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Plants containing high concentrations of selenium (Se) have long been recognized for their toxic effects on animals. Marco Polo, traveling in China in 1295, was probably describing signs of Se poisoning when he wrote that the hooves of his livestock became swollen and dropped off when they grazed plants growing in certain areas (Rosenfeld and Beath 1964). Loss of hair and nails in humans, presumably suffering from chronic Se ingestion was described in Colombia by Father Simon Pedro in 1560 [National Research Council (NRC) 1976, 1983]. Guang-Qi (1987) has also described and illustrated chronic selenium toxicosis in some Chinese people

In previous experiments, ruminants preferred evening-harvested (PM-alfalfa) over morning-harvested (AM-alfalfa) harvested alfalfa hay when given a choice. Therefore, could strategic use of PM-alfalfa fed as a pellet or included as a component of receiving diets stimulate naive sheep to increase DMI early in the receiving period? Experiments were conducted to 1) determine preferences of naive sheep for pellets prepared from PM- and AM-alfalfa, 2) measure performance of wether lambs fed pellets prepared from PM- and AM-alfalfa, and 3) measure performance and productivity of ewe lambs fed receiving diets formulated with PM- and AM-alfalfa. Pelleting PM-alfalfa resulted in pellets having similar (P > 0.05) palatability to naive sheep as pellets prepared from AM-alfalfa. Inclusion of PM-alfalfa in receiving diets fed to ewe lambs resulted in greater consumption of alfalfa stem fractions (P 0.76). Based on data from this study, strategic dietary use of pellets or hay prepared from evening-harvested alfalfa did not stimulate naive sheep to increase DMI. Lack of commonality between experiments reported herein and other research may be because 1) sheep cannot discriminate as well as other livestock between AM- and PM-alfalfa, or 2) pelleting or including in mixed diets masks sheep-preferred characteristics of PM-alfalfa. Based on the alfalfa hay used in these experiments, it was not advantageous to use pellets or hay prepared from evening-harvested alfalfa for the specific purpose of encouraging naive sheep to increase DMI.

The effects of land use and management practice on soil physical, chemical and microbiological properties may provide essential information for assessing sustainability and environmental impact. This study compared the effects of 41 years of no-tillage (NT) with continuous apple orchard, with those of conventional tillage (CT) with wheat–soybean rotation and another of puddling (PD) with continuous rice on the characteristics of a pumice Andisol in a temperate region of northern Japan. Higher values for bulk density, penetration resistance, pH, C/N ratio, exchangeable Na (X-Na), Fe, and Mn were observed for PD than NT and CT. On the other hand, organic matter, EC, N, exchangeable K (X-K), exchangeable Ca (X-Ca) and Cu were significantly higher for NT than CT and PD. Highest content of Zn was found in CT compared to other practices. The three-phase composition at pF 2.0 was significantly affected by land use and tillage practices. The solid phase and liquid phase were greater under PD than under NT and CT, while air phase was greater under CT than under NT and PD. Significantly higher values for saturated hydraulic conductivity was found in CT than NT and PD. Total phospholipid fatty acid (PLFA) and PLFA for bacteria, aerobes and cyanobacteria were remarkably higher in NT than CT and PD, regardless of depth. On the other hand, PLFA for methane-oxidizing bacteria, sulfate-reducing bacteria and mycorrhizae were significantly higher in CT than NT and PD. PLFA for fungi was significantly higher in surface (0–10 cm) soils than subsurface (10–20 cm) soils regardless of treatments. Highest bacterial and fungal diversity evaluated by DNA band number in DGGE analysis based on PCR amplification of 16S rDNA and 18S rDNA fragments, respectively, were observed in surface soil of PD. The result suggests a linkage between microbial community and tillage practices in temperate Andisol. This study also justifies the need of measuring soil characteristics based on soil microbial communities.

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.

