Penicillin is given to horses to avoid any sort of streptococcal infections, which lead to fever, strep throat, toxic shock syndrome, etc. Usually, it is given in injection form and pressed against the chest muscles. In case a horse acts agitated against those, an alternate option can be giving penicillin in liquid form orally. Typically, a horse requires one dose of 3 ml penicillin twice a day, for one whole week. Only Penicillin V is suitable enough to be given orally.