Comparing Logistic and Michaelis-Menten Multiphasic Models for Analysis of in vitro Gas Production Profiles of some Starchy Feedstuffs

Two multi-phasic models (logistic (LOG) and Michaelis-Menten (MM)) with three sub-curves were used to describe gas production kinetics of corn (CG), barley (BG), wheat (WG) and triticale (TG) grains. In each model sub curve, 1 describes the gas production caused by fermentation of the soluble fraction, gas production caused by fermentation of the non-soluble fraction is described in sub curve 2 and sub curve 3 represents gas production by microbial turnover. With MM model TG and WG had highest gas production from the soluble fraction followed by BG and CG. With LOG model there was no difference in gas production from the soluble fraction between BG and CG (P>0.05) and TG and WG (P>0.05) but TG and WG had higher gas volume from this fraction comparing to CG and BG (P<0.05). For gas production caused by fermentation of the non-soluble fraction, CG had the highest volume using MM model and CG and BG had higher volume with LOG model comparing to WG and TG (P<0.05). With MM model BG had highest gas production by microbial turnover but with LOG model WG and TG had higher gas production for the third sub curve. The LOG model had a slightly better fitting performance comparing to MM model in the present study but considering the methodology of this trial and the nature of models it does not necessarily represent the superiority of LOG model over MM model.