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Selenium in Soil-Plant-Animal Systems: An Unresolved Issue in Georgia Uttam Saha, Leticia Sonon, Jason Mowrer, Dennis Hancock, Nicholas Hill, Gary Heusner,

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Presentation on theme: "Selenium in Soil-Plant-Animal Systems: An Unresolved Issue in Georgia Uttam Saha, Leticia Sonon, Jason Mowrer, Dennis Hancock, Nicholas Hill, Gary Heusner,"— Presentation transcript:

1 Selenium in Soil-Plant-Animal Systems: An Unresolved Issue in Georgia Uttam Saha, Leticia Sonon, Jason Mowrer, Dennis Hancock, Nicholas Hill, Gary Heusner, Lawton Stewart, and David E. Kissel The University of Georgia Athens, GA 30602

2 Talk Outline  Brief History of Se Research  Occurrence and Chemistry Se in Soils  Extraction, Speciation, and Bioavailability of Soil Se  Selenium in Animal and Human Nutrition  Status of Se in the US Grains and Forages  Selenium Supplementation in Livestock  Agronomic Biofortification of Se  Our Preliminary Survey of Se in GA Forages  Concluding Remarks

3  Discovery as a New Element: 1818, Jons Jakob Berzelius in Gripsholm, Sweden. He was looking for, and found, a toxic element that was contributing to workers’ illness in the acid plant  Commercial Use: 266 tons/year in US and 1,600 tons/year Worldwide  Biological Significance: Toxicity lameness and death in grazing livestock in Dakotas and Wyoming (Franke, 1934). Loss of hair and nails in humans in columbia (Father Pedro Simon in 1560) Essentiality Essential Nutrient: In 1957 (Schwarz and Foltz, 1957) Growth Response in Chicks: Alvin Moxon, a graduate student at South Dakota State University in the early 1930s Selenium and glutathione peroxidase: Rotruck et al., (1973) from Wisconsin and Dr. Flohé et al. (1973) from Germany Brief History of Selenium Research

4  Since 1973, the topic SELENIUM has been an entirely new era of research that continues today  Conor Reilly estimated in 1996 that Se had been the subject of over 100,000 published technical papers (Reilly,1996)  Today, a Google search for “selenium research” yields over 3.2 million web links History of Selenium Research

5 Selenium: A metalloid, with Properties of both Metal and Non-metal  Chemical Analog of S  Many Interrelations in Biology  Abundance of Se in the earth crust:  0.05-0.09 mg/kg  1/6000 th of S  1/50 th of As  50 Se minerals  Heavy metal sulfide (Ag, Cu, Pb, Hg, Ni)  Selenide  Seleno-sulfide Chemical similarity of Se (0.191 nm) and S (0.184 nm):

6 Common selenium concentration in selected materials (McNeal and Balistrieri,1989; Fordyce et al., 1998; Malisa, 2001)

7 Chemistry of Selenium in Soils  Parent materials: Cretaceous shales versus igneous rocks  Se speciation (Eh-pH): Se(VI), Se(IV), Se(0), Se(-II) -Well-oxidized vs. submerged soils -Acid vs. alkaline soils  Soil texture: Binding ability of clay  Mineralogy: Oxides vs. phyllosilicates  Competing ions: Sulfate and Phosphate  Organic matter: Binds Se Cretaceous Shales Se-Rich Soils Igneous Rocks Se-Deficient Soils Arid/Semiarid Climate Humid Climate/Irrigated

8 Eh-pH diagram of Se in soils (Mayland et al., 1989) H 2 SeHSe − 0 0 0 Se (-II): Selenides Se (+VI): Selenate Se (+IV): Selenite Se (0): Ground state SOIL Grassland Paddy Field H 2 SeO 4 0 HSeO 4 − SeO 4 -2 pK 1 -3.0 pK 2 1.70 H 2 SeO 3 0 HSeO 3 − SeO 3 -2 pK 1 2.61 pK 2 8.32 H 2 Se HSe − Se -2 pK 1 3.90 pK 2 11.0 Proton Dissociation Equilibria Redox Equilibria pe+pH >15: Selenate pe+pH = 7.5-15: Selenite pe+pH: <7.5: Selenide

9 Contrasting sorption behavior of selenite and selenate Outer-sphere Complex Inner-sphere Complex Note: Selenite is more toxic than selenate: Arch.Environ.Conta.Toxicol. 24:182-86 (1993)

