The current study was conducted to evaluation of the effects of extrusion process on chemical composition, quality parameters, in situ rumen degradability, oxidative stability, and fatty acid profile changes of flaxseed during long term storage. In a completely randomized design, flaxseed ground (GF) or mixed with alfalfa hay and pistachio by-products with 80:10:10 (by mass) proportions and extruded (EF). There was no difference between ground and extruded flaxseed for dry matter content (P>0.05). But, the content of crude protein (CP) and ether extract (EE) reduced and the ash content significantly increased after extrusion process (P<0.05). EF treatment significantly had higher oil lost (OL) and bulk density (BD) than GF (P<0.05) and the angle of repose (AR) in GF treatment was slightly higher than EF. Extrusion significantly reduced proportion of unsaturated fatty acids and increased peroxide value (PV) in the flaxseed (P<0.05). Also, PV linearly increased during storage period (P<0.05) and this increase was significantly higher in EF treatment than GF (P<0.05). In addition, slowly degradable fraction (b), potential DM degradability (a+b) and effective DM degradability of flaxseed reduced, but soluble DM fraction (a) and the rate of degradation of the slowly degradable DM (c) increased by extrusion (P<0.05).

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