I have collars and harness for Fiona, when we first got her, I stupidly left her harness on in her crate all day, and when my boyfriend came home, he called, and told me she totally chewed it to pieces....so one word of advise....if you use a crate, DONT LEAVE THE HARNESS ON!
You can also try putting bitter apple spray on it, so it doesn't taste to good!