How to declare the type after a string?

I need to do something like this:

private string stringValue = "SheepController"; //SheepController is the name of another script
private **stringValue** animal1;

So it would be like writing:

private SheepController animal1;

Is this even possible? Because it will differ from each level in my game, what script I would like to add to a gameobject.

Not sure of your game, but one common way is to declare a base class with a common interface and then derive the other classes from it. There are other solutions. Here is one question that talks about the issue: