Chapter G: Selenium poisoning in livestock

Selenium in certain soils may be taken up by plants in amounts sufficient to make forage toxic to animals. Seleniterous forage can be found in semiarid areas on soils typically derived from Cretaceous geologic material in the Western United States and Canada. Intoxication of livestock by seleniterous plants has been classified as acute or chronic. Acute poisoning results from consuming plants containing high selenium concentrations. Chronic selenium poisoning has been described in two forms: alkali disease and blind staggers. Alkali disease results from prolonged ingestion of plants containing, 5-40 ppm selenium in inorganic or organic forms. Alkali disease causes loss or hair, lameness, weight loss and probably reduces reproductive efficiency . Blind staggers is said to result from the consumption or selenium indicator plants. These plants, in contrast to the nonaccumulators, contain selenium in water soluble, nonprotein forms. Blind staggers causes animals to wander, walk in circles, and to have difficulty in swallowing; in addition, it may cause blindness. Information is presented that questions the attribution of blind staggers to selenium toxicosis

Reproductive response of ewes fed alfalfa pellets containing sodium selenate or astragalus bisulcatus as a selenium source

Selenium fed to open cycling ewes in the form of sodium selenate or Astragalus bisulcatus (a selenium accumulator plant) at 24 or 29 ppm selenium, respectively, in alfalfa hay pellets did not alter the estrous cycle length, estrus behavior, progesterone or estrogen profiles, pregnancy rate or outcome of parturition (P>0.05). There was wool loss in some ewes fed seleniferous pellets and the mean whole blood selenium levels were 0.45, 1.3 and 2.4 ppm, respectively, for control, A bisulcatus and sodium selenate; however, ewe condition and appearance remained good. All lambs appeared normal and the number of lambs born and the individual and total lamb weight averages were not significantly (P>0.05) different between treatment groups and control group

Selenium in seleniferous environments

Selenium is biologically important because (i) it is essential in animal and possibly plant metabolism, (ii) in many areas diets do not contain sufficient Se to meet animals' needs, and (iii) in other areas it is toxic to animals when it occurrs in high concentrations in soil, water, plants, fly ash, or in aerosols. Animals require 0.05 to 0.1 mg Se/kg in their diets to prevent Se deficiency but suffer Se toxicosis when dietary levels exceed 5 to 15 mg Se/kg. The earth's crustal materials generally contain <0.1 mg Se/kg. Higher concentrations are found in Cretaceous shales. The Se-accumulator plants growing on the seleniferous soils may contain hundreds or even thousands of mg Se/kg. However, the nonaccumulator grasses and forbs seldom accumulate >50 mg Se/kg and more often contain <5 mg Se/kg. Soils and plants may discharge volatile forms of Se into the atmosphere. However, plants may also absorb measurable amounts of gaseous Se from the atmosphere. Anthropogenic activities impact the amount of Se entering our nation's lakes, rivers, and the atmosphere. Combustion of coal and incineration of municipal waste exhaust Se into the environment. In addition, crop-fallow and irrigation practices that allow leaching waters to pass through seleniferous strata prior to intersecting with surface flow, augment the Se levels encountered by plant and animal life

Selenium poisoning in livestock: a review and progress

Selenium in certain soils may be taken up by plants in amounts to render them toxic. Seleniferous forage can be found in most of the western states. Intoxication of livestock by seleniferous plants has been classified as acute and chronic. Acute poisoning results from consumption of plants having high levels of Se; chronic Se poisoning has been described in two forms— alkali disease and blind staggers. Alkali disease is said to result from the consumption of seleniferous grains and grasses, and is manifest by loss of hair, lameness, and loss of weight. Blind staggers is slid to result from the consumption of Se indicator plants and is manifest by wandering, circling, loss of ability to swallow, and blindness. Some research casts doubt on the above classification of Se poisoning. Research using pigs (Sus scrofa domesticus) indicates that the source of Se does not alter the type of lesion or signs of poisoning observed. There are data available that suggest that blind staggers is not related to Se poisoning

Comparative toxicity of selenium from seleno-DL-methionine, sodium selenate, and Astragalus bisulcatus in pigs

