• Comparison of Bite-Count and Rumen Evacuation Techniques to Estimate Cattle Diet Quality

      Damiran, Daalkhaijav; DelCurto, Timothy; Findholt, Scott L.; Johnson, Bruce K.; Vavra, Martin (Society for Range Management, 2013-01-01)
      We conducted a study to compare the bite-count technique (BC) of estimating forage intake and synthesized diet quality to direct estimates of diet quantity and quality with the use of the rumen evacuation technique (RE). We used four rumen-fistulated steers to evaluate both techniques. Four enclosures in a mixed-conifer rangeland were used. Each enclosure contained two 0.25-ha paddocks that were either nonstocked or stocked by cattle to remove 32+/-4% of standing crop. We recorded bite-count data during foraging bouts for each steer in each paddock, and then evacuated each rumen following each foraging bout during summer (August). Paddocks stocked prior to each 20-min trial had a reduced (P<0.05) quantity offorage consumed regardless of technique. BC and RE gave similar (P>0.10) results on diet quantity and digestibility. However, BC-derived estimates were lower (P<0.05) for crude protein (CP), acid detergent fiber (ADF), ash, and neutraldetergent fiber (NDF). In summary, although BC has the advantage of not requiring rumen-fistulated animals, it did not yield comparable results to RE under range conditions with dense and diverse vegetation. Therefore, investigators should calibrate bite-count technique against fistula technique to solve any accuracy problem in their specific experimental conditions whenever possible.
    • Fuels Reduction in a Western Coniferous Forest: Effects on Quantity and Quality of Forage for Elk

      Long, Ryan A.; Rachlow, Janet L.; Kie, John G.; Vavra, Martin (Society for Range Management, 2008-05-01)
      Use of mechanical thinning and prescribed fire to reduce fuels in dry forest ecosystems has become increasingly common in western North America. Nevertheless, few studies have quantified effects of fuels reduction treatments on wildlife. We evaluated effects of fuels reduction on quantity and quality of forage available to elk (Cervus elaphus) in northeastern Oregon. From 2001 to 2003, 26 stands of true fir (Abies spp.) and Douglas-fir (Pseudotsuga menziesii [Mirbel] Franco) were thinned and burned, whereas 27 similar stands were left untreated to serve as experimental controls. We estimated percentage of cover, percentage of in vitro dry-matter digestibility (digestibility), and percentage of nitrogen (%N) of 16 important forage species and genera in treatment and control stands during spring (May-June) and summer (July-August) of 2005 and 2006. Quantity and quality of forage were lower in summer than spring in both stand types. In contrast, total cover of forage was higher in treatment than in control stands during spring, whereas the opposite was true during summer. For graminoids, %N was higher in control than in treatment stands whereas digestibility did not differ between stand types. For forbs, neither index of forage quality differed between stand types. When treatment stands were separated by years since burning, %N and digestibility of forbs and %N of graminoids increased from 2 to 5 yr following treatment, and by the fifth year after burning had exceeded maximum values observed in control stands in both seasons. As a result of the interacting effects of fuels reduction and season on forage characteristics, treated stands provided better foraging opportunities for elk during spring, whereas control stands provided better foraging opportunities during summer. Consequently, maintaining a mosaic of burned and unburned (late successional) habitat may be of greater benefit to elk than burning a large proportion of a landscape. 
    • Improving Elk Habitat Characteristics with Livestock Grazing

      Vavra, Martin; Sheehy, Dennis P. (Society for Range Management, 1996-10-01)
    • Influence of Cow Age on Grazing Distribution in a Mixed-Conifer Forest

