Name the two components of cattle feed?

The main component of a ration for cattle is roughage (hay, pasture, or even silage, to some extent). The second component is what is called a "high concentrate" feed such as grain or by-products. Non-fattener diets for cattle should make up at least 60% roughage.

A feed by itself primarily is analyzed nutritionally by protein (as "crude protein") and energy (as TDN or "total digestible nutrients"). There are other equally important components that need to be looked at, such as fibre content (neutral detergent fibre and acid detergent fibre), calcium, phosphorus, potassium, magnesium, and even sodium. All of these will determine if the feed is nutritionally enough to feed to cattle, or if an additional feed (or more) needs to be added so that cattle are getting their full nutritional requirements.

Saying that, it is extremely rare that one feed will contain enough nutrients to meet most requirements of most bovines.