Final answer:
Evidence supporting the claim about the negative effects of feeding corn to livestock in CAFOs includes scientific studies on livestock health, the environmental impact of using arable land for feed, and the human health issues arising from diets high in corn-fed meat and processed foods.
Step-by-step explanation:
The claim that cattle in concentrated animal feeding operations (CAFOs) are forced to eat corn and that this diet has considerable costs to their health, the environment, and ultimately to the health of humans rests on several pieces of evidence. Scientific studies on the negative effects of corn-based diets on livestock health are the primary source supporting this claim. These studies are often summarized in reports by respected organizations such as the National Academy of Sciences, making the findings more accessible to the public.
Concerns regarding the environmental impact of land use for animal-based food production and pollution also contribute to the argument. It is noted that animal nutrition, when based on grass, pasture, and silage, sometimes uses land that is not suitable for other agricultural purposes. However, the larger industrial practice of feeding livestock corn is typically done on arable land, which could be used to produce food directly edible by humans or for other ecosystem services, such as biofuel production.
Finally, health impacts on humans, such as a rise in obesity-related health issues potentially linked to corn sweeteners like high fructose corn syrup (HFCS), have been observed and are also a point of debate concerning CAFO practices. The over-dependence on a diet high in fatty, corn-fed meats, alongside sugary processed foods, exacerbates health issues, especially among the poor, resulting in wider socio-economic repercussions.