Rachel A. Frost

Seasonal Change in Forage Value of Rangeland Weeds in Northern Idaho

Abstract Prescribed grazing is an effective tool for controlling some rangeland weeds. Forage quality of eight nonnative rangeland weeds common to northern Idaho was determined. Five collection sites were established for each weed species: rush skeletonweed, meadow hawkweed, houndstongue, sulfur cinquefoil, yellow starthistle, Dalmatian toadflax, hoary cress, and tansy ragwort. Plants were collected at rosette, bolt, flower, and seed set stages; dried and separated into leaves, stems, flowers, or seed; and analyzed separately for crude protein (CP), neutral detergent fiber (NDF), and mineral content (ash). As expected, plants became more fibrous as they matured because stems increased in NDF value throughout the season and the leaf ∶ stem ratio of most weeds we examined decreased throughout the season. In general, the weeds we examined expressed only moderate fiber levels, beginning the season with NDF values near 34% in the rosette stage and becoming near 52% NDF in the seed set stage. CP values were near 25% in the rosette stage for houndstongue, rush skeletonweed, and hoary cress whereas other weeds we examined had about 15% CP in the rosette. As the season advanced, all plants lost protein content and ended the season with CP values from 5 to 8% at seed set. Ash values declined for all species as the season progressed. Our results indicate that these weeds have forage values similar to many native plants and could be reasonable forage resources for livestock. We did not examine the content of secondary compounds in these weeds that may render them unpalatable and limit their forage value. Nomenclature: Dalmatian toadflax, Linaria dalmatica (L.) P. Mill. LINDA; hoary cress, Lepidium draba (L.) Desv. LEDRD; houndstongue, Cynoglossum officinale L. CYWOF; meadow hawkweed, Hieracium caespitosum Dumort. HIECA; rush skeletonweed, Chondrilla juncea L. CHOJU; sulfur cinquefoil, Potentilla recta L. PTLRC; tansy ragwort, Senecia jacobeae L. SENJA; yellow starthistle, Centaurea solstitialis L. CENSO

Age and body condition of goats influence consumption of juniper and monoterpene-treated feed.

Abstract Redberry juniper (Juniperus pinchotii Sudworth) is an invasive, evergreen tree that is rapidly expanding throughout western and central Texas. Goats will consume some juniper on rangelands; however, intake is limited. The objective of our research was to determine how the age and body condition of goats influence their consumption of juniper and an artificial feed containing 4 monoterpenes. Two separate experiments were conducted. Experiment 1 examined the intake of redberry juniper foliage and used 39 goats either young (2 yr) or mature (> 6 yr). One-half of each age group was fed appropriate basal rations to reach either a high (HBC) or low body condition (LBC). Goats in LBC ate more (P < 0.01, 8.6 g · kg−1 body weight [BW] ± 0.7 SE) juniper than those in HBC (2.3 g · kg−1 BW ± 0.3 SE), and young animals consumed more (P < 0.05, 7.2 g · kg−1 BW ± 0.7 SE) juniper than mature goats (3.9 g · kg−1 BW ± 0.5 SE) across body condition treatments. In experiment 2, 36 goats, either young (2 yr) or mature (> 6 yr) and in either HBC or LBC, were offered a synthetic ration treated with 20.8 g · kg−1 of 4 monoterpenes found in redberry juniper. Goats in LBC ate more (P < 0.01, 25.3 g · kg−1  BW  ± 1.0 SE) of the terpene-treated feed than those in HBC (17.5 g · kg−1 BW ± 0.7 SE), and young animals ate more (P < 0.05, 22.5 g · kg−1 BW ± 0.8 SE) than mature goats (20.3 g · kg−1 BW ± 0.8 SE) across body condition treatments. Total intake as a proportion of body weight was also affected by body condition. Age and body condition are important factors that influence intake of chemically defended plants. A better understanding of how these attributes affect diet selection will aid livestock producers in improving grazing management.

