Growing Beef Newsletter
June 2025, Volume 15, Issue 12
Dung Dynasty:
Using targeted deworming to promote fecal pat degradation and limit anthelmintic resistance in an intensive rotational grazing system.
Dr. Megan Hindman, clinical assistant professor, CVM Veterinary Field Services; Dr. Grant Dewell; DVM, Ph.D; Abby Dies; and Sam Millard
Cattle are the original model for sustainability. They are able to take a moderate to poor forage that no other species will eat to reproduce, convert it to food for other species to consume, and provide fertilizer for the forage it took in the first place. In 2017, it is estimated that 29% of all U.S. land is primarily used for livestock grazing.1 It is estimated that 20-47% of pastures are smothered by dung after 200 grazing days.2 In order to maintain the grazing pasture, dung beetles play a critical role in the sustainability of cattle production in the U.S.
Dung beetles, also known as scarabs, play a vital role in sustainability for cattle production in the U.S. Depending on the type of dung beetle, each has a role in releasing fertilizer and freeing pastures from the feces for new growth to form. There are three functional types of dung beetles worldwide: dwellers, tunnelers, and rollers. Dwellers work to aerate the dung so it can be broken down by nature more efficiently by mother nature than ones that do not have dung beetles. Tunnelers burrow underneath and integrate dung into the soil to act as fertilizer. And finally, rollers spread the dung over large distances and bury it, fertilizing the soil across the pastures. All of these combined release nitrogen, ammonia, phosphate, and organic matter, and in turn reduce soil compaction as well. Which, in a study completed in Florida, has equated to $120 million saved by freeing and fertilizing grazed pastures.3
Over the years, more farmers and ranchers have become more aware of the value of dung beetles, and questions are being raised about maintaining the overall population. One of the questions being asked has been whether do parasiticides we commonly use in beef cattle practice impact the effects of dung beetles in the pasture. Several studies have shown negative effects across the globe on macrocyclic lactones (ex., Ivermectin) and the dung beetles.4,5,6 However, none have been done in the United States. It is also known that macrocyclic lactones are predominately excreted through the feces, and anywhere from 62-98% of the active ingredient has been found.7 Therefore, there was a need to evaluate macrocyclic lactones and the effects of fecal pat degradation and dung beetle populations in a commercial cow-calf operation in Iowa. Our original hypothesis was that macrocyclic lactone would have an effect on dung beetles compared to cattle that did not receive it.
Methods and Materials
Cattle
Approximately 274 black Angus cows were used in this study from a farm located in south central Iowa. Cows were split in four different age groups two year olds (n=47), three-year-olds (n=47), young cows, 4-7 years of age ( n=70), and old cows, 8-15 years of age (n=110). Each cow-calf pair was managed separately in different pastures. Treatment groups for year one were two-year-olds and the young cows. Negative controls were three-year-olds and the old cows. At the beginning of June, each of the treated cows received 500 mcg/kg (1mL/ 22 lb body weight) of doramectin (Dectomax) topically down the back by weight. Calves did not receive any treatment in any treatment group. Additionally, a fecal sample was collected on 10 cows randomly per group to undergo a Modified Wisconsin McMaster test at the beginning of the study and at weaning. Finally, calves were weighed at weaning time to determine an average daily gain between birth and weaning.
Dung beetle
Dung beetle traps were placed throughout each pasture in a five-by-five dice pattern. Dung beetle traps consisted of digging a hole in the ground and placing a bucket into the hole. The bucket was filled with mineral oil to coat the bottom of the bucket completely. A grate was placed over the top of the bucket, and finally, a ball of fresh feces wrapped in a cheese cloth was placed over the grate. Traps were secured with a fence around them to ensure cows or calves did not step into the bucket. Traps were checked every week for four weeks and freshened every week as well. Dung beetles were identified in the trap and were counted for weekly pasture counts.
Fecal pat degradation
One fresh fecal pat was isolated by a fence around it per pasture. Every week, approximately a 1g sample was taken from it and weighed, then dried down in a convection oven to determine the dry matter percentage of the fecal pat.
Statistics
A commercially available statistical program, R, was used to determine if there were any statistical differences between dung beetle counts, fecal pat degradation, and calf performance between treatment groups.
Results and discussion
This is preliminary data from one year of a two-year study. There was no statistical difference between treatment groups and the number of dung beetles collected between intervals. There was also no difference in dry matter percentage between treatment groups.
Treatment did have a small statistical difference (p <0.05) in female calves only for both weaning weight and average daily gain between cows that received doramectin and cows that did not (Table 1). No treatment difference was noted in calf performance between male calves. There was no statistical difference between dung beetle populations between treated and non-treated pastures (Figure 1).
Based on this preliminary data set, there is no evidence that doramectin decreases the population of dung beetles or fecal pat degradation in a cow-calf operation in central Iowa. However, a continuation of this study needs to be completed in order to note if there is a pasture or age of cow effect from this study.
Acknowledgements: IVMA Bovine Pre-conditioning Grant for funds to complete the project, McNay Research Farm for the cattle, and Zoetis for supplying the Dectomax for this project.
References
1. Service UER. Major land uses. United States Department of Agriculture. 2018;.
2. Marten GC, Donker JD. Selective Grazing Induced by Animal Excreta I. Evidence of Occurrence and Superficial Remedy1. Journal of Dairy Science 1964;47:773-776.
3. Stanbrook-Buyer R, Bhat M, King JR. Economic value of dung removal by dung beetles in US sub-tropical pastures. Basic and Applied Ecology 2024;79:123-130.
4. Basto-Estrella GS, Rodríguez-Vivas RI, Delfín-González H, et al. Dung beetle (Coleoptera: Scarabaeinae) diversity and seasonality in response to use of macrocyclic lactones at cattle ranches in the mexican neotropics. Insect Conservation and Diversity 2014;7:73-81.
5. Lumaret JP, Galante E, Lumbreras C, et al. Field Effects of Ivermectin Residues on Dung Beetles. Journal of Applied Ecology 1993;30:428-436.
6. Verdú JR, Lobo JM, Sánchez-Piñero F, et al. Ivermectin residues disrupt dung beetle diversity, soil properties and ecosystem functioning: An interdisciplinary field study. Science of The Total Environment 2018;618:219-228.
7. Strong L. Avermectins: a review of their impact on insects of cattle dung. Bulletin of Entomological Research 1992;82:265-274.
This monthly newsletter is free and provides timely information on topics that matter most to Iowa beef producers. You’re welcome to use information and articles from the newsletter - simply credit Iowa Beef Center.
