While cows won't walk down stairs on their own, it has been proven that cows will walk down stairs if you force them to. So, yes, cows can walk down stairs. They just avoid the situation as much as possible, as they are not evolutionarily prepared for such steep slopes and foreign leg movements. Are Cows Really Unable to Walk Down Stairs? | Britannica
They can get up/down and through some places one might fear to tread. This is especially true if the grass appears greener on the other side of the obstruction...don't ask how I know.
We seem to be avoiding some obvious questions here.
Are any TDPRI members actual cows? Sensitivity, people! Let’s be inclusive.
Can humans digest alfalfa, or easily buck off a sweaty, ill-tempered cowboy? Can they extend their tongue far enough to wrap it around a corn stalk and pull it into their mouth—aside from Gene Simmons?