A cow's number one job and the definition of a profitable cow is that she rasies a healthy calf every year.  It doesn't have to be the biggest calf in the crop every year, better an average calf than 2 big calves then none at all the third year.  A profitable cow is not necessarily one that is nice and plump all the time.  Such a cow is likely not providing as much as it could to its calf.  A profitable cow will build condition when she's dry then put that extra into her calf and she'll breed back doing it.

A profitable cow also need longevity.  Studies have varied on how long it takes a cow to earn back the cost of raising her to her first calf, but there can be no doubt that the longer a cow can be productive the more profitable she will be.  This takes good structure, good feet, and a correct udder and some luck too.   The tools most commonly used cattle breeding, the growth and milk epd's, ignore the things that make a cow most profitable.  410, pictured at 9 years of age is a fairly profitable cow.

In producing grass fed beef - size matters.  Popular beef cattle are simply to big to grow and finish on a strictly forage diet in a reasonable amount of time. This bull is a around a frame 3, but in the middle of the breeding season is gaining weight and weights around 1800 pounds. Short and thick with a tremendous rump.  Sired by OCC Emblazon.