They need two Covexin 8 shots 4 to 6 weeks apart. At the time of castration, I give a tetanus antitoxin as a precaution. If they have had two Covexin 8 shots prior to castration, you are adequately covered. My vet does my castrations. I recently had two bull calves about 3 months old castrated. I told the vet they had their two Covexin 8 shots but I told him to hold them until I gave them an antitoxin. He said he didn't think the antitoxin was needed. I still gave it.
PS: there are two types of shots for tetanus. One is a toxoid preparation. It immunizes against the toxin produced by the tetanus organism. The other is an antitoxin. It counter acts the toxin. If a cow has a puncture wound, you Administer the antitoxin as an immediate action to counter the toxin expecially if the cow has not been immunized by previous toxoid vaccinations.
