I put a layer of lawn clippings on top of the pea straw in my vegetable garden. Fresh grass clippings often form a crust on top and then get stinky underneath so don't make very good mulch unless spread very thinly. I have laid a thick layer but I don't think there will be a problem because:
- the straw underneath will allow air flow and
- the chooks will have endless hours of joy scratching and mixing it.
I will buy some bags of animal manure and add it to the mix and when I plant I will plant into compost.