Philip J. Urness

Effect of Grazing Horses Managed as Manipulatros of Big Game Winter Range.

A sagebrush-grass range in northern Utah, a critical winter area for deer and elk, was grazed by domestic horses in order to evaluate their potential to reduce selectively herbaceous vegetation which competes with bitterbrush (Purshia tridentata), an important big game winter forage. The diets of horses were recorded during spring and summer grazing under two stocking levels on small pastures. Horses consumed largely grass species throughout the study period in this high seral community. Forbs were important forage only under heavy stocking. No use of bitterbrush was recorded. Rate of forage disappearance, expressed on a peranimal-weight basis, was found to be lower on heavily stocked pastures. All pastures grazed by horses responded with increased seasonal twig production of bitterbrush over the non-grazed state. Seasonal twig production was greatest in response to heavy stocking during early July. Herds of migratory mule deer (Odocoileus hemionus hemionus) and elk (Cervus elaphus nelsoni) in the Rocky Mountains and Great Basin often rely on foothill rangelands dominated by big sagebrush (Artemisia tridentata) and other more palatable shrubs for winter browse. Winter deer mortality in Utah appears to be inversely related to the amount of palatable browse species available (Robinette et al 1952). Bitterbrush supplies important browse on many big game winter ranges in this area. Much of present bitterbrush range in our western states is considered to be seral communities created and maintained by perturbations of some sort (Ellison 1960). Extensive livestock grazing on palatable grasses and forbs in the late 1800’s and early 1900’s led, in part, to widespread successional changes favoring bitterbrush, which was frequently subordinate in the pristine vegetation (Hull and Hull 1974). In response to an increase in palatable shrubs and intensive management, elk and deer prospered by mid-century. In recent years, increasing urbanization near many foothill winter range areas has promoted a trend towards protection of big game winter range from livestock use because of water quality and soil erosion concerns. On many protected rangelands, succession is now favoring grasses since they receive little use during the growing season to balance heavy winter use of shrubs by big game (Smith 1949, Urness 1976). As palatable shrubs disappear from the community, productivity of these lands as deer winter habitat decreases. Declines in the Intermountain Region of deer herd productivity in the mid-1970’s (Connolly 1981) may have been partially due to these plant community changes. It is well recognized that controlled livestock grazing can be used in a manipulative sense to direct plant community succession (Anderson and Scherzinger 1975, Lewis 1969). Research with catAt the time of the research authors were graduate research assistant and associate professor, Range Science Dept., UMC-52, Logan, Utah 84322. Reinerisnow research assistant Range and Wildlife Manage. Dep., Texas Tech Univ. Lubbock, 79409. The authors wish to acknowledge Charles H. Jensen for his advice on the study design and layout. Statistical analysis was assisted by Dr. Ronald V. Sisson and Mr. David L. Turner. Thanks are also due to John Moody and Deborah Bowdenfortheir help in collecting the field data, and to the Starwood Ranch, Aspen, Cola., for generously loaning the study animals. The study was supported in part by the Utah Division of Wildlife Resources, Project W-105-R. Manuscript received August 20, I98 I. JOURNAL OF RANGE MANAGEMENT 35(5). September 1982 tle and sheep has shown that the productivity of bitterbrush can be increased by springtime grazing of competing herbaceous vegetation (Smith and Doe11 1968, Jensen et al. 1972, Smith et al. 1979). One problem encountered when using sheep or cattle for this purpose is that both animals consume bitterbrush. Smith and Doe11 (1968) found that on moderately stocked pastures bitterbrush utilization by cattle increased dramatically in July, in some cases exceeding utilization of grasses. Jensen et al. (I 972), in developing guidelines for sheep grazing on big game winter range, also reported heavy use of bitterbrush beginning in July. Both investigations suggested that stocking and season ofhvestock use must be precisely controlled to avoid excessive utilization of bitterbrush. The use of horse grazing as a “biological tool” to enhance bitterbrush on big game winter range was investigated in this study because horses were presumed to select for grass species (Stoddart et al. 1975, p. 257, Wagner 1978). The objectives of this study were twofold: (1) to investigate the use of spring-summer horse grazing as a means of increasing the seasonal production of bitterbrush, and (2) to determine the effect of grazing season and stocking intensity on the diets of horses grazing sagebrush-grass rangeland.

