Growing interest in sustainable, profitable farming has been highlighted within the dairy industry. This is partly due to increasing cost of feed, and rising concern surrounding the environmental impact of the livestock industry. In the past, traits regarding efficiency have not been included into the selection index due to high phenotyping costs. Through genomics, constraints such as high costs can be overcome, allowing novel traits which were prohibitively expensive in the past, to be included into national genetic evaluations. Prior to including feed efficiency into a selection index, its implications must be investigated. Of the feed efficiency traits investigated, residual feed intake (RFI) had the lowest impact on the overall index response to selection. Suggesting RFI would be the optimal trait to include into a selection index, to improve feed efficiency. Dry matter intake also showed merit but needs to be further investigated to validate the results of this work.