• Impact of locoweed poisoning on grazing steer weight gains

      Ralphs, M. H.; Graham, D.; Duff, G.; Stegelmeier, B. L.; James, L. F. (Society for Range Management, 2000-01-01)
      Emaciation is one of the clinical signs of locoweed poisoning but few studies have documented impacts of locoweed poisoning on weight gains. Stocker steers (British X Continental cross, 200-210 kg) were grazed on locoweed-infested, short-grass prairie in 1996 and 1997 in northeast New Mexico. Each year, half the steers were averted to locoweed to allow them to graze locoweed-infested pastures without eating locoweed. They did not graze locoweed and steadily gained weight (0.50 kg/day in 1996 and 0.71 kg/day in 1997). The other group of steers were allowed to graze locoweed under natural grazing conditions and became intoxicated. Weight gains were not affected for the first 3 weeks, but thereafter the steers lost weight in both years. In 1996, non-averted steers consumed locoweed for a season average of 20% of bites. They were severely intoxicated and did not begin gaining weight for 50 days after they stopped eating locoweed. Steers in the 1997 trial consumed less locoweed (11% of bites) than those in 1996 and they recovered more rapidly. Seasonal weight gains were 21 to 30 kg less for locoed steers than control steers in 1996 and 1997, respectively. Locoweed poisoning will cause weight loss, and severely intoxicated cattle require a lengthy recover period after they cease grazing locoweed before weight gains resume. Stocker cattle should not be placed on locoweed-infested rangelands until green grass is abundant and locoweed begins to mature.
    • Larkspur chemistry: Toxic alkaloids in tall larkspurs

      Manners, G. D.; Pfister, J. A.; Ralphs, M. H.; Panter, K. E.; Olsen, J. D. (Society for Range Management, 1992-01-01)
      Three species of tall larkspur (Delphinium barbeyi (Huth), Delphinium occidentale (Wats.) Wats, and Delphinium glaucescens) that are toxic to cattle were chemically analyzed to determine “total alkaloid” content. D. barbeyi and D. occidentale contained more “total alkaloids” than D. glaucescens. The “total alkaloid” content of all plant tissues in the 3 species declined as the growing season progressed. Variation in the occurrence of specific diterpenoid alkaloids was established by gas chromatographic analysis of D. barbeyi plant tissues at different phenological growth stages. Highest yields of specific alkaloids were found in early growth stage plant tissues. Deltaline was the most prominent diterpenoid alkaloid in D. barbeyi and 14-0-acetyldictyocarpine is a new diterpenoid alkaloid with high occurrence in this plant. The toxicity of specific diterpenoid alkaloids obtained from the tall larkspurs evaluated in a mouse bioassay showed methyllcaconitine to be highly toxic. Other diterpenoid alkaloids isolated from the 3 Iarkspurs showed much lower levels of toxicity compared to methyllycaconitine
    • Long term change in vegetation following herbicide control of larkspur

      Ralphs, M. H. (Society for Range Management, 1995-09-01)
      Larkspur (Delphinium spp.) control can reduce cattle deaths on mountain rangelands, but vegetation cover must be maintained to protect watersheds from erosion. The objective of this study was to evaluate the long term impact of herbicides on larkspur control and cover of associated species. Duncecap larkspur (Delphinium occidentale S. Watts) near Oakley Ida., and tall larkspur (D. barbeyi Huth) near Manti Utah, were the target species. Picloram (4-amino-3,5,6-trichloro-2-pyridinecarboxylic acid) was applied at 1.1, 2.2, and 4.5 kg ae/ha; glyphosate (N-(phosphonomethyl)glycine) was applied at 0.06, 1.1, and 2.2 kg ai/ha; and metsulfuron (1-[[[[(4-methoxy-6-methyl-1,3,5-triazin-2-yl)amine]carbonyl ]amino]sulfonyl]benzoic acid) was applied at 0.035, 0.07, and 0.14 kg ai/ha. Picloram at 2.2 kg/ha maintained long-term control of both larkspur species (> 80%) when applied in the vegetative, bud, and flower growth stages. Total grass cover was higher on picloram plots than other treatments. Forb cover declined and bare ground was greater in picloram plots than other treatments at Manti. Metsulfuron controlled duncecap larkspur when applied in the vegetative stage. However, long-term control of tall larkspur at Manti declined as new tall larkspur seedlings established. Glyphosate controlled both larkspurs when applied in the vegetative and bud stages, but it allowed undesirable annual and rhizomatous forbs and shrubs to increase by the end of the study. Grass cover was lower on glyphosate plots than on other treatments. Bare ground was higher on glyphosate plots than other treatments at Oakley, but was intermediate at Manti.
    • Mechanism by which ammonium fertilizers kill tall larkspur

