What CAB bashers don;t tell is that CAB sets guide lines for ribeye size 10- 16 sq in . no matter what Yield Grade .The carcass must have less than 1" fat thickness.
Meat graders assign a yield grade to a carcass by evaluating:
1 the amount of external fat;
2 the hot carcass weight;
3 the amount of kidney, pelvic, and heart fat; and
4 the area of the ribeye muscle.
Yield Grade 1
The carcass is covered with a thin layer of external fat over the loin and rib; there are slight deposits of fat in the flank, cod or udder, kidney, pelvic and heart regions. Usually, there is a very thin layer of fat over the outside of the round and over the chuck.
Yield Grade 2
The carcass is almost completely covered with external fat, but lean is very visible through the fat over the outside of the round, chuck, and neck. Usually, there is a slightly thin layer of fat over the inside round, loin, and rib, with a slightly thick layer of fat over the rump and sirloin.
Yield Grade 3
The carcass is usually completely covered with external fat; lean is plainly visible through the fat only on the lower part of the outside of the round and neck. Usually, there is a slightly thick layer of fat over the rump and sirloin. Also, there are usually slightly larger deposits of fat in the flank, cod or udder, kidney, pelvic and heart regions.
Yield Grade 4
The carcass is usually completely covered with external fat, except that muscle is visible in the shank, outside of the flank and plate regions. Usually, there is a moderately thick layer of external fat over the inside of the round, loin, and rib, along with a thick layer of fat over the rump and sirloin. There are usually large deposits of fat in the flank, cod or udder, kidney, pelvic and heart regions.
Yield Grade 5
Generally, the carcass is covered with a thick layer of fat on all external surfaces. Extensive fat is found in the brisket, cod or udder, kidney, pelvic and heart regions.
Expected percentage of boneless, closely trimmed retail cuts from beef carcasses within the various yield grades
Yield Grade % BCTRC
1 > 52.3
2 52.3 - 50.0
3 50.0 - 47.7
4 47.7 - 45.4
5 < 45.4