Be aware! There could be a large ungulate on your path of travel. However, due to the static nature of signs and the (relatively) dynamic nature of cows, I have never seen cows at these signs. Instead of ignoring the posted warning, I use them as (cow)bells of mindfulness.
An opportunity to regain focus and clear my mind of of distracting clutter. These cubist cows, Picasso's sketches of bulls, tetrahedral bovines are harbingers of awareness like the parrot on Pala in Aldous Huxley's Island.
I like to keep my mind focused while driving, these signs help.
Make good judgement a habit. When you see signs that would normally give you pause or hesitation, but currently do not apply- Be mindful. Picture the the likelihood versus consequence graph as it applies to the decisions you are currently using. Picture the graphic below while making decisions, the more often you use this thinking, the more habitual it will become.