3 letters every beef eater needs to know- WDA- weight for day of age. Dr Garrigus taught me this as an animals science undergrad. As pointed earlier in this thread. Since grass is low in energy content (caloric) animals gain weight much slower. Therefore grass fed animals will be much older by the time they reach weight and desired finish levels. Small framed cattle -4 and 5 frames- might still
Be able reach acceptable levels on grass/clover mix. 6 frames and up have no shot. If you must go grass fed, you definitely want to go with an early maturing, easy fleshing low frame score animal. Herefords or angus may fit this bill. Definitely need fo stay away from continental breeds like charolais, simmental, and limousine.