By Kristen Tribe

". . . these are things that we tell people in print, but we haven’t had a way to show them graphically," says Dr. Robert Lyons, range specialist, Texas Cooperative Extension – The Texas A&M University System at Uvalde.

He and Dr. Rick Machen, Extension livestock specialist, also of Uvalde, have been using GPS (Global Positioning Systems) collars to evaluate the behavior of grazing beef cattle and using the data they collect to illustrate many points about range management and to help improve landowners’ understanding and management of grazing distribution.

The issue was first brought to their attention when a landowner’s cattle were losing weight, even though the stocking rate seemed acceptable. Upon further inspection, they realized there were many brushy areas that were not accessible to the cattle, and most likely, the stocking rate was set according to total acres available and not according to grazeable acres.

"In other words, if you’ve got 10,000 acres and you can only use half of it, then the half you can use is your grazeable acreage. Grazeable acres are what you use to set your stocking rates," Lyons explains.

For example, although ranchers have been told that cattle avoid brushy areas, no one had actually been able to document a herd’s location and behavior pictorially within a pasture or ranch to illustrate this point.

Lyons and Machen recognized that graphic "proof" could make many aspects of range management easier to understand, including the concept of grazeable acres, but it took them about a while to decide how to approach the project.

In the end, Lyons says they finally "stumbled across the existence of the GPS collars that could collect the kind of information we needed."

These particular collars are made by a company in Canada and were originally used for wildlife, like moose and bison. The data collection device in the collar, about the size of a 3x5 index card, communicates with a constellation of satellites to note latitude, longitude and time.

The collars run off batteries, and Lyons says at first they had a battery that would only run for six days taking readings at 15-minute intervals. Now they have the capability to get readings for 17 days at five-minute intervals and for even more days, if they lengthen the intervals. This capability allows even more flexibility in future studies.

"If you think about it, the only other way we could get this kind of information would be to put someone out there to follow the cows around for 24 hours," says Lyons.

There is also an "activity counter" on the collar that measures vertical and horizontal head motion, which indicates if the animal was grazing or resting.

To retrieve the data, the collars are removed at the end of a study period and brought back to the office to download the information. Then they can find out where the cattle were at any time of day and have a good idea of what they were doing.

Lyons then uses ArcView, mapping software, to create a "picture" of the data gathered. When he’s done, you can actually trace the path the cow followed and tell how much time she spent in each place.

To illustrate how access to water could affect grazing distribution, Lyons and Machen established an 11-day trial.

With water sources at the north and south ends of a long, narrow pasture, they went through different sequences of access to water during this 11-day trial, first with both water sources on, and then only one or the other water source on, to see where the cows would go and how they would react.

Once all the data was compiled, it was obvious that the cattle favored an open area near the north end of the pasture and avoided an open area that was close to water at the south end.

In fact, when water was only on at the north end, cattle did not venture very far toward the south end of the pasture. Only when the water was off at the north end and on at the south end, did grazing become more evenly spread across the pasture.

While there were also brushy areas that the cattle avoided within this pasture, Lyons and Machen were puzzled at the lack of use within the open area near the south end. Although this area appeared grazeable, cattle tended to avoid it.

"The question was why, since it’s open and close to water, but the answer was it’s rocky," says Lyons. "We expected the brush to be a deterrent to cattle use, but I never thought about rock being such a big factor."

In another trial, the cattle had access to six pastures, but there was one they didn’t go into at all. Lyons thought there must have been a mistake – the gate must have been closed.

But when they checked, they found that the gate had been open. The cattle just didn’t want to go into the pasture, even though the entrance was right next to the water source.

Again, they found rocks just inside the pasture. Also, in this trial, cattle demonstrated a strong preference for one of the two major range sites on this ranch.

"Every time we found an open area that cows wouldn’t go into, we’d find some rock," Lyons says. ". . . they either avoided those areas or used them less, even though they were within a quarter to a tenth of a mile from water."

He says that their preliminary data suggests that if there is 30 percent to 35 percent rock cover, cattle won’t use the area. Anything below 30 percent rock cover may affect their use, but it doesn’t seem to prevent it.

"So we were back to the grazeable acres issue again that started this project," says Machen. "They’ve got six pastures available and they’re only using five, so what’s the effective stocking rate? These kinds of findings really fell in well, with what our original interest had been."

In these trials, Lyons and Machen demonstrated that distance to water, topography and vegetation types all affect grazing distribution. With the proper management tools and understanding, these issues can either be overcome or built into the ranch management plan to avoid overuse of areas.

If you’re looking to draw animals into less desirable areas, one way this can be done is by controlling their access to water or provide new water sources in the places where you want them to graze.

Lyons recommends not making cattle travel more than ¼ to ½ mile between forage and water in rough areas and no more than 1 mile on level ground. This may mean you have to build drinking troughs, dig wells or even put in pipelines to transport water.

Machen says you can also do the same thing with supplements, like salt and other minerals, and he hopes to do a similar study with the GPS collars to demonstrate this.

Clearing brush to grow grass for cattle is a natural instinct among cattleman. However, before clearing, consider what you will have when the brush is gone. From the results of the GPS collar studies conducted so far, rock cover should be one of the considerations.

"If rock cover is dense enough that cattle won’t use an area even when cleared of brush, then maybe you need to reconsider what the best management for the area is," Lyons explains. "It may be best to leave these kinds of areas for wildlife habitat, but as a rancher, you need to take these areas into account realizing that they will provide little if any grazing when you set your stocking rate."

Other times, there may be plenty of grass, but not the type your cattle prefer.

"It’s only forage for the cow if she eats it, and they have preferences," says Lyons. "Some studies have shown 80 percent of the diet coming from 1 percent of the standing crop. In an Oregon study, two grasses out of the 11 that the cattle had to choose from accounted for 80 percent of the diet."

For example, Machen says in one of their original studies, he would come across hooded windmill grass that looked like someone took a weedeater to it, while nearby grasses were virtually untouched. The cattle got what they wanted and then moved on to the next bunch of preferred grass.

This tendency to search for preferred forages can be detrimental at times such as the spring becomes cattle may spend all day "chasing the green," the more palatable, new growth that is in short supply.

Lyons says this grass doesn’t meet their nutritional needs because they can’t eat enough of it in a day due to the limited amount available. Cattle can end up losing weight even though they’re spending more time grazing.

If you’re looking to improve the palatability of the plants you have, nitrogen fertilization can do the trick for some species, but it’s an expensive venture, just to improve grazing distribution. It’s only worth it if you may also increase your forage production at the same time.

If conditions are right, you can also use prescribed burning, which removes old growth and makes more new growth available.

Also examine the layout of your fences because they can be set up in a way that discourages cattle from using all pastures equally. Shade also influences grazing behavior on hot, summer days, but it’s not been proven that artificial shade will increase grazing activity.

Although it’s too bad you can’t retire the old farm truck, check the cows via satellite, and track their every move, simple observation will help you learn valuable information about your rangeland and perhaps improve grazing distribution.

Every rangeland will have different grazing obstacles, but as long as you keep these in mind when you set the stocking rate, they shouldn’t lessen your ability to make a profit.