      Walburger, Kenric J.; Wells, Micah; Vavra, Martin; DelCurto, Timothy; Johnson, Bruce; Coe, Pricilla (Society for Range Management, 2009-05-01)
      Optimal distribution of cattle on forested rangelands has long been a subject of concern specifically related to uniform and sustainable use of forage resources. Our objective was to determine if cow age influenced distribution and resource use on forested rangelands. This study was conducted from 1991 to 2001 at the US Department of Agriculture Starkey Experimental Forest and Range, northeastern Oregon, a mixed-conifer forested rangeland. We used 43 039 locations of cattle taken from 1 h prior to sunrise until 4 h after sunrise and 4 h prior to sundown until 1 h after sundown from 15 July to 30 August to evaluate cattle distribution patterns during peak foraging time. Cattle were grouped into four age classes: 2- and 3-yr-old cattle, 4- and 5-yr-old cattle, 6- and 7- yr-old cattle, and cattle > 8 yr old. All age classes preferred areas with gentler slopes (P < 0.05), westerly aspects (P < 0.05), farther from water (P < 0.05), and with greater forage production (P < 0.05) than pasture averages. Cattle older than 3 yr of age selected areas with less canopy closure (P < 0.05) than the mean value for the pasture. Young cows (< 4 yr old) selected lower elevations and steeper slopes than the oldest cows (P<0.05). In summary, cow age and correspondingly its experience directly influences distribution patterns and forage resource use of cattle at the Starkey Experimental Forest and Range. 
    • Influence of Forest Management and Previous Herbivory on Cattle Diets

      Walburger, Kenric J.; DelCurto, Timothy; Vavra, Martin (Society for Range Management, 2007-03-01)
      Grazing cattle and timber harvest are common practices associated with forested rangelands. Therefore, the objective was to document the effects of timber harvest and herbivory on nutritional quality and botanical composition of steer diets in grand fir (Abies grandis [Dougl. ex D. Don] Lindl.) and ponderosa pine (Pinus ponderosa P. C. Lawson) forests. Three replicated grand fir sites were arranged as a split-plot design; timber harvest treatments—1) no harvest (CON), 2) thinning (TH), 3) clearcut (CL)— were whole plots, and herbivory treatments—1) large ungulate grazing (Graze), 2) wild ungulate grazing (CExc), and 3) exclusion of large ungulate grazing (TExc)—were the subplots. Three replicated ponderosa pine sites were arranged as a split-plot design; timber harvest treatments—1) CON and 2) TH—were whole plots, and herbivory treatments—1) GR, 2) BG, and 3) EX—were subplots. Diet samples were collected in June and August of 2001 and 2002. Crude protein, in vitro organic matter digestibility, acid detergent fiber, and neutral detergent fiber of the diets were only affected by season of use and were higher (P < 0.05) quality during the June grazing period. Botanical composition of diets was determined with the use of microhistological analysis of ruminal masticate. Within grand fir sites, graminoids were the major constituent in the diet (65%-91%), forbs intermediate (8%- 31%), and shrubs least (0.2%-3.5%). Within ponderosa pine sites graminoids were the major constituent in the diet (83%-88%), forbs intermediate (10%-14%), and shrubs least (2%-3%). Season of use did not affect (P > 0.10) botanical composition in either grand fir or ponderosa pine sites. Timing of grazing had a greater influence on diet quality; however, previous herbivory and(or) timber harvest had a greater influence on composition of diets than did timing of grazing. 
    • Livestock and Big Game Forage Relationships

      Vavra, Martin (Society for Range Management, 1992-04-01)
    • Livestock Forage Conditioning Among Six Northern Great Basin Grasses

