• A Comparison of Esophageal Fistula and Fecal Material to Determine Steer Diets

      Vavra, M.; Rice, R. W.; Hansen, R. M. (Society for Range Management, 1978-01-01)
      Cattle diets were determined by esophageal fistula and fecal material collection procedures from yearling cattle grazing shortgrass range in northeastern Colorado. Diets were quantified by microhistological procedures from samples collected in June, July, August, and December of 1969; and June, July, and August of 1970. Total grasses occurred significantly less in esophageal samples, while total forbs were significantly lower in fecal samples. Individual grass species did not appear to follow a set pattern of variation from esophageal to fecal sampling; some were greater in fecal samples while others were greater in fistula samples. Forbs occurred at greater percentages in fistula samples, with the exception of burning bush (Kochia scoparia) in 1969. Correlation and regression analysis revealed little relationship in botanical composition determined on fecal and esophageal samples. However, an importance value ranking revealed esophageal and fecal samples were similar when individual species were ranked from the most common to the least common in the diet.
    • A Comparison of Four Methods Used to Determine the Diets of Large Herbivores

      McInnis, M. L.; Vavra, M.; Krueger, W. C. (Society for Range Management, 1983-05-01)
      Esophageal fistulation, stomach content analysis, fecal analysis, and forage utilization were compared as techniques for determining food habits of large herbivores. Each technique was evaluated based upon information collected using bi-fistulated (esophageal and rumen) sheep during 2 study phases. In the first study phase, microscope slide mounts were made of plant fragments collected from the esophagus, rumen, and feces of 10 confined sheep fed a hand-composited mixture of forage. Dietary composition as determined by each technique was compared to the original feed. Stomach content analysis and fecal analysis produced dietary estimates higher in grasses and lower in forbs than the known feed values. Esophageal fistulation results were not significantly different from the known feed values. In the second study phase, esophageal, rumen, and fecal collections were gathered from 16 sheep grazing a common plant community. Ocular estimates of forage utilization were made concurrently. All data were converted to percent composition on a dry weight basis for comparisons. Significant differences in percent diet composition among techniques occurred for 18 of the 31 plant species consumed. Diets determined by stomach content analysis and fecal analysis were significantly higher in grasses and lower in forbs than those determined by esophageal fistulation and ocular estimates of utilization.
    • Botanical Composition of Determination of Range Herbivore Diets: A Review

      Holechek, J. L.; Vavra, M.; Pieper, R. D. (Society for Range Management, 1982-05-01)
      Procedures used for estimating the botanical composition of the range herbivore's diet include diet observation, utilization techniques, fistula sampling, and fecal analysis. Each of these procedures has important limitations. Direct observation requires minimal time and equipment inputs but accuracy and precision are a problem, particularly with wild animals. Utilization studies are generally unsuitable when plants are actively growing and more than one herbivore is using the area under study. Fistula methods are accurate but are difficult to use with wild animals. In addition they are costly and require considerable time. The esophageal fistula is preferable to the rumen fistula because it provides more accurate information and requires less labor. Stomach analysis involves animal sacrifice and, therefore, is generally restricted to wild animals with large populations. However, trocar sampling of the rumen contents is a new method that avoids this problem. Fecal analysis has been used extensively in recent years to evaluate diet botanical composition of wild herbivores. This procedure gives good precision but accuracy is a problem because of differential digestion between plant species. Techniques are available that can be used to reduce this source of error. Microhistological analysis has become the most widely used method for quantifying botanical composition of masticated forage or fecal material. Recent studies show microhistological analysis can give an accurate representation of percent diet botanical composition by weight if observers use had compounded diets to check their accuracy. A new procedure, infrared spectrophotometry, may have considerable potential for evaluating herbivore diet botanical composition of fistula or fecal samples.
    • Cattle Diet and Daily Gains on a Mountain Riparian Meadow in Northeastern Oregon

