This question comes from a facebook fan. Thanks for the Question Sylvia! The Answer to your question is…….. it depends 
Horse manure can be a good amendment to your organic garden as long as you take a few things into consideration.
The first, is it seasoned? Horse (and cow, chicken, rabbit, etc.) manure will burn your plants if its fresh, so make sure it has finished “cooking” (at least 6 months old) before you add it to your garden.
B.) You will want to find out what they are feeding the horses. Unfortunately, many of the feed we give livestock today is plain and simple poison. More and more crops are genetically modified (GMO alfalfa has shown to cause kidney and liver failure, yet was still approved.) and other crops are sprayed with pesticides that stay on the plants that the horse eats. Some of it makes the journey out the other end of the horse, and if your put it in your garden, ends up on your dinner plate.
3rd.) Anti-biotics! Anti-biotics will pass out of the animal as well, and just as before if you add it to your garden…..
Of course, it’s up to you what you add to your garden. I for one stick to worm castings. Worms break their food down at a molecular level leaving clean organic deliciousness for your plants, that won’t burn them (our you in the long run). You can also ( I do ) use broad leaf plants as a living mulch to fertilize your garden.
If You or anyone else has a question about organic gardening feel free to ask through the contact page on our website, or our facebook page!
Before we got chickens I used to go pick up free horse manure. I ended up preferring leaf mulch because the horse “compost” we got was too fresh — more wood shavings than poop. Of course, that is awesome for the horses because it means they aren’t standing in a grungy barn… but not as good for the gardener.
Very nice post on this, thanks!
I was going to use horse manure, but the more I read maybe this isn’t a good idea for a raised garden. what is the best organic dirt for my raised garden?
Worm Casting by far are the best.
To avoid GMO problems source your manures from Amish farms. The old method was adding manure in the fall after the growing season, till or dug in the soil followed by sheet composting of leaves and dead grass or straw.
I would still be cautious even when dealing with the Amish. I have heard of some Amish in the north east using pesticides.