DFB, It sounds like your friend is talking his calves right thru to what is called finishing (ready for slaughter). He is right it takes about two years. I sell my calves as soon as they can be weaned, usually about 400 to 500 lbs.
Grazing is expressed in acres/head. The numbers can vary greatly from one part of the country to another, it also depends on if the pasture is native or improved, and of course the weather. For example, in the Hill Country of Texas, native pasture is about 14 acres per head. During a drought the number of acres goes up, and up, until the drought ends.
Volumes have been written on cattle feeding and the subject is often debated. How much a particular animal will eat depends on a number of factors, from the breed to the quality of forage or hay available. The most important thing to keep in mind is that the poorer the quality of forage/hay the longer it takes to go thru a cow's digestive system, and they will actually eat less. A certain amount of protein is needed to keep bacteria in the rumen active. The number one thing a supplement should do is to provide digestable protein. If a good supplement is provided, even poor forage can be used.
Right now, I have very little grass, and some the hay I've been getting is not very high in protein. I've been feeding 20% protein range cubes daily. There is some laziness in this. I like to check them daily, and when I feed cubes, I don't have to hunt them up. They find me.
I'm just maintaining these cows, not finishing them. Feeding out cattle for slaughter, is a little different, but the basics remain the same.
I may have gotten long winded here, but believe me, I barely scratched the surface. If your interested, I recommend the Oklahoma State University, Animal Science web site. Also if You can find it a book named "Beef Cattle" by Neuman and Lusby. Hope I didn't bore you too much.
Ernie
"Do not be uneasy about me, I am among friends"
David Crockett 1836 (in a letter to his family)