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 50 mg Se/kg and more often contain

The Pathfinder Uranium Mine which is located in southeastern Wyoming, was actively mined during the 1960's-1980's. Reclamation involved returning the spoil/overburden and replacing the salvaged topsoil. The area was revegetated in 1974-1977, but was not grazed until 1980-85. A grazing experiment was then conducted to determine solubility of mineral elements in soil, uptake by plants and absorption by grazing animals. Blood sera were collected at 28-30 day intervals during the three grazing/growing seasons in 1980-1982. Blood sera samples were frozen and later analyzed by ICP. When compared to published data, plants on the reclaimed site contained lower concentrations of Ca, Mg, Mn, P, and Zn; but higher concentrations of Cd, Cr and Ni than plants on adjacent undisturbed sites. When compared to expected blood sera data, animals grazing on the reclaimed site had lower concentrations of B. Ca, Cu, Mg, and Na; but higher concentrations of Cr and Fe than would be expected for most grazing animals. Livestock producers are advised to provide supplements of Ca, Mg, Mn, P, and Zn to minimize deficiency of these elements in livestock nutrition when grazing these reclaimed lands.

We are investigating the biotransfer of accumulated Se by the plant in several phytoremediation systems. In study I, we evaluated the biotransfer of Se from Indian mustard, a Brassica species, to the insect-cabbage looper (Trichoplusia ni); mortality, deterrence, and biomagnification of Se were examined. We determined that feeding behavior of food chain consumers was affected not only by the plant concentration of Se, but also by the mobility of the insects and choice of feed available. In study II, we examined the survival and development of beet armyworm (Spodoptera exigua) fed Se-enriched plant tissues from different lines of saltbush (Atriplex spp.) After feeding on lines of saltbush that produced high biomass and accumulated high concentrations of Se, insect growth and survival was reduced. In studies III, IV, and V, lambs, dairy cows, and rabbits were fed Se-enriched Brassica and Medicago (alfalfa) plants as part of their feed ration. None of the tested animals exhibited any Se toxicity symptoms, but they had increased levels of Se in most tissues sampled (e.g., organs, blood, urine, feces), excluding milk. In study VI, we evaluated biotransfer of Se from broccoli to rats to determine efficacy of Se for reducing colon cancer. We found that Se-enriched plant material was more effective than inorganic sources of Se for preventing precancerous colon lesions. Results from all studies clearly show that Se absorbed by plants can be transferred biologically in an intentional or unintentional manner to insects and animals.

HiMag is an experimental cultivar derived from Missouri 96 (Mo96) and Kentucky 31 (K31) tall fescue (Festuca arundinacea Schreb.) parentage for increased calcium (Ca), magnesium (Mg), and reduced potassium (K)/ (Ca+Mg). Our objective was to determine productivity and mineral characteristics of endophyte-free (E-) HiMag in relation to standard tall fescue cultivars when grown in the Southern Piedmont Land Resource Area. In experiment 1, HiMag (E-) and K31 (E-) were grown at two levels of phosphorus (P), K, and lime additions to both severely eroded, and noneroded Cecil soil (clayey, kaolinitic, thermic family of Typic Hapludults). Herbage Ca and Mg were greater and K/(Ca+ Mg) and yield were less for HiMag than for K31. Phosphorus and K concentrations were not different. Herbage yields, P, Ca, and Mg concentrations were increased by P, K, and lime additions. In experiment 2, HiMag(E-), K31(E-), endophyte-infected K31(E+), Mo I(E+), Mo II (E+), and AU Triumph (E-) were planted either in a prepared seedbed or planted without tillage into the Cecil soil. HiMag yields were not different from Mo-I, Mo-II or K31(E±), but were less than

PANTER, K. E., HARTLEY, W. J., JAMES, L. F., MAYLAND, H. F., STEGELMEIER, B. L., AND KECHELE, P. O. (1996). Fundam. Appl. Toxicol. 32, 217-223. 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-met hionine 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-DL-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. Field observation and experimental trials in the United States have shown a great variety of syndromes and pathology resulting from ingestion of certain species of Astragalus by livestock. The syndromes include disease conditions induced by the nitro-containing Astragalus (A. miser), the swainsonine-containing Astragalus (A. lentiginosus, locoweeds), and the selenium-containing Astragalus (A. bisulcatus). These syndromes have been reviewed by James et al. (1981). Two Se-accumulating plants (A. bisulcatus and A. praelongus) and inorganic Se compounds have been shown to produce neurological signs and microscopic lesions of focal symmetrical polioencephalomalacia and poliomyelomalacia when fed to young pigs (Hartley et al., 1984). Both plant species also contain small amounts of swainsonine, an amannosidase inhibitor that causes the lesions and clinical syndrome known as locoism. This toxin might contribute to the development of lesions when animals are poisoned eating these plants. In previous studies of Se intoxication, organic Se was fed to growing pigs in the form of selenocystine . The animals failed to thrive and had varying degrees of hepatic fibrosis, but neither neurological signs nor histological lesions were seen in the central nervous system (Hartley et al., 1984). The biochemical parameters of some of these pigs have been reported (Baker et al., 1989). This report details additional trials including dosing with seleno-DL-methionine (organic form of Se) and a comparison of the resulting tissue Se and histological lesions with those seen in animals treated with sodium selenate (inorganic form of Se) or A. bisulcatus (nonprotein, water-soluble plant forms of Se) at the same Se dose.

