Cows in dairy farm keep on losing health

So, playing the last experimental, i tamed myself some cows in a dairy farm. The problem is they keep losing life… They are not bleeding, i have checked.

Do i have to feed them? They have a lot of hay there, why won’t they eat by themselves?

Maybe they lose life because i don’t milk them?

Actually, looking at this picture, it seems they are losing health because they’re damaging themselves on the barbed wire fence… That would be strange irl.