Selenium in Soil-Plant-Animal Systems: An Unresolved Issue in

GeorgiaUttam Saha, Leticia Sonon, Jason Mowrer,

Dennis Hancock, Nicholas Hill, Gary Heusner, Lawton Stewart, and David E. Kissel

The University of GeorgiaAthens, GA 30602

Talk OutlineBrief 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

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 plantCommercial 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

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

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/kg1/6000th of S1/50th of As

50 Se mineralsHeavy metal sulfide (Ag, Cu, Pb, Hg, Ni)

SelenideSeleno-sulfide

Chemical similarity of Se (0.191 nm) and S (0.184 nm):

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

Malisa, 2001)

(World mean: 0.4)

Chemistry of Selenium in SoilsParent materials: Cretaceous shales versus igneous rocksSe speciation (Eh-pH): Se(VI), Se(IV), Se(0), Se(-II)

-Well-oxidized vs. submerged soils

-Acid vs. alkaline soilsSoil texture: Binding ability of clayMineralogy: Oxides vs. phyllosilicatesCompeting ions: Sulfate and PhosphateOrganic matter: Binds Se

Cretaceous Shales Se-Rich Soils

Igneous Rocks Se-Deficient Soils

Arid/Semiarid Climate

Humid Climate/Irrigated

Eh-pH diagram of Se in soils (Mayland et al., 1989)

H2Se HSe−

0

0

0

Se (-II): Selenides

Se (+VI): Selenate

Se (+IV): Selenite

Se (0): Ground state

SOIL

Grassland

Paddy Field

H2SeO40 HSeO4

− SeO4-2

pK1

-3.0

pK2

1.70

H2SeO30 HSeO3

− SeO3-2

pK1

2.61

pK2

8.32

H2Se HSe− Se-2pK1

3.90

pK2

11.0

Proton Dissociation Equilibria

Redox Equilibria

pe+pH >15: Selenate

pe+pH = 7.5-15: Selenite

pe+pH: <7.5: Selenide

Sorbent

Selenite Selenate

ReferenceSorption mechanism

•Behaves like phosphate

•Strongly sorbed

•Inner-sphereBidentate

•Behaves like sulfate

•Weakly sorbed

•Outer-sphere

Science 238:783-86, 1987

SSSAJ 64:101-11, 2000

Soils, individual soil components, or spcimenminerals

Am-Fe(OH)3 &Goethite

SSSAJ 52:954-58, 1988SSSAJ 53:70-74, 1989

SSSAJ 51:1161-65, 1987

J .Soil Sci. 40:17-28, 1989Env.Sci.Tech. 24:1848-56, 1990

•Inner-sphereBidentate

•Inner-sphereBidentate

Contrasting sorption behavior of selenite and selenate

Outer-sphereComplex

Inner-sphereComplex

Note: Selenite is more toxic than selenate: Arch.Environ.Conta.Toxicol. 24:182-86 (1993)

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 SeByers et al. (1938) Hawaiian soils: 6 to 15 ppm total Se

Did not produce seleniferousvegetation

Olsen et al. (1942)South Dakota Soils: ≥1 ppm total SeRavikovitch and Margolin (1975)Israeli soils: ≥1 ppm total Se

Did produce Se-toxicvegetation

Total Se is not a reliable index of plant available Se

Plant-Available Se in SoilsExtractants Used: Hot Water, NH4HCO3-DTPA,

CaCl2, Ca(NO3)2 and K2SO4

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)

Plant Available Se is Not Related to Total Se in Soil

Maeta and Mizuno (1993)

Similar amounts of Se extracted by Hot Water and DTPA and were correlated with Se uptake by

alfalfa

(Soltanpour and Workman, 1980)

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 Se Extracted Significant Correlation

Extractant Procedure Reference µg/kg with Plant Se Content

Hot Water 10g+50mL, reflux 30 min Jump and Sabey (1989) 40.1±14.8 Raya, Wheat, Rice, and Maize

on boiling water bath

1M AB + 0.005M DTPA 10g+20 mL, shake 20 min Jump and Sabey (1989) 39.8±18.8 Rice

0.5 M Na2CO3 1g+20mL, shake 30 min Jump and Sabey (1989) 32.4±10.4 None

0.25 M KCl 1g+25mL, shake 30 min Chao and Sanzolone (1989) 53.3±21.1 Maize

0.1 M KH2PO4 1g+25mL, shake 30 min Chao and Sanzolone (1989) 123.6±34.7 Maize

Reference for Extrac. Proc.