Infrared reflectance analysis of forage quality for elk

Feeding trials and chemical analysis are the two most common methods used to estimate forage quality. Feeding trials are labor intensive and costly, therefore limited in use. Laboratory methods that predict forage value based on chemical composition and in vitro digestibility are also expensive and time-consuming. Infrared reflectance (IR) techniques have been developed that have potential for rapid, routine prediction of a wide variety of forage quality characteristics and animal responses to these forages. During the early 1960s, the Agricultural Research Service developed near-infrared spectroscopy to determine moisture, oil, and protein content of ground grain. In 1971, commercial instruments using these principles were available to the grain industry (Williams 1975). The objectives of this study were to assess the potential of the IR technique, using fecal or diet samples, to predict forage quality parameters and elk (Cervus elaphus) weight response.

Biological Manipulation of Blackbrush by Goat Browsing

Domestic goat browsing was used to stimulate twig production by blackbrush. Precipitation, soil depth and stoniness, branch location, and the number of years of browsing and rest from browsing affected twig production (P<O.05). As precipitation doubled, production increased by a factor of 1.9. Twig production by plants growing on deep soils(71 cm) was 1.9 times that by plants growing on shallow soils (39 cm). Older branches growing on the outer edges of blackbrush plants (terminal branches) produced 4.6 times more current seasons twigs than sprouts and young branches (basal branches) growing within the shrub canopy. Heavily browsed plants increased twig production by a factor of 3.6 relative to control plants, and production remained at this level, even after 4 consecutive years of browsing. Annual twig production declined with rest from browsing. However, plants that were browsed and subsequently rested for 2 years yielded an aggregate 1.6 times more available forage than plants that were browsed on a yearly basis. This was due to an accumulation of twigs ranging in age from I to 3

Establishing browse utilization from twig diameters.

Measurement of twig lengths before and after browsing and measurement of twig diameter after browsing are two techniques to estimate utilization. The two techniques were compared for bitterbrush (Purshia tridentata) and cliffrose (Cowania stansburiana). Utilization percentages determined from the two approaches were highly correlated. However, regression equations were not required to estimate utilization from the diameter measurements alone. Correction factors were obtained by subtracting the twig tip diameter of unbrowsed twigs from diameter at the browsed tip and from basal diameter; then dividing the corrected browsed-tip diameter by the corrected basal diameter and multiplying by 100. By using the correction factor, valid estimates of percentage utilization were obtained. The numerical value for twig-tip diameter can be obtained from measuring twig tips of a representative number of unbrowsed twigs. Estimating utilization from twig diameter has two major advantages: (1) accurate estimates of utilization can be reconstructed from postbrowsing measurement alone and (2) making a single annual visit to the rangeland can represent a considerable time saving. Estimating percentage utilization of selected, key browse species provides important information for sound range and big game management programs. A common management technique of measuring twig lengths before and after browsing was suggested by Nelson ( 1930) and was later modified by Aldous (1945) and Smith and Urness (1962). It received favor because it was accurate and restricted observer bias (Jensen and Scatter 1977). However, primAuthors are wildlife biologist, Utah State Division of Wildlife Resources, Department of Range Science, UMC-52, Utah State University, Logan 84322 and associate professor, Department of Range Science, UMC-52, Utah State University, Logan 84322. Manuscript received September 10, 1979. JOURNAL OF RANGE MANAGEMENT 34(2), March 1981 ary disadvantages are that it requires measurement both spring and fall and permanently marking branches of the key browse plants (Basile and Hutchings 1966). Another method, requiring a single annual visit, predicts percentage utilization of twig lengths or weights from twig diameter measurements. Julander (1937) discounted using diameter measuremems because of difficulty in securing them. Basile and Hutchings (1966) and Lyon (1970) concluded that length-diameter and weight-diameter relationships offer promising methods for estimating utilization of shrubs from post-browsing diameter measurements. Ferguson and Marsden (1977) developed equations for estimating overwinter utilization of bitterbrush (Purshia tridentata) in southern Idaho. Our study tested the ability and utility of diameter measurements to predict utilization by mule deer Odocoileus hemionus) and field conditions. Examining plants browsed by mule deer represents an important extension of studies where twigs were hand-clipped by researchers to simulate browsing, and is a necessary step to determine reliability of the method for application by range and wildlife managers. The work was supported by Utah Division of Wildlife Resources Federal Aid Project W-105-R.

