Comparison of mathematical models to evaluate various in situ ruminant feed crude protein degradation kinetics

摘要

The in situ technique is a direct method of measuring the rumen degradation kinetics of a feed. It was suggested to describe the data obtained by this technique by an exponential curve (0rskov and McDonald, 1979). This first order exponential model isa most common procedure for determining crude protein and dry matter degradation coefficients. However, very low attention has been paid to the choice of mathematical model to fit the curves and goodness-of-fit of the model. Different mathematical models were evaluated to describe raminal dry matter (DM) and crude protein (CP) degradation kinetics of various feeds (Lopez et al., 1999; Fathi et al, 2006). In the present study, two different mathematical models of a straight line or a negative exponential (Fathi et al, 2006) were selected to evaluate crude protein (CP) degradation kinetics of various ruminant feeds including alfalfa hay, corn and whole barley silages, barley and corn grains, cottonseed and soybean meals using data obtained from the in situ technique.