Kittens keep eating dog food

We have two kittens around the age of 6 months. They are fed dry & wet Blue Buffalo Kitten food. They eat the food just fine, but they also keep snacking on the dog's dry food (Blue Buffalo Puppy). (Snacking like 10% of their total intake). Since it's a high-grade food I don't worry too much about it except for the fact that cats NEED taurine (which is not in dog food). I really don't want to have to lock the cats up while I feed the dog.

Does anyone know of a supplement I can give them that will ensure they receive extra taurine?

If they're eating 10% or less of it as their diet, that's similar to the percentage of treat recommended in a diet. Many treats do not have taurine either, but the cats don't need taurine supplements because of it. If they eat all of their food consistently and only take treats from the dog bowl, you shouldn't need any supplements.

Is the dog bowl next to the cat bowls? If so, you might want to move it so the cats don't so readily associate it with food.

You need to stop leaving the dry dog food in the bowl. Train the dog to be eating 2 x a day and leave the food out for 1/2 hour. Then take it up. While the dog is eating, lock the kittens in a room until the food is gone or taken up.

Believe me the dog will learn to eat when food is served. And feed the kittens on a counter where the dog cannot get to their food.