      Ralphs, M. H.; Woolsey, L.; Bowns, J. E. (Society for Range Management, 2003-09-01)
      Environmental concerns of using pesticides on public lands have greatly reduced the use of herbicides to control tall larkspur (Delphinium barbeyi Huth). An alternative method of control used ammonium sulfate placed at the base of individual plants. The objective of this study was to determine the mechanism by which fertilizers kill tall larkspur. We hypothesize the salt from the fertilizers kill the plant. We applied ammonium sulfate, ammonium nitrate and sodium chloride at equivalent salt concentrations and evaluated their effect on tall larkspur plants. There was no difference among treatments in larkspur mortality (P > 0.10). The high rate of all treatments (ammonium sulfate 400 g plant-1, ammonium nitrate 264 g, and sodium chloride 180 g, at equivalent salt concentrations) killed greater than 70% of larkspur plants. We conclude the salt in fertilizers kills tall larkspur, not the nitrogen. It is necessary to place the fertilizer or salt at the base of the plant to concentrate it in the root zone, rather than broadcast it. At the end of the study, bare areas left around the dead tall larkspur plants were only 13% of the original size of the tall larkspur plants at Yampa Colo. and Cedar Ut., and 46% at Emery Ut., indicating the surrounding vegetation was quickly filling in the vacated space. The relative cost of materials per plant for both ammonium sulfate and nitrate was 12.9 cents, and 2.6 cents for salt.
    • Persistence of aversions to larkspur in naive and native cattle

      Ralphs, M. H. (Society for Range Management, 1997-07-01)
      The objective of this study was to create and maintain a long lasting aversion to tall larkspur (Delphinium barbeyi Huth) under field grazing conditions. Two grazing trials were conducted: the first used cattle naive to larkspur, and the second used cattle that were familiar with larkspur. In the first trial, 12 mature cows that were not familiar with larkspur were randomly allocated to Averted and Control groups (n = 6). They were fed larkspur (a novel food) and the Averted group was dosed with lithium chloride (200 mg/kg body weight) to create the aversion. Both groups were then taken to larkspur-infested mountain rangeland where they grazed in 2 separate pastures during the late summer of 1993, 1993, 1994, and 1995. The aversion was not reinforced in 1994 or 1995. Diets were quantified by bite count. The Averted group abstained from eating larkspur for 3 years. The Control group grazed larkspur for an average of 14% of bites. Three Control cows died from larkspur poisoning in 1993, and another cow was poisoned, but survived in 1994. During the last 2 weeks of the 1995 trial, the Averted and Control groups were placed together, and the social influence of the Control cows eating larkspur caused the Averted cows to sample larkspur and gradually extinguished the aversion. In the second trial (1994 and 1995), 5 native cows that had grazed on the allotment and were familiar with larkspur were averted to larkspur by the procedure described above. They abstained from eating larkspur while grazing separately, but extinguished the aversion when placed with non-averted Control cows at the end of the study in 1995. Aversions are retained in long term memory and may last indefinitely if averted cattle graze separately.
    • Plant toxins and palatability to herbivores

      Molyneux, R. J.; Ralphs, M. H. (Society for Range Management, 1992-01-01)
      A complex relationship exists between the presence of toxins in a plant species and the palatability of that plant. The nature of the toxin and its concentration within the plant can generally be precisely defined, given a reasonable amount of research commitment, but the measurement of palatability, especially in livestock, is much more difficult to achieve. We hypothesize that analysis of possible roles of toxins in plants, their metabolic activity in animals, and physical and temporal distribution within the plant can be used to examine whether or not such compounds may significantly increase or reduce palatability to mammalian herbivores. Thus, if the toxin is effective in preventing predation of the plant or plant part by insect herbivores, or if it provides the plant with a competitive advantage versus other species, but does not produce adverse effects upon large mammals until significant quantities of biomass are consumed, then the toxin-palatability relationship is not significant. This concept is illustrated by examination of the toxicity produced in livestock by consumption of alkaloid-containing groundsel (Senecio) and locoweed (Astragalus and Oxytropis) species. The prevention of predation by localization of the toxin, mobilization to the site of attack, or production at a particular stage of growth provides opportunities for the application of management techniques designed to reduce exposure of livestock to natural plant toxicants.
    • Population cycles of broom snakeweed in the Colorado Plateau and Snake River Plains

