Why steer 534?

Pollan's purpose for introducing steer 534 was to inform the reader about the way cows are being treated. In my opinion I think he is trying to persuade readers in a way as well. I think that he tries to persuade readers that cows should stick to their old fashioned natural diet which consisted of hay or grass. However since corn is pushing aside the needs of other animals and crops, cows are forced to eat corn 24/7.