Here are some of the most common used ingredients. They are listed from best to worst, the ratings go from 1-5 hearts (5 being the best) depending on quality of the ingredient used. The misleading words used in pet food ingredients might shock you. They are in alphabetical order and by category ; Grains & Meats.

Grains should be whole ground to give the best over all protein source and be the easiest to digest. Non-whole grains can cause allergies, because they are harder to digest, and some can lead to diabetes and help onset arthritis. Also It is a cheep way to boost protein ratings on the package.

Meats should be, and is most commonly, the first item listed as a protein source. Cats and dogs are natural carnivores and their main source of protein should be a quality meat source, but not all meat sources are equal as you will find out.

Grains :

BARLEY :

• ground whole grain barley, whole ground barley (5 hearts) This is an excellent source of nutrients and dietary fiber, and is a low gluten grain, non-allergenic.
• pearled barley (4 hearts) Not whole ground, but a wonderful grain,less nutritive is low in gluten and flavorful.
• barley (3 hearts) Excellent source of nutrients, great grain for pets, but not "whole ground." Can be of any quality.
• barley grass (3 hearts) Misleading, additive for dietary "greens," not enough used for nutritional benefits unless listed high on the label.
• barley malt flour (2 hearts) Misleading this is waste product of brewing industry, sweetened for flavor, can be used as filler, stripped of nutrients.

CORN* :

• ground whole grain corn (2 hearts) Contains all nutrients/protein of corn, but should not be # 1 listed ingredient. 
• corn germ meal (3 hearts) Protein filler, ground whole grain corn is best.
• whole grain corn (2 hearts) Misleading - contains all nutrients of corn but indicates the use of feed-grade or below (old, moldy), can cause allergies, weight gain, blood sugar imbalances.
• corn gluten, corn meal & corn gluten meal (1 heart) Misleading and most used,  this is a waste product, cheap, non-nutritive filler but used as protein source, can cause allergies, weight gain and sugar imbalances.
• ground corn, ground yellow corn (1 heart) Misleading is not "whole ground," often indicates the use of feed-grade or below (old, moldy), known to cause allergies, weight gain, blood sugar imbalances 

       *  corn is an OK source of protein for cats but dogs can't assimilate corn as protein and causes
          allergies, is hard on thier digestive system and can cause "Blote". The Ratings are 2 hearts higher 
          for cats than dogs The Ratings shown are for dogs.

WHEATS :

• ground whole grain sorghum or millet (5 hearts)  Very nutritive grain, easy to digest, and alkalizing to the body.
• ground whole wheat (5 hearts) Whole ground is excellent, but not considered the best grain choice for dogs.
• whole wheat (4 hearts) Nutritionally complete grain, good source of grain protein but known to cause allergies.
• ground whole grain wheat (3 hearts) Slightly misleading whole ground is more nutritious, good source of protein, fiber but "grain" indicates feed-grade can be old, moldy.
• ground wheat, ground wheat flour (2 hearts) Misleading not "whole" ground, flower is over processed, indicates poor quality known to cause digestive upset, allergies and feeds arthritis.
• whole grain wheat (2 hearts) Misleading contains all nutrients of wheat but grain indicates the use of feed-grade or below (old, moldy), not human-grade (healthier, fresher), known to cause allergies.
• wheat, wheat gluten, wheat bran, wheat mill run (1 heart) Misleading not whole ground, poor feed-grade quality, known to cause allergies, digestive upset, causes premature aging and feeds arthritis 
  

RICE :

• whole ground brown rice (5 hearts) is whole ground, very nutritive grain, source of protein, dietary fiber.
• brown rice, (3 hearts) Slightly misleading, does not have to be whole ground when used in dry foods! Usually found whole in cans.
• ground whole rice, rice bran (3 hearts) is whole ground, but not brown rice, nutritive grain, source of protein and dietary fiber. 
• ground rice (2 hearts) not whole indicates white rice, but still contains good nutritional value, protein and fiber.  
• brown rice flour (2 hearts) Misleading, cheap filler, does not have to be whole ground when used in dry foods! Usually found whole in cans. Flower is over processed and holds little nutrition.
• brewer’s rice (1 hearts) Most commonly used and misleading, is waste product from breweries, cheap, non-nutritive filler can be harsh on intestines and turns into sugar in the system quickly, leads to hyperactivity and diabetes.
• rice, rice flour, rice glutten, rice hulls, rice protein concentrate (1 hearts) Misleading not Brown Rice, used as filler, always indicates white rice, not whole, 

OATS :

• whole ground oats, oat bran, oat groats, oat meal (5 hearts) Excellent fiber and grain source, easy on the digestive tract, good for colon health, balances body's pH.
• oat fiber (3 hearts) Slightly misleading this is a non-nutritive filler. not whole oat.

SOY:

• soy protein concentrate, soy protein isolate, soybean meal (3 hearts) This is a protein extracted form soy or soy seeds, dogs can not convert soy to protein can bloat/die. Good source of protein and fiber for cats
• soy flour, soy hulls, soybean mill run (1 heart) Cheap source of grain protein, filler, can cause bloat/death in dogs.

