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Toxic Rangeland Plants ~ To Eat or Not to EatREM 456 –University of Idaho --- Karen LaunchbaughAnti-Quality & Toxic Agents1) Compounds Resistant to DigestionLignin, silica, tanninsMost common defenses in grassesDecrease positive feedback (i.e., reduce palatability)2) Inhibit DigestionKill rumen microbesLike, essential oils in sagebrush or pineBind nutrients making them indigestibleLike tannins that bind proteins3) Compounds that are “Toxic”What is a “Toxic” Plants?Plant that causes negative digestive or physiological effect. What effects do toxic plants have?DeathBirth Defects (called “Teratogenic” effects)Reproductive DysfunctionBloatDermatitis and Skin Sores Neurological EffectsEtc., etc., etc.How animals avoid toxic plants? Animals learn based on consequences Skin Defense SystemsCauses Pain276987013335028098751000125Gut Defense SystemCauses Nausea Skin Defense System:Gut Defense System:Why do plants make “toxins”?Anti-microbialAnti-herbivore insects and mammalsAnti-plant called allelopathy To mediate environmental extremesUV RadiationLow temperatureMoisture stressOften called “Secondary Compounds”Primary metabolism contributes to growth and reproductionSecondary metabolism does not lead to growth and reproduction… often producing toxins.Excessive primary metabolites (like nitrates) can also be toxic.Toxicity depends on Plant Attributes Phenological stage (or stage of development like bolting, flowering, etc.) Ecological site or soil nutrient levelsWeather (e.g., frost or high temperature) Environmental stress (e.g., drought) Plant part (e.g., leaves may be more toxic than stems or other parts) Toxicity depends on Animal Attributes Amount eaten“The poison depends on dose”Animal speciesRumen microbesLiver activityCellular enzymesOther plants in the dietSome plants cancel each other outOther combinations become more toxicHormonal stateBody conditionToxic Agents in PlantsAlkaloidsMost powerful of toxic plant substances caffeine, morphine, codeine, heroine, cocaineOften toxic in small quantitiesRemain toxic as plant matures or freezesCauses nervous disordersNegative reinforcement in skin-defense system (cause pain or sensitivity)Often don’t make animals sick so they eat a lot of plants containing alkaloidsPlants that contain AlkaloidsLupinesLocoweedsLarkspursBitterweedWater hemlockGlycosidesNaturally occurring compounds found in many rangeland plants and foragesBlock oxygen transport and release in bloodCan be highly toxic even causing deathDon’t usually provide a negative post digestive feedback Highly variable in time and space - Careful management to prevent high ingestion levels Plants that contain GlycosidesJohnson grassChoke cherryMountain-mahoganyBur buttercupWhite clover ServiceberryNitratesNitrates accumulate in plants under certain conditions:High nitrogen soilsDroughtLow light conditionsTreatments with some herbicides (i.e. 2,4-D)Block ability of blood to carry oxygenDoesn’t usually cause illness leading to aversionsPlants that contain NitratesCareless weedRussian thistle Silverleaf nightshadeKochiaSoluble OxalatesAffect the nervous systemMostly toxic to sheep (only occasionally toxic to cattle)Plants that contain OxalatesHalogeton Greasewood TanninsReduce protein digestionDon’t cause nausea leading to aversions accept at very high levelsDecrease weight gain because of decreased protein availabilityLethal at high quantities – not common but can occur such as does in “oak poisoning”Plants that contain TanninsMost oak-brushes Blackbrush MulesearEssential Oils or TerpenesGive distinctive odor to plant (an essence)Kill rumen microbes (i.e. “pine-sol effect”)Can cause illness and nauseaDecrease weight gainLethal in high quantitiesPlants that contain Essential OilsSagebrush Juniper PineCompounds that cause PhotosensitizationCauses swelling of head and ears.Sloughing of skin when exposed to sun.Prevents liver ability to breakdown certain pigmentsCan cause deathDoes not generally cause illness that could lead to conditioned flavor aversions.Plants that cause PhotosensitizationSt. John’swort Horsebrush Plants substances causing DermatitisToxins that are poisonous upon contactAffect skin defense systemRarely lethal but cause production lossesPlants causing DermatitisPoison ivy Poison sumac Poison oak Preventing Animal PoisoningProvide adequate supply of good forageProvide salt and mineralsDon’t put hungry animals in pastures with abundant toxic plantsBe careful when introducing animals to new pasturesBe aware of conditions that create toxic plants and where toxic plants are locatedPreventing Animal PoisoningConsider removing animals from pastures that have been treated with herbicidesGraze pastures in seasons when poisonous plants are least toxicPrevent introducing toxic plants or try to control toxic plantsUse the correct animal species ................
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