Changes in the viscoelastic behaviour of the rumenal digesta mat of sheep fed on pasture or chaffed lucerne hay

Abstract

We examined the changes in the physical properties of the digesta mat over a period of 24 h after cessation of feeding, in sheep that had been maintained on pasture or fed chaffed lucerne hay. The dry matter content of the digesta mat declined at similar rates in both dietary groups, although it was generally higher in sheep fed lucerne. Median particle size declined in the digesta mats of both dietary groups at similar rates in samples taken after 8 h, but median particle size was significantly greater in sheep fed chopped lucerne hay than in those fed grass. Thus, particles were not reduced to a common size suggesting that factors in addition to particle size governed the rate of breakdown of the rumen mat. The relationship between the elastic and loss moduli was of a consistent pattern in all samples taken from the rumen mat indicating that it behaved as a weak gel. The elastic and loss moduli of the digesta mats of sheep that had been fed pasture or chopped lucerne hay converged to similar values after 12 h and declined broadly at similar rates after this. The relationship between these two moduli and the dry matter content of the rumen mat were of similar curvilinear form for sheep on both diets. These findings suggest that the rate of breakdown of the rumen mat is more likely to be governed by its composite behaviour than by the size of the constituent particles.

Particle Size Distribution of Brown and White Rice during Gastric Digestion Measured by Image Analysis

“…There are few studies examining the particle size distribution of gastric contents, particularly the size and shape of particles as they are digested (Lentle and others ). However, particle size distribution plays a key role in the viscosity and overall behavior of gastric and intestinal chyme (Takahashi and Sakata ; Dikeman and others ).…”

“…However, the particle size distribution during gastric digestion in vivo has not been studied at length. Lentle and others () determined the particle size distribution of pasture or chopped lucerne hay diets in sheep. In another study, Lentle and others () determined the particle size distribution of chopped lucerne hay in sheep and wallabies during gastric digestion using wet sieving.…”