The effect of expanded and extruded process on pellets physical properties and in sacco rumen degradability
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- Master's theses (IPV) 
Rumen degradability kinetics was investigated for concentrates with different physical functional properties. Three diets with SBM (30%) and barley (70%) were produced by ether expanded press process (Con) or by an extrusion process using two distinct procedures giving pellets with either high density (HD) or Low density (LD). The procedures in grinding, mixing and cooling were the same. Con was produced in expander where its cooking time was only seconds. LD and HD were produced in the extrusion process with the temperature of 120 and 90 oC respectively. Feed physical properties of three diet pellets, including durability, hardness, stability, density were detected. Ruminal degradation of dry matter was conducted by in sacco methods. In total, durability in the extrusion process group, LD (95.8%) and HD (99%), showed higher than expanding process (92%). Concentrate produced in HD has the highest hardness (112.01 N). LD group is floating with low specific density (0.70 g/ml) and low bulk density (412.3 g/L). Both HD and Con have high sinking velocity with similar high specific density (SD) and high Bulk density. Change of specific SD in rumen fluid for HD group is less, for LD is large but still not over 1.0 g/ml. The extruded concentrate showed high fluid stability (WSI) than the expanded concentrate. The extrusion process can be used to alter the degradation rate of concentrate DM in dairy cows. It is possible to shift the digestion of nutrients from rumen to the small intestine. Extruded concentrate reduced effective DM degradability (ED) in sacco compared to the expanded concentrate. The reduction of ED was most pronounced for HD concentrate with the highest WSI and highest density. The pattern of DM degradation in sacco was similar between pelleted and ground concentrate.