I don't have all the answers, I can't say that grain-free isn't better for dogs, but nor can I find any evidence that proves that to be true
I would recommend reading Dog Food Logic by Linda P Case who discusses 'grain free' and it's marketing in numerous essays which are based upon scientific study. Very few dogs have allergies to grain - one of the main reasons we are encouraged to buy grain free. Chicken is a common allergen in dogs.
Like @Boogie I feed Skinners , but the duck and rice as its lower fat and Sam cant tolerate much fat . No added nasties , absolutely ideal, for him . I add , for him, because what suits one dog maybe wont suit another , its all about finding a decent food that suits the dog and the pocket !
I look at ingredients in a number of ways..firstly what are the top 5 ingredients? How many different protein sources are used in the ingredient list? Eg beef, chicken, salmon, duck...thirdly how novel are these protein sources? Are they a commonly used protein source? Chicken and beef vs venison for example. Finally, where is the protein sourced from. I then consider my dogs, what do they in terms of total calorific values, protein and fat content. Here are a few examples... Fresh duck (55%) : high quality source of animal protein. Potatoes (24%) : an easily digested carbohydrate. Peas (10%) : added protein and fibre source. Sugar beet pulp (1%) : a natural blend of digestible and indigestible fibres promoting intestinal health. Duck fat (3%) : a high quality extremely palatable fat. 2. Whole rice (40%), duck meat meal (20%), naked oats, peas, whole linseed, sunflower oil, beet pulp, vitamins and minerals. 3 Freshly prepared Lamb (20%), freshly prepared duck (20%), dried duck (18%), sweet potato, potato, dried lamb (5%), dried rabbit (3%) 4 Freshly Prepared Salmon (46%), Dried Salmon (18%), Potato, Sweet Potato, Tapioca, Chick Pea Flour, Salmon Oil (5%), Pea Fibre, Lucerne, Salmon Stock (1%), Vitamins, Minerals, Dried Apple, Dried Carrot, Lovage Powder, Aniseed, Fenugreek, Seaweed 5. Ground Whole Grain Corn, Meat And Bone Meal (Source Of Calcium), Corn Gluten Meal, Animal Fat (Source Of Omega 6 [Preserved With Bha & Citric Acid]), Soybean Meal Four of the above I would consider...one certainly not!