10 Plant-Available Se in Soils Selenium is not an essential element for plant But the Se contents of plants are extremely important Roberts and Party (1942) Puerto Rico Soils: 1-10 ppm total Se Byers et al. (1938) Hawaiian soils: 6 to 15 ppm total Se Did not produce seleniferous vegetation Olsen et al. (1942) South Dakota Soils: ≥1 ppm total Se Ravikovitch and Margolin (1975) Israeli soils: ≥1 ppm total Se Did produce Se-toxic vegetation Total Se is not a reliable index of plant available Se

11 Plant-Available Se in Soils  Extractants Used: Hot Water, NH 4 HCO 3 -DTPA, CaCl 2, Ca(NO 3 ) 2 and K 2 SO 4  Water Extractable (1:5, Soil:Water, Boil 30 min) Se in Soils: US Soils: 50 ppb to 38 ppm, >80% had <100 ppb (Byers et al., 1938) 2-7% of the low total Se (0.19-0.74 ppm) in some Canadian soils (Levesque, 1974) 0.33-2.9% of high total Se (20-850 ppm) in some Irish soils (Fleming and Walsh, 1957)

12 Plant Available Se is Not Related to Total Se in Soil Maeta and Mizuno (1993)

13 Similar amounts of Se extracted by Hot Water and DTPA and were correlated with Se uptake by alfalfa (Soltanpour and Workman, 1980)

14 Efficacy of various extractants to estimate plant bio- available Se (Dhillon et al., 2005: Austr. J. Soil Res. 43:639) Included 15 soils with pH 7.67-8.22 & total Se, 2276±655 µg/kg Reference for Extrac. Proc.

15 Sequential Extraction Scheme: Various Operationally Defined Solid Phase Association of Soil Se (Chao and Sanzolone, 1989)

16 5 Fractions Keys 1. 0.25M KCl: Water-Soluble + Non-specifically Adsorbed Selenate: Highly Available 2. 0.1M K 2 HPO 4 : Exchangeable + Specifically Adsorbed Selenite: Available 3. 4M HCl: Oxide (Am and Cryst.)-, Carbonate-, Acid- volatile Sulfide-, and Hydrolyzable OM-Bound 4. KClO 3 + Conc. HCl: Sulfides- and Complex Humified OM-Bound 5. HF + HNO 3 + HClO 4 : Resistant Siliceous Materials- Bound Fractions Contrasting Distribution of Soil Se (Chao and Sanzolone, 1989) Hawaiian Soils California Soils ≈ 0.2 mg/kg ≈ 1.35 mg/kg

17 Various Operationally Defined Solid Phase Association of Se in a Soil Profile from Northeastern Wyoming (Sharmasarkar and Vance, 1994)

18 Humifide Organic Se Fractionation Scheme (Gustafsson and Johnsson, 1992)

19 Hydrophobic-Fulvate Fraction: Most Enriched with Se in A Podzolic Forest Soil (pH 4.0-4.7) of Sweeden (Gustafsson and Johnsson, 1992) C:Se ratios in plants: much higher; 30 x 10 6 : 1 in Swedish wheat (Lindberg & Bingefors, 1970) and even higher in Finnish Timothy grass (Sippola, 1979). 148 576 727 527 327 144

20 Organic C content: 6-9 g/kg; pH 6.9-8.0 %Extracted Organic-C by Alkaline pyrophosphate C:Se Atomic ratio in the alkaline pyrophosphate extract ¶ ¶ § § Organic Selenium Distribution in Selected California Soils Abrams et al. (1990) ppm Narrower C:Se than Swedish Forest Soil  Widely variable total Se &  Low OM content

21 Hydrophobic-Fulvate Fraction: Enriched with Se Also in Alkaline California soils (pH 6.9-8.0), Abrams et al. (1990) Selenomethionine Soldal and Nissen (1978) showed active plant uptake of methionine

22 Foods or feeds CO 2 + H 2 O + Energy Oxidation Reduction of O 2 + NFR: Nitrogen Free Radicals e.g., NO −  ROS and NFR damage living cells, notably their proteins, lipids (fat), and nucleic acids -Oxidative Damage  The glutathione peroxidase (GSHpx) family of selenoproteins (or enzymes) help to prevent the formation of ROS and NFR and also act as their Scavanger -Antioxidant activity  In mammals, 19 such selenoproteins have so far been recognized with known functions and all of them are enzymes (Behne and Kyriakopoulos, 2001) FUNCTIONS OF SELENIUM IN ANIMALS AND HUMANS ROS:

23 Interaction of Selenium with Vitamin E and other Nutrients Complementary  Vitamin E: Great partner, complements Antioxidant activity  Others: Sulfur containing amino acids, cystine and methionine; vitamin C; and synthetic antioxidant ethoxyquin Antagonists  Affect the absorption and metabolism of Se: S and Ca