      Ganskopp, Dave; Aguilera, Lisa; Vavra, Martin (Society for Range Management, 2007-01-01)
      Studies of Anderson and Scherzinger’s forage conditioning hypothesis have generated varied results. Our objectives were: 1) to evaluate late summer/early fall forage quality of crested wheatgrass (Agropyron desertorum [Fisch. ex Link] J. A. Schultes), bluebunch wheatgrass (Pseudoroegneria spicata [Pursh] A. Löve), Idaho fescue (Festuca idahoensis Elmer), bottlebrush squirreltail (Elymus elymoides [Raf.] Swezey), Thurber’s needlegrass (Achnatherum thurberianum [Piper] Barkworth), and basin wildrye (Leymus cinereus [Scribn. Merr.] A. Löve) from ungrazed paddocks and paddocks grazed at vegetative, boot, and anthesis; and 2) test hypotheses that postgrazing regrowth yields were correlated with soil moisture content when grazing occurred. Crop-year precipitation for 1997 and 1998 was 134% and 205% of average. Crude protein (CP) and in vitro dry matter digestibility (IVDMD) of ungrazed grasses displayed expected declines in quality. Among ungrazed grasses, late summer/ early fall CP was 5.7% in 1997 and 3.6% in 1998; IVDMD was 47% and 41%, respectively. Late summer/early fall forage quality was elevated by vegetative, boot stage, or anthesis grazing. The phenologically youngest regrowth always ranked highest in CP and IVDMD. Among grasses, respective 1997 CP and IVDMD means were 9.0% and 55% for regrowth following anthesis grazing. No regrowth followed anthesis grazing in 1998, but CP and IVDMD means from boot stage treatments were 5.5% and 47%, respectively. With CP measures, a species by treatment interaction occurred in 1997, but species reacted similarly in 1998. Vegetative, boot stage, and anthesis grazing in 1997 caused respective late summer/early fall standing crop reductions of 34%, 42%, and 58%; and 34%, 54%, and 100% reductions in 1998. Forage conditioning responses were lower for bluebunch wheatgrass and crested wheatgrass than other grasses. Soil moisture content was a poor predictor of regrowth yields. Managed cattle grazing can successfully enhance late season forage quality. 
    • Livestock Grazing and Wildlife: Developing Compatibilities

      Vavra, Martin (Society for Range Management, 2005-03-01)
      Livestock grazing has been considered detrimental to wildlife habitat. Managed grazing programs, however, have the potential to maintain habitat diversity and quality. In cases in which single-species management predominates (sage-grouse [Centrocercus urophasianus] or elk [Cervus elaphus nelsoni] winter range), grazing systems specific to species’ needs can be implemented. Managed livestock grazing can have 4 general impacts on vegetation: 1) alter the composition of the plant community, 2) increase the productivity of selected species, 3) increase the nutritive quality of the forage, and 4) increase the diversity of the habitat by altering its structure. Implementing a grazing management plan to enhance wildlife habitat requires an interdisciplinary approach. Knowledge of plant community dynamics, habitat requirements of affected wildlife species, and potential effects on the livestock used are basic to successful system design. However, any habitat change made for a featured species may create adverse, neutral, or beneficial changes for other species. Management actions, other than development of a grazing system, are often required for habitat manipulations to be successful. More research efforts are needed to understand complementary grazing systems on a landscape scale. 
    • Stocking Rate and Fuels Reduction Effects on Beef Cattle Diet Composition and Quality

      Clark, Abe; DelCurto, Tim; Vavra, Martin; Dick, Brian L. (Society for Range Management, 2013-11-01)
      An experiment was conducted to evaluate the influence of forest fuels reduction on diet quality, botanical composition, relative preference, and foraging efficiency of beef cattle grazing at different stocking rates. A split plot factorial design was used, with whole plots (3 ha) being fuel reduced or no treatment (control), and split plots (1 ha) within whole plots were grazed to three levels of forage utilization; (low) 3 heifers .  ha-1, (moderate) 6 heifers ha-1, (high) 9 heifers ha-1, with a 48-h grazing duration. Grazing treatments were applied in August of 2005 and 2006. Cattle diet composition and masticate samples were collected during 20-min grazing bouts using six ruminally cannulated cows in each experimental unit. Relative preference indices indicated a strong preference for grass regardless of treatment and stocking rate. Grass consumption was lower in control pastures (P<0.05) and tended (P<0.095) to decrease with increased stocking rates. Shrub use was higher in control pastures displaying a quadratic effect (P<0.05) due to stocking, whereas shrub use increased with stocking rate across all treatments. Cattle grazing control pastures consumed diets higher in crude protein compared to cattle grazing treated pastures (P<0.05). In vitro dry matter digestibility values were lower (P<0.05) in control sites and tended (P=0.10) to decrease with increased stocking rates. In both control and treated pastures, bites per minute and grams consumed per minute declined (P=0.003) with increased stocking, indicating foraging efficiency of cattle decreases with increased stocking rates. Our data indicated cattle grazing late season grand fir habitat types have a strong preference for grasses regardless of treatment or stocking rate. However, as stocking rate increased in both control and treated pastures, grass consumption decreased, shrub consumption increased, and foraging efficiency decreased.