I would not feed EUK/IAMS at all - it is very poor quality, tons of fillers/allergens. And, keep in mind that IAMS was BUSTED FOR CRUEL ANIMAL TESTING. Ick.
Personally, I find that most vets know very, VERY little about nutrition options - probably bc they simply don't have the time to keep up with it. I recommend doing your own research and be the advocate for your dog's nutrition. Feeding lower quality foods can actually result in higher vet bills - just read those posts about people's dogs who are suffering terribly from allergies. Read about EUK here, this is the one you're feeding (it's rated 1 star):
http://www.dogfoodanalysis.com/dog_f...ct=116&cat=all
Good foods are: Canidae, Orijen, Evangers, Wellness, California Natural, Timberwolf, Innova. Good luck w/ your baby!