      Holechek, J. L.; Vavra, M.; Skovlin, J. (Society for Range Management, 1982-11-01)
      Cattle weight gains, diet botanical composition, and diet quality on a riparian meadow range in the Blue Mountains of eastern Oregon were evaluated in the late summer and fall in 1976, 1977, and 1978. Pregnant yearling heifers were used to evaluate livestock performance. Esophageally fistulated cows were used to evaluate diet botanical composition and diet quality. Cattle diets showed little difference in botanical composition between periods or years. Grasses comprised an average of 80% of the diet during the 3 year period. Kentucky bluegrass (Poa pratensis) was the most important grass in cattle diets and had the highest percent cover on the study pastures. Cattle diet quality showed little change within or between years. Crude protein concentrations appeared adequate for cattle to gain .5 kg per day. However, estimated digestible energy concentrations averaged only 80% of that recommended by the NRC. Daily gains were erratic between and within years averaging .41 kg for the 3 years. Average daily gains on the meadow were better than or equal to those reported in other studies for upland and upland and meadow pastures at the Starkey Range for the same periods. Separate fencing and deferred grazing of mountain meadows could improve cattle performance and aid ranchers in gathering cattle at the end of the grazing season. In addition deferred grazing should result in pasture improvement and provide better habitat for nesting birds. The primary disadvantage of deferred use of meadows would be the cost of fencing.
    • Cattle Diets in the Blue Mountains of Oregon II. Forests

      Holechek, J. L.; Vavra, M.; Skovlin, J.; Krueger, W. C. (Society for Range Management, 1982-03-01)
      Esophageally fistulated cows were used on forested range in northeastern Oregon to collect diet samples which were then analyzed by the microhistological technique. Grasses, forbs, and shrubs averaged 61, 16, and 23% of the diet, respectively. Composition of diets differed among years and with seasonal advance. Idaho fescue and elk sedge were the most important forage species consumed. Forbs were used heavily in the early part of the grazing season before maturation. Browse comprised as much as 47% of the diet when green grass was unavailable. Cattle were opportunistic grazers and did not limit their selection to grass species. On forested ranges cattle diets varied among grazing periods within each year as well as among years.
    • Cattle Diets in the Blue Mountains of Oregon, I. Grasslands

      Holechek, J. L.; Vavra, M.; Skovlin, J.; Krueger, W. C. (Society for Range Management, 1982-01-01)
      Esophageally fistulated cows were used to determine cattle diets on grassland range in northeastern Oregon in 1976, 1977, and 1978. Idaho fescue, bluebunch wheatgrass, and Sandberg bluegrass were the most common species in the diets. Forb consumption declined while grass consumption increased with seasonal advance from late spring to fall. Food habits depended largely on phenological development of forage species. Forbs were preferred over grasses early in the grazing season; then after forbs reached maturity, cattle were selective for the plants that remained green. Diet similarities were compared between periods within years, and between years within periods. When diets were pooled into late spring, early summer, late summer and fall groups, late spring diets were least similar to the others. Diet variation from year to year was also less later in the grazing season. Utilization of Idaho fescue and bluebunch wheatgrass should be considered in grazing management decisions on grasslands in the Blue Mountains.
    • Comparison of Micro- and Macro- Digestion Methods for Fiber Analysis in Forages and Ruminant Diets

      Holechek, J. L.; Vavra, M. (Society for Range Management, 1982-11-01)
      Micro-methods for analyses of neutral detergent fiber (NDF), acid detergent fiber (ADF), and permanganate lignin were compared to the macro-methods of Van Soest (1963) and Van Soest and Wine (1967, 1968). Differences between the two methods were small although the micro-methods gave better precision for ADF while the macro-method gave better precision NDF and lignin. Time and reagents needed for analysis were reduced over 60% with the micro-digestion methods.
    • Coordinating Beef Cattle Management with the Range Forage Resource

      Vavra, M.; Raleigh, R. J. (Society for Range Management, 1976-11-01)
      Seasonal changes in forage production and quality occur due to climatic factors, principally precipitation. Increased efficiency of livestock production could occur if livestock management were coordinated to the changes that occur in forage quality. Traditionally, calves are born in the spring in much of the western United States. Weaning then occurs sometime in late fall. Management practices of early weaning, supplementation on the range, time of calving, and length of the breeding period can be incorporated into a livestock system to take advantage of forage at its highest quality and therefore to maximize beef production from the existing forage resource.
    • Correcting for Differential Digestibility in Microhistological Analyses Involving Common Coastal Forages of the Pacific Northwest

