Theses and Dissertations at Montana State University (MSU)
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Item Effects of training on cattle grazing spotted knapweed and Canada thistle(Montana State University - Bozeman, College of Agriculture, 2013) Tierney, Katie Rene'; Chairperson, Graduate Committee: Bret E. OlsonSpotted knapweed (Centaurea stoebe L.) and Canada thistle (Cirsium arvense (L.) Scop.) are changing and degrading North American rangeland ecosystems by replacing native grasses and forbs. Conventional control methods are often not cost-effective. Using livestock to manage invasive species offers a potentially cost effective alternative. The objectives of our first study were to determine if: 1) cattle trained to consume spotted knapweed and Canada thistle in 2004 retained their training in 2011, 2) calves and yearlings of the 2004 trained cattle consume more spotted knapweed and Canada thistle than calves and yearlings from untrained cows, and 3) yearlings trained to graze Canada thistle in mid-July consume more of the weed than untrained yearlings in late July and late August. In our 2011 study, trained cattle did not spend more time grazing spotted knapweed or Canada thistle than untrained cattle. In 2011, calves and yearlings from trained cattle did not spend more time grazing spotted knapweed or Canada thistle than those from untrained cattle. Yearlings trained to graze Canada thistle consumed similar amounts as untrained yearlings when grazed in July and less than untrained yearlings in August. The objectives of our second study were to determine if: 1) individual cattle spent similar amounts of time grazing spotted knapweed in 2011 and 2012, and 2) individual yearlings affect time spent grazing spotted knapweed of their peers. Individual animals tended to spend similar amounts of time grazing spotted knapweed in July of 2011 and 2012. Grazing yearlings, that tended to spend high or low amounts of time grazing spotted knapweed, together did not affect their time spent grazing this weed. Cattle innately grazed spotted knapweed (20-50% of their time grazing) and, to a much lesser extent, Canada thistle (0-17% of their time grazing); training did not result in greater amounts of time spent grazing these weeds. Individual cattle with the innate behavior to graze spotted knapweed can be identified and retained in herds to potentially increase grazing of spotted knapweed. With proper grazing management, cattle grazing can be used as one tool in an integrative approach to control spotted knapweed on rangelands.Item Defoliation effects on Spotted Knapweed seed production and viability(Montana State University - Bozeman, College of Agriculture, 2008) Benzel, Katie Rebecca; Chairperson, Graduate Committee: Jeffrey C. Mosley; Tracy K. Brewer (co-chair)Spotted knapweed (Centaurea stoebe L.) is a deeply taprooted perennial forb infesting millions of hectares of rangeland in western North America. Spotted knapweed forms large monocultures, which lowers plant diversity, reduces livestock and wildlife forage, and increases surface water runoff and sediment yield. It can produce 5,000-40,000 seeds m-2 year-1, and often produces new flowers after prescribed sheep grazing or mowing defoliates spotted knapweed plants during the bolting or flowering stage. Research has yet to determine if new flowers produced following spring/summer defoliation produce viable seeds by the end of the growing season. The purpose of this 2-year study was to determine the appropriate timing(s) or combination(s) of timings of defoliation on spotted knapweed to reduce viable seed production. Ten spotted knapweed plants, located on spotted knapweed-infested rangeland in west-central Montana, were hand-clipped for each of the following treatments: 1) 35-40% relative utilization of above-ground biomass when plants were in the bolting stage; 2) 100% of buds removed at late-bud/early-flowering stage; 3) 100% of flowers removed at full-flowering stage; 4) Treatment 1+Treatment 2; 5) Treatment 1+Treatment 3; 6) Treatment 2+Treatment 3; 7) Treatment 1+Treatment 2+Treatment 3; and 8) unclipped control. The number of buds/flowerheads per plant, number of seeds per plant, percent viability of seeds, and number of viable seeds per plant were determined when seeds were in the well-developed stage, but seedhead bracts were still tightly closed (mid-August through September). Clipping at any timing or combination of timings reduced the number of buds/flowerheads per plant (P < 0.01), number of seeds per plant (P < 0.01), percent viability of seeds (P < 0.01), and number of viable seeds per plant (P < 0.01) both years compared with the unclipped control. Clipping during the bolting stage reduced the number of viable seeds by nearly 90% compared with no clipping. Clipping during the late-bud/early-flower or full-flower stage reduced the