ABSTRACT In developing a mathematical model to allow prediction of growth in mammals, the simulation of amino acid metabolism is of particular importance because the predicted rate of protein deposition has a disproportionate influence on predicted body mass. In reality, the absorption and metabolism of amino acids in mammals is complex and highly integrated with continuous flux within and between body cells. To model amino acid transactions, however, a simplified construct of metabolism describing discrete physiological and metabolic processes must be developed. In the construct discussed here, a distinction is made between maintenance processes and those processes associated with growth. Growth is viewed as a function of nutrient deposition and support costs directly related to nutrient deposition. Several processes are emphasized and discussed, including food and amino acid intake, amino acid absorption, amino acid losses at maintenance, net protein deposition, inevitable amino acid catabolism, gut endogenous amino acid loss correlated with food intake, the turnover of body protein associated with new protein synthesis, the synthesis of non-amino acidÃ, non-protein nitrogen-containing compounds and preferential amino acid catabolism. The modeling of animal growth has become mainstream over the last two decades and models are being used increasingly in research, teaching, and in commercial practice. As models become more causal and less empirical, their validity and utility will be enhanced.
Implications
The mathematical modeling of animal growth has become an important tool in animal science research and teaching. Moreover, the use of animal growth models in commercial practice offers, among other applications, a new and situation-specific approach to nutrient requirement estimation and to the development of feeding regimens. As basic knowledge is developed on the growth and metabolism of the pig, pig growth models will become causal, thus having enhanced validity and utility.
Key Words: Amino Acids, Models, Pig, Protein, Simulation
© 2003, by the American Society of Animal Science. All rights reserved.
J. Anim. Sci. 2003. 81(E. Suppl. 2):E60-E67
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