      Leslie, D. M.; Vavra, M.; Starkey, E. E.; Slater, R. C. (Society for Range Management, 1983-11-01)
      The accuracy of microhistological techniques to describe herbivore diets can be affected by differential digestibility of ingested forages. Correction factors were developed to adjust for those effects in 17 common forages of coastal, forested ranges of the Pacific Northwest. Two ferns, a moss and a sedge were overestimated by microhistological analysis in all seasons, while most shrubs, forbs and a grass were underestimated. Trees were not consistently over- or underestimated. Phenology significantly affected the degree of over- or underestimation of most forages. Failure to correct for differential digestibility will significantly bias results of microhistological techniques such as fecal analyses.
    • Deer and Elk Use on Foothill Rangelands in Northeastern Oregon

      Miller, R. F.; Krueger, W. C.; Vavra, M. (Society for Range Management, 1981-05-01)
      Forested foothills of the Wallowa Mountains in northeastern Oregon provide spring and early summer range for deer and elk. Deer and elk use varied both between plant communities and seasonally within plant communities. Plant species composition of big game diets also varied with season. Bunchgrass and logged communities collectively occupying 57% of the land area studied, provided 90% of the big game diet during spring and early summer. Grasses made up 52% of the diet, forbs 38%, and browse 10%. Timothy and western goatsbeard were the two most important species consumed by big game. Pellet groups did not reliably estimate the value of various communities to deer and elk for forage use.
    • Dietary Relationships Among Feral Horses, Cattle, and Pronghorn in Southeastern Oregon

      McInnis, M. L.; Vavra, M. (Society for Range Management, 1987-01-01)
      Management of sympatric ungulates on multiple use lands requires knowledge of how species exploit resources available to them. We examined seasonal food habits, dietary overlap, and dietary quality of sympatric feral horses (Equus caballus), cattle (Bos taurus),, and pronghorn (Antilocapra americana) in south-eastern Oregon from May 1979 through March 1981. Seasonal diets of each ungulate species were determined by microhistological analysis of feces. At least 88% of the mean annual diets of horses and cattle consisted of grasses. Principal species consumed by these ungulates were bottlebrush squirreltail (Sitanion hystrix (Nutt.) J.G.Smith), bearded bluebunch wheatgrass (Agropyron spicatum (Pursh) Scribn. & Smith), and Thurber needlegrass (Stipa thurberiana Piper). Because dietary overlap between horses and cattle was high each season (62-78%), we concluded a strong potential existed for exploitative competition under conditions of limited forage availability. Pronghorn diets consisted largely of woody sagebrush (Artemisia) species in fall and winter, and a mixture of forbs in spring and summer. Dietary overlap between horses and pronghorn varied from 7% (summer) to 26% (winter). Overlap between cattle and pronghorn varied from 8% (winter) to 25% (spring). These lower levels of overlap indicate a wider buffer between noncompetitive coexistence and exploitative competition. Pronghorn generally selected diets containing higher levels of crude protein (CP) and lower levels of acid-detergent fiber (ADF) than horses or cattle. We observed few differences in seasonal dietary quality between horses and cattle.
    • Drought Effects on Diet and Weight Gains of Yearling Heifers in Northeastern Oregon

      Holechek, J. L.; Vavra, M. (Society for Range Management, 1983-03-01)
      Daily weight gains and diets of cattle were evaluated during a year with average precipitation and in a drought year on mountain range in northeastern Oregon. Forage intake was evaluated only in the drought year. Esophageally fistulated heifers were used to sample diet quality and botanical composition. Botanical composition of cattle diets was different (P<.05) in the late spring and early summer between years. When green grass and forbs were not available, browse was heavily utilized. Livestock weight gains and forage intake in the latter part of the grazing season were reduced (P<.05) during the drought year. This is attributed to depletion of browse, primarily common snowberry (Symphoricarpos albus). Diet crude protein and neutral detergent fiber concentrations were significantly (P<.05) correlated with average daily gains. When ruminants are consuming diets with more than one forage class, neutral detergent fiber and composition and yield of volatile fatty acids may more accurately evaluate the energy status of the diet than digestibility. Supplementation of crude protein could potentially improve average daily gains during drought years if browse was unavailable. Ranges with a high component of forbs and shrubs will ameliorate the negative effects of drought on average daily gains.
    • Effects of Late Season Cattle Grazing on Riparian Plant Communities

