If you work your dog regularly, then why not phone some of the pet dog insurance policies and find out what is excluded?
If you can get something from them in writing, then they won't be able to exempt the whole policy if you do make a claim
Insurance companies employ teams whose job is to look for any evidence in order to get out of paying for as many claims as they can, and if your vet has a record of your dog working, then it may be enough for the whole policy to be invalidated