Grazing for Change

Exploring the science behind sustainable farming practices and their impact on ecosystem health

It was on a Livestock Research and Innovation Corporation farm tour that Dr. Heather Murphy, an environmental engineer in OVC’s Department of Pathobiology, first encountered rotational grazing. At that time, she noted that the positive impacts reported on this farming practice were mostly anecdotal.
Shortly after, Murphy began to delve into the science, finding out how setting up cattle to graze in a rotational manner, or moving from one paddock area to another, could improve soil, animal and human health.
Unlike conventional grazing, where cattle have access to the entire pasture, the cattle in a rotational grazing system rotate between smaller subdivided paddocks within the larger pasture. This allows the soil to rest and the vegetation to regenerate between grazing sessions.

Murphy, Canada Research Chair in One Health, wanted to find out whether rotational grazing could produce healthier cattle, shedding fewer pathogens that can end up in soil and waterways and potentially impact human and animal health.

To answer these questions, Murphy and Dr. Kari Dunfield, Canada Research Chair in Environmental Microbiology of Agroecosystems, assembled a team of five University of Guelph scientists to examine the impacts of rotational grazing on the overall ecosystem in a first-of-its-kind, multi-year study.
The study uses the One Health approach, in which multidisciplinary research teams collaborate to solve complex problems that could impact the health and well-being of humans, animals and the environment.
“The One Health approach is what makes our research study unique,” says Murphy. “No one has looked holistically at the impacts of cattle grazing practices on the entire ecosystem in terms of pathogen transmission.”
This study began in 2021 with researchers looking at the impact of cattle grazing practices on water, soil and wildlife while examining herd health and antimicrobial resistance. It involved more than 28 students who benefited from hands-on sample collection and analysis.

Improved soil health and carbon sequestering

“We already know that pastures have proven benefits for soil health and sequester more carbon compared to conventional grain-based agricultural systems,” says Dunfield, a professor in the School of Environmental Sciences at the Ontario Agricultural College. “We’re interested to see if there are additional benefits with rotational grazing systems.”

In rotational grazing, cow feces are distributed sequentially throughout the pasture, allowing the soil to uniformly absorb nutrients and increase water infiltration and biodiversity. The result is more nutrient-rich soil, more efficiently grazed pastures and greater potential to store carbon. Additionally, spreading the manure evenly may speed up pathogen die-off compared to conventional systems where it tends to accumulate in specific areas of the pasture.

Understanding the impacts of grazing on water quality

Murphy, who specializes in water-related research, is also collecting water samples to gauge groundwater and surface water contamination levels, particularly after rainfall. She says that on conventionally grazed farms, cattle favour specific parts of the pasture, resulting in a concentration of fecal matter.
“Following rainfall, the fecal matter on conventional farms may be washed out more readily into the surrounding waterways compared to rotationally grazed farms where it is spread more evenly,” says Murphy. “This leads us to believe that on rotationally grazed farms, the fecal matter has a better chance of drying out, allowing pathogens that could contaminate water sources to die off more quickly.”
According to Murphy, pathogens in the manure could find their way into surface water and groundwater that we may end up drinking.
“Fewer organisms reaching the environment is ultimately important for human health as we may see fewer water- and food-borne illnesses in humans due to exposure through recreation, drinking and irrigation.”

Using wildlife as indicators of pathogens in the environment

Dr. Claire Jardine, regional director of the Canadian Wildlife Health Cooperative for Ontario and Nunavut, is also involved in the study. Her team is examining samples from wildlife, including mice and voles collected along the edges of beef farms to gauge the transmission of pathogens.
Jardine, an associate professor in OVC’s Department of Pathobiology, believes that some pathogens, including some resistant bacteria found in wildlife, may provide insight into what’s happening in their surroundings.
“Some of our previous studies indicate that resistant bacteria found in wildlife are just a reflection of what’s going on in the environment,” says Jardine. “In some cases, after wildlife are exposed to bacteria, those bacteria can show up in the wild animal’s intestinal system and can then be cleared. Wildlife are not necessarily maintaining these bacteria in their ecosystems over the long term, but they are useful for comparing the occurrence of pathogens in different environments.”

Could rotational grazing reduce pathogens and limit antimicrobial resistance?
Another focus of the research is the impact on levels of antimicrobial-resistant pathogens. Antimicrobial resistance occurs when bacteria, viruses, fungi and parasites no longer respond to medicines, making infections harder to treat.
Over prolonged periods of use, antimicrobials such as antibiotics, antivirals, antifungals and antiparasitics lose their efficacy. On beef farms, these medications are used to treat or prevent disease in cows and can pass through cows’ manure into the environment.

Dr. Nicole Ricker, an assistant professor in the Department of Pathobiology, is testing hundreds of fecal samples for antimicrobial-resistant bacteria. Preliminary results show lower levels of antimicrobial-resistant bacteria in samples gathered on rotationally grazed farms, which Ricker attributes to the overall health of such herds.
“We hypothesize that we will see lower incidence of disease on these farms, which could be attributed to fewer opportunities for cross-contamination from the herd’s fecal matter,” says Ricker. “Healthier cows require less medication, which translates into less antimicrobial-resistant bacteria being created and shed through their stool.”

Dr. Charlotte Winder, associate professor in OVC’s Department of Population Medicine, is supporting survey data collected to provide information on antimicrobial use and health outcomes of the herds being studied.
Hands-on training for OVC students
Carly Dinga, a master of science student in the Department of Pathobiology, is working alongside the U of G researchers to analyze samples for pathogens that pose potential threats for both humans and cattle, with the goal of applying this knowledge in her future career in public health.
“It’s interesting to see how different pieces work together to solve a complex problem,” says Dinga. “Understanding how pathogens move through the environment and how people and animals might come into contact with them may help reduce the risk of disease among these populations.”

Defining future farming best practices
Rotational grazing has been around since the 1950s, yet some industries have been slow to adopt the practice. Implementation requires fencing or pasture partitioning and a water source that can be easily accessible from various paddocks. This also means additional time investment for farmers, many of whom have multiple jobs.
“For our study, we tried to pair conventional and traditional farmers in the same geographic area for easy comparison,” says Murphy. “For example, we have two neighbours: one is a conventional farmer, and the other is a rotational farmer. One has practised conventional farming all his life and does not see the need to switch over. The other neighbour practises rotational grazing and sees the health and yield benefits in his cattle.”
The research team hopes that real-life examples of farmers enrolled in the study will demonstrate to other farmers that rotational grazing practices are not only beneficial but attainable.

This research is funded in part by U of G’s Food from Thought research funding program, which supports the development of innovative solutions that improve the sustainability and productivity of agricultural production at global, landscape and micro scales. Additional funding was provided in 2022 by the Beef Farmers of Ontario to expand the number of participants in this study to 10 beef farms across Ontario. The multi-year research project is expected to wrap up by spring 2025.

This story was originally published in the Crest Magazine (Summer 2024)