Pedigree is not a great food. To learn more about food, take a look at the label:
The first ingredient is what there is most of -
Pedigree Adult with Chicken:
Cereals (min. 4% Wheat, min. 4% Maize, min. 4% Rice In The White Kibble), Meat and Animal Derivatives (min. 4% Chicken In The Brown Kibble), Oils and Fats, Derivatives Of Vegetable Origin (min. 3% Dried Beet Pulp), Minerals, Vegetable Protein Extracts.
Protein 22%, Oils and Fats 15%, Fibre 8%, Ash 3%, Omega 6 Fatty Acids: 2.4%, Omega 3 Fatty Acids: 0.15%, Vitamin A 6000 iu/kg, Vitamin D3: 600 IU/kg, Vitamin E 160mg/kg. Vitamin levels guaranteed until best before date. Total Copper as Copper Sulphate 10mg/kg. EC permitted antioxidants BHA, BHT. Colourants (permitted EC additives) Ponceau 4R, Brilliant Blue, Tartrazine, Titanium Dioxide, Iron Oxide. Preservatives (permitted EC additives) Potassium Sorbate.
So the first ingredient is ceral - this is a bulker which means it is not neccesarily useful to the dog. Because of this the dog needs to eat more to get the same nutrition than some other foods. It also means they will go to the toilet more.
Also note the meat content - 4% chicken! This means that although the protein content is 22%, only 4% is chicken. The rest is derivatives which mean it can be any part of the animal and can be whatever meat is cheapest on the market at any time - beef, lamb, tripe etc, and could be hoof, beak atc etc.
Also the protein is not always meat protein, they can use vegetable proteins which are not as much use to the dog.
Compare this to another brand like Wellness Adult Chicken:
Deboned Chicken, Chicken Meal, Oatmeal, Ground Barley, Ground Brown Rice, Tomato Pomace, Rye Flour, Canola Oil (preserved with mixed tocopherols), Tomatoes, Rice Bran, Whitefish, Natural Chicken Flavor, Carrots, Spinach, Sweet Potatoes, Apples, Blueberries, Ground Flaxseed, Ground Millet, Dicalcium Phosphate, Calcium Carbonate, Potassium Chloride, Vitamins [Beta-Carotene, Vitamin E Supplement, Ascorbic Acid (Vitamin C), Vitamin A Supplement, Niacin, d-Calcium Pantothenate, Riboflavin, Vitamin D-3 Supplement, Pyridoxine Hydrochloride, Thiamine Mononitrate, Folic Acid, Biotin, Vitamin B-12 Supplement], Minerals [Zinc Sulfate, Zinc Proteinate, Iron Proteinate, Ferrous Sulfate, Copper Proteinate, Copper Sulfate, Manganese Proteinate, Manganese Sulfate, Sodium Selenite], Choline Chloride, Mixed Tocopherols (added to preserve freshness), Taurine, Glucosamine Hydrochloride, Chondroitin Sulfate, Chicory Root Extract, Garlic Powder, Yucca Schidigera Extract, Green Tea Extract, Dried Lactobacillus plantarum, Enterococcus faecium, Lactobacillus casei, Lactobacillus acidophilus fermentation products, Rosemary Extract.
The first item on the list is chicken -that means that is what there is most of. It has a minimum protein content of 22% which from the ingresients mainly comes from meat rather than veg. It also has good additives such as glocosamine - good for joint health etc.
Do some label reading and you'll notice that Pedigree is one of the lower end brands. Its just heavily advertised, well known about and appears cheap. You're dog will eat so much of it your cost per day would probably be similar on a better food.