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This Article Full Text Full Text (PDF) All Versions of this Article: jas.2006-738v1 85/10/2498    most recent 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 Kebreab, E. Articles by France, J. Search for Related Content PubMed PubMed Citation Articles by Kebreab, E. Articles by France, J.

Comparative evaluation of mathematical functions to describe growth and efficiency of phosphorus utilization in growing pigs¹

E. Kebreab^*,,2, M. Schulin-Zeuthen^*, S. Lopez, J. Soler, R. S. Dias^*, C. F. M. de Lange^* and J. France^*

^* Centre for Nutrition Modelling, Department of Animal and Poultry Science, University of Guelph, Guelph, N1G 2W1, Canada; and National Centre for Livestock and Environment, Department of Animal Science, University of Manitoba, Winnipeg, Manitoba R3T 2N2, Canada; and Departmento Produccion Animal, Universidad de León, 24071 Leon, Spain; and IRTA, Centre de Control Porcí, 17121 Monells, Girona, Spain

² Corresponding author: kebreabe{at}cc.umanitoba.ca

Success of pig production depends on maximizing return over feed costs and addressing potential nutrient pollution to the environment. Mathematical modeling has been used to describe many important aspects of inputs and outputs of pork production. This study was undertaken to compare 4 mathematical functions for the best fit in terms of describing specific data sets on pig growth and, in a separate experiment, to compare these 4 functions for describing of P utilization for growth. Two data sets with growth data were used to conduct growth analysis and another data set was used for P efficiency analysis. All data sets were constructed from independent trials that measured BW, age, and intake. Four growth functions representing diminishing returns (monomolecular), sigmoidal with a fixed point of inflection (Gompertz), and sigmoidal with a variable point of inflection (Richards and von Bertalanffy) were used. Meta-analysis of the data was conducted to identify the most appropriate functions for growth and P utilization. Based on Bayesian information criteria, the Richards equation described the BW vs. age data best. The additional parameter of the Richards equation was necessary because the data required a lower point of inflection (138 d) than the Gompertz, with a fixed point of inflexion at 1/e times the final BW (189 d), could accommodate. Lack of flexibility in the Gompertz equation was a limitation to accurate prediction. The monomolecular equation was best at determining efficiencies of P utilization for BW gain compared with the sigmoidal functions. The parameter estimate for the rate constant in all functions decreased as available P intake increased. Average efficiencies during different stages of growth were calculated and offer insight into targeting stages where high feed (nutrient) input is required and when adjustments are needed to accommodate the loss of efficiency and the reduction of potential pollution problems. It is recommended that the Richards and monomolecular equations be included in future growth and nutrient efficiency analyses.

Key Words: function • growth • phosphorus • pig