      Ralphs, M. H.; Sanders, K. D. (Society for Range Management, 2002-07-01)
      Broom snakeweed (Gutierrezia sarothrae (Pursh) Britt. Rusby) is one of the most widespread range weeds in North America. The objective of this study was to monitor broom snakeweed populations in the salt-desert shrub community of the Colorado Plateau and in crested wheatgrass (Agropyron desertorum (Link) Schultes) seedings typical of the Snake River Plains and Great Basin, and determine if its population cycles are related to precipitation patterns. Foliar cover of broom snakeweed and associated plant species was measured along 7.6 or 33 m transects by the line intercept technique. Density of snakeweed age classes (seedling, juvenile, mature) was counted in 1 m2 quadrats at the beginning and end of each transect. Correlations were made between snakeweed cover and density, and seasonal precipitation. The snakeweed population at the Colorado Plateau site completed 2 cycles over the 13 year study period, dying out in the drought of 1989-90 and again in 2001. There were positive correlations between density of snakeweed classes and seasonal precipitation: seedlings with spring precipitation (r = 0.63); juveniles with winter precipitation (r = 0.69); and mature plants with previous fall precipitation (r = 0.62). Only 1 cycle occurred at the Snake River Plains site. Following the snakeweed invasion into crested wheatgrass seedings in the mid 1980's, the population was at the top of its population cycle when the study began in 1990, dropped back and fluctuated between 6-10% cover from 1992 to 1999, and died out in 2001. Although density of mature plants did not change much during the middle part of the study, the change in snakeweed cover was correlated with spring (r = 0.81) and total precipitation (r = 0.60), reflecting increase and decrease in size of plants in response to precipitation.
    • Prescribed Burning: Vegetative Change, Forage Production, Cost, and Returns on Six Demonstration Burns in Utah

      Ralphs, M. H.; Busby, F. E. (Society for Range Management, 1979-07-01)
      Six demonstration burns were conducted between 1974 and 1976 as part of the Utah Rangeland Development Program. Big sagebrush (Artemisia tridentata), the target species, was essentially eliminated on the areas that were burned. Five of the six burns were seeded, with predominately crested wheatgrass (Agropyron desertorum). Despite the severe drought only one seeding was considered a failure. Forage production increased several-fold above preburn production and is expected to continue to increase as the grass stands mature. An economic analysis of the 1974 burn showed an internal rate of return of 17%. Great risks were associated with the use of fire. Extensive precautions were taken to minimize hazards but variable weather conditions in late summer greatly increased the chance of the fire escaping. Prescribed burning is inexpensive and effective in controlling big sagebrush when adequate safety precautions are taken.
    • Prior feeding practices do not influence locoweed consumption

      Ralphs, M. H.; Greathouse, G.; Knight, A. P.; Doherty, D.; Graham, J. D.; Stegelmeier, B. L.; James, L. F. (Society for Range Management, 2002-07-01)
      Anecdotal evidence suggests that cattle fed alfalfa hay during the winter are inclined to graze locoweed on spring range. Two studies were conducted to compare the influence of feeding alfalfa hay vs grass hay during the winter on subsequent consumption of white locoweed (Oxytropis sericea Nutt. ex TG) in the spring. Eight cows were daily fed alfalfa hay (15.2% CP in 1998, 17.1% CP in 2000) and 8 cows were daily fed grass hay (10.7% CP in 1998, 12.1% CP in 2000) plus 20% protein molasses block during the January-April winter feeding period. Treatment groups grazed in separate pastures (8 ha) on white locoweed-infested range in May and June in northern Colorado in 1998 and in northeast New Mexico in 2000. Diets were estimated by bite count. There was no difference in locoweed consumption between the 2 groups (P > 0.22). Cattle grazed locoweed for 5% of diets in Colorado and 10% of diets in New Mexico. Feeding alfalfa hay over winter did not predispose cattle to graze locoweed in the spring. Previous research showed other feeding practices or supplements do not affect locoweed consumption or poisoning. Prevention of locoweed poisoning requires denying access to locoweed when it is relatively more palatable than associated forages.
    • Prior grazing by sheep reduces waxy larkspur consumption by cattle: An observation

