Crab/fish meal. Which is to say leftovers after processing, dried and ground. https://www.feedipedia.org/node/664
At the end of the day, non-pasture food animal raising boils down to getting enough nutrients and time into them to hit your target slaughter weight, subject to feed conversion ratio for the species.
Cheaper nutrients = higher margins or lower product prices
So there's a lot of repurposing of sanitized animal byproducts. At the end of the day, as Cyberpunk 2020 quipped, "Parts is parts. Dead is dead. Dead guys is parts."
Anyone who's not comfortable with that should either go vegetarian or raise / buy into local meat.
Cows are herbivores. Feeding them meat is abhorrent.
How can we really know what cows know? What we know is they follow a herbivorous diet when possible. Their teeth and digestive system are optimized for consuming plants.
> Why would the fact that they don’t predate on other animals in the wild make it “abhorrent” to feed them animal products in captivity?
The reason you said.
"Meat" is a relative term though.
If I dry carcasses with some muscle and tissue still on them, grind it up into a powder, and add that powder to grain, is that meat?
"For dust thou art, and unto dust shalt thou return," etc.
What you described - desiccated waste meat and grain - is a dog biscuit.
Now with 50% less horse!
One weirdo from the herd showed a preference for it one time. Whereas if you threw it among your dogs they'd likely fight over it. That's the difference.
As others are noting, it's the wacky industrial modernity doing its grossly myopic hyper-optimization thing that's the problem (and not just in animal husbandry or agriculture...).
My favorite fact is that animals are allowed a certain percentage of plastics in their feed, and it’s not a tiny percentage. It’s a significant number.