It is legal to toss a rock, a small bush, a mosquito, or a earthworm into a fire in most places.
In those same places it is likely illegal to toss a live cat into a fire.
In this context sentience is about "should I care about how this clump of atom _feels_" and/or "it is possible to be unduly cruel to this clump of atoms".
In farming it mostly means that you cannot cause unnecessary suffering too much outside of the Overton window; not about recognizing bodily autonomy to cattle.
The purpose of introducing this kind of law is to continue to expand the legal recognition of what we now consider to be ethical, based on our continually expanding understanding of the world.
The cows aren’t in a position to protest in some animal rights movement, so some interested (and compassionate) humans are working on their behalf.
In the commonly accepted and emotionally charged connotation of rape, no. Inseminating a cow is likely no different to the cow than an antibiotic shot.
Look at any thread on any social media platform featuring bestiality, esp. regarding dogs or cats. The vast majority of people will explicitly use the word rape, and also call for all kinds of horrible punishments for the perpetrator.
I can think of no sensible, morally relevant difference between these instances and what happens to female animals through artificial insemination. "It doesnt hurt" isn't an excuse, because you can certainly think of bestiality that doesn't hurt the animal (or features physical pain to the same degree as artificial insemination).
Cows are sentient, does that mean the guy who artificially inseminates them is raping them?