Do cattle get to have antibiotics given to them?

Yes. Antibiotics are mainly put in baby animal feed. Baby animals like chicks and calves have medicated feed, but you can choose un-medicated feed if you like.

Ionophores are a form of antibiotic that are added to the feed of feedlot cattle. They act to reduce the incidence of bloat and to increase feed efficiency by changing microflora dynamics. Doing so gets the rumen microbe community to produce less methane--a gas wasted via eructation--and more propionate, which can be more readily used by the animal. Ionophores are also used to reduce incidences of coccidiOSis in cattle.

Antibiotics, in sub-therapeutic levels, are also given to dairy cattle, pigs and poultry to promote growth and feed efficiency. Note these feed additives are not given at the same levels, and are very often different from the antibiotics needed to be administered to animals with bacterial infections.