How much penicillin to give to a 900lb bull?

While visiting a farm, a bull had broken his penis. In order to help him with the healing process and any infections that would come from this terrible incident, the farm hand had to administer penicillin to him. On the bottle, there was a dosage of penicillin per 1kg. But she only knew the weight of the animal in pounds --> 900lbs. So she asks... how many kilograms in 900lbs? Luckily, being math savvy, I could quickly do a calculation/estimation of the amount of kilograms, and then we just had to multiply the amount by the required amount of penicillin per kg. Even a farm hand needs to do this simple math....