A Constitutive Model for the Rheological Behavior of Sheep Rumen Digesta

Abstract

In this work we used rheometer measurements to determine a non-Newtonian model describing the small strain rheology of rumen digesta. Rumen digesta were collected from three sheep fed ryegrass and subjected to small amplitude oscillatory shear testing on a rheometer using a parallel plate geometry at a constant strain rate of 1% and a frequency range from 0.01 Hz to 100 Hz. The digesta were found to exhibit shear thinning behavior that was well described by a power law model with a flow behavior index of approximately 0.05. The storage modulus and loss modulus were frequency dependent and exhibited a crossover in the frequency range 40 - 60 Hz The Cox-Merz relationship was satisfied over a limited frequency range from 0.01 Hz to 0.1 Hz. Inter-animal and intra-animal variation in the be on the order of 20%