Poisonous plants that impair normal reproductive functions in livestock include Veratrum californicum Durand, lupines, ponderosa pine (Pinus ponderosa Dougl.), broom snakeweed (Gutierrezia sarothrae (Pursh) Britt. Rusby), locoweeds (Astragalus and Oxytropis spp.), selenium-containing forages, phytoestrogenic plants, endophyte-infected grasses and others. In this review we focus on lupines, locoweeds and ponderosa pine needles to demonstrate the broad and diverse effects that poisonous plants have on reproduction. Certain lupines (Lupinus spp.) contain quinolizidine and piperidine alkaloids that are fetotoxic and when grazed by pregnant cattle during specific stages of gestation induce skeletal birth defects and cleft palate, "crooked calf disease". Poison-hemlock (Conium maculatum) and some Nicotiana spp. contain similar alkaloids and induce identical birth defects in cattle, pigs, goats and sheep when ingested at certain stages of gestation. Locoweeds (species of the Astragalus and Oxytropis genera containing the indolizidine alkaloid swainsonine) interfere with most processes of reproduction when grazed for prolonged periods of time. Animals can recover normal reproductive function if withdrawn from locoweed grazing before severe poisoning occurs. While most animals may recover reproductive function, permanent neurological deficits may preclude normal reproductive behavior. Ponderosa and lodgepole pine needles (Pinus spp.) cause abortion in cattle when grazed during the last trimester of gestation. The specific chemical constituents responsible for the abortions belong to a class of compounds called labdane resin acids, including isocupressic acid (ICA), succinyl ICA, and acetyl ICA. Basic management recommendations to reduce reproductive losses to poisonous plants include: (1) keep good records; (2) know what poisonous plants grow on ranges and understand their effects; (3) develop a management plan to provide for alternate grazing in poisonous plant-free pastures during critical times; (4) provide for balanced nutrition, including protein, energy, minerals and vitamins; (5) maintain a good herd health program; (6) integrate an herbicide treatment program to reduce poisonous plant populations or to maintain clean pastures for alternate grazing; and, (7) manage the range for maximum forage production.

In the past, excessive numbers of livestock on western U.S. rangelands, reoccurring droughts, and lack of management resulted in retrogression of plant communities. Poisonous plants and other less palatable species increased with declining range condition and livestock were forced to eat these poisonous species because of a shortage of desirable forage, resulting in large, catastrophic losses. The level of management on most western rangelands has improved during the last 60 years, resulting in marked improvement in range condition; yet losses to poisonous plants still occur, though not as large and catastrophic as in the past. Some poisonous species are major components of the pristine, pre-European plant communities [tall larkspur (Delphinium barbeyi Huth), Veratrum californicum Durand, water hemlock (Cicuta douglasii (DC.)Coult. Rose), bracken fern (Pteridium aquilinum (L.) Kuhn), chokecherry (Prunus virginiana L.), Ponderosa pine (Pinus ponderosa Lawson), and various oak species (Quercus spp.)]. Although populations of many poisonous seral increaser species have declined with better management, they are still components of plant communities and fluctuate with changing precipitation patterns [locoweed (Astragalus and Oxytropis spp.), lupine (Lupinus spp.), death camas (Zigadenus spp.), snakeweed (Gutierrezia spp.), threadleaf groundsel (Senecio longolobis Benth.), low larkspur (Delphinium nuttallianum Pritz.), timber milkvetch (Astragalus miser Dougl. ex Hook.), redstem peavine (A. emoryanus (Rydb.) Cory), western bitterweed (Hymenoxys odorata D.C.), orange sneezeweed (Helenium hoopesii Gray), twin leaf senna (Cassia roemeriana Schelle), and white snakeroot (Eupatorium rugosum Houtt)]. Many of the alien invader species are poisonous: [Halogeton glomeratus (Bieb.) C.A. Mey, St. Johnswort (Hypericum perforatum L.), poison hemlock (Conium maculatum L.), tansy ragwort (Senecio jacobaea L.), hounds tongue (Cynoglossum officinale L.), leafy spurge (Euphorbia esula L.), yellow star thistle (Centaurea solstitialis L.) and other knapweeds (Centaurea spp.)]. Poisoning occurs when livestock consume these plants because they are either relatively more palatable than the associated forage, or from management mistakes of running short of desirable forage.