Meats: 

BEEF :

• beef meal (5 hearts)  Meal is dehydrated whole muscle meat and concentrated, more quality animal protein for the money and packs more protein pound for pound.
• beef broth (5 hearts) Excellent source of flavoring instead of plain water in can or dry foods.
• beef liver (3 hearts) Excellent source of iron and flavor, avoid it in dry foods as too much beef liver can become toxic, safe in can foods as secondary protein, flavor ingredient.
• beef (2 hearts) Misleading, contains over 70% water in the muscles, increases ranking on labels, when water is removed will not make top 5 ingredients in dry foods, less quality animal protein nutrition! Best used in canned food.
• beef & bone meal (2 hearts) Misleading in dry foods, increases ranking, mosly bone, bone meal is difficult to digest (the body does not absorb it as calcium), less protein nutrition!. Can be diseased tissues and organs not fit for human consumption and often rancid, 4-D source.
• beef by-products (1 heart)  Misleading, includes any internal part of the cow other than the meat, can be diseased tissues and organs not fit for human consumption often from 4-D, rancid sources.
• beef tallow, beef tallow (preserved with BHA), beef tallow preserved with BHA and mixed-tocopherols (source of vitamin E) beef tallow preserved with mixed-tocopherols (source of vitamin E) (1 heart) Misleading, this is a terrible source of fat includes old restaurant grease, is very hard to digest, leads to diarrhea, premature aging. BHA is a chemical used as a preservative with potential carcinogen affects, mixed- tocopherols and "Vitamin E" are used to mislead consumer. Indicates very poor quality product.

CHICKEN :

• chicken meal (5 hearts) Meal is dehydrated whole muscle meat and concentrated, more quality animal protein for the money and packs more protein pound for pound. Excellent source of protein for cats, good source for dogs in dry foods.
• chicken broth (5 hearts) Excellent source of flavor, instead of plain water for processing can food.
• chicken fat,  chicken fat (naturally preserved with mixed tocopherols) chicken fat (preserved with mixed tocopherols and citric acid) (4 hearts) Good source of energy and flavor, ok to be preserved with Vitamin E and C, but dogs do better with vegetable and fish oils.
• chicken liver (3 hearts) Excellent Source of flavor and iron, necessary for red blood cell production. Although too much liver can be toxic.
• chicken, chicken, fresh (2 hearts) Misleading, contains over 80% water in the muscles, increases ranking on labels, when water is removed will not make top 5 ingredients in dry foods, less quality animal protein nutrition! Best used in canned food.
• Chicken by-product, chicken by-product meal (1 heart) Misleading, Concentrated ground up carcasses, can be diseased tissues and organs not fit for human consumption often from rancid sources, beaks, feet. 
• poultry (1 heart) Misleading, non-human grade quality, can include any foul, often includes diseased meat,
• poultry by-product meal, poultry by-products  (1 heart) Misleading, contains ground up carcasses, can include already dead or diseased foul, all the internal parts that are void of healthy meat, includes whole ground up foul, meal is concentrated.
• poultry fat (preserved with BHA),  poultry fat (preserved with mixed tocopherols) (1 heart) Misleading can be any foul, often rancid prior to preserving with Vitamin E (gimmicky, to cover poor quality fat used). BHA possible carcinogenic preservative.

FISH :

• herring oil, menhaden fish oil,  (5 hearts) Excellent source of fatty acids.
• mackerel, menhaden fish meal, ocean fish, ocean whitefish, Salmon (5 stars) Good source of cold water fish, high in fatty acids.
• cod, catfish, catfish meal, herring meal (4 hearts) This is a good source of protein & fatty acids, but some of the natural oils are lost when turned to meal.
• fish broth (3 hearts)  Better that plain water for processing in can foods.
• fish meal, fish meal (natural source of glucosamine) fish meal (source of dha), fish meal (source of fish oil) (2 hearts) Misleading, any type of fish, can include rancid source of "throw away" catches. Gimmick, not enough glucosamine provided to have therapeutic benefits, low in fatty acids as meal often has the oil removed from it.
• fish, fish oil, fish oil (preserved with mixed tocopherols) (1 hearts) Misleading, any type of fish, can include rancid source of "throw away" catches and can be preserved with Vitamin E (gimmicky to cover poor quality oil). May contain high levels of mercury.

LAMB :

• lamb meal (5 hearts) Meal is dehydrated whole muscle meat and concentrated, more quality animal protein for the money and packs more protein pound for pound. Less likely to cause allergies than regular lamb meat, easy to digest.
• lamb broth, lamb stock (5 hearts) Used as flavoring in dry foods and is more nutritious than simple water used for processing can foods.
• lamb (2 hearts) Misleading contains over 70% water in the muscles, increases ranking on labels, when water is removed will not make top 5 ingredients in dry foods, less qualiy animal protein nutrition! Best used in canned food.
• lamb digest, lamb tripe (2 hearts) Misleading is low in proteins, mostly internal parts with no muscle tissue, can contain diseased and tumorus parts.
• lamb liver (2 hearts) Misleading uses Lamb to mislead customers, this is only an OK source of iron, necessary for red blood cell production. Although too much liver can be toxic, fine in can food when it's not a primary ingredient.

 
NON-DISCRIPTIVE MEATS :

• animal digest (1 heart) Misleading, animal tissues can be from euthenized  cats and dogs and diseaded animal tissues (tumors) and organs, Rendered, by chemical and/or enzymatic processing.
• animal fat, animal fat (preserved with BHA/BHT),  animal fat (preserved with vitamin E mixed tocopherols) (1 heart) Very misleading, any cheap animal source can be from euthenized  cats and dogs and diseaded animal tissues (tumors) and organs, BHA/BHT is chemically preserved with carcinogens,often rancid prior to preserving with Vitamin E (gimmicky to cover poor quality fat).
• meat, meat & meat juices, meat and bone meal (natural source of calcium), meat and liver meal, meat by-products (1 heart) Very misleading, contains non-descriptive animal flesh, can be from euthenized  cats and dogs and diseased animal tissues (tumors) and organs indicates 4-D meat. Meat juices are the fluids of the cells and tissues from whole ground up animals, and bone meal can not be digested and absorbed as calcium!
• liver (1 heart) Misleading, source can include any mammal tissue, too much liver can become toxic to the body when used in dry foods, used as flavor, normally is a minimal source of iron.