      Kauffman, J. B.; Krueger, W. C.; Vavra, M. (Society for Range Management, 1983-11-01)
      Livestock impacts on riparian plant community composition, structure, and productivity were evaluated. After 3 years of comparison between fall grazed and exclosed (nongrazed) areas, 4 plant communities out of 10 sampled displayed some significant species composition and productivity differences. Two meadow types and the Douglas hawthorne (Crataegus douglasii) community type had significant differences in standing phytomass. These also were utilized more heavily than any other communities sampled. Shrub use was generally light except on willow (Salix spp.)-dominated gravel bars. On gravel bars, succession appeared to be retarded by livestock grazing. Few differences were recorded in other plant communities sampled, particularly those communities with a forest canopy.
    • Effects of Range Improvement on Roosevelt Elk Winter Nutrition

      Mereszczak, I. M.; Krueger, W. C.; Vavra, M. (Society for Range Management, 1981-05-01)
      Three pasture types dominate the Beneke Creek Wildlife Management Area on this Roosevelt elk winter range in northwestern Oregon. In winter, elk showed a strong preference for perennial ryegrass pastures that were hayed the previous summer and fall fertilized over bentgrass pastures also hayed and fertilized or unmanaged bentgrass pastures. These perennial ryegrass pastures provided forage that met minimal requirements for digestible protein and digestible energy all winter while both bentgrass pasture types were deficient in these nutrients through winter. Improvement of bentgrass pastures by conversion to ryegrass should result in higher rates of elk reproduction and better survival of offspring.
    • Factors Influencing Microhistological Analysis of Herbivore Diets

      Vavra, M.; Holechek, J. L. (Society for Range Management, 1980-09-01)
      A study simulating herbivore diets was conducted to compare actual and estimated diet constituents as influenced by sample preparation technique and in vitro digestion. Nine plant species, three each representing grass, forb, and shrub forage classes were hand composited into three mixtures so that one forage class dominated each mixture. Samples of each mixture were then allotted to eight treatments involving combinations of grinding through a micro-Wiley mill, soaking in sodium hydroxide and in vitro digestion. Samples were then analyzed for botanical composition using the microhistological technique. In vitro digestion had the greatest impact on the difference between estimated and actual means. In digested samples grasses were overestimated while shrubs and forbs were underestimated. The preferred treatment involved grinding in a micro-Wiley mill and the sodium hydroxide soak.
    • Fistula Sample Numbers Required to Determine Cattle Diets on Forest and Grassland Ranges

      Holechek, J. L.; Vavra, M. (Society for Range Management, 1983-05-01)
      The variation among esophageal fistulated (EF) cattle in diet nutritive content and botanical composition selection was evaluated on forest and grassland range in the Blue Mountains of eastern Oregon during the summer of 1976. Botanical composition of diet samples was determined with microhistological analysis. Nutritive value was evaluated by analyses for crude protein, acid detergent fiber, permanganate lignin, and in vitro organic matter digestibility. Four collections were made from 4 EF heifers during each of 4 28-day periods on each vegetation type. Collections were alternated between morning and afternoon on each vegetation type. EF cattle selected diets of different (P<.05) botanical composition and nutritive quality in the early morning compared with the late afternoon. They grazed open grassland areas in the morning and shaded areas in the afternoon. Several more EF cattle and collections were required to determine diet botanical composition than nutritive quality on both the forest and grassland. A minimum of 4 EF cattle and 4 collections were needed to adequately sample diet nutritive characteristics on the grassland and forest pastures. The data indicated collections should be rotated between morning and afternoon on ranges supporting a mosaic of grassland and forest plant communities.
    • Food Habits of Cattle on Shortgrass Range in Northeastern Colorado