Effects of goat browsing on gambel oak communities in northern Utah.

Replicated populations of 5 shrub species were monitored over a 3-year period to assess community responses to intensive browsing by Spanish-type goats. Response variables included stem density, stem-size distribution skewness, stem diameter-stem production relations, and sprout abundance and weight. No species exhibited a density change. Size distribution skewness increased only in browsed oak (Quercus gambelii Nutt.) populations. Sprout weights also increased in browsed oak populations, but declined in comparably browsed serviceberry (Amelanchier alnifolia Nutt.) populations. The only other significant sprouting response was an increase in sprout numbers in browsed snowberry (Symphoricarpos oreophilus Gray) populations. Relationships between basal stem diameter and stem production of 4 species were altered by goat use. The slopes of these relations were consistently lower in browsed populations of oak and serviceberry than in adjacent control populations, indicating that browsing reduced productivity, especially of large stems. Conversely, slopes of rabbit-brush (Chrysothamnus viscidiflorus lanceolatus (Hook.) Nutt.) relations increased in goat-browsed pastures relative to those of control populations; rabbitbrush was avoided by goats. Similarly, big sagebrush (Artemisia tridentata wyomingensis Nutt.) was avoided and its stem production responded positively in communities subjected to goat browsing. Important cumulative effects of goat browsing included declines in productivity of serviceberry and oak, and an increase in that of sagebrush.

Effects of cattle grazing on mule deer diet and area selection.

Split enclosures, half grazed and half ungrnzed by cattle in summer, were compared for mule deer habitat use in late summer using tame deer. Diet composition, dietary nutrition, and area selected for grazing by mule deer were used PS criteria to assess the grazing effects of cattle. Generally few dietary or nutritional differences were determined. Nonetheless, deer preferred to forage on areas ungrnzed by livestock at low deer use levels, hut this preference rapidly decreased as deer use increased. Many reported studies have indicated proper livestock grazing maintains or improves habitat for mule deer (Odocoileus hemionus) (Smith 1949, Smith and Doe11 1968, Jensen et al. 1972, Longhurstetal. 1979,Smithetal. 1979,Neal 1981, Urness 1981, Rciner and Urness 1982, and others). In such management situations short-term direct effects~primarily competition for forage and habitat-may adversely affect mule deer. Although many studies have dealt with dietary overlap between livestock and mule deer (Hansen and Reid 1975, Hubbard and Hansen 1976, Hansen et al. 1977, Vavra and Sneva 1978. Campbell and Johnson 1983, and others). few have determined changes in mule deer foraging behavior and quantified the results. Previous study in this area (Austinand Urness 1985) determined forage production and plant variety were abundant in spring and early summer, and that forage selection by mule deer only became potentially restricted in late summer. Therefore the effects of livestock grazing on mule deer would also be expected to be most critical in late summer. Consequently it was the intent ofthis study to compare late summer diet and area preferences of mule deer on contiguous areas grazed and ungrazed by cattle.

Diameter-Length,- Weight Relations for Blackbrush ( Coleogyne ramosissima) Branches

Regression was used to relate branch diameter to branch length (r = 0.85) and weight (# = 0.94) for blackbrush plants in southwestern Utah. These regression equations were subsequently used to estimate blackbrush utilization by domestic goats in a browsing study. The diameter-length equation compared favorably with before-and-after measurements for accuracy and greatly reduced man-hour costs in determining utilization. Estimates of utilization based on the diameter-weight equation were less than estimates based on the before-and-after approach or the diameter-length equation; the diameter-weight equation accounted for leaves and thus provided a more accurate estimate of utilization. Blackbrush (Coleogyne ramosissima) is a shrub occurring in nearly monospecific stands on millions of hectares of rangeland in the southwestern United States. The terminal twigs of blackbrush branches tend to die back for several centimeters from the tip resulting in a spinescent growth form. Death of terminal buds suppresses apical dominance and allows lateral twig development, which has a pronounced effect on compacting the plants. As a result of the compacted, spinescent growth form, the accessibility and palatability of blackbrush forage is low for cattle. Domestic goats were used to modify the growth form of blackbrush in southwestern Utah (Provenza 1977). Winter goat browsing removed spinescent material from blackbrush plants, which

Nutritional value of fresh Gambel oak browse for Spanish goats.

