NO!
You need to either wait until the toppings have rotted down enough to not be attractive, or strip graze them so they only get a tiny amount at a time. They can easily gorge on toppings if they have dried nicely as hay. I speak from experience!!
Personally I would exercise extreme caution if putting horses on to pasture which has been topped - and treat it as you would lawn cuttings, i.e. don't!
If you did put them on it, and they got colic, it would be a horrible death for them and you'd feel eternally awful about it.
If a smaller field I remove the cuttings, if larger then I keep the horses off it until the clippings have either started to rot down or have totally dried through so they are like hay.
If it is just the dried out long blades which mean there is only a small amount of cuttings then it is probably ok. However, if there is a lot of cuttings and they are green, they no.
thanks for everyones help. i have only topped around the edges of my field because the brambles where over growing and it was about a month and a half ago now, so what do you think?