they could be seedlings of any number of things. Ash and field maple look identical at this stage.They look like Sycamore seedlings - section off or move your horse(s) as a soon as you can.
Doesn't look like an ash seedling.We have no sycamore trees nearby, probably ash as we have 4 ash tries bordering field
It's impossible to tell apart seedlings from a variety of trees at this stage. I have loads of ash seedlings in my garden and they look identical to the field maple seedlings I have at the field.Doesn't look like an ash seedling.
Take good photos of the seedlings and keep a couple in pots to see what the leaves are like when fully formed. Next year, you'll have a better idea of what you're finding.either pull them