Here's a 2 minute video clip from yesterday's stage of the Criterium du Dauphine. It's from French TV, but you don't need to know the language to understand what you are watching.
You don't see this every day, especially here in the United States. Because unless you are at the rodeo, the only time you see a cow at a sporting event is when you are stuffing your face with an all beef hot dog.
But when the "stadium" is the countryside in and around the great mountain ranges of Europe, things happen. I seem to recall goats on the road during one of last year's Tour de France stages. Maybe it was at the Vuelta a Espana, I don't remember. However, I do remember that it's the only time that Mary has shown any interest in watching cycling on TV.
But I digress. My point is that running into a cow at 40 KPH (25 MPH) would suck. Those things must weigh at least 1700 pounds. The average rider (including the bike) is probably somewhere between 160 and 170 pounds. Ouch.
As I understand it, the cows were fine. And all the riders were more or less fine.