COMPOSITION
The simple composition of this makes it easy to see what the subject is. I like how the cow is looking at you, and fills most of the frame. My only comment would be that a horizontal framing might work better, because there is soemthing almost unnerving about seeing half of the subject cropped out of the frame.
TECHNIQUE
The focus here is awesome. I like how the detail really shows, even to the numbers on the eartag (well, almost). I, personally, like the lighting because it gives the whole picture a warm feeling, but it does seem a bit harsh. The angle of perspective here (looking down on the cow) is interesting, and I think effective because it eliminates a lot of potential background clutter.
OVERALL EFFECT
I found it funny because I am familiar with this saying. Others may or may not be. Even so, the cow has a "who do you think you are" look, and that adds to the humor. Good work.
Interestign framing here. But it seems a little plain... maybe if it were from a different perspective? Like taken from the cow's eye level? Dunno. This could work with the Got Milk challenge too! heh
Photos of cows always make me laugh, cause I am reminded of a little joke I got in an email when I first got internet. Anyway, I think the shot is very nice. The angle and framing are good. I like how you have the entire shadow of the cow in the shot. The lighting seems a bit strange around his eyes. maybe kind of too bright? oh well, he's still a cutie. good luck in the challenge.