Horse manure, worming and compost
This week the Compost Conversation has enlisted the help of local vet and large animal specialist, Dr. Paul O’Connor, to better understand horse health and what that means for our compost. Paul grew up on a farm, has a long-term affinity with large farm animals and is a partner at Kangaroo Flat Vet Clinic.
In my conversation with Dr. Paul, he emphasised that wild horses’ natural protection against parasitic worms is to roam widely and avoid eating grass from where they have recently defecated.
Domestic horses, ‘set stocked’ in a small paddock will initially defecate in one spot and try to avoid eating from that area, but given time, paddocks become full of manure, the soil becomes compacted and vegetation dies. ‘Horse sick’ is the term Dr. Paul used to describe this kind of paddock.
Horse owners can reduce the impact of manure build up by regularly cleaning manure out of the paddocks.
This is the main reason we composters have access to so much horse manure. Composting, particularly hot composting (over 55o c) kills parasitic worms and their eggs.
However, even with regular manure removal, set stocking makes horses very susceptible to worm infestations, resulting in domestic horses getting routine worming treatments. Although recommended at quarterly intervals by drug companies, ‘Anthelmintics’ (anti-worm treatments) are sometimes administered as often as monthly in heavily stocked spaces to stressed horses.
Dr. Paul said “a healthy horse, regularly rotated through fresh pasture - with additional rotations of chooks, sheep or other livestock for even better results - might only require ‘worming’ treatment once a year”. He also recommended faecal testing for worm ‘shedding’, to allow more targeted treatment only to horses that are struggling with parasites.
Anthelmintics can kill or dislodge worms in the horse’s gut, but Paul noted they can also kill earthworms and dung beetles in the soil, both creatures working towards making paddocks healthier!
“When we over-administer anthelmintics, we encourage treatment resistance in the worm population, which usually leads to more potent drugs being developed and more regular treatments being required” said Dr. Paul.
What has all this to do with compost? Our compost worms will also be impacted by these worm treatments, so we don’t want to put recently treated manure in our compost.
Resting manure for a month used to be recommended for Ivermectin - the most common worm treatment - but Paul warned that new, more potent vermicides, like Moxidectin, persist longer, and need about 3 months to be safe.
If composters know when worming treatments have happened (and which ones), collected manure can be put aside to rest until safe. Dr. Paul recommends “if you don’t know the worming schedule, the best approach is to rest manure for at least 3 months before adding it to your compost”
Dr. Paul reminds us “Horse owners have a big responsibility to make sure their love of horses doesn’t end in unhealthy animals, damaged landscapes and an increasing use of ever more potent drugs”.
AUTHOR: JOEL MEADOWS
Joel Meadows works with *Yes In My Back Yard, (YIMBY), a community-scale composting initiative in Castlemaine and surrounds. Send questions or comments to hello@yimbycompost.com or to book in for a compost workshop!
This was first published in the Midland Express on 23 October 2024