Dosing less can benefit dung beetles

by Enrico Villamaino

A newly published academic paper has outlined the potential dangers of using endectocides (veterinary parasiticides) in cattle.

The lead researcher was Domhnall Finch, a doctoral candidate at the University of Sussex in Brighton, England. Finch has focused his studies on movement ecology.

“I am interested in how management practices might impact wildlife, woodland thinning, the use of veterinary products, the difference alternate grass swards can have on biodiversity and livestock and what practical solutions we can come up with to solve these issues,” Finch said.

While a number of studies have analyzed the impact of antiparasitic cattle treatments on dung beetles, Finch’s study specifically focused on the impacts on the Aphodiine dung beetle, a vital food source for a range of bat and bird species.

“The majority of scientific literature shows the negative impacts that products such as ivermectin can have on these species, the environment and the health of the soil,” Finch explained, adding, “However, there are contrasting results in the literature, with some studies showing dung beetles being attracted to dung which contains residues of endectocides. The aim of our research is to find a consensus.”

Ivermectin is one of the most commonly used antiparasitic drugs in the U.S.

The results of Finch’s study illustrate how endectocides have a significant negative effect on both adult Aphodiine dung beetles and their larvae. When compared with control groups, they found that dung samples from cattle treated with these products had approximately one-third fewer dung beetle larvae. Ivermectin was shown to have the largest negative effect on the beetles.

Finch’s findings confirm that Aphodiine dung beetles are drawn to the chemical residue. “What’s particularly worrying is that when we looked at the occurrence rates of beetles in the dung, the adults actually seemed to be more attracted to the dung of cattle treated with antiparasitics, but because of the toxicity of those chemicals, their larvae have poor survival rates and face impaired development,” he said.

Over time, this decreases the dung beetle population in the biosphere. This negatively impacts the diet of local bird and bat species.

In addition, the reduction of dung beetles can deny the local ecosystem a number of benefits. Dung beetles help to control the pest fly population, quickly clear dung from pasture lands and promote rapid grass regrowth through nutrient cycling and soil aeration. Finch added, “Studies have proven that they can help to reduce the prevalence of worm infections in cattle, which is ironic when we consider that they’re now under threat from the chemical products which essentially do the same thing.”

Finch wants to see these problems addressed, but acknowledges there is currently no complete solution. “The results of our work highlight that more research is needed to determine the effects of newer agents. Very little research has been conducted on comparing different products under the same field experiment. This gap in our knowledge is critical to fill if we are to come up with safer solutions to this problem. There are products that have less of an impact on the environment but none that we are aware of are completely safe.”

To reduce the potential impacts of endectocides, Finch advocates that farmers work closely with veterinary practitioners and focus the use of chemical treatments solely on the animals that may need it. This would introduce less endectocides into the ecosystem than treating the entire herd at once. Livestock should then be kept indoors for a period of time after treatment to allow the majority of residues to pass through the animal.

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