Pharmacokinetic differences in exposure to camphor after intraruminal dosing in selectively bred lines of goats

A pharmacokinetic dosing study with camphor was used to determine whether selection lines of high-juniper-consuming goats (HJC, n = 12) and low-juniper-consuming goats (LJC, n = 12) differed in their respective disposition kinetics. Postdosing plasma camphor concentrations were used to examine whether a timed single blood sample collected after intraruminal administration of camphor would be a useful screening test to aid in the identification of HJC. Yearling female Boer x Spanish goats (n = 24) received a single intraruminal dose of monoterpene cocktail (0.270 g/kg of BW) containing 4 different monoterpenes that represented their composition previously reported for Ashe juniper (Juniperus ashei). Camphor, the predominant monoterpene in Ashe juniper, was 49.6% of the mix and was the monoterpene analyzed for this study. Blood samples were taken at 15 time points from 0 to 8 h after dosing. Concentrations of camphor were measured in plasma using solid phase extraction and gas chromatography/flame-ionization detection analysis. Maximal plasma concentration of camphor was greater for LJC than HJC (P = 0.01), and area under the curve extrapolated to infinity was greater for LJC than HJC (P < 0.01). Total systemic exposure (area under the curve) to camphor was 5 times less in HJC goats. We conclude that 1) HJC goats possess internal mechanisms to reduce the bioavailability of camphor, and 2) a blood sample taken at 45 min or at 60 min after intraruminal administration of camphor may be useful for identifying HJC individual animals from within large populations of goats.

Sulfur Cinquefoil (Potentilla recta) Response to Defoliation on Foothill Rangeland

Abstract Sulfur cinquefoil is an invasive, perennial forb on rangelands of western Canada and the United States. Sulfur cinquefoil reproduces solely by seed and it is a prolific seed producer. Our 2-yr study (2006, 2007) investigated the optimal timing and intensity of defoliation to decrease aboveground productivity and seed production of sulfur cinquefoil plants on foothill rangeland in southwestern Montana. Each year, 150 sulfur cinquefoil plants within a 430-m2 enclosure were tagged for identification and randomly assigned to one of 15 clipping treatments with 10 plants per treatment. Clipping treatments were conducted at three timings: (preflower [early June], flowering [late June], and seedset [mid-July]) and all possible combinations of timings for a total of seven timing treatments clipped to two stubble heights (7.5 cm or 15 cm), comprising 14 unique treatments. The final (15th) treatment consisted of an unclipped control. Response variables collected at senescence (late July) included aboveground biomass; number of buds, flowers and fruits on each plant; and number and viability of seeds produced. Results indicated that defoliation of sulfur cinquefoil can effectively reduce its yield and seed production. All clipping treatments reduced aboveground biomass of sulfur cinquefoil compared with control plants (P ≤ 0.05), except clipping to 15 cm during preflowering in the wetter year of 2006. Clipping to either 7.5 cm or 15 cm at all times or combinations of timings reduced the number of buds, flowers, fruits, and seeds produced by sulfur cinquefoil (P ≤ 0.05). Viable seed production was reduced 99 to 100% when plants were clipped once to either 7.5 or 15 cm during flowering or seedset. Results suggest that targeted livestock grazing or mowing applied one time per season during flowering or seedset could effectively suppress the biomass production and viable seed production of sulfur cinquefoil. Nomenclature: Sulfur cinquefoil, Potentilla recta L. PTLRC Management Implications: Sulfur cinquefoil is a nonnative, perennial, invasive weed that currently infests thousands of acres of rangeland and abandoned cropland in the western United States and Canada. This plant is a concern because it produces thousands of seeds and is capable of invading undisturbed rangeland. There are no approved biological controls, and herbicide treatment is expensive; therefore, we evaluated the potential for defoliation to reduce yield and seed production of sulfur cinquefoil. Hand-clipping treatments were applied at 14 different timing and intensity combinations to determine those most appropriate to suppress sulfur cinquefoil. Overall, clipped plants produced ∼ 80% less aboveground forage and > 90% fewer viable seeds than control plants. Clipping applied when sulfur cinquefoil plants were flowering or in early seedset had the greatest impact on forage and seed production. Plants clipped one time to either a 15- or 7.5-cm stubble height at flower or later were unable to produce any viable seed during the current growing season. Multiple defoliations were not necessary to decrease seed production if the first defoliation occurred at the flower stage or later. The intensity of the defoliation did not matter so long as the fruits were removed from the plant. Because of the longevity and abundant seed production of the plant, areas infested with sulfur cinquefoil likely have a large soil seed bank, and multiple years of uniform defoliation will be necessary before any noticeable change in the existing population can be determined. However, defoliation holds potential to reduce the competitive ability of sulfur cinquefoil as well as the ability of the plant to add to the seed bank. Targeted livestock grazing or mowing are two potential ways to defoliate sulfur cinquefoil at the appropriate timing and intensity to suppress the plant on rangeland or pasture.

