My sprocker had it for a while and through deliberation, different foods wet, dry half and half and the vets, now she is fed on tesco dried food and has never looked back since we changed to that, no smellie dog, brilliant coat and full steam ahead. works like a trojan all day.
Many Years ago my 5 labs (all same line) were fed on a mix of nubblimix and tripe, 4 out of 5 loved it the other was a disaster when fed on a mix, it run out of her, tripe on its own ( the proper stuff ) fantastic, ended up she had wild rice and tripe all of her life and never had any further problems, vet said her stomach didn't like it full stop, perhaps it was rough on the lining as it had maize and stuff in the mix - who knows ? another one of the mysteries of life
I'm thinking with spaniels you have just got to find the right roughage the dog can handle and maintain the balance and the glands at the rear end.