      Ralphs, M. H.; Olsen, J. D. (Society for Range Management, 1992-03-01)
      Sheep are more resistent to larkspur poisoning than cattle. Grazing larkspur with sheep before cattle turn-in may reduce the threat of cattle poisoning. Two 2.1-ha pastures were established in Upper Ruby Valley in southwest Montana in 1987 and 1989. A band of sheep grazed 1 pasture in mid-June in both years. Sheep grazed 70% of larkspur stalks in 1987 and 35% in 1988. Because sheep grazed little larkspur in 1988, larkspur was hand decapitated to simulate the use obtained in 1987 for the subsequent cattle grazing portion of the trial. Five cows were placed in each pasture immediately following sheep grazing in 1987 and after a 3-week delay in 1998. Cattle diets were quantified by bite counts. Waxy larkspur consumption by cattle in the sheep-grazed pasture was lower than in the cattle-only pasture especially during and after rainstorms in 1987 and throughout the study in 1988. One cow died from larkspur poisoning in the cattle-only pasture in 1988. If sheep will graze waxy larkspur, subsequent consumption by cattle can apparently be reduced on this site, thus reducing the risk of poisoning.
    • Reducing livestock losses from poisonous plants through grazing management

      Taylor, C. A.; Ralphs, M. H. (Society for Range Management, 1992-01-01)
      Stocking rate, multi-species grazing, and grazing systems are 3 components of grazing management that can be manipulated to minimize losses in animal production due to consumption of poisonous plants. Our study evaluated 3 case studies where either all or some of the above components of grazing management were the experimental treatments. For study 1 the grazing treatments included 3 rates of stocking; a 4-pasture, 3-herd grazing system; and combinations of different kinds of livestock that were measured for 21 years. For study 2 the grazing treatments included 2 rates of stocking, 4 different grazing systems, and combinations of either all sheep or a ratio of 3:2 cattle to sheep (au equivalents) for 11 years. Study 3 measured cattle poisoned by locoweed prior to and following the implementation of a 3-herd, 4-pasture grazing system over 6 years. Sheep death losses to bitterweed (Hymenoxys odorufa DC.) poisoning occurred in 13 of the 21 years on continuously grazed pastures heavily stocked with sheep and only 8 years under both moderate and light stocking rates. Regardless of the stocking rate, death losses were greatest on pastures stocked with sheep only and least with the combination of livestock species on conjunction with a 4-pasture, 3-herd grazing system. Stocking rate, multi-species grazing, or grazing system seemed to have little effect on goat losses due to oak (Quercus spp.) consumption. Cattle and sheep were not affected by sacahuista (Nolina texauo Wats.) in this study; however, their inclusion in the grazing herd reduced goat death losses from 5% with goats only to 2.5 and 1.5% for combinations of cattle and goats and cattle, sheep, and goats, respectively. In study 2 sheep death losses from bitterweed poisoning under continuous yearlong grazing treatments averaged 5.2% vs 3.7% for grazing treatments with some type of grazing system. Death losses were greatest under yearlong continuous grazing stocked at 10.4 ha/auy with 100% sheep and least under yearlong continuous grazing stocked at 15.2 ha/auy with 4% sheep. In study 3 the number of sick calves declined from 20% to about 3% with the implementation of a new grazing system. The reduction in sickness and loss was attributed to the reduction in grazing pressure and the shorter grazing season. It is concluded that for these case studies tactical management decisions such as proper stocking rate, combinations of animal species to be grazed, and grazing system used played an important role in minimizing livestock death losses to poisonous plants.
    • Reproductive losses to poisonous plants: Influence of management strategies

      Panter, K. E.; James, L. F.; Gardner, D. R.; Ralphs, M. H.; Pfister, J. A.; Stegelmeier, B. L.; Lee, S. T. (Society for Range Management, 2002-05-01)
      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.
    • Research observation: Influence of over-wintering feed regimen on consumption of locoweed by steers

      Ralphs, M. H.; Graham, D.; Galyean, M. L.; James, L. F. (Society for Range Management, 1997-05-01)
      Many producers believe cattle grazing wheat pasture during the winter are likely to graze actively growing locoweed when turned onto short-grass prairie in the spring. White locoweed (Oxytropis sericea Nutt, ex T&G) consumption was compared in a spring grazing study between steers wintered on irrigated 'TAM 105' wheat (Triticum aestivum L.) pasture (Wheat) and steers wintered on native range (Range). Range steers consumed locoweed for 43% of bites compared to 17% for the Wheat steers, and began eating locoweed before steers in the Wheat group. We rejected the hypothesis that steers wintered on wheat are more inclined to graze locoweed than steers wintered on native range.
    • Seasonal grazing of locoweeds by cattle in northeastern New Mexico

