The picture on many milk cartons shows cows grazing on a pasture next to a country barn and a silo — but the reality is very different.

More and more milk comes from confined animal feeding operations (CAFOs), where large herds live in feedlots, awaiting their thrice-daily trip to the milking barn. A factory farm with 2,000 cows produces as much sewage as a small city, yet there’s no treatment plant.

Across the country, big dairies are coming under increased criticism for polluting the air and the water. In New Mexico, they’re in the midst of a manure war.

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