I grew up on a farm and always used Penn G. on any sick animals, always as a series of shots. I read on another site where they give the first dose as a sq shot, the rest are given orally. I have been doing it orally now for years and never had any animal not get the full benefit of the penn G. I do the same with thing with wormers for goats, Bio Mycin, LA-200, Vitamin B Complex, Baytril, Banamine, basically everything is given orally after the first dose. I have done this with calves, goats and small pigs, haven't lost one yet.
Lots of folks may not know about Bio-Mycin 200 (Oxytetracycline). It is a good replacement for LA-200 because it doesn't burn at the site of injection. It stays in the blood longer so it doesn't need 2x daily injections either.