      Ralphs, M. H.; Graham, D.; Molyneux, R. J.; James, L. F. (Society for Range Management, 1993-09-01)
      Locoweed poisoning generally occurs in early spring. We evaluated cattle grazing of woolly locoweed (Astragalus mollissimus var. mollissimus Torr.) at Gladstone, N.M., and of white locoweed (Oxytropis sericea Nutt. ex T&G) at Capulin, N.M., through the spring and into early summer as the phenological development of warm-season grasses progressed from dormancy to rapid growth. Diets of 8 mature cows were quantified by bite count at each location. Cattle initially rejected woolly locoweed at Gladstone, even though it was the only green forage available in late March and early April. Gladstone cattle were then restricted to a small 7-ha pasture where high grazing pressure and limited feed forced them to graze woolly locoweed (41% of bites). When these cows returned to a larger pasture of unlimited forage availability, they continued eating woolly locoweed (23% of bites). At Capulin, cattle with a history of eating locoweed (loco-eaters) consumed more white locoweed (23% of bites) thin cattle without a history of eating locoweed (6% of bites) during the April grazing period. When warm-season grasses started rapid growth and locoweed matured in June, cattle ceased grazing both locoweed species.
    • Social facilitation influences cattle to graze locoweed

      Ralphs, M. H.; Graham, D.; James, L. F. (Society for Range Management, 1994-03-01)
      Many ranchers claim that if a cow starts eating locoweed, she will teach others to eat it. Three grazing trials were conducted to evaluate the role of social facilitation in starting cattle to graze locoweed. The first trial was conducted near Gladstone, N.M., using mature cows grazing woolly locoweed (Astragalus mollissimus var. mollissimus Torr). The second trial was conducted on the Raft River Mountains in northwestern Utah, using yearling cattle grazing white locoweed (Oxytropis sericea Nutt). The third trial was conducted to determine if aversion-conditioned yearling cattle would consume white locoweed when placed with cattle that were eating locoweed (loco-eaters). Cattle conditioned to eat locoweed and naive animals in trials 1 and 2 first grazed in separate pastures to evaluate their initial acceptance of locoweed. The groups in the respective trials then were placed together to evaluate the influence of social facilitation on locoweed consumption. Locoweed consumption was quantified by bite count. Naive cattle in trials 1 and 2 sampled small quantities of locoweed while grazing separately. However, they greatly increased locoweed consumption when placed with the loco-eaters. Aversion-conditioned cattle in trial 3 did not consume locoweed while grazing separately. When placed with loco-eaters, they gradually increased consumption of white locoweed, in contrast to the immediate acceptance of locoweed by naive cattle in trials 1 and 2. The aversion extinguished and averted animals eventually accepted white locoweed at levels comparable to loco-eaters. Results of this study demonstrate that social facilitation can cause cattle to start eating locoweed.
    • Storms influence cattle to graze larkspur: an observation

      Ralphs, M. H.; Jensen, D. T.; Pfister, J. A.; Nielsen, D. B.; James, L. F. (Society for Range Management, 1994-07-01)
      Livestock producers report cattle deaths from larkspur (Delphinium spp.) poisoning increase during stormy periods. In controlled grazing studies, we observed cattle increase larkspur consumption during stormy weather. Periods of "gluttonous" larkspur consumption generally coincided with storms during a 1990 grazing study. Cattle consumed larkspur almost exclusively for 20-30 min periods during storms, as opposed to intermittent grazing of larkspur flowers, pods, and leaves. In 1991 weather parameters were measured and correlated with larkspur consumption. Larkspur consumption was negatively correlated with decreasing temperature and barometric pressure (r = -0.45 and -0.60 respectively); and positively correlated with increasing relative humidity, leaf wetness, and precipitation (r = 0.45, 0.74, and 0.27, respectively). Understanding consumption patterns of cattle grazing larkspur will aid in developing management strategies to reduce cattle deaths.
    • Toxic alkaloid concentration in tall larkspur species in the western U.S

