Reducing potential harmful effects on the environment before applying wormer treatments to cattle is at the centre of livestock Integrated Pest Management (IPM). Research carried out in the USA by Dr Bryony Sands puts some meaningful data behind IPM principles.
Many classes of veterinary pesticides have negative environmental impacts on beneficial pasture insects, in particular invertebrates living in the dung. These beneficial insects provide vital pasture ecosystem services such as decomposition, nutrient cycling, pest and parasite suppression and improved soil drainage and health.
Livestock IPM aims to use alternative techniques to control pests to improve environmental outcomes.
In 2022, Bryony carried out a grazing dairy trial in the USA, looking at how effective IPM strategies used by farmers are at controlling parasites, while at the same time supporting beneficial insects and improving soil health.
She worked with 29 dairy farmers who were already implementing IPM practices. These included different grazing strategies, such as continuous (set-stocked), rotational (groups moving every three to ten days) and Management Intensive Grazing (MIG)(aka Mob grazing), which incorporated moves every 12 to 24 hours.
Treatments included chemical parasiticides, alternative treatments such as parasitoid wasps and essential oils for fly control or no treatments at all.
Rotational grazing strategies effectively controlled internal parasites of cattle. Faecal egg counts taken on the farms grazing in this way were comparable to farms where chemical wormers were being used.
The higher the number of dung beetles, the lower the number of pest flies that were present. Similarly, cattle had reduced gastrointestinal parasite eggs in their faeces when there were more dung beetles around.
These results show how beneficial beetles in dung compete for dung resources with pest and parasites, either by reducing the breeding site or by directly predating them.
Further work also showed how dung beetle species richness was significantly lower on farms using certain parasiticides, with wide variation in the effect different products had – from fenbendazole having the least effect to eprinomectin having the worst.
It also showed how dung beetles contribute to improved soil health outcomes such as higher active carbon and lower compaction.
The research showed that IPM strategies, can contribute to effective pest and parasite control, while supporting beneficial insects such as dung beetles.
But with such complex and interconnected pasture ecosystems, there are often multiple trade-offs associated with management decisions taken about how to graze, where to graze and how long to graze cattle in certain fields.
Further research may look at aspects such as residual grazing height to determine how this might benefit dung beetles, earthworms and other beneficial creatures living in the soil.
Dr Bryony Sands has an MSc in veterinary parasitology and PhD in agricultural entomology from the University of Bristol. She is currently a postdoctoral research fellow at the University of Vermont, USA.
Environmental impact of antiparasiticides
COWS and SCOPS group members are working together to work out how best to communicate the environmental impact of using cattle and sheep wormers to farmers.
“Antiparasiticides are essential for animal health and welfare yet we know they can be environmentally harmful, “ says Jason Rankin, chair of COWS.
“We are always mindful of promoting the ‘use as little as possible, but as much as necessary,’ approach, as this works to help slow the development of resistance. But, usefully, this will also limit any harmful environmental impact.
“We shall continue to promote a test before treating approach, encourage correct application, such as making sure the right dose is applied at the right time and that application equipment is clean and calibrated correctly. Following these simple steps, will help retain the products we have for longer, while protecting our pasture fauna.”