Little information is available on the nutritional value of fresh browse for ruminants. This study examined the nutritive value of Gambel oak (Quercus gambelii Nutt.) for Spanish goats. Fresh Gambel oak browse was harvested at 2 phenological stages and mixed with chopped alfalfa hay to formulate 6 diets, varying in oak content. Diets included 95% juvenile oak/5% alfalfa (95J), 80% juvenile oak/20% alfalfa (80J), 65% juvenile oak/35% alfalfa (65J), 80% mature oak/20% alfalfa (80M), 40% mature oak/60% alfalfa (40M), and an alfalfa control (ALF). Diets were evaluated for goats using a series of digestion-balance trials, in a completely randomized design. Dry matter intake was highest (P < 0.01) for animals on diets with mature oak (80M-37.8, 40M-34.5 grams kg(-1) day(-1), and lowest on diets containing juvenile oak (95J-23.6, 80J-31.6, 65J-29.9 grams kg(-1) day(-1)). Digestibility of dry matter and cell wall components was lower (P < 0.01) for mature oak diets, and higher for juvenile oak diets. Digestibility coefficients for dry matter were as follows: (80M-57.8%, 40M-58.8%, 95J-68.6%, 80J-65.3%, 65J-66.3%. Digestibility coefficients for cell wall were: 80M-33.1%, 40M-37.4%, 95J-53.7%, 80J-45.8%, 65J-47.3%. All diets provided nitrogen and energy in excess of maintenance requirements, as reflected by weight gains for all animals in every trial. Fecal and urinary nitrogen losses did not appear to be related to tannin content of the diets, since juvenile oak diets resulted in reduced nitrogen outputs, presumably due to reduced nitrogen intakes for these diets. We conclude that Gambel oak, even juvenile material in high dietary percentages (95%), provides adequate nutrients and should be considered a valuable forage for goats in oakbrush habitats.

Spring livestock grazing affects crested wheatgrass regrowth and winter use by mule deer.

Areas grazed and ungrazed by cattle in spring were compared for regrowth of crested wheatgrass on a big sagebrush-grass range. Overwinter utilization of crested wheatgrass by tame mule deer and their grazing area preferences were assessed under 3 snow cover conditions-snow free, partial, and complete. Results showed regrowth production was usually higher on areas previously ungrazed by livestock. Overwinter utilization of crested wheatgrass by deer was determined to be greater on ungrazed areas in both percentage of available grass used and weight per unit area consumed. Thus, interference from cured growth limiting green grass availability was more than compensated by increased production. The percentage of grass in the diet was generally higher on areas ungrazed by cattle, and deer preferred these areas under snow free and partial snow cover conditions; no preference was exhibited during complete snow cover. Recommendationsfor livestock grazing of seeded, foothill ranges where deer use is critical are discussed. Few winter rangelands are used exclusively by either domestic or wild ungulates, rather, use is usually sympatric, but not necessarily simultaneous. Critical foothill ranges used by mule deer (Odocoileus hemionus) in the winter are typically grazed by livestock during spring, fall or both. As demands for and values of wildlife recreation increase, managing these critical ranges primarily for wildlife habitat becomes monetarily and socially justifiable (Hendee 1974, Wennergren et al. 1977). The purpose of this study was to determine the influence of spring livestock grazing on a big sagebrush (Artemisia tridentata)crested wheatgrass (Agropyon desertorum) range on overwinter forage utilization and area choice by mule deer.

Alfalfa hay crop loss due to mule deer depredation.

To define alfalfa crop loss from depredating mule deer, the spotlight count and paired plot techniques were applied in 12 fields located throughout Utah. Protected and grazed plots were used to determine alfalfa loss. A significant relationship between deer-nights of grazing and alfalfa loss was determined. Based on our studies, we recommend using 2.4 kg/deer-night for mule deer depredation of alfalfa using the spotlight count assessment technique. Nutritional quality of alfalfa was not different between grazed and protected plots.