Composting and Spreading Horse Manure in Pastures

Updated June 28, 2024 | By: Dr. Lydia Gray
horse manure compost pile

"The removal of horse manure is a challenge for all horse barns. If manure is spread rather than removed from paddocks in late fall will it be fully composted by the spring to grow grass or will it just breed more parasites and put horses at risk? This is the big discussion currently at our barn along with worming schedules and what wormers are best."

- PM, Connecticut

Dear PM,

I certainly hope there were some wagers placed pending the outcome of this “big discussion” (stall cleaning, blanket washing, arena raking, etc)! Seriously though, it’s an excellent question and you’re right, manure removal is a major challenge for horse barns across the country.

Fortunately there are some excellent resources available to provide ideas and assistance on this topic, namely your state’s extension office. These agents know and understand the needs and available resources in your specific state, and can address issues like: what to do with manure.

They will be the first to tell you that spreading manure in paddocks or pastures is technically not “composting.” While the manure will eventually break down, true composting is the combining of organic matter with water and air in certain ratios so that microorganisms set to work chemically decomposing the raw materials and generating heat in the process. When this heat exceeds 40°C (104°F) for a minimum of two weeks, strongyle larvae and even the hardier ascarid eggs will be killed. Non-composted horse manure should never be spread on pastures as this will increase the level of parasite contamination.

That last sentence comes from an EXCELLENT resource for all things equine parasite-related, the published Internal Parasite Control Guidelines by the American Association of Equine Practitioners (AAEP). Ask your veterinarian for a copy or Google it yourself. The guidelines go on to say that, while infective strongyle larvae can survive only a few weeks in hot weather, they can live for as many as six or nine months during colder weather! So yes, spreading manure from paddocks onto pastures during the cold winter will just distribute parasites across a wider range and set the horses up for increased infestation come spring when the parasite eggs hatch.

Barns in northern latitudes are instructed only to spread manure on closed pastures (meaning they will not be used for a while) during the hot, dry months of summer such as July and August so that parasite eggs and larvae will be killed. Northern-located barns should NOT spread manure in the fall, winter, or spring.

I strongly encourage you to read the AAEP Internal Parasite Control Guidelines and discuss them with your veterinarian and your barn owner/manager (and UPS delivery man, if he’s interested!). Not only do the guidelines clearly explain proper environmental management to reduce parasite transmission, they also cover when and why to perform fecal egg counts, which dewormers are still effective where, and how deworming affects anthelmintic resistance and the parasite “refugia.” I’ll end there leaving you to figure that word out on your own.

Ask the Vet Video on How to Compost Horse Manure and Bedding

In this video, Dr. Gray explains how to compost horse manure and bedding on your farm.

Learn more about proper parasite control practices by reading our deworming guide.

SmartPak strongly encourages you to consult your veterinarian regarding specific questions about your horse's health. This information is not intended to diagnose or treat any disease, and is purely educational.