. Author(s): Johnson, H. A. Baldwin, R. L. Calvert, C. C.
Chapter: 24 (Page no: 317) Modelling relationships between homoeorhetic and homoeostatic control of metabolism: application to growing pigs. Author(s): Sauvant, D. Lovatto, P. A.
Chapter: 25 (Page no: 329) Model for the interpretation of energy metabolism in farm animals. Author(s): Chudy, A.
Chapter: 26 (Page no: 347) Linear models of nitrogen utilization in dairy cows. Author(s): Kebreab, E. Allison, R. Mansbridge, R. Beever, D. E. France, J.
Chapter: 27 (Page no: 353) Isotope dilution models for partitioning amino acid uptake by the liver, mammary gland and hindlimb tissues of ruminants. Author(s): Crompton, L. A. France, J. Bequette, B. J. Maas, J. A. Hanigan, M. D. Lomax, M. A. Dijkstra, J.
Chapter: 28 (Page no: 361) The conversion of a scientific model describing dairy cow nutrition and production to an industry tool: the CPM dairy project. Author(s): Boston, R. C. Fox, D. G. Sniffen, C. Janczewski, E. Munson, R. Chalupa, W.
Chapter: 29 (Page no: 379) The utilization of prediction models to optimize farm animal production systems: the case of a growing pig model. Author(s): Bailleul, P. J. dit Bernier, J. F. Milgen, J. van Sauvant, D. Pomar, C.
Chapter: 30 (Page no: 393) A pig model for feed evaluation. Author(s): Danfær, A.

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