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

Success of pig production depends on maximizing return over feed costs and addressing po- tential nutrient pollution to the environment. Mathe- matical modeling has been used to describe many im- portant aspects of inputs and outputs of pork produc- tion. This study was undertaken to compare 4 mathematical functions for the best fit in terms of de- scribing specific data sets on pig growth and, in a sepa- rate experiment, to compare these 4 functions for de- scribing 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 (Rich- ards 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 Bayes-