To all:
I used to work in a meat packing plant. I followed a USDA grader in the cooler and put the grade on the carcasses with a roller and an ink can filled with food grade ink. At that time there were 4 grades. Prime. Choice. Good. and utility. The select grade didn’t come until later when some do-good dieticians and politicians began worrying about consumer health.
All the grade measured was the amount of marbling/fat in the meat. Prime has the most marbling and so on.
As far as determining the breed of a carcass after the skin is off and it is hanging in the cooler, I found it impossible to tell. The only way is by the id tag put on the carcass at time of kill.
For more information. Holstein cattle are dairy. The meat is a different color as well as the fat. And, dairy carcasses are relatively easy to identify by their shape when hanging in a cooler.
Interestingly, Certified Angus Beef does not have to come from the Angus breed.
I also know several farmers ( friends for over 30 years) that buy Holstein bull calves, raise them for beef, and sell them to dealers that sell the beef as certified Angus beef.
They said the rules on what is certified Angus is so loose that any beef with black in the hide can get the label.