Defensive properties of pyrrolizidine alkaloids against microorganisms

The understanding of the selection factors that drive chemical diversification of secondary metabolites of constitutive defence systems in plants, such as pyrrolizidine alkaloids (PAs), is still incomplete. Historically, plants always have been confronted with microorganisms. Long before herbivores existed on this planet, plants had to cope with microbial pathogens. Therefore, plant pathogenic microorganisms may have played an important role in the early evolution of the secondary metabolite diversity. In this review, we discuss the impact that plant-produced PAs have on plant-associated microorganisms. The objective of the review is to present the current knowledge on PAs with respect to anti-microbial activities, adaptation and detoxification by microorganisms, pathogenic fungi, root protection and PA induction. Many in vitro experiments showed effects of PAs on microorganisms. These results point to the potential of microorganisms to be important for the evolution of PAs. However, only a few in vivo studies have been published and support the results of the in vitro studies. In conclusion, the topics pointed out in this review need further exploration by carrying out ecological experiments and field studies

Poisonous Plants and Plant Toxins That Are Likely to Contaminate Hay and Other Prepared Feeds in the Western United States

Livestock poisoning by toxic plants is a relatively common problem in pastures and rangelands and it is estimated to annually cost the livestock industry more than $200 million. However, these estimates are for grazing animals and the total cost is probably much greater because many animals are poisoned by contaminated feeds. Many poisonous plants are accessible to grazing livestock, but they are generally avoided and are not eaten, or they are eaten at doses that they do not produce detectable disease. In such cases toxic plants may not be more than a problem of displacing desirable nutritious plants. However, this is not always the case, especially when toxic plants contaminate prepared feeds. Poisonous plants incorporated in preserved forages, such as hay and silage, are much more likely to be eaten. This may occur because of increased competition from herd mates or by increased feeding pressure as prepared feeds are most often used in winter when alternative food sources are exhausted. Alternatively, the plants may become more palatable as they are diluted with palatable feed or the previously distasteful plant components are altered during forage preparation or storage. In addition, normally safe forages, under certain conditions, can produce and accumulate toxins. Identifying these toxic contaminates and understanding when forages may be toxic is critical in reducing poisoning and ensuring quality animal products. Our objectives of this review are to present basic principles of identifying contaminated feeds and sampling forages, introduce several common forages that under certain conditions can be toxic, present a brief description of plants that we have found contaminating feed in the western United States, and review how to treat or avoid such poisonings. The Rangelands archives are made available by the Society for Range Management and the University of Arizona Libraries. Contact [email protected] for further information.Migrated from OJS platform March 202

Locoweed Poisoning in Livestock

The Rangelands archives are made available by the Society for Range Management and the University of Arizona Libraries. Contact [email protected] for further information.Migrated from OJS platform March 202

Neurologic disease in range goatsassociated with Oxytropis sericea (Locoweed) poisoning and water deprivation

About 200/2500 Spanish goats foraging on mountain rangelands of western Montana developed neurologic disease with severe rear limb weakness, knuckling of the rear fetlocks, and a hopping gait. Sick goats were of all ages and in good flesh, though they often had dull, shaggy coats. Some mildly affected animals recovered after being moved to feed lots, but others progressed to recumbency, seizures and death. At necropsy both moribund and clinically affected animals had few gross lesions; 1 animal had contusions and puncture wounds on rear legs and perineum, suggestive of predator bites. Histologic lesions included mild vacuolation of neurons and visceral epithelial cells, mild diffuse cerebral edema with minimal neuronal pyknosis, and random, multifocal Wallarian degeneration of spinal cord axons. Affected animals had elevated serum sodium, potassium and chloride levels; other mineral analyses and serum biochemistries were within normal limits. Locoweed-induced depression and inhibition of neuromuscular function coupled with water deprivation due to predation pressure allowed development of neurologic disease and hypernatremia

Respiratory Elimination ofSelenium in Sheep Given the Accumulator Plant Symphyotrichum spathulatum (WesternMountain Aster)

