Regarding Brian Perkins' use of the term "dairy efficiency" to represent the ratio between milk production and dry matter intakes (in the January 20 Hoard's Dairyman Intel item, "Think dairy, not feed, efficiency"), I have found the term "component efficiency" gaining ground as it is both more descriptive of the measurement and more relative to the issue. Component efficiency ratio compares dry matter intake of lactating cows to the amount of butterfat and protein produced by that cow (or group or herd).
Some use pounds of DMI per cow per day divided by pounds of butterfat and protein per cow per day. Others use the inverse and multiply by 100. We benchmark this as a beginning point when comparing feed costs between farms. If the biology is inefficient, don't look at the cost of feed or price of components to solve the problem.
–Bruce Dehm, New York