There's not a lot of what I would call Ag. schools that play D1 hockey. But if I were to start searching I would probably start with Nebraska-Omaha, North Dakota, Minnesota, Wisconsin, Michigan State, and Ohio State.
D1 Hockey is mostly played in the upper midwest and out east. I really have no idea about D3, I know it is popular in Minnesota and Wisconsin but I'm not sure about the rest of the country.
If you don't mind my asking; why do you ask?