Cattle folks have discussed beef cow efficiency for years now but I don't think that we've actually made much progress. We have breeding values, like $ Energy, to help us but we still see 1400 lb cows that wean 400 lb calves. Larger cows or more milking ability won't generally increase cow efficiency.
One of the earliest measures of cow efficiency was to wean a calf that was 50% of the cow's bodyweight. That is still a figure that is worth watching. So let's modify that requirement a little. What about a cow that weans 50% of her bodyweight of a high quality calf every year with a minimum of extra attention and feed in your environment. That's a decent place to start a discussion but how would you get there?
You could begin by culling cows that don't meet your goals and focus your breeding program on those that do. Culling cows and heifers which don't breed in a reasonable period of time (say 3 or 4 heat cycles) in your environment is a good place to start.
What if your environment consists of high-endophyte fescue? Herds that have culled non-breeding, poor producers for years, likely have animals that are better adapted or fescue tolerant. I think that we are on the cusp of genetically identifying those fescue-tolerant individuals. How would you like to be the first to have a herd of Angus, for example, that could be certified as "fescue-tolerant" seedstock? Cha-ching!
We have also seen an increase in the use of high milk EPDs, so you might think that would translate into better cow efficiency, but not so. Increased milking ability comes at a high nutrient "expense". This increased milk many times comes at the expense of rebreeding in your environment (which may not include a lot of supplemental feed). Monitor body condition to see if the cows' nutrient needs are being met. The efficient cow must calve every year. You can overcome a lot of deficiencies with a feed bucket in the short run but you should be selecting for efficiency for the long term.
What about the bull side of the genetic equation? Does your bull supplier put selection pressure on his/her purebred herd or do they "feed 'em up" so that all the yearling bulls will sell? Don't you think that bulls should be developed in an environment that is similar to yours? Is it their fault? Probably not, since they generally supply what we purchase i.e. fat bulls! Range bulls need to be developed like young athletes not like pudgy, soda-swigging, video-game playing teenagers. Think about it.
Take a look at the two pictures. One is of cows being wintered (late February) on accumulated fescue pasture with natural protein blocks. The other is of the remainder of the cow herd being fed corn silage and supplement. The cows on the "almost-dead" grass are in our purebred herd while the silage-fed cows represent the commercial herd. Are we crazy?! Who would do that? Well, someone that wants to select breeding stock that is efficient and adapted to a fescue-based forage program. That's what we ultimately market in the southeast-forages.