What can you do for a cow that has runny nose and a cough?

That all depends on what you are referring to as "a cold." Bovine Respiratory Disease (BRD) is probably what you're referring to when asking about a cow "getting a cold." The best thing you could probably do is go to the vet to get some medicine to give to her via needle and syringe. Anything but Micotil is best for her, but you have to be more cautious of what you should give her if she's a dairy cow that is producing milk for you.