Beneful dog food is among the lower quality dog foods. The first ingredient is usually corn, which is hard for dogs to digest and can cause digestive problems if the dog has a sensitive stomach. The main protein source is meat by-products which is basically a dice roll when it comes to knowing what meat is actually used.
The AAFCO definition of chicken by-product meal is “a meal consisting of the ground, rendered, clean parts of the carcass of slaughtered chicken, such as necks, feet, undeveloped eggs and intestines, exclusive of feathers, except in such amounts as might occur unavoidable in good processing practice.”
Your best bet is to look for a healthier dog food with good protein sources, carb sources, and vitamin sources.
One of my favourite brands of dog food that uses whole foods that are human grade is Wellness dog food http://www.wellnessdogfoodcoupon.com/ that link takes you to a site where you can find coupons and reviews about Wellness. Enjoy!