Thanks for the kind words!
That’s a good question too! Here’s a video on what happens to non-meat parts of cattle, but no mention of the brains. This article in Discover has more detail, written around Mad Cow Disease and focusing on the UK market.
It says “Renderers process brains for use in laboratory reagents, pharmaceuticals, and cosmetics.” So I assume that the brains, with many other inedible parts, go to a rendering facility. I’m not sure if the brain goes to one particular thing or gets mixed up with other, similar parts for cosmetics, though. Maybe my readers can give a more specific answer?
The Discover article is interesting, makes you think about how dead cattle are all around us.