High soluble‐sulfate (SO4) concentrations affect water quality, soil chemistry, plant sulfur (S) levels, and possibly ruminant‐animal health. The objective of this greenhouse pot study was to determine the potential for accumulating high levels of S by tansy mustard (Descurainia pinnata (Walt.) Britton), kochia (Kochia scoparia L. Schrad.), yellow sweet clover (Melilotus officinalis L.), slender wheatgrass (Elymus trachycaulus (Link) Gould ex Shinners), and sunflower (Helianthus annuus L.). Plants were grown on both a Brinegar (fine‐loamy Ultic Argixeroll) and Portneuf (coarse silty Durixerollic Calciorthid) soil. Each species received five‐SO4 levels. The saturation extract electrical conductivity (EC) of the cropped soils ranged from 6 to 16 dS/m, while the soluble SO4 varied from 16 to 200 mmolc/kg soil. Soil solutions were saturated or very nearly saturated with respect to gypsum at the conclusion of each study. Plant dry matter yield, except of grass growing on the non‐calcareous soil, was n...

Canola (Brassica napus) grown as a selected plant species for field phytoremediation of selenium (Se) may be harvested and utilized as Se-enriched forage for marginally Se-deficient lambs and cows. Two field studies were conducted under controlled conditions to evaluate the accumulation of Se into different animal tissues, including blood, excreta, and milk. In Study 1, treatments consisted of feeding lambs freshly cut Se-enriched canola (containing approximately 4 mg Se kg(-1) DM) or control canola (containing

Selenium (Se) occurs in various forms in soils, including inorganic selenite and selenate and organic selenomethionine. Plant uptake of the inorganic, but not the organic forms, has been studied extensively. Organic-Se uptake was therefore examined in two-grooved milkvetch (Astragalus bisulcatus (Hook.) Gray), a Se-accumulating forb, and western wheatgrass (Pascopyrum smithii (Rydb.) Love), a non-Se accumulating grass. Plants were grown for 56 days in nutrient culture enriched with 1 or 2 mg Se liter-1 as sodium selenite or 0.3 or 0.6 mg Se liter-1 as Se-DL-methionine or Se-DL-cystine. Growth was not affected by the Se treatments. Selenium concentrations in shoots were proportional to nutrient-solution concentrations for both species grown in sodium selenite and selenocystine, and for wheatgrass when grown in selenomethionine. Selenium concentrations in milkvetch were not increased by the higher concentration of selenomethionine. Shoots of milkvetch, growing in the low-Se treatment contained 243, 283, and 47 micrograms Se g-1, for the sodium selenite, selenomethionine, and selenocystine treatments, respectively, whereas values for the wheatgrass were 20, 32, and 17. Shoot:root Se concentrations were 1.2, 0.7, and 0.4 in milkvetch and 0.1, 0.5, and 0.1 in wheatgrass for the sodium selenite, selenomethionine, and selenocystine, respectively. Selenium is more readily transported to shoots in the accumulator plant, or conversely; there is a barrier to Se movement to shoots in the nonaccumulator plant. Wheatgrass contained sufficient Se to be of concern in animal toxicosis and because of greater dry matter yield accumulated as much or more Se than did the milkvetch.

