When it comes to painting cows or anything for that matter, you must focus on the shape, not the object. If you tell yourself you are going to paint or draw a cow you will run the risk of going on auto-pilot and start drawing with images in your mind rather than what is right in front of you.
Really look at the shapes and piece it together one stroke at a time and then if you put down what you actually see then step back a few feet and take a look. You will see something that "reads" what you are trying to say. Up close it may look like a blob but step back and it probably makes more sense than you thought it would :D