The best thing is to make your chicken broth yourself.
That way you have control over what exactly goes into it and it's a very simple thing to do.
Buy a whole chicken (or one that is cut up but bone0in if you prefer), stick it in a big pot and cover with cold water. Boil until the bones pull out easily, on average about an hour and a half to two hours.
Once it's done, take the chicken (or chicken pieces) out of the broth and debone them. If you want lower fat broth, remove the skin before cooking.
If you want to make the broth a bit more interesting, add a few cut up cloves of garlic and a teaspoon each of fresh or dried herbs (e.g. rosemary, parsley, oregano, thyme - I use all of them) to the cold water and let them cook with the chicken.
Another thing I do is after I remove the chicken for deboning, I keep the stock boiling on low and add a pound of cut up veggies (carrots, green beans, broccoli, sweet potatoes, zucchini) and cook them until tender.
At this point you can add the chunks of meat back in and have an excellent human dinner as well
or you can drain the stock, puree the cooked veggies in a blender, then add the puree back to the liquid and mix in well.
Water down to desired consistency if you want. Freeze in containers.
I usually make enough of this for several human meals and also use part of it as pet food. You can also add rice or noodles if you want a more substantial meal.