Grass tetany (hypomagnesemia) may be an important factor limiting productivity of animals grazing Russian wildrye [Psathyrostachys juncea (Fisch.) Nevski]. This malady is associated with relatively low concentrations in the forage of Mg and Ca, and high values for K and K/(Ca+Mg). We studied the genetic variablity in a Russian wildrye breeding population for mineral elements that relate to grass tetany in ruminants. Forty-five progeny lines, established as spaced plants in a randomized complete block, were sampled at the pre-boot and boot stages in each of 2 years and analyzed for Mg, Ca, K, and P. Although seasonal variation was evident, K/(Ca+Mg) of the progeny lines ranged from 3.2 to 4.6, well above the 2.2 level at which a 5% incidence of grass tetany has been found in dairy cattle. With few exceptions, progenies differed for all traits evaluated. Differences among progenies were relatively consistent over harvests for all traits. A reduced tetany potential (RTP) was computed as the sum of normalized Mg and reciprocal of K/(Ca+Mg) values, providing an estimate of the grass tetany risk for individual progeny lines. The variation among progenies, and the magnitude of broad-sense heritability estimates for RTP (0.48) and K/(Ca+Mg) values (0.31), indicate that mineral ion composition of this breeding population can be altered through breeding. The high K/(Ca+Mg) values in the population suggest that it may be helpful to introduce genetic factors conditioning lower grass tetany potential from other sources. Intercharacter correlations suggest that breeding for higher levels of Mg will be accompanied by increased Ca and, to a lesser extent, increased K.

The level of soluble tissue phosphorus (PO4‐P) may be correlated with the plant P nutritional status, but the amount extracted depends upon dry matter losses or the amount of enzymatic or heat—induced hydrolysis of organic P compounds during sample drying. Alfalfa (Medieago sativa L) and sugarbeet (Beta vulgaris L) plant parts grown under low and high soil P conditions, were freeze‐dried or oven‐dried at 40, 56, 70, or 100 C. Total K, P, and 0.35 N acetic‐acid‐soluble P (measured as PO ‐P) were determined. Dry matter losses were 0, 6.5, 3.6, 5.5, and 4.9 percent for the respective drying methods. The total‐P values, once corrected for dry matter losses, were not affected by the drying methods. The corrected PO4‐P values were 0.15, 0.17, 0.16, 0.16, and 0.19 percent, while the (PO4‐P)/P values were 0.63, 0.69, 0.67, 0.68, and 0.78 for each of the respective drying methods. The potential utility of extractable PO4‐P in describing the plants’ P nutritional status will depend upon rigorous sampledryi...

Grass tetany, a Mg deficiency of ruminants, accounts for significant economic losses to Western cattlemen during the spring grazing period on Agropyron desertorum. This nutritional deficiency may also occur when ruminants graze other temperate grasses, but the soil-plant-animal factors leading to the problem are not well understood. The objective of this study was to provide definitive data relating seasonal changes in the chemical composition of forage to the occurrence of grass tetany on semiarid grasslands. The field experiment was established on two calcareous soils where grass tetany had previously occurred. Agropyron desertorum forage was harvested from both sites at regular intervals during the spring tetany period in each of 5 years. The forage samples were analyzed for mineral elements, N, total water-soluble carbohydrates (TWSC), higher fatty acids (HFA), ash alkalinity, and aconitic acid. High levels of N and HFA, which are known from other studies to reduce Mg availability to the animal, coincided with the occurrence of tetany. The low Mg concentrations measured in the forage probably provided only marginal levels of available Mg to the grazing animals. A rapid increase in the ratio of N/TWSC coincided with the onset of tetany, and may be the primary factor which indirectly decreases Mg availability and precipitates the occurrence of tetany. Although the relationship of the protein/energy imbalance to grass tetany has been suggested previously, as far as the authors are aware this is the first time that N/TWSC values obtained during the growing season have been documented in conjunction with the occurrence of grass tetany.

The hypothesis that excess dietary selenite ameliorates lead (Pb) toxicosis in domestic sheep was tested. Twenty 6–8-yr-old ewes fed alfalfa pellets were assigned to the following treatments: (1) control; (2) 9.8 mg Pb/kg body weight (b.w.)/d as PbCO3; (3) 3 mg Se/animal/d as Na2SeO3·5H2O; or (4) a combination of treatments 2 and 3. The gelatin-encapsulated salts were given orally. The study was terminated on d 104, by which time three animals in the Pb group and all five animals in the Pb+Se group had died. All remaining animals were slaughtered on d 104. Lead and Se concentrations were determined in six biweekly-collected blood samples and in soft tissues and bone. Sheep on the control and Se treatments had similar feed intakes, body weights, and tissue Pb levels. Those in the Pb+Se group had lower feed intake, but higher blood Pb values compared with the Pb group. Feeding either element increased (P

