The Use of R Programming Language for Modelling In vitro Rumen Fermentation Gas Production

Abstract

The in vitro gas production technique is one of the feed evaluation methods that capture the characteristics of rumen microbial fermentation in response to the gas produced by feed ingredients. The gas production response is related and modelled to a unit of time with several parameters using non-linear regression mathematical equations. To facilitate this task, a script program in R has been developed that can perform the intended calculations. The calculation process uses nonlinear mathematical equations with intercepts. The equation shows that gas production (P) (mL) is influenced by several constants that indicate the share of gas production from the soluble fraction (FA) (mL), gas production from the potentially soluble part (FB) (mL), gas production rate (KC) (mL/h) and incubation time (T) (h). In addition to P and T, the three constants are tried to be derived by the program created. The data set is taken from several in vitro gas production studies that have been conducted previously. The Neway Software program of curve fitting calculations was used to validate the results, as the mean difference was tested using an unpaired T-test. Both programs showed the same calculation results for FA (P=0.9996), FB (P=0.9998), and KC (P=0.9962). The residual standard error (RSE) and R-square (R2) values of both programs also came with the same result they were RSE (P =0.9978), and R2 (P=0.6087) respectively. This shows that the R program script made can carry out the calculation process of making a model of the gas production equation for modeling in vitro gas production from rumen fermentation.