It is indeed true. Cats are classed as wild and dogs are domestic. Sheep and cows are also classed as domestic/cattle so you have to report it if you hit them too. Although if you go ploughing into a cow at 60mph you probably won't be able to report it:bang:
to be fair if you hit a sheep the chances are you were tanking it so you wont get away with that lightly!. dont take much weight to do a lot of damage at speed