In recent years livestock death losses from poisonous plants in the western United States have averaged about 2-3% annually. A review of 36 grazing studies in North America shows poisonous plant availability and death losses of livestock from poisonous plants are closely associated with grazing intensity. Across studies, livestock death losses to poisonous plants average about 2.0% under moderate grazing compared with 4.8% under heavy grazing intensities. Sheep and goat losses from poisonous plants appear to be increased more by heavy stocking than those from cattle. Impacts of poisonous plants on livestock reproductive success are difficult to quantify, but probably reduce calf and lamb crops, even when grazing intensities are conservative. Increased poisonous plant consumption may explain in part why calf and lamb crops average about 7% lower under heavy compared to moderate grazing. With the exception of 1 Texas study, rotation and continuous/season long grazing systems show little differences in livestock death losses under comparable stocking rates. Certain plants, such as locoweeds (Astragalus sp.) and larkspur (Delphinium sp.), can elevate livestock death losses, even when grazing intensities are moderate or conservative. Special management programs that involve careful timing of grazing, aversive conditioning, and creation of locoweed (or larkspur)-free pastures can reduce problems with these plants. Use of adapted livestock is a critical part of minimizing poisonous plant problems. However, on some rangelands, such as those with infestations of locoweed and larkspurs, naive livestock may be less affected by poisonous plants than familiar livestock. Knowledge of poisonous plant identification, conditions of toxicity, and affects on the animal, in conjunction with conservative grazing, will in most cases avoid excessive death and productivity losses from poisonous plants. In some cases livestock can be conditioned or trained to not consume poisonous plants. It can be concluded that most livestock losses from poisonous plants are caused by poor management.

In 1992 and 1993, pastures of WW-Spar Old World bluestem (Bothriochloa ischaemum L.) were maintained at 2 levels of soil water, rainfall and rainfall plus 25 mm/week of supplementary irrigation. At both moisture levels the grass was maintained at 2 levels of standing crop, averaging 1,548 and 2,154 kg ha(-1), using continuous variable stocking. Measurements were made to determine how different levels of soil moisture interacted with grazing intensity to change leaf area index, leaf-stem and live-dead ratios, tiller density, and the proportion of gross leaf production that was grazed (harvest efficiency). The proportions of live to dead, and leaf and stem biomass, remained constant under the different levels of soil water content. Soil water content alone had no effect on leaf area index, tiller density and the proportion of live or dead, leaf and stem. Winter tiller survival was significantly higher in the pastures with higher soil water content. Increasing soil water content and increasing grazing intensity interacted to reduce the proportion of dead leaf, increase production of new tillers, and increase the proportion of leaf grazed by decreasing leaf that died and was not grazed. This study indicates that if continuously grazed Old World bluestem was maintained at a standing crop of 1,500 kg ha(-1), harvest efficiency would be higher in wet years or under irrigation than if standing crop was higher.

