Oyster Mushrooms as stock feed - nutritional benefit after harvesting mushrooms

I am looking at growing oyster mushrooms as a combined small business selling the mushrooms, and also providing cheaper stored feed for farm animals.

This article from last year shows that growing oyster mushroom substrate to 30 days increases the energy and protein content and palatiability of the original substrate material.

I also ready somewhere in a non-academic article a few years ago that the spent substrate after harvesting mushrooms is more nutritious to pigs than the original material, but can't find that now.

Does anyone out there know more or have access to a research database through a university to search this out?

Oops, forgot the link - here it is:

https://link.springer.com/article/10.1186/s40497-019-0174-2

I dont have any more resources, but I came across this idea before when looking it what oyster mushrooms do to lignin.
This works on straw and woodchips as well.
I wonder if it could be part of turning lignin heavy "waste" into alcohol for fuel.

Here's a link that talks about using it on woodchips and straw:

https://www.wur.nl/en/article/Fungi-turns-straw-into-digestible-feed.htm#:~:text=Fungi%20can%20break%20down%20lignin,capable%20of%20breaking%20down%20lignin.&text=They%20take%20nutrients%20from%20the,valuable%20carbohydrates%20are%20being%20spared.

I think that it can supplement their diet. I like to think of feed/food that has been colonized by mushroom as a type of condiment/herbal medicine aka not to binge on but to be eaten for their wonderful flavor and benefits.  

Straw/woodchip starts off as indigestible. It has zero food value. Saying that spent grain has “more” food value than zero doesn’t say much.

How much more are we talking about? What about all the remaining indigestible material? Is it a preferred food, or do you need to starve you animals to get them to eat it?

My chickens have shown essentially zero interest in mushroom mycelium, or mushroom fruiting bodies when I have thrown them in the run. I’m not sure how I would get them to eat a meaningful quantity of either as a food source.

I find animals and their feed to be very situational.

I've seen chickens devour mycelium and mushrooms, but I totally believe that some flocks would spurn it. I have ducks that don't like slugs, but in the past I've had flocks that devoured them. I think it's worth a shot, and if it doesn't work right away you can try to teach them or get a different breed line.