Is the DH used in the minors?

It's easier too answer this way. The National League is the only professional league at any level that does not use the DH at all. Every other one does...

Paki is wrong. The DH is used in all minor leagues at all levels, and is also used in most college and high school baseball, the Pacific League in Japan, South Korean professional baseball, and Latin American professional baseball.
Interestingly, in AA and AAA baseball, the DH is NOT used IF BOTH teams playing are NL affiliates. In the Pacific Coast League (AAA), the DH is NOT used if both teams are NL affiliates AND both agree to not use the DH before the game starts.

No, the DH used in all American League parks only.