Sequential Extraction Scheme: Various Operationally Defined Solid Phase

Association of Soil Se (Chao and Sanzolone, 1989)

5 Fractions Keys

1. 0.25M KCl: Water-Soluble + Non-specifically Adsorbed Selenate: Highly Available

2. 0.1M K2HPO4: Exchangeable + Specifically Adsorbed Selenite: Available

3. 4M HCl: Oxide (Am and Cryst.)-, Carbonate-, Acid-volatile Sulfide-, and Hydrolyzable OM-Bound

4. KClO3 + Conc. HCl: Sulfides- and Complex Humified OM-Bound

5. HF + HNO3 + HClO4: Resistant Siliceous Materials-Bound

Fractions

Ave

rag

e D

istr

ibu

tio

n,

%Contrasting Distribution of Soil Se (Chao and Sanzolone, 1989)

CaCO3 OM Fe Mn Total Se pH Equivalent % % (mg/kg) (mg/kg)

a. 7 Hawaiian Soils 6.17 4.24 21.4 2621 4.08b. 11 California Soils 8.15 2.65 0.59 3.91 513 2.64

Average

Hawaiian Soils

California Soils

≈ 0.2 mg/kg

≈ 1.35 mg/kg

Depth 0.25 M KCl 1 M KH2PO4 4 N HCl KClO3 + 12 N HCl HNO3 + HClO4 + HF(cm) (Water Soluble) (Adsorbed) (Acid Leachable) (Organic-bound) (Siliceous) SUM Total

mg/kg

0-15 8 9 10 36 29 92 0.258

15-30 7 20 20 22 21 93 0.269

30-56 5 38 19 12 12 87 0.359

56-76 6 30 14 11 11 86 0.281

76-107 3 15 34 11 11 88 0.312

107-132 1 18 44 15 15 98 0.275

% of Total

Extractant and Phase-Asscociation of Soil Se

Various Operationally Defined Solid Phase Association of Se in a Soil Profile from

Northeastern Wyoming

(Sharmasarkar and Vance, 1994)

Extract 5g Soil for 1 h twice with 25 mL0.02 M NaH2PO4

Supernatent: Adsorbed Se

Residue: Extract 16 h with with 50 mL of0.1 M Na4P2O7+O.1 M NaOH, pH 8

Supernatent: Organic SeAdust pH of 25 mL pH 1.5 with 6 M HCI

Supernatent: Fulvate-bound Se

Residue: Humate-bound Se

•Elute through a 14-cm XAD-8 non-ionic resin column •Elute 25 mL HCI at pH 2 to collect 50 mL of eluate

Elute:

Hydrophilic-Fulvatebound Se

Leach the column with 25 mL 0.1 M NaOH +

25 mL DIW

Leachate:

Hydrophobic-Fulvatebound Se

Dissolved with 20 mL0.1 M NaOH

Solution: Humate-bound Se

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

Organic Matter Humate Hydrophobic-Fulvate Hydrophilic-Fulvate

Total Se Organic Se

Horizon C : Se C : Se C : S : Se C : S : Se

E 85 84 0.632 X 106 : 1 0.704 X 106 : 1 0.434 X 106 : 852 : 1 0.711 X 106 : 2862 : 1

Bs1 285 280 0.355X106 : 1 0.395 X 106 : 1 0.336 X 106 : 642 : 1 0.454 X 106 : 1518 : 1

Bs2 364 347 0.290 X 106 : 1 0.250 X 106 : 1 0.250 X 106 : 568 : 1 0.342 X 106 : 1271 : 1

Bs3 293 280 0.224 X 106 : 1 0.257 X 106 : 1 0.217 X 106 : 531 : 1 0.336 X 106 : 1443 : 1

B/C 135 119 0.290 X 106 : 1 0.349 X 106 : 1 0.276 X 106 : 617 : 1 0.487 X 106 : 1604 : 1

C1 62 54 0.382 X 106 : 1 0.467 X 106 : 1 0.362 X 106 : 666 : 1 0.553 X 106 : 2245 : 1

ATOMIC RATIO

µg/kg

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 106 : 1 in Swedish wheat (Lindberg & Bingefors, 1970) and even higher in Finnish Timothy grass (Sippola, 1979).

148576727

527327144

Soils Total Se % extr. OC C : Se Ratio

Tachi 72 36 0.714 X 106 : 1

Lillis 590 18 0.067 X 106 : 1

Nahrub 1020 31 0.067 X 106 : 1

Ciervo wet 700 44 0.067 X 106 : 1

Ciervo clay 1080 32 0.067 X 106 : 1

Panoche 1170 25 0.033 X 106 : 1

Yolo 290 33 0.164 X 106 : 1

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 SoilsAbrams et al. (1990)

ppm

Narrower C:Se than Swedish Forest Soil

Widely variable total Se &

Low OM content

Hydrophobic-Fulvate Fraction: Enriched with SeAlso in Alkaline California soils (pH 6.9-8.0), Abrams et al.

