What people often refer to as horse manure is actually stable waste which has much more soft wood shavings than horse poop and I call it stable waste. It also contains a lot of the urine absorbed by those shavings which contains a bit more than half of NPK excreted by the animals as I recall.
If you're looking for a quick N punch a top dressing of manure will probably deliver it if it doesn't all get tied up composting the shavings. Incorporating stable waste into the soil- hot or mellowed a bit- sometimes really ties up the nutrients if the wood is still intact. Straight manure might give you more N than you want, especially if applied to bearing age fruit trees. If the trees are young and you want to make them bigger quick I'd use it only as a top dressing in spring.