The ACFA link you sent doesn't seem to say what you referenced, that I could find. In fact, I've never seen anyone say that cattle is fed decent corn in any stage of life except "finishing" (which reduced gaminess), and even then 80% is the high end.

A more accurate number is that 86% of a an animal's diet is human-inedible (see below), roughages and byproducts. That number CAN easily be moved closer to 100% at the cost of gaminess, but I have had beef that was not "finished" and it was ok. I'm definitely ok sacrificing a little corn to get the improved flavor.

Note the 86%? That's animals in general. If you focus on cows, that number crosses to 90%. And if we're talking all non-vegan products, MILK (for those not allergic to it like myself) is incredibly nitritious compared to the total potential human nutritional value of a dairy cow's intake.

Is the waste product of corn and soy included in these numbers?

Since I cannot seem to trace your references, I'm not sure. But it's covered in the numbers I linked. Every single reputable or researched reference I have ever seen on the topic (as well as the actual cattle ranches I've lived near) put a bare minimum of 85% of a cow's diet as inedibles. And why would it be anything else? Those inedibles are dramatically cheaper than buying edible corn.

...and stepping back, I'd like to point out that we're discussing the paltry percent of some of the least nutritionally valuable crops in the world are eaten by cows, who by any honest analysis produces one of the most nutrious staple foods known to man.

[–] Urik@lemmy.ca 3 points 1 year ago

The figure was almost by the middle of the page, search for the string "AT THE FEEDLOT, CATTLE ARE FED A DIET OF 80% GRAIN AND 20% FORAGES. (SILAGE AND HAY)", on the section "Start weight, finish weight".

As for the others:
Here's the USDA source: https://www.ers.usda.gov/topics/crops/corn-and-other-feed-grains/feed-grains-sector-at-a-glance/:

Corn is a major component of livestock feed. Feed use, a derived demand, is closely related to the number of animals (cattle, hogs, and poultry) that are fed corn and typically accounts for about 40 percent of total domestic corn use. The amount of corn used for feed also depends on the crop's supply and price, the amount of supplemental ingredients used in feed rations, and the supplies and prices of competing ingredients.

And regarding soy, here's from the WWF: https://wwf.panda.org/discover/our_focus/food_practice/sustainable_production/soy/

We may not eat large quantities of soy directly, but the animals we eat, or from which we consume eggs or milk, do. In fact, almost 80% of the world’s soybean crop is fed to livestock, especially for beef, chicken, egg and dairy production (milk, cheeses, butter, yogurt, etc).

You obviously know way more than me about the subject but you gotta excuse me for taking anything from a website called "sacredcow" talking about the "plant-based industry" at the top of the page with a grain of salt, everything else I've seen online points to animal farming being incredible inefficient and a huge contributor to global warming and water waste.