Fiber digestion from different size particles produced by mastication

Abstract

The dynamics of fiber digestion related to the size of masticated and ruminated digesta particles were studied in two in vitro digestion experiments. Masticated samples of coastal bermuda hay were fractionated into several ranges of size particles. The particles retained on the largest sieve were separated into stem and leaf fractions. Particles retained on other sieves were studied as whole plant. The fraction retained on the second largest sieve as well as the leaf fraction and stem fraction were studied at both their retaining sizes as well as when ground. In a second experiment, masticated samples and ruminated samples of corn silage were separately fractionated into various particle size ranges. The largest masticated fraction was separated into cob, leaf, epithelium and pith fractions. The second largest masticated fraction was separated into leaf and stem fractions. Masticated fractions retained on all other sieves as well as all ruminated fractions were studied as whole plant. The leaf and cob particles separated from the largest sieve were studied at both their retaining sizes, as well as when ground. All fractions in both experiments were subjected to in vitro digestion for a maximum of 168 hr. Various deterministic (A.D., E and EE) and stochastic (G) models were fitted to the data of both experiments. Models containing both parameters t and I significantly improved the fit of E, EE and G models (a=.025, a=.050 and a=.005, respectively), while the addition of only one of the two parameters did not improve the fit of all models. The stochastic model resulted in a better fit to the coastal bermuda data than either E (a=.005) or EE (a=.025) model. When fitted to the corn silage data, the G model was not significantly better than the E model, while it was superior to the EE model (a=.005). The size of the digesting particles had a direct relationship with time delay of digestion in the case of coastal bermuda particles (a=.05), as well as those of the masticated (a=.01) and digesta (a=.05) fractions of corn silage. The size of digesting particles did not show any significant relationship with rate of digestion. A significant inverse relationship (a=.05) between the size of the digesting particles and the extent of digestion (F480) was observed only for the coastal bermuda data.