If your job and personal opinion don't mix?

I'm a veterinary technician and being so, part of my job is to recommend certain services and products. We have to recommend Science Diet food to clients. If a pet is overweight, put them on science diet w/d, if the pet has allergies, recommend science diet z/d, etc... its the only brand we, and most animal hospitals sell. The problem is I don't feel comfortable recommending it. I think the food is absolute crap. I personally feed my pets blue buffalo, and I wish I could recommend it to clients. And to be honest, I did last week, and I kind of felt guilty like i'm a trader to my clinic, but at the same time, I care more about the pet then the dr. making a profit on his crappy food. But what should I do? I really don't want to endorse this crappy food, and I cringe when the dr. suggests it to the client and they're all for it, and I know it's full of fillers and by-products and grains, and I just want to be like "no! put your pet on Innova, or wellness, or blue buffalo!! they will be soo much healthier" but I can't. Any suggestions?