111 research outputs found
Forage-induced animal disorders
Forages are a major source of nutrients for herbivores
around the world. In the United States and Canada about
110 million cattle, 7.4 million sheep, 1.4 million goats,
and 7.4 million horses depend on forages for all or part
of their nutritional needs (Table 45.1). Sometimes the
balance of nutrients or presence of some constituent in
the forage will have negative effects on animal health.
This chapter presents some of these forage-induced
health problems, including bloat, milk fever, grass tetany,
laminitis, nitrate poisoning, mineral imbalances, and effects
of toxic secondary compounds
Influence of Short-Term Glucocorticoid Therapy on Regulatory T Cells In Vivo
Background: Pre- and early clinical studies on patients with autoimmune diseases suggested that induction of regulatory T(Treg) cells may contribute to the immunosuppressive effects of glucocorticoids(GCs). Objective: We readdressed the influence of GC therapy on Treg cells in immunocompetent human subjects and naı¨ve mice. Methods: Mice were treated with increasing doses of intravenous dexamethasone followed by oral taper, and Treg cells in spleen and blood were analyzed by FACS. Sixteen patients with sudden hearing loss but without an inflammatory disease received high-dose intravenous prednisolone followed by stepwise dose reduction to low oral prednisolone. Peripheral blood Treg cells were analyzed prior and after a 14 day GC therapy based on different markers. Results: Repeated GC administration to mice for three days dose-dependently decreased the absolute numbers of Treg cells in blood (100 mg dexamethasone/kg body weight: 2.861.86104 cells/ml vs. 336116104 in control mice) and spleen (dexamethasone: 2.861.96105/spleen vs. 956226105/spleen in control mice), which slowly recovered after 14 days taper in spleen but not in blood. The relative frequency of FOXP3+ Treg cells amongst the CD4+ T cells also decreased in a dose dependent manner with the effect being more pronounced in blood than in spleen. The suppressive capacity of Treg cells was unaltered by GC treatment in vitro. In immunocompetent humans, GCs induced mild T cell lymphocytosis. However, it did not change the relative frequency of circulating Treg cells in a relevant manner, although there was some variation depending on the definition of the Treg cells (FOXP3+: 4.061.5% vs 3.461.5%*; AITR+: 0.660.4 vs 0.560.3%, CD127low: 4.061.3 vs 5.063.0%* and CTLA4+: 13.8611.5 vs 15.6612.5%; * p,0.05). Conclusion: Short-term GC therapy does not induce the hitherto supposed increase in circulating Treg cell frequency, neither in immunocompetent humans nor in mice. Thus, it is questionable that the clinical efficacy of GCs is achieved by modulating Treg cell numbers
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Review of toxic glycosides in rangeland and pasture forages
Ruminants are a diverse group of mammals, both domestic and wild species, that exhibit microbial fermentation prior to gastrointestinal activity. During the digestive process, glycosides and other natural products are exposed to ruminal microorganisms and metabolised as substrates. Most compounds are converted into nutrients but some become toxic metabolites. At least 10 types of toxic glycosides occur in forage species. Glycosides are characterized by the presence of one or more sugars linked to the alcohol or thiol functions of the non-sugar portion of the molecule, which is called the aglycone. The biological activity of the glycoside is usually determined by the chemical nature of the aglycone. The aglycones are released by microbial enzymes and may undergo further enzymatic or non-enzymatic transformations to yield toxic metabolites that can be absorbed from the gastrointestinal tract. Microbial detoxification of the aglycone is also possible. Further biotransformation of the aglycone can occur in the liver. A review is presented on glycosides that are toxic to ruminants. The discussion covers aliphatic nitrocompounds, cyanogenic glycosides, cardiac glycosides, saponins, glucosinolates, diterpenoid glycosides, bracken glycosides, calcinogens, phenolic glycosides and ranunculin. Clinical signs of poisoning and treatment of livestock as well as management strategies for the prevention of poisoning are considered.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
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Metabolism and absorption of toxic glycosides by ruminants
Paper presented at the "Symposium on Ingestion of Poisonous Plants by Livestock," February 15, 1990, Reno, Nevada.The cyanogenic glycoside prunasin is the toxic component in a number of browse species (serviceberry, Amelanchier alnifolia, and chokecherry, Pnmus virginiana); and glycosides of 3-nitropropanol (NPOH), such as miserotoxin, are the poisonous principle in a number of Astragalus species such as timber milkvetch, A. miser var. serotinus. Hydrolysis of the glycosidic bond in rumen contents is the first step in the bioactivation of the glycosides. Diet influences populations of rumen microorganisms and diet may induce the proliferation of bacteria that function in glycoside hydrolysis and detoxification. The absorption of NPOH from the reticulo-rumen was examined in cattle on alfalfa hay and corn silage diets. 3- nitropropionic acid (NPA), the lethal metabolite of NPOH, was detected in both plasma and urine. The plasma levels of NPA were reduced when the diet enhanced the rate of NPOH detoxification in the rumen. The enhancement was achieved with a feed supplement containing nitroethane, a synthetic analogue of NPOH that is much less toxic than the natural toxin. The high levels of NPA in urine (>30 ppm) suggested a procedure for detecting livestock poisoning by nitro-bearing plants. The absorption of hydrogen cyanide (HCN) from the reticulo-rumen was also examined in cattle given sublethal doses of prunasin from serviceberry. Metabolites of HCN in blood and plasma were detected at low levels (<5 ppm) during the initial 6-hour sampling period. High levels of thiocyanate (<20 ppm), a metabolite of HCN, were detected in urine samples collected at 24-48 hours and this also suggested a diagnostic procedure for detecting HCN poisoning in cattle.This material was digitized as part of a cooperative project between the Society for Range Management and the University of Arizona Libraries.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