number of viable seeds by nearly 100% compared with no clipping. Defoliation of spotted knapweed via prescribed sheep grazing or mowing in summer should effectively suppress viable seed production of spotted knapweed.Item Summer diets of sheep grazing spotted knapweed-infested foothill rangeland in Western Montana(Montana State University - Bozeman, College of Agriculture, 2005) Thrift, Brian Douglas; Chairperson, Graduate Committee: Jeffrey C. Mosley.Spotted knapweed (Centaurea biebersteinii DC.) is a perennial, invasive forb that infests millions of hectares of private and public rangelands in western North America. Previous research indicates that spotted knapweed is nutritious and readily grazed by domestic sheep (Ovis aries), but no studies have investigated prescription grazing of spotted knapweed within different levels of infestation or on a landscape scale. This twoyear study quantified the diets of a ewe-lamb band (n almost equals 800 ewes, 1120 lambs) that prescriptively grazed spotted knapweed-infested foothill rangeland in western Montana. Sheep grazed within light and moderate infestations of spotted knapweed (13% and 36% of vegetative composition, respectively) until perennial grasses were reduced to a 5 to 8- cm residual stubble height. Diets were estimated in mid-June and mid-July by clipping current year's standing crop immediately before and after grazing. Clipped samples were analyzed for CP, NDF, and ADF to estimate nutritive quality. Relative preference indices were calculated to evaluate diet selection by sheep. Sheep ate more spotted knapweed in moderate versus light infestations (64 vs. 26% of their diets, respectively; P<0.01), and spotted knapweed averaged 45% of sheep diets between June and July (P=0.61). Within light infestations, sheep ate fewer graminoids in June than July (17 vs. 55% of their diet, respectively; P<0.01). Sheep diets in moderate infestations averaged 33% graminoids regardless of month (P=0.18). Sheep did not select for graminoids in light infestations in June, but did select for spotted knapweed leaves in moderate infestations during July. Nutritive quality of sheep diets was similar to sheep grazing uninfested rangeland. Relative utilization of graminoids averaged 15%, except under exceptionally hot and dry weather conditions. Relative utilization of spotted knapweed averaged 45%. Previous research suggests that this level of spotted knapweed utilization may render herbicide application uneconomical. My results indicate that sheep can prescriptively graze moderate spotted knapweed infestations in either June or July, but to limit graminoid consumption, light infestations should be grazed in June vs. July.Item Providing supplement, with or without peg, to reduce the effects of cnicin and enhance grazing of spotted knapweed by sheep and cattle(Montana State University - Bozeman, College of Agriculture, 2006) Cheeseman, Melany; Chairperson, Graduate Committee: Bret E. Olson.Spotted knapweed (Centaurea maculosa Lam.), an invasive forb from Eurasia, infests over 1.7 million hectares in Montana and costs millions of dollars in forage losses each year. Some wildlife and livestock graze this species, however, most large herbivores, including cattle and horses, avoid spotted knapweed and prefer native plants. Some herbivores may avoid or reduce their intake of spotted knapweed because the plant contains cnicin. Cnicin is a bitter-tasting sesquiterpene lactone that may cause negative post-ingestive consequences in the rumen. If an appropriate supplement and/or antitoxicant can be identified that will reduce the negative post-ingestive effects of cnicin to rumen microbes, sheep and cattle may consume more spotted knapweed and grazing may help control this invasive species. I determined the effects of cnicin, rates of an anti-toxicant (polyethylene glycol), and a nutrient/energy supplement, with or without polyethylene glycol, on sheep and cattle rumen microbial activity, efficiency, and mass using a modified in vitro system. Sheep and cattle rumen microbes were negatively affected by cnicin. Polyethylene glycol, at the rates provided, had limited effects on sheep and cattle rumen microbial response to spotted knapweed plant parts. The nutrient/energy supplement, with or without polyethylene glycol, enhanced sheep and cattle rumen microbial efficiency. Because the nutrient/energy supplement may reduce some of the negative effects of cnicin on rumen microbes, sheep and cattle may consume more spotted knapweed in the field when provided with the supplement. I hypothesized that providing a nutrient/energy supplement, with or without polyethylene glycol, would increase sheep and cattle intake and time spent consuming spotted knapweed in a drylot, and in the field in July and August. Animal behaviors were recorded by focal animal sampling. Providing a nutrient/energy supplement, with