UNION - Results from studies conducted over the past four years offer strong evidence that properly managed cattle grazing can be compatible with healthy streams (riparian areas), according to Tim DelCurto, an Oregon State University range beef cattle scientist.
DelCurto heads an interdisciplinary team of scientists from two Pacific Northwest universities and the U.S. Forest Service who are studying the impacts of managed livestock grazing during summer months on stream ecosystems in eastern Oregon.
"Over the last few years the research team has focused on mapping livestock distribution in a grazing area that includes a stream in order to find out where cattle migrate in the area during the day," DelCurto said.
The study is located at the OSU Eastern Oregon Agricultural Research Center's Hall Ranch east of Union.
The team found that cattle tend to graze in areas a good distance away from the stream during the early morning hours. The cattle then search for water in late morning and finally seek shade, or graze less intensively during hot afternoon hours. Also, cattle tended to spend the afternoon in the same areas as they drank, then move away from the water source in the evening.
The researchers assessed strategies for improving livestock distribution by luring cattle away from streams, DelCurto said.
"We found that providing sources of water - called off-stream water - and salt in grazing areas will draw cattle away from a stream, usually in the afternoon hours," he said.
In the study, the distribution of cattle that had the stream as the only water source was compared to the distribution of cattle with access to off-stream water and salt. Cattle with the stream as the only water source were, on average, 150 to 200 feet away from the stream from 3 to 9 p.m.
By comparison, cattle in the off-stream water group tended to be, on average, 350 to 400 feet away from the stream during those same hours.
"This isn't necessarily a new finding," said DelCurto. "We've known for years that providing off-stream water and salt draws cattle away from streams as they graze. "The difference here is that we're quantifying what the cattle actually do as they graze, how far they go from the stream and how long they stay away.
"Careful, accurate measurement of these behaviors hasn't been done before," he added.
This type of carefully detailed research is important because livestock managers have always said "this or that" grazing strategy works, DelCurto pointed out.
"The response from critics has been, 'how do you know it works'," DelCurto said. "What's lacking in the debate is hard data and that's what we're generating with the study."
Research team members are Mike McInnis, range scientist, and John Tanaka, range economist, Oregon State University; Patrick Momont, beef cattle nutritionist, and Neal Rimbey, range economist, University of Idaho; and James McIver, forestry specialist, USDA Forest Service.
The study also focused on timing of grazing and biological indicators in and near the riparian zone.
"Timing of grazing is a measurement of grazing time versus resting time along with consideration of where cattle move as they graze on a day-to-day and seasonal basis," DelCurto said. "This information will help our understanding of what cattle do, depending on time of season and weather conditions, when a stream or creek lies within their grazing range."
The study of biological indicators includes what DelCurto calls "green line stability," or the condition of stream banks. In the study researchers classified stream banks as covered (with vegetation) and stable (not broken down by the weight of livestock trampling); or uncovered (vegetation removed by grazing) and unstable (broken down by trampling).
Researchers compared a non-grazed control area with grazing areas where cattle had access to off-stream water sources and grazing areas with a stream as the only source of water for cattle. The research team found that the amount of uncovered/unstable streambank increased due to grazing in both experimental treatments, but increased less (3.5 percent) in grazing areas with off-stream water.
Uncovered/unstable streambank increased 8.6 percent in grazing areas with a stream as the only water source.
"Our research results support the conclusion that streams in grazing areas with off-stream water and salt have better stream bank stability and retain more vegetative cover than streams in grazing areas with no off-stream water or salt," said DelCurto. "This finding supports the contention that application of strategies to improve livestock distribution can reduce livestock impacts on riparian areas."
Ultimately, DelCurto said, the researchers hope their studies will find that careful management of livestock to insure uniform distribution throughout grazing areas is a better solution for protecting riparian areas than fencing streams or excluding grazing altogether.
Over the previous four years, this research received funding from the Environmental Protection Agency Agriculture in Concert with the Environment program, the Blue Mountain Natural Resource Institute, and the U.S. Department of Agriculture Sustainable Agriculture Research and Education program.
Current research is focused on animal factors, such as age, lactation, stage of lactation and breed, that may influence distribution patterns and resource use, DelCurto said.