
I've never added anything to my dogs' food. If they don't like it or don't finish it - tough. I never change their food either. I changed Sam's from Proplan to Arden Grange recently because his skin was very flaky on it. i don't like messing with their feeding habits. My dogs don't get scraps or anything but lick the yogurt pot when I've finished. I guess if you start adding stuff to make it more attractive to a dog, then you're kind of turning it into a fussy eater. Same when you keep changing brand, flavour etc. My Sam went through a phase of hardly eating half of what he was supposed to for a good while. I never gave in and he just got over it (mind you, he wasn't getting thin, or else i would probably have had to react!). It was just a phase, the routine might have been different, the weather etc... All this has a big influence on his appetite. Now, competition with the little one has turned him into a food-obsessed doggie!
Dogs have so few taste buds compared to us. Fussy eating is often more a behavioural issue than a matter of taste. What I say is : if your dog is fine on this food, then don't mess about, don't change it, don't add stuff only to make it tastier.
Besides, if it's a good complete food, you shouldn't have to add so much. Tripe, Lamb fresh or in frozen blocks, ok. But not all the veg, rice etc that are already present in his food, which dogs then don't need so much of.