Yes you can use horse manure providing that they haven't been given worming medicine. This is important because the medicine sterilises the manure and may retard microbial metabolism and reproduction, which is the source of the heat in compost. Although chicken manure is "hot", that is, quite high in nitrogen (or heat in this case), so you may have enough manure if you mix it well. 20% chicken manure, 40% green material (not from legumes) and 40% carbon material (dried leaves, woodchip is great or shredded cardboard). Watered to 50% moisture and turned when the temperature gets to about 60ºC. When you stick your hand in the pile and you aren't able to hold it there, that's when you flip it. Perfect moisture is when one handful of mixed material yields one drop of liquid. Most importantly the pile should not smell bad.

For other sources of nitrogen, try to use any available legume green leaf material. These form most of the plant family Fabaceae. If you're a big coffee drinker another idea is to dry out and
save your spent coffee grounds.