Maybe they convert some of the carbon into a more available form than decaying plants? Either way they definitely don't increase the amount of mico-nutrients, supposedly they return 85% and they burn most of the carbon they eat. And what does the figure 85% relate to? Do they return 85% per $hit. Or over a period of time? If they're continuously returning 85% eventually you end up with zero.

They return and enhance biology (microbial) back to the soil, which in turn stimulates nutrient availability. Plants get their nutrients through the biological processes that take place in the soil. It's all extremely complex, but in short, less biology=less healthy soil. Roundabout, cows help to stimulate and enhance microbes, which stimulate plants to optimize photosynthesis, which encourages them to release more root exudates (carbon; aka food for microbes) into the soil. Which in turn helps the biology thrive even more and start building soil aggregates, which store water, provide housing for the microbes and start storing carbon. It's a beautiful, feedback loop. Cows are an extremely useful tool in the process.

kzfaq.info/get/bejne/Z9OHmMaj3dKvg4U.htmlsi=ATUQvgN7sY8kl9ow

vet here - microbial growth in cattle digestive system is phenomenal - the microbes are what do the digesting and what ultimately provide energy to ruminants - the byproduct of microbial digestion + the microbes are recycled into soils as nutrient value. It is magical - but also biology. And yes, thermodynamics still applies - reread ruminant nutrition