Rumen-bypass microcapsules were prepared by a spray-dry method for protection against microbial hydrogenation in the rumen (neutral pH). Porous starch was used as the core material, and the microcapsules were prepared by a triple coating of Eudragit E100, AS-HF, and shellac. Capsules were generated with yield of about 48% and a mean particle diameter of 20-30 microm. The microcapsules had high stability in a neutral solution that mimicked a ruminal pH (pH 6.5). Moreover, when microcapsules were incubated in the presence of ruminal microorganisms, about 65% of the microcapsules were resistant to digestion in ruminal fluids, and protection of the inclusion substance was observed. In addition, the efficiency of release of these microcapsules was about 85% within only 30 min in the abomasal environment (pH 3.0).