I had this with my Lab, he started to eat his brand new kennels.
I bought some Cribox, its like a REALLY bitter paste that the horsey lot use to stop their nags "cribbing" (eating stable door).
http://www.ebay.co.uk/itm/Hydrophan...t=UK_Horse_Wear_Equipment&hash=item3f0772368c
My vet, many years ago suggested I use tobasco sauce as an alternative, it didn't work, he carried on chewing the furniture, and I ended up with a spaniel that could happily stomache the remains of any curry he got his chops to, had to chuckle one day when even he bit off more than he could chew, after doing the necessary he promptly sat his arse in the nearest puddle and wouldn't move! Brilliant, we all know that feeling!
