Used horse bedding pellets as mulch, over growing garden sprouts?

What about used horse bedding pellets as mulch, over growing garden sprouts - would the ammonia from the horse pee be too much for the plants?
Does anyone have experience with used / spoiled horse bedding pellets in the garden?

I use the pellets under my rabbit cages to soak up urine, and found they don't work well as mulch, unless they're mixed with other carbon mulch material. Not sure about horse urine, but rabbit urine tends to be really hot, due to the high amount of ammonia.
Since the pellets basically turn to sawdust when wet, I dump the trays of manure, urine, and pellets in a compost pile to help heat the pile and sit there until I need to top up the worm bins/beds with more food for the worms.

I use horse bedding pellets, which are simply pellets of compressed pine sawdust, in the midst of summer. That’s when I need carbons/browns to compost my grass clippings. A few handsfull mixed in with each grass catcher bag really gets the pile up to 140-150 degrees fast, and keeps the grass from forming thick, slimy, anaerobic mattes.

Once the leaves start falling, I don’t need them.