Forgetting non-stun processes for a moment, most know that the majority of slaughterhouses in Australia use "stunning" (the rendering of the animal insensible). In fact, this is the basis upon which slaughter of animals is heralded as "humane". But do you know what the failure… twitter.com/i/web/status/1…
Field study estimates of efficacy of bolt gun stunning for cows vary from 2% to 0.1% failure (including those found by a revered consultant to the Meat and Livestock industry, Dr Temple Grandin). That sounds pretty good right! Statistics are very good for whitewashing horrific… twitter.com/i/web/status/1…
If you’re going to list micronutrients and say they’re missing from PBDs, you should probably check which ones are already made by our bodies, and which have plant alternatives (iron) or precursors (beta carotene). Also one Brazil nut supples RDA for selenium.
According to Defra, in 2019 the U.K used 182,000ha of land for oats, yielding 6 tonnes of oats per ha
Based on your figures that dairy cows use 925000 ha of land, and assuming, as you did, only 35% of that is croppable, that would allow for 323,750 ha to grow oats on.