Yes, you can use horse manure for fertilizing. But it must be composted properly. You must consider the nitrogen as well as the pathogens. Set aside an area for the manure so it can break down to the point of not being recognoizable as horse manure. When it is ready, it will look like fresh soil & will have absolutely NO smell. This could take a year or more, so be prepared to be patient.
I am sorry to say you should not use it quickly. But there is always next year.
I was talking to my Husband about this. (his family is/were Grain elevator owners for generations & so he knows a bit about gardening/farming in general.
He reminded me that when we lived on a small farm, my uncle came over every year to get fresh horse manure from us for his garden. he would work the manure in well with his exsisting soil. BUT having said that, I do not think I would use ANY kind of fresh manure...you would not wish to burn or contaminate your plants.