Selenium (Se) is a necessary mineral required by mammals and poultry. If toxic amounts are ingested, expired air becomes a potentially important, but poorly investigated, route of elimination. A study was performed to evaluate respiratory toxicokinetics of Se in sheep. Sheep were gavaged with the accumulator plant Symphyotrichum spathulatum at Se equivalent doses of 0, 2, 4, 6 or 8 mg/kg BW. As positive controls an additional two sheep were gavaged with purified sodium selenite at 4 mg Se/kg BW and two sheep were gavaged with purified selenomethionine (Se-Met) at 8 mg Se/kg BW. Expired air samples were collected prior to dosing and at 1, 2, 4 and 8 hrs post dosing. Samples were collected from both sheep in the control, selenite and Se-Met groups and from 4 sheep in each of the plant-Se treatment groups. The air Se concentrations of the Se-Met group were statistically higher (P \u3c 0.05) than all other groups at each time point of collection. The selenite, 2 and 4 mg plant-Se/kg BW groups all had peak concentrations at the 2 hr collection time. The 8 mg plant-Se/kg BW group showed a linear increase in respiratory Se concentration through 8 hours. The 6 mg plant-Se/kg BW group peaked at 1 hour, then dropped and peaked again at 4 hours and finally dropped between 4 and 8 hours. At 8 hours, the 8 mg plant-Se/kg BW group was significantly higher (P \u3c 0.05) than all other groups. The elimination profile for Se-Met was dissimilar to any of the other treatments, with greater than 20 times the concentration of Se in the expired air than the high dose plant Se or the selenite treatments. The 4 mg selenite and 4 mg plant Se had similar elimination profiles, although the 4 mg plant Se had significantly greater (P \u3c 0.05) concentrations at 2, 4 and 8 hrs. The total dose of the plant Se appreciably altered the elimination profile. These findings indicate that both dose and chemical form of Se affect respiratory elimination kinetics

The Toxicity and Kinetics of Larkspur Alkaloid, Methyllycaconitine, in Mice

Larkspur poisoning sporadically kills from 5 to 15% of the cattle on North American mountain rangelands. Of the 40 different diterpenoid larkspur alkaloids, the one that is thought to be responsible for much of the toxicity has been identified as methyllycaconitine (MLA). Little is known of MLA toxicokinetics or excretion. The purpose of this study was to further characterize the clinical effects of MLA toxicity in mice and determine the toxicokinetics of MLA excretion. Eight groups of mice were dosed intravenously with 2.0 mg/kg of BW of MLA, killed, and necropsied at 0, 1, 2, 5, 10, 15, 30, and 60 min after injection. Treated animals were reluctant to move, trembled, and developed dyspnea, muscular twitches, and convulsions. Within several minutes, the clinical signs abated and behavior slowly returned to normal over approximately 20 min. At necropsy serum, brain, liver, kidney, and skeletal muscle were collected and frozen. Blood and tissues were extracted and analyzed for MLA with HPLC and electron spray mass spectrometry. Blood MLA elimination followed a normal biphasic redistribution and excretion pattern (r = 0.99) with a K of elimination of 0.0376 and half-life of 18.4 min. Other tissues had similar clearance rates. These data indicate the MLA is rapidly distributed and excreted. In mice, the clinical effects of poisoning seem to affect the central nervous system, causing dyspnea and explosive muscular twitches and convulsions. Because livestock commonly eat larkspur at subclinical doses, they are likely to have larkspur alkaloids in many tissues. These results suggest that animals exposed to larkspur should rapidly excrete MLA (within several hours) and that the residues in animal tissues are not likely to be a problem if animals are given several days to allow toxin clearance

Impact of locoweed poisoning on grazing steer weight gains

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.The Journal of Range Management archives are made available by the Society for Range Management and the University of Arizona Libraries. Contact [email protected] for further information.Migrated from OJS platform August 202