This is the "market for lemons" problem: Consumers can't tell actually humane treatment from fake, which ends up economically pressuring farms to cut corners and go towards the fake.
You could register a trademark and have a certification program for "humane" milk / meat producers to use. Then go around raising awareness of what "pasture-raised" and "grass-fed" really means. If you do a good job of communicating, people will be happy to pay the extra $0.50 (or $1) to know the cows are actually chilling in the fields and not cooped up in a pen.