Selenium is an essential micronutrient, although ingestion in excess in pigs can cause disease conditions including neurological dysfunction and chronic skin and hoof lesions. Controlled feeding trials in growing swine, using the same Se content in feed sources, resulted in higher concentrations (p 0.05) of Se in blood and organs of pigs fed seleno-DL-methionine compared with those receiving Astragalus bisulcatus or sodium selenate. Clinical signs of Se toxicity including neurological signs of paralysis were more severe and occurred sooner in the A. bisulcatus group than in the sodium selenate or seleno-DL-methionine groups. All five pigs fed A. bisulcatus developed neurological signs of paralysis, and in four the signs occurred within 5 days of the start of treatment. Four of five pigs fed sodium selenate also developed paralysis, but this occurred 4 to 21 days after treatment began. The fifth pig in the group developed signs of chronic selenosis. Two of five pigs fed seleno-DL-methionine developed paralysis on 9 and 24 days, respectively, and the remaining three developed chronic selenosis. Selenium fed to pigs in three forms [plant (A. bisulcatus), sodium selenate, or seleno-DL-methionine] resulted in neurological dysfunction and lesions of symmetrical poliomyelomalacia. These were most severe in the A. bisulcatus group, which also had polioencephalomalacia. Although seleno-m-methionine caused the greater increase in tissue and blood Se concentrations, this did not correlate with severity of pathological changes, since animals fed A. bisulcatus developed more severe and disseminated lesions

Selenium poisoning in cattle (Chapter 74)

Selenium is readily absorbed by all plants. However certain soils contain selenium in amounts and forms that render some plants toxic to animals, plants have been divided into two groups according to their ability to accumulate selenium: (i) primary selenium-accumulators or indicator plants, which include species of the Astragalus, Haplopappus and Stanleya genera. These plants accumulate low molecular weight, water soluble organic compounds and selenate (Anon., 1980) to give selenium levels of 50 to several thousand mg kg-1; and (ii) non-accumulator plants which include grasses, shrubs, small grains, alfalfa and some forbs. These plants usually accumulate less than 50mg kg-1 (generally 5-12mg kg-1) selenium as organic forms in plant proteins. Selenium poisoning in livestock most frequently involves these non-accumulator plants

Avaliação da toxicidade das favas de Stryphnodendron fissuratum (Mimosoideae) em vacas gestantes

Com o objetivo de avaliar a toxicidade de diferentes concentrações das favas de Stryphnodendron fissuratum em vacas prenhes, as favas desta árvore foram moídas, misturadas à ração comercial e fornecidas a oito vacas nas doses totais de 6,5g/kg, 7,5g/kg, 9g/kg e 10g/kg. Os animais que receberam doses de 6,5g/kg pariram bezerros normais e aqueles que receberam 7,5g/kg pariram bezerros fracos que não sobreviveram. Doses de 9g/kg resultaram no nascimento de um bezerro imaturo e de outro bezerro com distiquíase, opacidade congênita das córneas e microftalmia. Ambas as vacas que ingeriram 10g/kg morreram, porém uma vaca abortou antes de morrer. Nas vacas que morreram, as lesões macroscópicas e histológicas do sistema digestivo e fígado foram semelhantes às descritas anteriormente na intoxicação por S. fissuratum. Nos bezerros e no feto abortado não foram observadas lesões macroscópicas ou histológicas significantes. A análise fitoquímica dos extratos metanólicos das favas de S. fissuratum revelou a presença de taninos hidrossolúveis, proantocianidinas, leucoantocianidinas e da saponina triterpénica β-amirina. Saponinas triterpénicas têm sido associadas com a toxicidade das favas de Stryphnodendron spp. e Enterolobium spp., que causam sinais clínicos semelhantes aos observados na intoxicação por S. fissuratum. Esta pesquisa confirmou a toxicidade das favas de S. fissuratum para bovinos, no entanto não foram confirmados os efeitos abortivos das mesmas, pois o aborto e as mortes neonatais observadas podem ser decorrentes dos efeitos tóxicos da planta nas mães. Novas pesquisas são necessárias para pesquisar se as favas da planta causam malformações semelhantes às observas em um dos bezerros nascidos vivos