Targeted Grazing: Applying the Research to the Land

T he discipline of range science is in part based on the observation that vegetation on rangelands changes in response to livestock grazing. 1 For much of the history of range science, livestock grazing was considered to affect range plants and ecological condition negatively. Thus range plants were classified as increasers, decreasers, or invaders as a function of their response to grazing . 2 The concept that grazing can be used to restore degraded rangelands is relatively new. 3 It requires a paradigm shift for most people from grazing animals reaping the benefits of the land to the land reaping the benefits of the grazing animals. Using livestock to accomplish vegetation management goals is referred to as targeted grazing. Targeted grazing is defined as the application of a particular kind of grazing animal at a specified season, duration, and intensity to accomplish specific vegetation management goals . 4 It is the last half of this definition that differentiates targeted grazing from traditional grazing. The focus is on the vegetation and the subsequent outcomes and changes in composition or structure, rather than the performance of the grazing animal. Where the potential for targeted grazing to create positive change on the landscape has been clearly demonstrated through research and the experiences of practitioners, it still struggles to gain recognition as a viable vegetation manage- ment option. The recently published handbook Targeted Grazing: A Natural Approach to Vegetation Management and Landscape Enhancement 5 was organized and written largely by range scientists to provide the scientific basis for targeted grazing. However, it did not provide much information on the practical and daily management decisions required by contract graziers and land managers. While the scientific basis for targeted grazing provides the foundation for under- standing and improving this technology, as with all grazing management it is the daily operations and decisions that determine its success. The diversity of situations to which this tool can be applied necessitates the exchange of real-life experiences to promote learning among practitioners and to inform land managers of the successful programs and potential pitfalls to avoid.... DOI: 10.2458/azu_rangelands_v34i1_forest

Elk Foraging Site Selection on Foothill and Mountain Rangeland in Spring

ABSTRACT Previous research suggests facilitative grazing by cattle during the preceding summer-fall can enhance spring foraging habitat of Rocky Mountain elk (Cervus elaphus nelsoni). However, previous studies were limited to 1 year or conducted within relatively small experimental pastures. We evaluated elk foraging site selection during spring across 4 years and 59 040 ha of foothill and mountain rangeland in northwestern Wyoming and west-central Montana. Elk in spring avoided foraging in nonforested portions of cattle-grazed pastures where cattle had not grazed during the previous summer — early fall. In contrast, elk selected foraging sites where cattle had grazed lightly (11 – 30% forage use) or moderately (31 –60% forage use), and selection by elk was stronger for moderately grazed sites. Neither moderate nor light cattle grazing intensity were correlated with any other elk habitat attribute that we sampled, and both moderate and light cattle grazing intensity exerted more influence on elk foraging site selection than any other variables, including distance to security cover, distance to primitive roads, distance to improved roads, aspect, or slope. We developed and validated a resource selection model that correctly classified 80 – 89% of elk foraging observations across five study sites and 4 years. Resource managers can use our model to map predicted changes in elk grazing distribution when considering potential habitat adjustments in security cover, roads, or cattle grazing intensities and distribution. Our results indicate that resource managers can use targeted cattle grazing in summer — early fall to purposely modify elk forage conditions to 1) increase elk foraging efficiency in spring, 2) lure elk away from places needing rest or deferment from spring elk grazing, or 3) lure elk away from places where elk in spring are experiencing conflicts with humans, predators, or other wildlife.

