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Barta Brothers Ranch research shows deferred, short-duration grazing similarWhen it comes to grazing upland range in the Sandhills of Nebraska, there's little difference between short-duration and deferred grazing systems in forage production, diet quality and animal performance, University of Nebraska-Lincoln range scientists found. In a nine-year grazing study at UNL's Barta Brothers Ranch near Rose in the eastern Nebraska Sandhills, Institute of Agriculture and Natural Resources researchers studied the plant and livestock response to short-duration grazing and deferred rotation systems. The university usually recommends the deferred rotation grazing system for semi-arid rangelands such as the uplands of the Nebraska Sandhills. However, short-duration grazing is thought to provide a consistent supply of high quality forage through the growing season, and therefore greater animal performance, said Walt Schacht, UNL range scientist. Researchers found lack of forage production and animal performance responses to short-duration grazing indicate that the higher input costs associated with short-duration grazing are not justified in the Nebraska Sandhills, said Jerry Volesky, range specialist at UNL's West Central Research and Extension Center at North Platte. "We're not saying ranchers shouldn't adopt short-duration grazing," Schacht said. "It did not result in negative plant or animal responses in our study. Our research results are indicating that there is no difference between the two, and that the extra infrastructure required of short-duration grazing isn't justified." Short-duration grazing involves rotationally grazing eight or more pastures, moving cattle frequently (every seven to 12 days). Each pasture is grazed two or more times during the grazing season, which is mid-May to mid-October in the Sandhills. "The basic premise behind short-duration grazing is that cattle will use the available forage efficiently because of improved distribution and timing of grazing," Schacht said. "The assumption is that the increased stocking density and multiple rotations through the pastures will result in more even use of forage and maintenance of the pasture forage in a more palatable and productive state." With short-duration grazing, ranchers have extra pastures and, therefore, flexibility on managing those pastures. However, short-duration grazing is more labor and management intensive. It requires more fencing and water development, Volesky said. Deferred grazing involves rotationally grazing four or five pastures with each one being grazed only once during the growing season. Cattle are moved every 30 to 40 days. One drawback is that the plants are stemmy by August and September which can be thought to lower harvest efficiency and forage quality. The last pasture in the rotation is not grazed until the end of the season when plants have full growth. "It is called deferred rotation because one pasture is being deferred, or not being grazed until the end of the season," Schacht said. "Every fourth or fifth year a pasture is deferred and allowed to gain vigor following several consecutive years of being grazed during the growing season." The study started in 1999 when the upland range of the Barta Brothers Ranch was divided into 24 pastures that averaged 130 acres each. Just over 3,000 acres of the 6,000-acre Sandhills ranch donated to UNL in 1992 by brothers Jim and Clifford Barta were used in this study. The ranch was donated to the university with the understanding that it would serve as a demonstration ranch, where practices commonly recommended could be tested and demonstrated at the ranch scale, Schacht said. The 24 pastures were divided into two blocks of 12 pastures each based on topography and plan species composition. Eight of the pastures in each block were allocated to a short-duration grazing system and the other four pastures were assigned to a deferred grazing rotation system. Each system was grazed annually by cow-calf pairs at .7 animal unit month per acre from May 15 to Oct. 15. Animal unit month is the amount of herbage a 1,000 pound beef animal will consume in 1 month. Researchers periodically collected diets of esophageally-fistulated cows grazing pastures in each system through the grazing seasons of 2005 and 2006. Twenty spayed heifers replaced 10 cow-calf pairs in each system in 2006 and 2007 and weight gains of the heifers were recorded. Researchers used spayed heifers for determining weight gains because they are more responsive to forage conditions than cows in terms of animal performance. Over the nine years of the study, herbage production ranged from 1,000 pounds per acre in 2002 to about 2,250 pounds per acre in several years. The annual variability in production was high because 2002 was a very dry year. Researchers also found that forage production did not differ between the two grazing systems regardless of whether it was a wet or dry year. Mean in vitro organic matter digestibility, neutral detergent fiber and crude protein content of cattle diets did not differ between the two systems. In addition, the decline in diet quality through the grazing season generally followed a similar pattern for the two systems. Weight gains of the spayed heifers also did not differ between the two systems, averaging about 1.75 and 2.15 pounds per head per day in 2006 and 2007, respectively. "We had some wet springs and dry summers and some dry springs and wet summers, but results were still similar," Volesky said. The study will conclude this year, but Volesky and Schacht expect results to remain the same. An economic analysis of this study also will be out soon. "Overall, we wanted to do a long-term comparison of these two specific grazing systems," Volesky said. "Oftentimes, some grassland responses don't necessarily show up in one or two years. This long-term study allows us to come up with better recommendations and suggestions to Sandhills ranchers in terms of what systems they might use that meet their management objectives and style and are sustainable." 6/30/08 Date: 6/20/08 Advertisement
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