IN-SACCO DISAPPEARANCE OF STARCH NITROGEN AND FAT IN PROCESSED GRAINS

The effect of extrusion or expansion treatment of wheat, barley, corn and sorghum grains on characteristics of rumen degradation was studied . Ruminal disappearance characteristics of dry matter, starch, nitroge n and fat in control and processed grains was determined using the in sacco method. In expanded cereals DM degradation rate was reduced in a ll grain types. In expanded corn the degradable DM fraction was also r educed. In extruded corn and sorghum rumen DM degradation rate was als o reduced. In sorghum, ruminal escape of DM increased by 8% and 5%, in extruded and expanded grains, respectively. The degradation rate of s tarch was reduced in expanded wheat and barley. Effective degradation of starch in the rumen was considerably lowered in expanded grains by 34%, 27%, 14% and 9% in wheat, barley, sorghum and corn, respectively. Extrusion also resulted in comparable reduction in effective degradat ion of starch in these grains by 27%, 27%, 17% and 6%, respectively. E xpansion decreased the N-degradation rate in all cereal types, and ext rusion decreased this in corn and wheat only. Negative fat degradation values were found at zero incubation time. However the data suggest t hat extensive disappearance of fat from cereals occurs in the rumen. I t was concluded that thermal processing of grains alters fermentation characteristics and may facilitate the achievement of optimal ruminal availability of energy: protein for microbial synthesis.