INFLUENCE OF FOODSTUFF PARTICLE-SIZE ON INSITU DEGRADATION OF NITROGEN IN THE RUMEN

This experiment studies the influence of foodstuff grinding on in situ degradation of feed nitrogen in the rumen. Six foodstuffs (peas, maize, barley, soya-bean meal, lucerne hay and cocksfoot hay) were ground using three different screen sizes 0.8, 3.0 and 6.0 mm, prior to incubation in the rumen. The increase in arithmetic mean and mean particle size of foodstuff with grinding varied with the nature of foodstuffs. Feed nitrogen degradability in the rumen decreases when the grinding screen changes from 0.8 to 6.0 mm, with a decrease of 12.3% for peas and 10.6% for maize; there is, however, no decrease for forages. For the same change of feed particle size, defined by arithmetic mean or mean particle size, the degradability response to an increase in grinding screen aperture is equal for all the feeds.