24 Some Basic Statistics  US Livestock population: Over 3 billions  Consume 37 million tons of plant protein per year  Produce an annual 5.4 million tons of animal protein for human consumption  Over half of 37 million tons of plant protein supplied by forages QUANTITY AND QUALITY OF FORAGES ARE EXTREMELY IMPORTANT

25 General Ranking of Soil Se Level (Oldfield, 1972)

26 Selenium Deficient and Seleniferous Soils of US Se Deficient Soils: 20 States (<0.5 mg/kg total Se) New England New York New Jersey Delaware Pennsylvania Maryland West Virginia Florida Ohio Indiana Illinois Michigan Wisconsin Washington State Oregon Montana Arizona Coastal regions of Virginia, Carolinas, and Georgia South Dakota Montana Wyoming Nebraska Kansas Colorado New Mexico High Se soils or seleniferous soils: 7 States (2 to 10 mg/kg total Se) (Cary et al., 1967; NRC, 1983)

27 Recommended levels Se in various animal diets (NRC, 1994, 1998, 2000, 2001, 2007, Lewis, 1995) Note: FDA regulations (FDA, 1997, 2004, 2005) allows Se supplementation: up to 0.3 mg/kg complete diet, regardless of Forage Se content Not >3mg/head/day

28 *Based on the analyses of 709 forage samples from 678 producers from 23 cooperating states including 28 samples from Georgia (Mortimer, 1999). **Maximum Tolerable Concentration, 5 mg/kg. Selenium Contents of Various Forages: US Nationwide Study

29 Regional distribution of forage and grain Se content in the United States and Canada (NRC, 1983) Position of Georgia  Low: Coastline  Variable: Other Parts  Adequate: Nowhere

30 Selenium Supplementation 1.0 Inorganic Supplements 1.1 Diets: Both sodium selenite and sodium selenate  Total diet Se <0.3 mg/kg; Daily intake <3mg/head 1.2 Direct injection or oral drenching  0.1 mg Se per kg live body weight (LBW) 1.3 Ruminal placement Soluble glass boluses Iron-based heavy pellets Osmotic pump

31 2.0 Organic Supplement:  Organic Se-enriched yeast (e.g., Sel-Plex®, Altech, Inc, Nicholasville, KY): Cocktail; >50% Selenomethionine Selenium Supplementation Limitations of Inorganic Se Suppl.  A substantial portion of supplemented Na-Selenite is reduced in the digestive tract and excreted as selenide via manure  Inability to build and maintain Se reserves  Low efficiency of placental Se transfer, and transfer to milk, meat and egg  Potential toxicity via pro-oxidant activity  Na-selenite + vitamin C Se(0) + Oxidized Vitamin C

32 Sulfur, the Chemical Analog of Se: Interferes with the Se Biotransformation-How? Biotransformation: Replacement of S by Se  For example:  Methionine to Selenomethionine  Cysteine to Selenocysteine  Se is Biologically-active, can form direct Se–C bonds  Se-C bonds: many biomolecules, selenoamino acids and selenoproteins (25-30 known) +Se

33 Chemical Similarity of S and Se: Presence of High S Affects the Biological Activity of Se Plant uptake from soil  S-rich soil: Se uptake affected Biotransformation: Replacement of S by Se  For example: Methionine to Selenomethionine  Presence of High S in affects this in both plants and animals Methionine to Selenomethionine in Animals  Large intake of S-rich feed ( such as, molasses, beet pulp, cruciferous plants, and corn-distilling byproducts like corn gluten ) would result in: -poor utilization and -higher excretion of Se The high S in some Georgia soils and forages merits special attention while assessing the Se status in GA livestock Size: Se (0.191 nm) and S (0.184 nm)

34 Evaluate the Effectiveness of Se-Supplementation

35 Classification of cattle based on blood selenium content Dargatznd Ross, 1996: J Anim Sci. 74:2891-2895

36 Sampling: Study of Se Status in US Beef Cows and Heifers by Region Dargatz and Ross, 1996: J Anim Sci. 74:2891-2895

37 Selenium Status in US Beef Cows and Heifers by Region Dargatz and Ross, 1996: J Anim Sci. 74:2891-2895 41%61%

38 Transfer of Se: Dams to Calves  Two Common Selenium Deficiency Disorders in Calves in the Southeast (McDowell et al., 2002):  Buckling: Weakness of Rear Legs and Eventual Paralysis  Shoulder Lameness” or “Flying Scapula: Bilateral dorsal scapular displacement  Seriously reduce the profit margin of a stocker or feedlot operation (Pirelli et al., 2000)  So Placental Transfer of Se from the Dams to the Calves is Important