or without polyethylene glycol, did not enhance sheep and cattle intake or time spent consuming spotted knapweed in a drylot, or in the field in July and August. Therefore, supplementing sheep and cattle with the nutrient/energy supplement, with or without polyethylene glycol, provided in these trials, may not be an appropriate method for managing the spread of spotted knapweed.Item Estimating spotted knapweed intake of sheep using NIRS technology(Montana State University - Bozeman, College of Agriculture, 2010) Rude, Mark Edward; Chairperson, Graduate Committee: Rodney W. Kott.Targeted grazing is proving to be effective in controling spotted knapweed infestations. Maximizing the potential of targeted grazing requires a method to determine the botanical composition of individual diets of grazing animals over time Fecal near infrared reflectance spectroscopy (NIRS) has been used to estimate the botanical composition of sheep consuming, leafy spurge, mountain big sage brush, and juniper, but has not been used to estimate dietary composition of sheep consuming spotted knapweed. Fecal NIRS spectra collected from three feeding trials were used to develop modified partial least squares regression equations to predict percent spotted knapweed in sheep diets. Independent validation of individualy developed equations resulted in R² values of .22 - .72. An equation developed by combining data from all three trials resulted in acceptable levels of precision (R²= .96) and was used to analyze data collected from range fecal sampling trials conducted in 2006. Two fecal sampling trials were conducted in 2006 to determine NIR's ability to detect differences in dietary composition of sheep grazing spotted knapweed infested range over time. Approximately 90 fecal samples were collected on July 13 and again on August 15 from a band of 900 ewes grazing spotted knapweed infested range to determine changes in diet over time. Fecal samples from five randomly selected ewes in the same band were collected weekly (June 22 - August 17) to detect variation in indiviudal intake over time On July 13, 55% of ewes from had 0-5% spotted knapweed in their diets while 44% had 5-20% spotted knapweed in their diets. On August 15, 1% of ewes, had <10% spotted knapweed in their diets and 44% had 20-25% spotted knapweed in their diets. With the exception of July 6, individual intake of spotted knapweed was similar (P > .05) from June 22, through July 20, but was greater (P > .05)from July 27 through August 17 than from June 22 through July 20. These results suggest that the appropriate time to apply grazing for spotted knapweed control is later in the growing season when sheep are including more of the target plant in their diet.Item Sequential cattle and sheep grazing for Spotted Knapweed control(Montana State University - Bozeman, College of Agriculture, 2008) Henderson, Stacee Lyn; Chairperson, Graduate Committee: Rodney W. KottSpotted knapweed (Centaurea stoebe L.) infests millions of hectares of native rangeland in North America. Spotted knapweed creates large monocultures, which decreases biodiversity, reduces livestock and wildlife forage, and increases surface water runoff and soil erosion. Sheep are an effective tool for controlling spotted knapweed and have been widely used on cattle ranches for weed control. However, cattle producers are concerned that sheep will over-utilize desirable graminoids. Therefore, research is needed to determine an effective grazing strategy using cattle and sheep that will adversely affect spotted knapweed, while minimizing over-use of desirable graminoids across the landscape. This 2-year study quantified graminoid and spotted knapweed utilization and diet composition and foraging behavior of cattle and sheep sequentially grazing 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 each pasture for 7 days, immediately followed by sheep grazing for 7 days in each month. Analysis of covariance was used to determine differences in diets, relative preference indices, foraging behavior, and utilization between June and July for cattle and sheep to determine the optimal month for implementing prescribed sheep grazing. Relative utilization of spotted knapweed did not differ between June and July and averaged 61.5%. Graminoid utilization was moderate (<45%). Cattle preferred forbs in June, spotted knapweed and forbs in July, and avoided graminoids in July. Sheep avoided graminoids in June and July, preferred forbs in June, and showed no preference or avoidance of spotted knapweed. Cattle ranches with large spotted knapweed infestations can effectively use prescribed sheep grazing immediately following cattle grazing in June or July to achieve high levels of use on spotted knapweed, thus reducing viable seeds incorporated into the soil, while maintaining optimal utilization levels on desirable graminoids.