You shouldn't really need to bulk out a complete food with anything else, this kind of defeats the purpose of feeding it.
This was my initial reaction too Nic. It was Burns who originally told me to bulk it up,but after a few weeks I swapped to JWB. When I went to see Billys behaviourist , she'd done quite a bit of work on dog foods, she told me to get him back on burns but bulk it up with Pasta, she said the benefits of Burns against the next leading brand far outweighed & that bulking it up was the best option. So I put him back on burns ( he loves it) and bulk it up. I don't do this every meal, just every other day. I throw a handful of brocolli & cauliflower & carrot in.
Billy gets quite hyper if he gets additives etc so was advised to stear clear of AG. But not all dogs suit the same
Am currently contemplating BARF though
Personally I'm not a fan of JWB or anything made by Iams but that's for ethical reasons.
Me neither, wasn't aware of JWB but never ever feed any Iams food.