This started as a comment to Susan's earlier post on equine therapy, but the comments are long enough for a full post. The connection between humans and animals within production agriculture has some interesting consequences for how we view and regulate the industry. I can recall the disposition (in the personality sense of the word) of many of the animals on my Dad's farm, and the connection made between us and the livestock. With horses, this connection was quite strong, but it extended to cattle as well (e.g., in the 1980s we had a dairy cow we nicknamed "OJ" because she could jump any fence we put up, and old cows with few teeth had a special status within the herd).
Interestingly, I did not experience or observe the same connection to swine or chickens. Perhaps the degree of financial investment per head failed to encourage the same mutual dependence. Perhaps the animals themselves are less aesthetically pleasing, or maybe they exhibit behavioral characteristics that make us somewhat reluctant to establish the same sort of relationship (e.g., they don't typically respond to the farmers voice or presence in the same way as larger animals).
So how is this relevant to regulating livestock production? Well, it may be that animal cruelty is more of a risk when the relationship between humans and animals holds little potential for mutual concern. Thus, for example, laws geared at horses and dogs may be some of the least necessary given the absence of mutual concern when it comes to chickens and hogs. If all animals occupy the same status, then protection ought to begin not with those that we cherish the most, but rather with those that we do not expect anyone to love.
As for production agriculture, as production becomes bigger (or, if you prefer, more factory-like or industrial), even the connections between more relational animals and their human caretakers (or "producers") may be lost. Stemming the tide of industrialization is, of course, difficult. With regard to dealing with its externalities, perhaps animal welfare regulation is more necessary in the industrial complex than it was when agriculture was structured along more Jeffersonian lines.