The following are chemical additives found in many pet supplements and food.
It is not meant to be an exhaustive list and so if you see an ingredient you don't recognise on a product label, be sure to research it online.
It's also safe to assume, that when such additives are included, it is for the benefit of the manufacturer concerned and not the pet (either to facilitate production or to create a significantly cheaper product).
NOTE:
Some of the additives are included more than once because they have multiple uses.
Artificial Colours:
E131 Patent Blue V (FD&C Blue 2)
E129 Allura Red AC (FD&C Red 40)
E102 Tartrazine (FD&C Yellow 5)
E110 Sunset Yellow FCF (FD&C Yellow 6)
Titanium dioxide
Artificial Preservatives:
E320 Butylated hydroxyanisole (BHA)
E321 Butylated hydroxytoluene (BHT)
E282 Calcium propionate
E330 Citric acid
E325 Sodium lactate
E237 Sodium propionate
Ethoxyquin
E310 Propyl gallate
Sodium benzoate - now banned in the UK
Sodium propionate
Artificial Sweeteners:
Sucralose
Anti-caking Agents:
E551 Silicon dioxide
E572 Magnesium stearate
Corn / Maize Derivatives:
These modified starch products are used as thickeners, stabilizers, binders and texturizing agents in many pet foods.
E1404 Oxidized starch
E1410 Monostarch phosphate
E1412 Distarch phosphate
E1413 Phosphated distarch phosphate
E1414 Acetylated distarch phosphate
E1420 Acetylated starch
E1422 Acetylated distarch adipate
E1440 Hydroxy propyl starch
E1442 Hydroxy propyl distarch phosphate
E1450 Starch sodium octenyl succinate
Other corn-derived food additives used include corn syrup solids, corn gluten meal, corn protein concentrate, corn oil, and dextrose.
And so many pet foods contain quite a bit of corn in various derivative forms beyond whole corn kernels.
Emulsifiers:
E322 Lecithins (phospholipids)
Mono and diglycerides
Polysorbate 80
Fillers / Binding / Bulking Agents:
Carrageenan
Cassia gum
Cellulose (wood pulp)
Corn gluten meal
Guar gum
Microcrystalline cellulose
Silica ('sand')
Silicon dioxide ('sand')
Soy protein isolate
Flavours:
Artificial meat flavours
Artificial smoke flavour
Propylene glycol
Flow Agents:
Magnesium stearate
Propylene glycol
Stearic acid
Gelling Agents:
Carboxymethyl cellulose
Carrageenan
Cassia gum
Lubricants:
Magnesium stearate
Stearic acid
Synthetic Amino Acids:
DL-methionine
L-carnitine
L-lysine
Lysine hydrochloride
Taurine
Tryptophan
Synthetic Minerals / Trace Elements:
Calcium carbonate
Calcium iodate
Calcium pantothenate
Calcium propionate
Calcium sulfate
Cobaltous carbonate
Cupric chelate
Cupric sulfate
Ferrous chelate
Ferrous sulfate
Iron sulfate
Manganese chelate
Manganese oxide
Manganous sulfate
Monodicalcium phosphate
Phosphorus
Potassium chloride
Potassium iodide
Selenium
Sodium chloride
Sodium hexametaphosphate
Sodium selenite
Zinc chelate
Zinc oxide
Zinc sulfate
Synthetic Vitamins:
Beta-carotene
Biotin
Folic acid
Niacin
Riboflavin
Vitamin A (retinyl acetate)
Vitamin B1
Vitamin B2
Vitamin B6
Vitamin B12
Vitamin C (E301 Sodium ascorbate)
Vitamin C monophosphate
Vitamin D3 (cholecalciferol)
Vitamin E
Vitamin E (alpha-tocopherol)
Vitamin K
Thickeners
E407 Carrageenan
E410 Locust bean gum (carob gum)
E412 Guar gum
E466 Sodium carboxymethyl cellulose
Unethical:
Chondroitin (from battery chickens / sharks)