      Vavra, M.; Rice, R. W.; Hansen, R. M.; Sims, P. L. (Society for Range Management, 1977-07-01)
      Cattle food habits and plant composition in the diets were similar on the light and heavily grazed pastures on shortgrass prairie near Nunn, Colorado. Blue grama (36% and 40%), scarlet globemallow (15% and 11%), and sun sedge (9% and 9%) collectively averaged about 60% of the monthly diets at both grazing intensities. The proportions between diets and available forage in each pasture were significantly related for the 12 major foods. Diversity indices of diets and available pasture vegetation were positively correlated. Preference indices averaged the same for the major forages. Significant differences in diet were observed between months and years at both intensities. Fireweed summer-cypress, western wheatgrass, evening-primrose, slimflower scurfpea, and scarlet globemallow ranked highest in preference; and although blue grama was the principal component in the cattle diets, only fringed sagewort ranked lower in preference.
    • Forage Intake by Cattle on Forest and Grassland Ranges in Northeastern Oregon

      Holechek, J. L.; Vavra, M. (Society for Range Management, 1982-11-01)
      Forage intake was determined with steers using total fecal collections on forest and grassland vegetation types on mountain range in northeastern Oregon in 1976, 1977, and 1978. Forage intake varied from 1.6 to 2.5% of body weight (BW) on dry matter basis with a mean value of 2.1%. Forage intake did not differ (P>.05) between the two vegetation types when data were pooled across periods and years. During the summer grazing periods cattle on the forest had higher (P<.05) intakes than cattle on the grassland vegetation type. This is explained by higher forb and shrub consumption, more shade and less advanced plant phenology on the forest compared to the grassland vegetation types. Fecal collections from 5 steers for 3 days were needed to estimate fecal dry matter output with 90% confidence that the estimate was within 10% of the mean.
    • Grazing System Influences on Cattle Performance on Mountain Range

      Holechek, J. L.; Berry, T. J.; Vavra, M. (Society for Range Management, 1987-01-01)
      A 5-year study was conducted to evaluate the influences of rest-rotation, deferred-rotation, and season-long grazing systems on cattle diet botanical composition and quality and weight gains on mountain rangeland in northeastern Oregon. The grazing season in each year lasted from 20 June to 10 October. Esophageally fistulated animals were used to evaluate diet quality and botanical composition. All study pastures included forest, grassland, and meadow vegetation types. Each pasture had a north and southfacing slope divided by a riparian zone and creek. The grazing pressure for each system was similar. Grazing intensity was the same as National Forest Allotments in the area. There were no differences (P>.05) in weight gains among the 3 systems when data were pooled across years. Crude protein, in vitro organic matter digestibility, and acid detergent fiber percentages in fistula samples did not differ (P>.05) among systems for any year of study or for data pooled across years. Mid-season movements of cattle under the rest-rotation system had little influence on their diet and performance compared with cattle under the season-long system. Key forages in cattle diets were Idaho fescue (Festuca idahoensis), bluebunch wheatgrass (Agropyron spicatum), and common snowberry (Symphoricarpos albus). Cattle diet botanical composition under the 3 grazing systems did not differ (P>.05).
    • Habitat Use by Federal Horses in the Northern Sagebrush Steppe

      Ganskopp, D.; Vavra, M. (Society for Range Management, 1986-05-01)
      Distribution patterns of feral horses (Equus caballus) relative to plant communities, herbaceous production, and perennial water sources were studied from April 1979 to March 1981 in Oregon's Owyhee Breaks. Repeated observations of radio-collared and easily identified horses allowed estimation of home range sizes and documentation of the plant communities utilized. A map of plant communities was constructed, and composition and herbaceous production of key communities sampled. Time-lapse cameras monitored the daylight watering patterns of horses. One hundred thirty-three horses were initially censused and identified on the study area with the total population subsequently increasing at an annual rate of 13%. Home ranges averaged 12 km2 with the minimum convex polygon procedure and 27 km2 with the 90% confidence ellipse method. No seasonal shifts in home ranges occurred, and no correlations were detected between home range size and number of horses per band, densities of perennial water sources, or levels of forage production within home ranges. Six distinct herds were identified on the area. Only one band of horses moved from one herd to another during the 2-year study. Animals in each herd made greatest use of the most prevalent plant community, with no community being universally preferred to over another. Watering activities were most intense during the first and last periods of daylight. Horses rapidly vacated the watering areas after drinking. A seasonal trend was observed in which horses remained slightly closer to perennial water sources during warm, dry summer months than during spring periods when additional seasonal sources were available. Seasonal differences were not statistically significant, however.