My sincereapologies for not being able to give credit to the author of thisinformation- I kept it because I found it of much value. It has to dowith a study on digestion times of fiber in the intestinal tract, whichis very important when trying to determine the right combinations ofpellets, greens and hay for your bunny.
Raspberry
Digestive Information-
Particle Sizes and Transit Times
Indigestible fiber is indigestible whether it's pulled off the bark ofa tree or blended into a feed, yet the size and type of the fiber canaffect the length of time it takes to pass through the GI(gastro-intestinal) tract.
Contrary to what you might expect, the large particles don't get stuckinside the rabbit while the small ones exit easily. It's the other wayaround.
Transit times of particles moving through the GI tract have beenmeasured, in several scientific studies, by placing markers in thefeed. High-fiber alfalfa meal, pelleted into large particles (up to3mm) moved through the digestive system in 14.1 hours in one study.When same high-fiber feed was ground to a finer size (1mm), it took15.9 hours to pass through the digestive tract.
Markers in a pelleted low-fiber high-starch feed passed in 20.1 hours(Gidenne 1992). Why are smaller fibers and high-starch feeds slower ingetting through? Because small particles and excess starch are sent tothe cecum for fermentation, and this takes extra time. Fluids and smallparticles are separated in the colon and moved backwards into the cecum(Cheeke 1987), while large particles are passed quickly through thecolon.
One study used particles up to 5mm in marked feed, which passed in 5hours (Sakaguchi 1992). This may closely approximate the size of chewedhay. I can say with strong certainty--from caring for disabled,diapered rabbits on a monitored diet with strictly scheduled feedingtimes--that the oat hay I give my rabbits in the morning is passed bythe afternoon (4-5 hours).
Fast and Slow
So which is more desirable, fast moving or slow moving particles? Someof both are needed: a sizable quantity of coarse indigestible organicmaterial to keep the gut working at an optimum rate and enough (but nottoo much) digestible material to be absorbed in the small intestine andcecum.
