Large particles increase viscosity and yield stress of pig cecal contents without changing basic viscoelastic properties

The viscosity of gut contents should influence digestion and absorption. Earlier investigators measured the viscosity of intestinal contents after the removal of solid particles. However, we previously found that removal of solid particles from pig cecal contents dramatically lowered the viscosity of the contents. Accordingly, we examined the contribution of large solid particles to viscoelastic parameters of gut contents in the present study. We removed large particles from pig cecal contents by filtration through surgical gauze. Then, we reconstructed the cecal contents by returning all, one half or none of the original amount of the large particles to the filtrate. We measured the viscosity, shear stress and shear rate of these reconstructed cecal contents using a tube-flow viscometer. The coefficient of viscosity was larger when the large-particle content was higher (P < 0.01). Cecal contents behaved as a non-Newtonian fluid and showed an apparent Bingham plastic nature irrespective of large-particle content. We calculated the yield stress of these fluids assuming that the fluids behave as Bingham plastic. The yield stress of the cecal contents was greater (P < 0.05) when the large-particle content was higher. The above results indicated that large particles elevated the viscosity and yield stress of gut contents without changing their basic viscoelastic character. Integrating the present and our previous results, we conclude that it is likely that finer particles such as bacteria should provide non-Newtonian and apparent Bingham plastic characteristics to pig cecal contents.