We spread the fresh manure on our allotment beds in the Autumn (after everything has been harvested), but we then cover them in membrane. We usually only get bindweed and brambles coming up in Spring.
Something I've just read, which may or not be important; the horse/cow may have just been wormed, if their dung lands up on a compost heap, it could kill the friendly worms in your compost pile.
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Horse Manure - When to Use — BBC Gardeners' World Magazine (gardenersworld.com)
As you can see, there's more to this than it seems!
Danger, danger, everywhere....
Cambridgeshire/Norfolk border.