White-tailed deer (Odocoileus virginianus dacotensis Zimm.) numbers in the central Black Hills have declined since the middle 1970s. Population status has been documented by a decline in hunter success, deer reproductive success, and fawn survival. Most management agencies believe habitat deterioration is the primary cause of population decline in the Black Hills. We evaluated habitat selection for a white-tailed deer herd in the central Black Hills of South Dakota and Wyoming. From July 1993-July 1996, 73 adult and yearling doe and 12 adult and yearling buck white-tailed deer were radiocollared and visually monitored. Habitat Information was collected at 4,662 white-tailed deer locations and 1,087 random locations. During winter, white-tailed deer selected ponderosa pine- (Pinus ponderosa P. C. Lawson) deciduous and burned pine cover types. Overstory-understory habitats selected included pine/grass-forb, pine/bear-berry (Arctostaphylos uva-ursi (L.) Spreng.), pine/snowberry (Symphoricarpos albus L.), burned pine/grass-forb, and pine/shrub habitats. Structural stages selected included sapling-pole pine stands with 70% canopy cover, burned pine sapling-pole and saw-timber stands with 40% canopy cover. During summer, white-tailed deer selected pine-deciduous, aspen (Populus tremuloides Michx.), aspen-coniferous, spruce (Picea glauca (Moench) Voss), and spruce-deciduous cover types. Overstory-understory habitats selected included pine/juniper Juniperus communis L.), aspen/shrubs, spruce/juniper, and spruce/shrub habitats. Structural stages selected included pine, aspen, and spruce sapling pole stands with all levels (0-40%, 41-70%,71-100%) of canopy cover. Results supported low habitat quality as a factor involved with the decline of the deer population. We recommend that habitat management techniques, such as aspen regeneration and prescribed burns, be used to Improve the habitat base in the central Black Hills.

Understanding the interacting effects of drought and grazing on runoff, erosion, and nutrient transport is essential for improved rangeland management. Research was conducted at the Fort Keogh Livestock and Range Research Laboratory located near Miles City, Mont. using 12, non-weighing lysimeters for 3 years. During years 1 and 3, no drought treatment was imposed. For year 2, one half of the lysimeters were covered to implement a drought treatment. The 3 grazing treatments were ungrazed, grazed during but not after drought, and grazed during and after drought. Runoff, sediment yield, and an array of nutrients in the runoff water were measured from the lysimeters. First year base line data with no grazing or drought treatments applied indicated no significant differences among lysimeters. Below normal precipitation occurred during year 2, resulting in no runoff from the drought treatment and negated the "non-drought" control. This prevented a direct assessment of the interaction among the drought and grazing treatments for this year. The drought treatment did produce significant reductions in water, sediment, and nutrient yield. No grazing impact was observed during year 2. The third year with more normal precipitation, there was a trend toward increased runoff, sediment, and nutrient yield from the second year drought treatment lysimeters. In the third year, both grazing treatments showed significantly greater runoff, sediment, and nutrient yield than the ungrazed treatment. Runoff and sediment yield tended to increase from the combination of drought and grazing treatments. The observed increases in runoff and sediment and reduced water quality from the drought and grazing treatments were measured against controls and when compared to the natural variability and water quality standards, they were concluded to be minimal.

Interest has been expressed in using silver sagebrush (Artemisia cana Pursh ssp. cana) in restoring the Northern Mixed Prairie in Saskatchewan. The objectives of this study were to determine the effects of seedbed manipulation treatments and autumn or spring sowing on establishment of silver sagebrush on sites previously seeded to native, perennial grasses. Seeds (achenes) were sown by broadcasting at 20 pure live seeds m(-2). Seedling emergence ranged from 5 to 6% of seeds sown. Most seedlings emerged in May and June; no seedlings emerged after July or in the second year after planting. Seventy-four to 84% of emerging seedlings survived the first growing season with 96 to 98% of these seedlings establishing. On upland sites, seedling emergence (1.1 seedlings m(-2) SE +/- 0.1) and establishment (0.9 seedlings m(-2) SE +/- 0.1) were similar between autumn and spring sowing and among seedbed manipulation treatments. On lowland sites, seedling emergence (1.4 seedlings m(-2) SE+0.2) and establishment (0.8 seedlings m(-2) SE +/- 0.2) were similar between autumn and spring seeding. Density of seedlings establishing was greatest when the seedbed was tilled. Establishment of silver sagebrush appears primarily limited by low numbers of seedlings emerging, indicating very specific safe site requirements for this shrub. Drastic disturbance of the seedbed is not required to establish silver sagebrush in established stands of perennial grasses. Sowing silver sagebrush in late autumn when temperatures are consistently below 0 degrees C or in early spring immediately after snowmelt is recommended.