Micronization of grains is an energy-consuming heat-based process and reducing treatment time in this method might be economically desirable. Different operational conditions including duration of the process (s), grain surface temperature at the end of the process (˚C), and distance between grain and burner (cm) in a micronizer machine were examined to assess the possibility of reducing processing time using in vitro gas production, in situ and enzymatic dry matter digestibility of corn grains. Treatments which were made by altering the above operational conditions in order included: Mic 1 (120 s, 155 ˚C, and 35 cm), Mic 2 (60 s, 155 ˚C, and 15 cm), Mic 3 (90 s, 165 ˚C, and 15 cm) and Mic 4 (120 s, 175 ˚C, and 15 cm). There were two batches of raw corn which were included Raw 1 and Raw 2 as the control for micronized corn grains (Mic 1, and Mic 2-Mic 4), respectively. Enzymatic dry matter (DM) digestibility in micronized corn grains (Mic 1=26.46 and Mic 3=29.27) was significantly (P<0.001) greater than their representative controls (Raw 1=22.17 and Raw 2=25.68) but increasing severity of the process, enhanced ruminal disappearance of dry matter (66.27 vs. 59.32 in Mic 4 and Raw 2, respectively. Out of 11 non-linear tested models, logistic-exponential without lag (LE0) showed the best performance for fitting gas production results indicated that the extent of gas production may decrease or increase by micronization depending upon the operational conditions. Overall, if the surface temperature of radiated grains at exiting (as a major indicator) is fixed and could be achieved by changing micronizer structure within a shorter time, similar in vitro and in situ performance in radiated corn grains can be obtained however, overheating may increase risk of ruminal acidosis.

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