Feed additives are mixed with mixture to increase the quality, disease prevention or feed conservation; short list as following:

Anthelmintic
medicine used to prevention from parasite infections.

Antibiotics
A kind of medicine synthesized by alive organisms (mould, fungi, bacteria, plants) having antiseptically properties, like: penicillin, streptomycin etc.

Antioxidants:
added to feed for reduction of oxidation and fat go off.

ß-carotene:
pro-vitamin A, usually provided with chlorophyll, but synthetic form can also be supplemented to feed.

Regulators
Substances added to soluble for adapt to pH changes. Used in ruminants nutrition for optimal pH : 6,2-6,5, which lets to digest feed and synthesize microbial protein : rumen microbial: bicarbonate, bentotin, magnesium monoxide

Choline
Water soluble vitamin associated with fat metabolism and transport. Common poultry and hogs feed additive. Most ruminants synthesize enough of choline but choline can be supplemented in cows at the first stadium of lactation diet.

Coccidiostatics (anticoccidian)
Medicine used in coccidiosis treatment. Coccidia is intestinal protozoa occuring in cattle and poultry intestines.resulting in diarrhoea and big wastage.