Nanon, A., Suksombat, W., Beauchemin, K. A. and Yang, W. Z. 2014. Short Communication: Assessment of lemongrass oil supplementation in a dairy diet on in vitro ruminal fermentation characteristics using the rumen simulation technique. Can. J. Anim. Sci. 94: 731-736. A study using a rumen simulation technique (Rusitec) was conducted to investigate the effect of increasing lemongrass oil (LMO) supplementation on ruminal fermentation characteristics of a dairy cow diet. Increasing LMO from 0, to 100 to 200 mg kg^-1 dry matter did not affect volatile fatty acid concentration, whereas LMO supplementation increased large and small peptide N and reduced ammonia N concentration. Adding 200 mg of LMO kg^-1 dry matter also increased microbial N production. However, feed digestibility was not affected by LMO supplementation. These results suggest that the addition of LMO may inhibit deamination in the rumen.