This is solvable problem. When consumers and producers don't have incentive to do the right thing very frequently the solution is to regulate.

As an example, if a producer declares they meet a specific standard this could mean they voluntarily undergo regular audit of their entire process including how the cows are treated.

We do this for many products and services. Here in Poland, eggs are regulated in many categories from hens kept in cages to free-range. When you buy eggs they are all individually stamped with a mark that clearly indicates how hens are kept and fed and you, as a customer, can choose the more expensive product but with a knowledge that you get what you pay for.