TL;DR for the title:
Employees [from this investigation] can be seen removing the intestines of dead, disease-infected piglets and mixing them with piglet feces in a blender — a mixture to be fed to the adult breeding pigs — causing one worker to gag.
The practice, called “feedback,” is common in the pork business (or “controlled oral exposure” in industry jargon).
The article itself goes into more depth about all the horrific things in the pork industry such as these
The pork industry has pushed pigs to their biological limits, leading to many bizarre practices beyond feedback, many of which are inhumane. To name one example recently in the news: There are horse farms that impregnate horses, extract their blood for a serum, abort their pregnancies, and then sell the serum to pig farms to induce puberty in young female pigs and produce larger litters. Holden Farms, like most pig breeding farms, confine pregnant pigs in gestation crates, cages so small they can’t turn around for practically their entire lives.
This is the best summary I could come up with:
Animal Outlook’s investigator said the farm had begun using feedback because some piglets were getting sick with diarrhea, losing weight, and their skin was turning from pink to a grayish hue.
Some pig researchers say that while feedback has clear benefits in fighting, for example, PEDv — a virus that caused hundreds of millions of dollars in economic loss to the pork industry a decade ago — it can be risky, and there’s no standard protocol.
Jim Reynolds, a bovine veterinarian in California who’s also worked with pigs and specializes in epidemiology, said the practice makes sense in theory, but he doesn’t recommend it in part because it risks exposing animals to unintended diseases.
That much was evident in the early 2010s fight over so-called pink slime, a mix of meat scraps processed with chemicals meant to kill bacteria, that was turned into filler for beef products.
While feedback may be particularly off-putting, it’s a symptom of a larger problem: America’s enduring desire for cheap, plentiful meat, which has given way to thousands of massive factory farms where stressed, genetically identical animals with poor immune systems are tightly packed together, providing the perfect conditions for disease to spread.
Industry has responded to consumer concerns with the practices brought to light in undercover investigations largely with empty gestures, like firing individual employees for abuse instead of meaningfully changing conditions for animals.
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It’s worth noting here what “feedback” is referring to for anyone skipping to the autotldr