The process of artificial insemination involves sticking a rod/hand with bull semen into their vaginas. Just do a quick search for this and you can see videos of how artificial insemination works. There’s also a process of hormone injections to ensure cows sync up for more efficient AI.
Usually most farmers justify this by talking about how it’s safer than letting a bull fuck the cow while it’s confined to a pen (how it was done in a bygone era).
Oh, and if you’re wondering about how they get the bull semen they have them fuck artificial vaginas, or masturbate them if that’s not working out.