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Alkaloid levels in a species of low larkspur and their stability in rumen fluid
A survey on the levels of the neurotoxic diterpenoid alkaloid methyllycaconitine (MLA) in low larkspur (Delphinium nuttallianum Pritz.) was conducted at rangeland sites in southern British Columbia. Freeze-dried plant samples representing vegetative, flower bud, and bloom stages of growth over 4 growing seasons were analyzed for MLA by high pressure liquid chromatography (HPLC). Differences in MLA concentration were found between sites (P 0.2). The vegetative stages of growth yielded the highest levels of MLA, approaching 1% of the dry matter at 1 site. On average, the reproductive stages of growth yielded half the amount of MLA as the vegetative stages. Differences in MLA levels between sites could not be attributed to the elevation or the weather during the growing season. It is suggested that topoedaphic effects may have an impact on low larkspur growth and toxicity. Preliminary results are also reported on the stability of MLA in bovine rumen contents. The alkaloid is not readily hydrolyzed in rumen contents and therefore is probably not detoxified by this pathway.This material was digitized as part of a cooperative project between the Society for Range Management and the University of Arizona Libraries.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
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Variability of Miserotoxin Concentration in Timber Milkvetch
The variability in miserotoxin concentration of 120 individual timber milkvetch plants was determined in the bud, flower, and pod stages of growth on rough fescue grassland, parkland, and Douglasfir zone locations. Although a broad dispersion in miserotoxin levels was evident within each sampling unit of ten plants, the grassland samples exhibited the greatest toxicity with an exceptional level (10.17 +/- 1.13%) occurring during the bud stage. The bud stage of the parkland samples yielded intermediate concentrations (5.22 +/- 1.18%) while forest plants contained lower miserotoxin levels (4.08 +/- 0.95% to 2.49 +/- 0.47%). A decline in miserotoxin levels occurred during the bud-to-pod interval at the grassland and parkland sites, but significant differences were not apparent between the progressive stages of growth at the forest locations. The timber milkvetch toxicity patterns based on the variability of individual plants confirmed previously described trends derived from composite sampling.This material was digitized as part of a cooperative project between the Society for Range Management and the University of Arizona Libraries.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
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Levels of a neurotoxic alkaloid in a species of low larkspur
A survey of the levels of the neurotoxic diterpenoid alkaloid methyllycaconitine (MLA) in low larkspur (Delphinium nuttallianum Pritz.) was conducted at 4 diverse rangeland sites in southern British Columbia. Freeze-dried plant samples representing 3 stages of growth over 2 growing seasons were analyzed for MLA by high pressure liquid chromatography. Significant differences were found among experimental sites (P0.2% on a dry weight basis) being associated with sites at higher elevations (900-975 m). At one site, an exceptional level of MLA (>0.3%) was observed during the flower bud stage of growth but in general the alkaloid levels remained fairly constant with advancing stages of growth. Measurement of the MLA concentrations in different plant parts revealed that reproductive parts contained higher levels of MLA than vegetative parts and this may well explain the increased toxicity of the upper portions of the plant.This material was digitized as part of a cooperative project between the Society for Range Management and the University of Arizona Libraries.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
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Miserotoxin Levels In Fertilized Astragalus miser var. serotinus
The effect of fall application of urea fertilizer on toxicity of timber milkvetch was examined in 2 growing seasons at 2 rangeland sites in southern British Columbia. On the grassland site, aerial application of urea at 100 kg N/ha did not affect levels of miserotoxin in timber milkvetch. At the forest clearcut site, 200 kg N/ha reduced toxin levels at later stages of growth in the first growing season. In the second year, however, an increase in the level of miserotoxin was detected at the clearcut.This material was digitized as part of a cooperative project between the Society for Range Management and the University of Arizona Libraries.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
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