It used to be common place to grind it up and put it in the feed for animals.
Ranchers do a ton of shit that is pretty disgusting and messed up. If you call them out for it they'll get pretty upset and call you a commie or unamerican.
A lot of ranchers have "dead piles" where they just let the bodies rot. Dairy ops also routinely do the same stuff, along with just dumping milk on the ground or in "manure pits" which often leak into the groundwater.
I grew up in this world. Small town, ranching/farming, conservative. The stuff ranchers and dairy ops do is mindblowingly fucked up. They call it tradition and if you call them out you will be attacked.
A while back the governor of Colorado was like "Yo let's designate one day where people don't eat beef. It'll be good for the environment." Colorado ranchers lost their fucking minds. They threw huge hissy fits and ran campaigns to get people to consume more meat on that day. So dumb. Find some videos of the ranchers basically crying and throwing fits, they're pretty funny https://www.koaa.com/news/covering-colorado/communities-gath...
You've got a very ignorant view of dairy farming. Now I'm sure there's some operations in those western desert states that behave that way but it is absolutely not the norm east of the Mississippi.
I've got a friend who owns a dairy farm. He doesn't keep dead cows around because the risk of introducing disease isn't worth it.
Manure gets treated in a "lagoon" (which looks like an open pit to you) wherein the water evaporated and bacteria breaks it down to become fertilizer for the next guy. The system is specifically designed to keep it from running off. Good dirt work is cheaper than having you people up his ass over pollution.
If he dumps milk it's like 20gal from purging equipment or something, not enough to matter. Milk is money so he tries to avoid dumping any. If he did want to dump a bunch of it, he could dump it straight into the lagoons because a liquid designed to be nutritious for growing mammals will be a walk in the park for bacteria that feed on what the mammals leave behind.
And 40yr ago when he dad owned the farm all of this was the same. The technology has changed a little but they weren't piling bodies then either.
Your friend might be able to get incentives to construct an electric producing bioreactor for their lagoon pit. Something to perhaps mention if they aren't aware.
If you drive through farm country you see "fat" advertisements for finishing cattle or increasing milk production. IE: https://energyfeeds.com/magnafat/
Normal feed/grazing isn't optimal or cost effective compared to other options, for the animal's full lifecycle.