Recovery and Viability of Sulfur Cinquefoil Seeds From the Feces of Sheep and Goats

Abstract Targeted grazing by sheep or goats is a potentially useful tool for suppressing the noxious weed sulfur cinquefoil (Potentilla recta L.). However, possible transmission of weed seeds by grazing livestock is a serious ecological concern that must be addressed in any targeted grazing prescription. We investigated the effect of sheep and goat digestion on the viability of sulfur cinquefoil seeds collected from live plants growing on a foothill rangeland site in southwestern Montana. Eight sheep and eight goats (all wethers) were each gavaged with 5 000 sulfur cinquefoil seeds. Four animals of each species received immature seeds, and four animals received mature seeds. All animals were fed ground grass hay in excess daily, and intake averaged 2.0% body weight · d−1. Total fecal collection began immediately after gavaging and continued for 7 consecutive days. Once each day, all identifiable sulfur cinquefoil seeds were recovered and counted from fecal subsamples. Seed viability before gavaging averaged 36% for immature seeds and 76% for mature seeds. Sheep and goats excreted similar numbers of viable seeds. Almost all (98%) of the viable seeds recovered from sheep and goats were excreted during Day 1 and Day 2 after gavaging. No viable seeds were recovered from either sheep or goats after Day 3. Our estimates of sulfur cinquefoil seed excretion and viability in sheep and goat feces are likely inflated compared with targeted grazing animals because gavaging with seeds bypassed mastication. Grazing livestock that consume sulfur cinquefoil seeds should be kept in a corral for at least 3 d to prevent transferring viable seeds to uninfested areas.

Targeted Sheep Grazing to Suppress Sulfur Cinquefoil (Potentilla recta) on Northwestern Montana Rangeland

ABSTRACT Sulfur cinquefoil (Potentilla recta L.), a perennial forb native to the eastern Mediterranean region of Eurasia, is a major noxious weed on rangelands of the northwestern United States and southwestern Canada. We assessed targeted sheep grazing to suppress sulfur cinquefoil in a 2-yr rangeland field experiment in northwestern Montana. We evaluated targeted sheep grazing with and without protein-energy supplementation (37 g crude protein [CP] sheep-1 d-1 and 0.17 kg total digestible nutrients [TDN] sheep-1 d-1) during late June (sulfur cinquefoil in early flowering stage) and mid-July (sulfur cinquefoil in late flowering—early seedset stage). Sheep readily consumed sulfur cinquefoil stems, leaves, flowers, and developing seed heads, with or without supplementation. Sulfur cinquefoil comprised the largest proportion of sheep diets during both late June and mid-July, averaging 46%, but more sulfur cinquefoil dry matter (DM) was consumed by sheep during mid-July (0.6 vs. 1.0 kg DM sheep-1 d-1 in June vs. July, respectively). Supplementation did not increase DM intake (DMI) of sulfur cinquefoil, nor did supplementation improve the nutritive quality of sheep diets. We also documented that 1) targeted sheep grazing achieved heavy utilization of sulfur cinquefoil (67%) while keeping perennial graminoid use light to moderate (18–41%); 2) targeted sheep grazing reduced viable seed production of sulfur cinquefoil by 97% in June-grazed paddocks and 95% in July-grazed paddocks; and 3) targeted sheep grazing reduced sulfur cinquefoil yield the next summer by 41% in June-grazed paddocks and 47% in July-grazed paddocks without decreasing yield or plant community composition of perennial graminoids. We conclude that supplemented or nonsupplemented targeted sheep grazing applied in either late June or mid-July can effectively suppress sulfur cinquefoil. Sheep nutrition and sulfur cinquefoil DMI will be optimized by targeted sheep grazing applied during mid-July.