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With Pony having been in a stall, I find myself in possession of more manure than usual. I brought some home but now I'm not sure about using it, since he was medicated (bute, muscle relaxers, and gastro guard). We still haven't gotten any more chickens, so I don't have any other poop to use for my compost pile and food trees.

I personally feel like there probably isn't any issue using this manure, since by the time it gets absorbed by the trees or compost pile, most of those chemicals will be gone. But is that true? Anyone have any links to studies about using medicated manure?
 

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If you go on Google Scholar (https://scholar.google.com/) and put in "composting manure medication" there are many articles that you could spend a lot of time perusing abstracts to see what the consensus is. I have a PhD in chemistry, and would say it would depend on the particular chemical, how it is metabolized (how fast and what to), and then how it or its metabolites break down when in a compost pile. I think how it affects the microbial community in your compost heap and then soil would be more of a concern than how it affects plants. I did not thoroughly read this paper (https://onlinelibrary.wiley.com/doi/full/10.1111/ejss.12494) but it suggests that antibiotics in animal manure used in compost can increase the spread of antibiotic resistant genes among a microbial community in soil. And I know that one is about antibiotics and that may not be relevant to you, but you could do searches specific for the chemicals that your horse has consumed (e.g., "composting manure phenylbutazone"). You would need to find out what muscle relaxers and gastro guard contain.
 

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Also, you could do searches to see what the specific compounds are metabolized to and then search for the toxicities of the metabolites. Other search terms you might want to include with compost/animal manure could be "pharmaceutical active compounds" and "organic contaminants" (organic being organic chemicals). It is a rapidly developing area of research with increases in agriculture and the use of medicines in animals, so it will be a rabbit hole of things to read I imagine! I have edited some papers about it in the past, but mainly about antibiotic residues, and it is a very interesting area of research.

If it was me, I would compost it because it is better to do that than not. However, I would not use it on food growing areas in case it affected the soil. Do you have room for a separate compost pile for it? We compost our dog poo and keep it all separate from food growing areas.
 

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Having owned/operated a large scale composting operation and been intimately familiar with EPA oversight, as well as the organic interest - testing on all sorts of levels, for all sorts of things I'll say that we found when properly composted for 12 weeks (active composting and curing) there were no longer traces of bute or ivermectin. Bute is remediated more quickly than the ivermectin but I would use 12 weeks as the baseline. This is in piles that are aerated, watered and turned to keep the process continuing and keep heat levels optimum for a set number of days as regulated by the USDA. Any other drug depends on the drug and I would need to know the name to see if it was one we covered. If I don't remember offhand I'd have to contact my X as most of those files he has access to. Methocarbamol which is fairly common for horses is not one we tested for as it was not used in the animals we collected from. It is primarily excreted in urine and metabolizes quickly so I would think not an issue especially once composted. We also had to test leachates and did not find contamination of any drug tested for in this. All were bound in the manure.
 

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That's great info above!

As a home composter, I think it would be hard to replicate "properly composted for 12 weeks (active composting and curing)" in "piles that are aerated, watered and turned to keep the process continuing and keep heat levels optimum for a set number of days". So I would still personally not use it on food areas, but I would absolutely compost it and use it somewhere.
 

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All you need is a thermometer to determine heat levels. Heat dries your pile and slows the process, dropping temps. Too much heat kills the beneficials. Dry piles look dry and feel dry. A little moisture added and then turning to add oxygen keeps it active.. It should feel like a wrung out sponge moisture wise. Actually quite easy for a home owner if you have a big enough pile, a ready source and a good eye for carbon to nitrogen and a strong back or willing labor. A single horse is enough for a good sized pile. But for your comfort level place it where you feel it will be best put to use in the just in case.


As a FYI for a home pile of large enough stature with a C:N of min 25:1 (max 40:1) you only need to sustain your temp in the 131F to 170F range for 3 days (you may or may not have to turn) and the rest of the time is curing. For us it was 15 days with a min of 5 of turns during that period then the rest was cure time. Most of our testing that was mandatory was because we were a reverse ratio N:C of greater than 80:1. We did have a specialty product that added mushroom waste from the growing operations in our area which helped up the C and made for a lighter product but still very N heavy. Our original was extremely dense.



Layer your pile alternating manure and bedding until you reach the largest size you are comfortable working with then start the process by mixing, adding water if necessary and taking the temps. The alternative is to build the pile, mixing as you go and letting it compost passively for 6 months or more.



The good thing about most drugs is that under the right conditions they break down quickly. Unlike some chemicals intended for herbicide and pesticide use. Capstone is one that comes to mind from the thread on grape vines. You spray it, an animal can eat it and it is excreted just as potent as when it was consumed for almost two years. I bet it goes even longer than that. Where we live (one area of the property we are on) there was a chemical sprayed that without major input and raising soil levels I could not grow most veggies. Wouldn't want to at this point. Grass grows great. A few broadleafs do OK. This was sprayed in the 70s. We are a hotbed for research which is not a good thing.





ATTRA is a great source for information on all sorts of subjects. Some of the info is free. Some nominal cost. They also put on informative clinics that are subject based.
 
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