      Ralphs, M. H.; Manners, G. D.; Pfister, J. A.; Gardner, D. R.; James, L. F. (Society for Range Management, 1997-09-01)
      Larkspur (Delphinium spp.) kills more cattle on mountain rangelands in the western U.S. than any other plant, disease or predator. The concentration of toxic alkaloids was measured in 4 larkspur species, at 10 locations, at 2-week intervals during the growing season. In addition, multi-year samples from previous studies were analyzed to determine year-to-year variation in toxic alkaloids. Mountain larkspur (D. glaucum Wats.) had the highest concentration of toxic alkaloids averaged over growth stages (1.01% of dry weight), tall, (D. barbeyi (L.) Huth) and waxy larkspur (D. glaucesens Rydb) were intermediate (0.65 and 0.49% respectively), and duncecap (D. occidentale S. Watts) was lowest (0.29%). Toxic alkaloid concentration generally declined as the plants matured. However, toxic alkaloids in tall larkspur at Yampa, Colo. increased slightly in the pod stage, and toxic alkaloids in waxy larkspur increased from the vegetative to the bud stage. Concentration of toxic alkaloids in tall and duncecap larkspur leaves were higher in plants growing in open sunlight than those shaded under aspen or conifer canopy. Toxic alkaloid concentration varied among individual plants (C.V. 20-60%). Knowledge of the toxic alkaloid concentration of larkspur populations can be used to predict the risk of larkspur poisoning.
    • Toxic alkaloid levels in tall larkspur (Delphinium barbeyi) in western Colorado

      Pfister, J. A.; Manners, G. D.; Gardner, D. R.; Ralphs, M. H. (Society for Range Management, 1994-09-01)
      Consumption of tall larkspur (Delphinium barbeyi L. Huth.) can be fatal to cattle grazing mountain rangeland during summer. Tall larkspur contains many alkaloids, but virtually all the toxicity is caused by methyl succidimido anthranoyl lycoctonine-type (MSAL) diterpenoid alkaloids. We measured the concentration of MSAL alkaloids (% of dry matter) in tall larkspur in various phenological stages during 1990, 1991, and 1992 near Yampa, Colorado. The site represented tall larkspur-infested rangelands on the western slope of the Rocky Mountains. Toxic alkaloid concentrations were greatest (0.4 to 0.6%) early in the growing season (bud stage). Toxic alkaloid concentrations were generally static during the flower and pod stages, or increased during the pod stage. Immature leaves had greater MSAL alkaloid concentrations early in the growing season compared to flowering parts. Alkaloid concentrations in pods were greater than in leaves (P<0.05; pod stage), as pod concentrations increased to 0.4% late in the growing season. In 2 of 3 years, plant parts did not differ in MSAL alkaloid concentrations, although weather conditions differed each year. Concentrations of toxic alkaloids did not seem to influence amounts of tall larkspur consumed by grazing cattle on the same sampling dates. Many livestock producers defer grazing of tall larkspur ranges until the plant is in the pod stage because of a general belief that toxicity is greatly reduced. Our results suggest that grazing tall larkspur ranges during the pod stage may exacerbate cattle losses if MSAL alkaloid concentrations do not decrease, yet consumption by cattle increases.
    • Utilization of larkspur by sheep

      Ralphs, M. H.; Bowns, J. E.; Manners, G. D. (Society for Range Management, 1991-11-01)
      Sheep are more resistent to larkspur (Delphinium spp.) poisoning than are cattle, and may be used as a biological tool to graze larkspur prior to cattle turn-in to reduce the risk of cattle poisoning. Sheep utilization of 3 species of larkspur was measured at 3 phenological growth states (vegetative, bud, and flower) at 5 locations. Utilization of waxy larkspur (D. glaucescens Wats), varied among years at Ruby, Mont. Use of duncecap larkspur (D. occidentals. Wats) at Oakley, Ida., was uniformly higher in all 3 growth stages due to closed herding practices. Use of tall larkspur (D. barbeyi Huth) increased as it matured. Trailing sheep through larkspur patches, or bedding them in patches greatly increased trampling of larkspur stalks and utilization of heads and leaves.
    • Utilization of White Locoweed (Oxytropis sericea Nutt.) by Range Cattle

      Ralphs, M. H.; James, L. F.; Pfister, J. A. (Society for Range Management, 1986-07-01)
      Utilization studies conducted on a high mountain range determined the quantity and timing of white locoweed (Oxytropis sericea Nutt.) consumption by cattle. Paired plots (one caged and one grazed) were clipped at the end of the grazing season to determine seasonal utilization. Biweekly visual appraisals were used to estimate percentage leaf grazed and number of reproductive stalks grazed and thus determine utilization patterns as the season progressed. Loco comprised 26% of the standing crop. Thirty-four percent of the available loco was utilized during the grazing season. Loco flower and pods (heads) were preferred to leaves. Utilization of loco heads increased linearly as the season progressed. Loco leaves were not consumed until the last 3 weeks of the grazing season. Loco heads also contained the highest concentration of the toxic alkaloid, swainsonine.