How much Penicillin?
I have a dairy farm and treating cows and horses is a natural thing to do. I call the vet he tells me how much and for how long. Last winter a horse was brought to my barn with a swollen leg, from kicking a tractor bucket, I called the vet he told me to give him 10cc of penicillin for 5 days. It worked just fine. Don’t be afraid to just call and speak to a vet, they don’t charge for over the phone advice and the are more than willing to help out. I had a filly with a leg infection from having her splint cut into her leg, my vet told me to stop over and pick up a tub of oral sulfa powder and told me tricks on how to administer it. He never charged me for the advice, just the powder.