This doesn't follow the rule of thirds to me because there are too many cows for one to be the focal point. (This would work for me if one was on a 1/3 line and was a different color)
I would've cropped a little tighter to get rid of the fence in the top right. I like to run my eyes all around the edges of the frame and make sure there aren't any little distractions like that acting to pull the viewers eyes away from the subject.
Cute picture. How'd you get the cows to look at you like that? Not sure how any of the intersection is the point of interest since all the cows seem equally inquisitive.
Those faces- hee hee. I love the bovine look. I wish this had a bit more interest. I love the cows, but to me, it would have worked even better if only the top two on the left, or the bottom two on the right were in the shot. Although it suits the challange, it has a busy snapshot sense with so many in the image.