QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text (PDF) Purchase Article View Shopping Cart Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Gill, M. Articles by Milligan, L. P. Search for Related Content PubMed PubMed Citation Articles by Gill, M. Articles by Milligan, L. P.

Mathematical Integration of Protein Metabolism in Growing Lambs^1,2,

Department of Animal and Poultry Science, University of Guelph, Guelph, Ontario N1G 2W1, Canada

A mathematical integration of whole-body protein synthesis and degradation based on protein metabolism in 10 individual tissues in growing lambs is described. The tissues represented are adipose, central nervous system (CNS), gastrointestinal tract (GIT), heart, kidney, liver, muscle, pancreatic and salivary glands (PSG), reticuloendothelial system (RES) and skin, together with a blood pool of amino acids. The fluxes represented in the equations are generally assumed to follow simple or modified mass-action kinetics. The fractional rates for protein synthesis in each tissue were calculated from published values for lambs, where these were available, or alternatively derived using assumptions based on data obtained with rats. The initial protein content of each tissue and the fractional degradation rate were assigned values calculated using data from a slaughter experiment. The model was used to examine whole-body protein synthesis at different rates of growth and to compare the relative contributions of each tissue. The GIT (25–26%) and skin (23–26%) had the highest contributions to total protein synthesis, followed by muscle (21–26%), liver (13–14%), RES (6–7%) and PSG (3–6%), while adipose, CNS, heart and kidney together contributed less than 5%. These values agree reasonably well with experimental values, and thus the model can be used to examine the effect of different growth rates on protein metabolism and its associated energy costs.

KEY WORDS: • protein • metabolism • growth • ruminants • computer simulation • mathematical model • lambs

¹ J. F. was in receipt of a research award from, and part of the operating costs were provided by, the Natural Sciences and Engineering Research Council of Canada, while M. G. received a travel grant from the Stapledon Memorial Trust. Both were on study leave from the Institute of Grassland and Animal Production.

² Presented in part as a short communication at a meeting of the Nutrition Society, 16–17 July 1987, Cambridge, England (Proc. Nutr. Soc. 47: 55A, 1988).

³ Present address: The AFRC Institute for Grassland and Animal Production, Hurley, Maidenhead, Berks. SL6 5LR, United Kingdom.

Manuscript received 8 July 1988. Revision accepted 13 April 1989.