What are some examples of ethos and pathos in The Omnivore's Dilemma (chapters 4 and 8)?

In order to establish credibility—the purpose of ethos in literature—in chapter four of The Omnivore's Dilemma, the author, Michael Pollan, goes to the lengths of purchasing a calf and following the young steer on its journey toward becoming "a wholesale box of beef" (Pollan, p. 71). This has the effect of making the animal more real and present to the reader; had Pollan simply described the process of beef cattle operations, the story's impact would have been greatly lessened. The tactic ties in nicely with the pathos of the chapter as well, as Pollan reminds us repeatedly that cattle evolved to dine exclusively on grass, yet we force them to consume corn in order to fatten them up more quickly. What would happen to us, as humans, if we were forced to eat only foods that were incompatible with our digestive systems?  
The tactic is repeated in a smaller way in chapter 8, All Flesh is Grass, when Pollan contacts Joel Salatin, owner of Polyface Farm in Virginia. When Pollan asks this "sustainable farm" owner if he can ship over "one of his chickens and maybe a steak, too" (Pollan, p. 133), he's told no—it's not sustainable to ship meat. If he wants to try the product, he has to travel to Virginia himself. The fact that Pollan does it, and that he spends a week on the farm getting his hands dirty, increases his credibility. The distinction between the pastoral acres of Polyface and the industrial warehouse visited in chapter 4 serves as another reminder that animals raised for human consumption should be treated humanely.