In this study, we investigated the effect of different processing methods (steam-flaking, micronized and micronized-flaking; F, M, and MF, respectively) of corn grains on various factors including water absorption index (WAI), damaged starch content (DSC), nutrient digestibility, gas production (GP), microbial crude protein (MCP) and effective utilizable crude protein (EUCP). Flaked treatments (F and MF) were used in whole, cracked and ground forms (1.5- and 3-mm), while non-processed corn grains (G) and M were only ground. All MF treatments showed higher ruminal digestibility of dry matter (DM) and starch, GP, as well as increased MCP and EUCP compared to other treatments (P<0.001). The F treatment in the whole form and ground micronized corn showed significantly lower (P<0.001) ruminal digestibility of DM and starch, as well as GP and MCP. However, the above two treatments exhibited greater in vitro disappearances of DM and starch in the small intestine. It can be concluded that post-flaking of infrared radiated corn may induce severe ruminal degradation above that of steam flaking. Therefore, a flake density greater than 0.41 kg/L may be appropriate for micronized-flaked corn when used in its whole form to achieve optimum ruminal degradation and maximum digestibility of starch in the small intestine.

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