39 Whole blood Se concentration: Cows versus Calves at 205 d in a Feeding Expt. (Davis et al., 2005)


41 Biofortification of Se in Pastures and Forages  Genetic Biofortification: Crop varieties with enhanced Se- accumulation characteristics  Agronomic Biofortification: Through Se Fertilizers Se contents of some N & P fertilizer materials (White et al. 2004) Fertilizer MaterialsApprox. Se Content, mg/kg AS: (NH 4 ) 2 SO 4 36 Ureanil PR: Phosphate rocks55 SSP: Single Superphosphate25 TSP: Triple Superphosphate<4  Replacement of AS by Urea and SSP by TSP  Automatic fertilizer inputs of Se to soils have fallen

42 Selenium in organic manures from Se-supplemented Livestock (Sager, 2006) PBA Uncertain, Speciation Unknown Suspect Selenide form: Unavailable?

43 Successful Agronomic Biofortification of Se in Pastures and Forages

44 ITEM Se-Fertilized Hay (182 µg Se/kg) + No Se- Mineral Se-Unfertilized Hay (15 µg Se/kg) + Se-Mineral Hay intake, kg/d 13.112.9 Se intake from hay, mg/d 2.390.19 Se intake from Mineral Suppl., mg/d 0.004.09 Total Se intake, mg/d 2.394.28 Body wt. change (11/22/02-01/21/03) +25.3 kg+19.0 kg Blood Serum Se conc. (µg/L) Initial (beginning of trial, 11/22/2002): Final (at Calving, 01/21/2003): Calf within 24 h of birth: 32.3 50.1 88.4 (111 in whole Blood) 31.8 45.7 39.3 (49.1 in whole blood) Note: Grass+Alfalfa mixed hay field fertilized with Na-selenite @10g Se/ha Comp. Feeding Trial: Se-Fertilized Hay vs. Se-Mineral Suppl. with third Trimester Beef Heifers (Pulsipher et al., 2004; Oregon State Univ.)

45 Forage with <100µg Se/kg is deficient; with 200µg Se/kg or higher is adequate LOQ: Limit of Quantitation, which is 14 µg Se/kg, Half of LOQ values were assigned to the samples reading below LOQ for calculation of means and standard deviation (SD) Se Conc. in Some GA Forages (grown in 2008-09): Our Preliminary Study

46 Agronomic Biofortification of Food and Feed Crops Best Example: Finland Finnish Ministry of Agriculture and Forestry (1983)  Low dietary Se intakes (25-30 µg/head/day)  Agronomic biofortification program The primary goal was a 10-fold increase in Se conc. Se was incorporated into all multi-nutrient fertilizers used in agriculture from 1 July 1984 onwards at rates:  For grain production and horticulture 16 mg Se/kg  For fodder crop and hay production 6 mg Se/kg Results: More than 10-fold increase 16 June 1990 onwards: 16 mg Se/kg, 6 mg Se/kg continued In 1998: 10 mg Se/kg adopted and continued

47 Before Addition of Se in Fert. Se Added: @16 mg/kg and 6 mg/kg Reduced Se Addition by 60% for food crops Estimated Se Intake Finnish Population to Meet Daily Energy Need of 10MJ or 2400 Kcal/head/d Before and After Se Fert. Se-Rich US Wheat Import Increased Se Conc. in 125 Food & Feed Crops

48  Selenium is a vital micronutrient in animal nutrition  Few National level studies on Se in GA forages and grains: Deficient or Marginally Deficient in Se Many years old Inadequate to reflect the actual scenario in the state No data on soil Se  National level survey of state veterinary diagnostic laboratories: Categorized Georgia as a state of mild Se deficiency CONCLUDING REMARKS

49  No detailed information about the Se status in soils, crops, and animal nutrition across the state so far: What is the total Se levels in GA soils?  Parent materials  Soil forming factors  Soil properties What is the scenario of Se-speciation and bio-available Se in GA soils? What is the scenario of Se levels in GA grains and forages?  Soil type  Plant species  Growing season CONCLUDING REMARKS

50 What is the scenario of Se supplementation in GA Livestock Farms? What is the scenario of Se status in various animals?  With and without supplements  In relation to the type and extent of supplements What is the scenario of Se transfer to the calves CONCLUDING REMARKS OUR PRELIMINARY STUDY  All five forages severely deficient (17-28 µg Se/kg)  Se deficiency in GA may be an issue, much bigger than what was thought


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