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, nitrogen and fat in control and processed grains was determined using the in sacco method. In expanded cereals DM degradation rate was reduced in all grain types. In expanded corn the degradable DM fraction was also reduced. In extruded corn and sorghum rumen DM degradation rate was also reduced. In sorghum, ruminal escape of DM increased by 8% and 5%, in extruded and expanded grains, respectively. The degradation rate of starch 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 degradation of starch in these grains by 27%, 27%, 17% and 6%, respectively. Expansion decreased the N-degradation rate in all cereal types, and extrusion decreased this in corn and wheat only. Negative fat degradation values were found at zero incubation time. However the data suggest that extensive disappearance of fat from cereals occurs in the rumen. It 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.