How Healthy Dung Communities Help Your Farm
30 August 2024With the price of inorganic fertilisers escalating, dung is becoming increasingly valued as a rich source of nitrogen and phosphorus. Within the dung, a diverse range of invertebrates, bacteria and fungi are hard at work. These decomposers play slightly different roles, working together to break down the dung, aerate the soil and recycle nutrients, thus improving soil health and pasture quality. Research also indicates that dung beetles can reduce the development and survival of livestock gastrointestinal parasites. Dung insects (including dung beetles and dung fly larvae) not only consume the eggs and larval stages of parasitic worms, but also speed up desiccation and aeration, making the dung less favourable for parasite larval growth. Healthy dung communities, therefore, play a key role in reducing reliance on anthelmintics (wormers and flukicides). It is estimated that dung beetles save the UK cattle industry approximately £367 million each year, with their value in reducing parasite burdens amounting to a saving of £196 million annually.
Dung beetles
With more than 60 species in the UK, dung beetles are probably the most well-known dung inhabitants. They inhabit a wide range of dung including sheep, cattle and horse. The UK’s most striking is the Dor beetle, with its relatively large size, spikey legs and metallic body. Dor beetles are tunnellers, meaning they don’t live in the dung itself, but instead tunnel into the soil below the dung, pulling the dung into their burrows to feed their own larvae. They are, therefore, particularly valuable in mixing dung back into the soil. When you explore dung, look for the characteristic burrows below the dung, dig into these and you may come across the C-shaped cream larvae of Dor beetles.
It is important not to overlook dung beetles of the genus Aphodius, which are small (typically less than 1 cm in length), pill-shaped, brown and relatively inconspicuous. However, if you take the time to delve into a cowpat, it is likely that these will be the most abundant creatures you find. These small dung beetles are dung dwellers, living and breeding in the dung itself.
If you look a little more closely at dung beetles, you will often see tiny chestnut brown mites clinging tightly to the beetle. These phoretic mites hitch a ride on the beetles, relying on them from transportation between dung patches. These mites are also thought to prey on the eggs and larvae of nematodes.
Other dung dwellers
Lots of fly species lay their eggs in dung, including dung flies, blowflies, house flies and the Heineken hoverfly. Unlike the larvae of dung beetles, which tend to be C-shaped, with distinct legs at the front of their bodies, these fly maggots are totally legless.
A wide range of fungi, known as coprophilous fungi (meaning dung-loving), also grow on dung, this includes orange saucer fungi that produce small round fruiting bodies that speckle cow pats. In secreting enzymes that can break down complex organic compounds such as proteins, fungi also play a key role in returning nutrients back into the soil.
How healthy is your dung community?
It is surprisingly easy to monitor the insects in dung. Look for fresh dung between April-June or September-October, which has had some time to allow dung insects to colonise it but is not too dry (i.e. moist dung without a glistening surface). You can simply break the dung apart in your hands (you should wear gloves!) to see what is living in it, or alternatively break it into a tray to explore the contents more thoroughly. Don’t forget to look for the characteristic tunnels of the Dor beetles in the soil below the dung. Keeping track of the type and number of invertebrates in dung will help determine if management practices are helping these beneficial invertebrates. Dung Beetles for Farmers have a useful dung beetle assessment protocol with a scorecard that will give an indication of the health of your dung beetle community.
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Actions to support healthy dung communities
Many chemical compounds used routinely to control parasites will also negatively impact on dung invertebrates. We need to reduce our reliance on chemical parasiticides for all sorts of reasons, including reducing selection for resistance, reducing chemical residues in meat and milk and reducing potentially adverse impacts on the environment.
Maintaining good health and ensuring the correct nutrition will help livestock naturally combat infestations. Breeding your own replacement stock where possible will reduce risks associated with bringing new livestock onto your farm and ensure young stock build resistance to their local parasites.
Grazing management is also crucial in reducing parasite burdens. Maintaining some level of winter grazing will help ensure dung is present year-round, while extending the period between grazing episodes will reduce the risk of livestock encountering dung and its associated parasites. With worm eggs tending to be found at the base of grass, taller grass may also reduce the risk of ingestion of infectious parasite larvae.
Many plants including bird’s-foot trefoil and chicory have natural anti-parasitic or anthelmintic properties and research has shown that lambs grazing on multispecies swards required fewer anthelmintic treatments than those on perennial ryegrass or perennial ryegrass and white clover swards. Graze species-rich grasslands or establish multi-species swards to optimise the benefits of these naturally occurring anthelminthics.
When action is needed to control intestinal parasites, this should be based on evidence from monitoring worm burdens using faecal egg counts (FECs). Anthelmintic need to be selected to target the parasite in question and it is important these are applied at the correct dose rate. Subsequent monitoring will help determine if treatment has been effective. Rather than treating all animals, Targeted Selective Treatment (TST) focusing on animals that show early signs of infestation (reduced daily live weight gain, poor body condition scoring, lower milk yield, FEC etc.) will help build natural resistance and reduce the need for wormers. Leaving some animals untreated will also ensure that some dung remains uncontaminated with anthelmintics. To further reduce risks to dung communities, keep treated animals inside, or use a ‘sacrificial’ field to contain the impact of wormers to a single location. These actions will not only reduce any adverse impacts on the dung community, but also reduce the risk of resistance to wormers developing. The SCOPS and COWS industry groups both have best practice advice on reducing environmental impacts of anthelmintics, advocating that we use ‘As little as possible, but as much as necessary!’
Many dung invertebrates require a variety of resources throughout their lifespan. For example, while the larvae of the Heineken hoverfly feed on dung, the adults require nectar. Promoting semi-natural habitats such as hedgerows, wetlands and farm woodlands will help provide a variety of resources to meet the requirements of a diversity of dung invertebrates.
Healthy dung communities reduce the need for synthetic fertilisers and veterinary medicines, helping farmers save money and reduce their carbon footprint. With parasites becoming resistant to anthelmintics, and climate change increasing the risk of parasites building up and spreading alongside new parasites emerging, dung invertebrate communities have a key role to play in building resilient farming systems.
Five Actions for Healthy Dung Communities
By Dr Lorna J Cole (SAC Consulting) and Dr Philip Skuce (Moredun Research Institute)
Additional Resources
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