I second what Corporal mentioned above...
I’m not sure how popular this idea will be, but we have used it on ill horses who could not chew properly before and I’ve recently done it through hay pinches this year and last year.
Disclaimer: I’m organic and know exactly what is in my grass and pastures and don‘t use chemicals…. Don’t do this if you don’t know, or if you use chemicals.
Ok, I mow using one of several mowers- riding, push mower with bagger, or a brush hog/6’ cutter. . (depends on where I am mowing and how tall the grass is) and either it gets collected in the mower bag or I hand rake it up. I collect it using the front loader on the tractor or a huge wagon and move it to an open, airy area of my driveway that rarely gets used.
I spread it out thin to dry. If it isn’t really sunny that day, I’ll even turn it over halfway and fluff it through the drying process with a rake or pitch fork, just like a farmer does to a hay field.
Once it is VERY dry, I either bag it and put it up for storage/to feed later, or feed it as needed.
As I mentioned above I have used this for the horses, but also for my other farm animals and I do this for my garden and compost heaps. It works really well. Certainly time consuming…... but I have been able to supplement my horse hay with half clippings when needed as well as using for all of my forage needs for my alpacas and non-milking goats.
Start now as the grass has more nutritional value while it is still trying to grow/make it to seed. Once it seeds and the days really shorten the value isn't as high.
Oh yeah… another disclaimer… you kinda need a fair amount of grass to mow, which my grass seems to multiply like rabbits when we actually have rain.