I am baking bread and it calls for shortening is there a substitute?

Also depends what they mean by shortening- the word has, unfortunately, been largely appropriated by Crisco, but it actually means any fat used to shorten a pastry. Which you wouldn't be likely to do with bread, so they probably mean Crisco. Assume it's not a large quantity, you could sub pretty much anything from lard to coconut oil if you're OK with the flavor- I'd probably go with butter.

It would depend on the kind of bread you're making, but I see no reason why you couldn't use butter for most varieties.