AMES — The chute closes around a cow, and Justin Bisinger works quickly to place a collar around her neck.
About a minute later, the Iowa State University graduate student is finished, the chute opens and the cow trots down the alley, shaking her head in a futile attempt to loosen her new “jewelry.”
But, this jewelry is extra-special — the collar contains global positioning (GPS) device that allows Bisinger and his adviser, ISU animal science professor Jim Russell, to track cow movement over two weeks.
Russell and his team have been studying cow movement at several farms, most notably ISU’s research farm near Rhodes.
“The reason that we got involved in this research was that there have been studies indicating that pastures in the Midwest are the greatest contributor of sediment and phosphorus to surface water resources,” Russell says. “For instance, one study estimated that pasture and rangeland in the Midwest contributes 37 percent of the phosphorus to the hypoxic zone in the Gulf of Mexico.
“What concerned me is there seemed to be little interest or knowledge of the effects of grazing management on water quality in pasture streams.”
And, he says, the research indicates cows do not spend as much time in creeks as many think. Russell’s research looked into how grazing management could be altered to help ease those concerns.
In addition to the Rhodes farm, research was conducted at ISU’s McNay research farm in South Central Iowa and the farms of cooperating producers in the Rathbun Lake Watershed.
The current study, funded by the Leopold Center, involves three systems and two pasture sizes. Within each pasture size, there are three management systems, including full stream access with or without off-stream water and restricted stream access to stabilized crossings.
Fifteen cows graze in the 30-acre pastures, while five cows graze in the 10-acre pastures. Two or three cows per pasture have collars.
The GPS records the position of each cow every 10 minutes, Russell says. The collars are kept on the cows for two weeks.
Russell says the amount of time spent in streams varies by pasture conditions.
“In the past, we’ve compared continuous grazing with full access to a stream, continuous grazing with stream access restricted to stabilized crossings, and rotational grazing with controlled access to the riparian paddock, or the paddock adjacent to the stream,” he says.
“We’ve also looked at pasture size and shape, the percentage of tall fescue, and shade distribution.
“In our current study, we’re looking at continuous grazing with full access to the stream with and without off-stream water and continuous grazing with stream access restricted to stabilized crossings in pastures with two sizes, 10 and 30 acres.”
Russell says time spent in the water varied based on pasture size.
“In 30-acre pastures with continuous grazing and full access to the stream, cows will spend 1 to 3 percent of their time in the stream and up to 14 percent of their time within 100 feet of a stream,” he says.
“In smaller pastures, cows spend six to 14 percent of their time in the stream and up to 30 percent of their time within 100 feet of a stream.”
He says controlling access to water will dramatically reduce those percentages.
“Restricting access to pasture streams to stabilized crossings or controlling grazing in a riparian paddock will reduce the proportion of time that cattle are in and near streams by 80 to 90 percent,” Russell says.
“This is particularly important in smaller pastures. We have not found off-stream water to effectively alter cow distribution in Midwestern pastures. In a recent study, we found that the effects of shade superseded those of off-stream water.”
He says the research indicates it is not necessary to deny cows access to water in a stream.
“There are alternatives like stabilized crossings or flash grazing of riparian paddocks in a rotational grazing system that will allow cattle restricted access to the water and, in the case of rotational grazing, the forage near the pasture streams,” Russell says. “As the major factor affecting congregation of cows near pasture streams is pasture size, these types of management practices become increasingly important in small pastures.
He adds the research proves some access to water is not a risk to water quality.
“What our research refutes is the belief that the only solution of sediment, phosphorus, and pathogen loading of pasture streams is exclusion fencing,” Russell says. “Instead, our research shows that the risks of sediment, phosphorus, and pathogen pollution associated with grazing may be significantly reduced by management practices that reduce the amount of time cattle congregate in and near pasture streams — the larger and wider the pasture, the less the need for these practices.”
He says little pollution associated with grazing occurred in the streams in the study.
“We found that 99 percent of the sediment and 95 percent of the phosphorus entering pasture streams comes from cut-bank erosion that is primarily the result of varying stream flow levels and other hydrologic variables that supersede any effects of grazing.”
Russell adds overgrazing of stream banks could increase the risk of impacting water quality.
“These results shouldn’t be interpreted to say that grazing cattle present no risk to stream water quality,” he says.
“Overgrazing or congregation of cattle near pasture streams may cause problems. So, implementation of management practices to reduce any risks that grazing cattle present to water quality by altering distribution in pastures should be considered.