The 2008 Joint Meeting of the Society for Range Management and the America Forage and Grassland Council. |
Monday, January 28, 2008 - 4:20 PM
Effects of Sequential Cattle and Sheep Grazing for Spotted Knapweed Control
Stacee L. Henderson, Tracy K. Brewer, Rodney W. Kott, and Jeffrey C. Mosley. Department of Animal and Range Sciences, Montana State University, Bozeman, MT 59717
Spotted knapweed (Centaurea stoebe L.) infests millions of hectares of native rangeland in North America. Prescribed sheep grazing can effectively control spotted knapweed, however, many cattle ranchers are concerned that sheep will consume too much cattle forage and harm desirable grasses while grazing to control spotted knapweed. We evaluated one grazing strategy in which a site is grazed by cattle and then followed immediately by sheep grazing in an attempt to minimize these potential adverse effects. This 2-year study quantified graminoid and spotted knapweed utilization and grazing behavior of cattle and sheep grazed sequentially on spotted knapweed-infested rangeland in western Montana . Twenty-one Targhee yearling wethers and 9 Black Angus yearling cattle were used. Animals were randomly assigned to one of 3, 0.81-ha pastures that were grazed in either mid-June or mid-July (n=6 pastures). Cattle grazed a pasture for 7 days, immediately followed by sheep grazing for 7 days. In Year 1, cattle utilization of graminoids and spotted knapweed in June and July did not differ, averaging 19% and 39%, respectively. Utilization of graminoids following cattle + sheep grazing was less in June than July (36% vs. 43%), and utilization of spotted knapweed was greater in June (63% vs. 62%). Feeding station interval of cattle and sheep did not differ between June and July, averaging 17 seconds and 12 seconds, respectively. Cattle and sheep took 14% and 28% more steps between feeding stations, respectively, in June vs. July. Preliminary results suggest that sequential cattle and sheep grazing in either June or July to control spotted knapweed can be applied to effectively attain >60% utilization on spotted knapweed while maintaining <50% utilization on desirable graminoids.