Feeding this EO complex impacted the production of these high producing dairy cows, primarily by enhancing milk fat synthesis which apparently was the result of an energetic shift away from body condition gain, suggesting that the EO complex may have enhanced acetate production and/or the ratio of acetate to propionate production in the rumen. However if the latter occurred, it likely did so in the absence of a change in nutrient digestibility as the whole tract digestion of OM, CP and aNDFom were not impacted by EO feeding.