I have a problem for kills animals

I have a problem to kill some animals, especially the problem comes from cows because, I see cows but I can not kill them, like for many animals. The second problem is the hitbox, a lot of cows don't have Hitbox but he was in the game, disconnecting and me reconnecting it makes such. Is this normal?

Note that I am french and and I have problem with English and many mistakes are to be expected.