A little mare we ride possibly has a UTI. She has been peeing pretty often. Its not bloody in appearance, but she is stopping to pee small amounts frequently. I was a vet tech for 10 years and have limited experience in horses, but am very comfortable giving injections if given the proper location and route. What should I give her. I know I can get penicillin injectable at the feed store or is there a preferred treatment? Funds are limited. I cant see paying a vet top dollar to come out and recommend a course of antibiotics that are three times overpriced. Thanks for the help.