An Alternative Robust Model for in situ Degradation Studies "Korkmaz-Uckardes"

Abstract

The first purpose of this study is to present an alternative robust model in order to describe ruminal degradation kinetics of forages and to minimize the fitting problems. For this purpose, the Korkmaz-Uckardes (KU) model, which has a logarithmic structure, was developed. The second purpose of this study is to estimate, by using the Korkmaz-Uckardes (KU) model, the parameters t(p) (the time to produce p% of partial dry matter disappearance in rumen) and Rt(p) (the rate of the partial dry matter disappearance in rumen at the time t(p)). These parameters will provide more useful data to compare feedstuffs in in situ degradation studies. The third purpose is to evaluate the performance of the Korkmaz-Uckardes (KU) model. Statistical criteria used to evaluate the performance of a model were analysis of residuals (Runs and Durbin Watson test) and goodness-of-fit test (residual mean square, coefficient of determination and accuracy factor). The analysis of residuals of the Korkmaz-Uckardes (KU) model was found to be non significant (P>0.05). The residuals are normally distributed. According to the goodness-of-fit test, the Korkmaz-Uckardes (KU) model applied to all data showed a very good fit (residual mean square (RMS)=15.854, R-2=0.9853 and accuracy factor (AF)=1.0387). According to the Pearson's correlation analysis, a significant relationship (r(2)=0.969) was found between observed and predicted values (P<0.001). The results indicate that the Korkmaz-Uckardes (KU) model can be used as an alternative model for describing and interpreting in situ dry matter degradation from natural feedstuffs.