tThis study consisted of two experiments that investigated the effect of extrusion of sorghumstarch on in situ ruminal and post-ruminal disappearance of dry matter (DM), starch andnitrogen (N) and the effects of substituting barley by the extruded sorghum on digestioncharacteristics, microbial N supply and growth in finishing lambs. Sorghum was extrudedusing the following four temperature and pressure combinations: T1 = 90◦C/17 bars,T2 = 115◦C/24 bars, T3 = 150◦C/55 bars and, T4 = 175◦C/95 bars. Ruminal, intestinal andtotal tract DM content, starch and N degradability of the extruded sorghum (T1, T2, T3,T4), unprocessed sorghum (T0; control) and barley grain (B) were determined using nylonbag and mobile bag techniques in a completely randomized block design (CRBD). Extrusionunder T3 conditions increased in vitro ruminal digestibility, solubility (a), fractional dis-appearance rate (c) and effective degradability (ED) of DM and starch in sorghum to nearsimilar to those of B. T3 also had higher (P<0.05) ruminal and intestinal digestion rates forDM, starch and N compared to T0, T1, T2 and T4 suggesting that extruding sorghum under T3conditions could be used as replacement of barley in lamb diets. In the second experiment,eighteen male Iranian Baluchi lambs were randomly allocated into three dietary treatmentsin a complete randomized design (CRD). Dietary grain in the treatment-concentrates werebarley (B) as control, barley and extruded sorghum (under T3 conditions) in equal propor-tion (BSE) and extruded sorghum (SE). Dry matter and N intakes were not affected by sourceof grain, but because of the higher starch content in sorghum, lambs on SEdiet had greaterstarch intake (995 g/d) and higher (P<0.01) starch (291 g/d) and N (53.1 g/d) outflow to thesmall intestine. Of the total input of starch to the small intestine, higher (P<0.01) amount(253 g/d) disappeared in SEcompared to B and BSElambs which was reflected by the higher.

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