Publisher Summary Freezing injury in plants represents a major economic loss to agriculture. Early research on freezing phenomena in plants centered on plant selection and classification according to their ability to become cold hardy and survive freezing temperatures. Recent work has centered on the differentiation between plants with or without the ability to harden. This chapter concentrates on the effects of low-temperature stress on cell membranes and other macromolecules in the cell and relates these to the overall plant response to chilling or frost injury. The freezing temperature of plant material is determined by the chemical potential of the plant water. The freezing point drops approximately 1°C for each 12 bars equivalent negative pressure (in the range of 0 to -10°C). Ice does not form spontaneously as the temperature drops to the freezing point of the plant water. Rather, the solution tends to undercool to variable and somewhat unpredictable temperatures. When nucleation does occur, it will generally be in the extracellular space. When tender plants show immediate frost injury from temperatures not lower than -3 or -4°C, the damage is caused primarily by ruptured cell membranes. Some nonhardy plants, such as peas and lettuce, can survive temperatures of -3 or -4°C for a few hours, even though ice is present in the plant tissue.

Buring at 10-15-year intervals has been recommended in the warm, grand fir (Abies grandis)-myrtle pachistima (Pachistima Lochsa River of northern Idaho (Leege 1979). Spring and autumn burning generally promote sprouting of most shrub species in this community and produce valuable browse (Leege and Hickey 1971, Wright 1978). Fire is also a valuable tool in shrub and timber management in the more xeric ponderosa pine (Pinus ponderosa)-common snowberry (Symphoricarpos albus) communities (Davis et al. 1980). Effects of fire on production and mineral content of shrubs in this community have not been documented.

Increasing available Mg in crested wheatgrass (Agropyron spp.) could reduce the incidence of grass tetany (hypomagnesemia) in ruminants grazing this forage. Raising the Mg levels might be done through genetic processes if enough variation in ion concentration existed in the Agropyrons. The purpose of this study was to determine the genetic variation in Mg, Ca, and K concentrations in 2 crested wheatgrass populations. Parent plants were vegetatively propagated to provide 6 replicates each of 12 clones of crested wheatgrass (A. desertorum) and 16 F3 clones of colchicine-induced tetraploid A. cristatum X natural tetraploid A. desertorum. Each plant was selected on a basis of seedling and mature plant vigor, forage, and seed yield, leafiness, resistance to pests, and response to environmental stress. The 2 populations were grown in separate, space-planted nurseries at Logan, Utah. Herbage was harvested at the pre-boot and early flowering stage in each of 2 years. Magnesium and Ca were determined by atomic absorption and K by flame emission. A reduced tetany potential (RTP) index for each clone was calculated as the sum of normalized Mg and (Ca+Mg)/K values. Significant (P & 0.01) differences for all traits were detected among clones in each population. All traits, except K and RTP, were closely correlated. Broad-sense heritability values for most traits ranged from 0.61 to 0.84. Enough genotypic variation existed in both populations to warrant breeding lines with higher concentrations of Mg and larger RTP values. Such changes could reduce the incidence of grass tetany in livestock grazing crested wheatgrass.

Grass tetany (hypomagnesemia) frequently occurs from March through June in cattle grazing crested wheatgrass in western United States. High levels of trans-aconitate and/or citrate, K, K/(Ca + Mg) ratios and low Mg in the grass are implicated in the etiology of the disease. In the moist 1967 season, during periods of "flush" growth following warming trends, trans-aconitate and K increased while Ca and Mg decreased in crested wheatgrass. These characteristics may explain the incidence of grass tetany during periods of "flush" growth. During the dry 1968 season, these trends were not observed. Growth chamber studies confirmed some of the reasons for changes in crested wheatgrass composition observed in 1967 and 1968.

Nitrogen availability, as shown by short-term uptake by barley, was significantly higher on soils from burned than from unburned areas 10 months after burning. Increased soil-nitrogen concentrations were observed at all depths on the burned as compared with the unburned treatment.

An apparatus has been designed and tested for measuring area of detached leaves of all shapes. The apparatus is easy to operate and gives accurate results rapidly. Measurement variability is generally less than 1%.