(1990)

Se

(µg/

kg) Selenomethioni

ne

Soldal and Nissen (1978) showed active plant uptake of methionine

Foods or feeds CO2 + H2O + Energy Oxidation

Reduction of O2

+ 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:

Interaction of Selenium with Vitamin E and other Nutrients

ComplementaryVitamin E: Great partner, complements Antioxidant activity

Others: Sulfur containing amino acids, cystine and methionine; vitamin C; and synthetic antioxidant ethoxyquin

AntagonistsAffect the absorption and metabolism of Se: S and Ca

Some Basic StatisticsUS 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

Soil Se classes

Very low

Low

Average

High

Very high

Se content (mg/kg)

<0.30

0.30-0.50

0.50-0.90

0.90-1.50

>1.50

General Ranking of Soil Se Level (Oldfield, 1972)

Selenium Deficient and Seleniferous Soils of USSe Deficient Soils: 20 States

(<0.5 mg/kg total Se)

New EnglandNew YorkNew JerseyDelawarePennsylvaniaMarylandWest VirginiaFloridaOhioIndianaIllinoisMichiganWisconsinWashington StateOregonMontanaArizonaCoastal regions of Virginia, Carolinas, and Georgia

South DakotaMontanaWyomingNebraskaKansasColoradoNew Mexico

High Se soils or seleniferous soils:7 States (2 to 10 mg/kg total Se)

(Cary et al., 1967; NRC, 1983)

Se Requirements

(mg/kg diet)

Beef Cattle 0.1

Dairy Cattle 0.3

Sheep 0.10-0.20

Growing Pigs 0.15-0.30

Gestating and Lactating Cows 0.15

Horse 0.1

Immature Laying Chickens 0.10-0.15

Laying Hens 0.05-0.08

Broiler Chicks 0.15

Animal

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

*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

Forage Type

Deficient Marginally deficient Adequate >MTC**

(<0.100 mg/kg) (0.101-0.199 mg/kg) (0.200-5.000 mg/kg) (>5.0 mg/kg)

Alfalfa/Alfalfa Mix 24 20 55 1Brome 45 25 30 0Bermuda 52 28 20 0Fescue 78 18 4 0Grass 49 29 23 0Native grass 39 27 24 0Orchard/Orchard grass mix 68 26 6 0Sudan 31 46 23 0Silage/Silage grass 32 23 45 0Cereal 20 28 52 0Other 43 18 43 0

Percentage of the analyzed samples under different Se levels*

Regional distribution of forage and grain Se content in the United States and

Canada(NRC, 1983)

Position of GeorgiaLow: CoastlineVariable: Other PartsAdequate: Nowhere

Selenium Supplementation1.0 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 drenching0.1 mg Se per kg live body weight (LBW)

1.3 Ruminal placement

Soluble glass boluses

Iron-based heavy

pellets

Osmotic pump

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

Sulfur, the Chemical Analog of Se: Interferes with the Se

Biotransformation-How?

Biotransformation: Replacement of S by SeFor example: Methionine to SelenomethionineCysteine to Selenocysteine

Se is Biologically-active, can form direct Se–C bondsSe-C bonds: many biomolecules, selenoamino acids and

selenoproteins (25-30 known)

+Se

+Se

Chemical Similarity of S and Se: Presence of High S Affects the

Biological Activity of SePlant uptake from soilS-rich soil: Se uptake affected

Biotransformation: Replacement of S by SeFor example: Methionine to SelenomethioninePresence of High S in affects this in both plants and animals

Methionine to Selenomethionine in AnimalsLarge 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)

Evaluate the Effectiveness of Se-Supplementation

Classification of cattle based on blood selenium content

Dargatznd Ross, 1996: J Anim Sci. 74:2891-2895

Classification

Whole Blood Se Conc. g/L

Severely deficient

0-50

Marginally deficient

51-80

Adequate

81-160

High adequate

161 or Higher

Sampling: Study of Se Status in US Beef Cows and Heifers by Region

Dargatz and Ross, 1996: J Anim Sci. 74:2891-2895

Selenium Status in US Beef Cows and Heifers by Region

Dargatz and Ross, 1996: J Anim Sci. 74:2891-2895

Se-Supplemented Not Supplemented Blood Se Level Class

West (19%)

Central (55%)

Southeast (61%)

West (81%)

Central (45%)

Southeast (39%)

% of the Total Animal Examined

Severely deficient

4.4

0.0

16.7

4.9

7.9

29.1

Marginally deficient

8.0 3.6 23.3 4.4 9.2 32.0

Adequate

20.3

30.9

40.9

13.1

36.5

30.8

High Adequate

67.3

65.5

19.1

77.6

46.5

8.1

Total

100

100

100

100

100

100

41%

61%

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

Whole blood Se concentration: Cows versus Calves at 205 d in a Feeding Expt. (Davis et

al., 2005)

INTERSTING FEEDING TRIAL RESULTSSelenium Transfer to Calf from Dam Receiving

Various Se Supplementation (Davis et al., 2005)

020406080

100120140160180200220

0 30 60 90 120 150 180 210

Who

le B

lood

Se

Con

c of

C

alve

s (

g/

L)

Control

Ba-Selenite Injection(Deposel)

Sodium seleniteinjection (Mu-Se)

Free-choice mineralmix (sodium selenite)

Free-choice mineralmix (Se-Yeast: Sel-Plex)

Severe Deficiency

Marginal Deficiency

Biofortification of Se in Pastures and Forages

Genetic Biofortification: Crop varieties with enhanced Se-accumulation characteristicsAgronomic Biofortification: Through Se Fertilizers Se contents of some N & P fertilizer materials (White et al.

2004)Fertilizer Materials Approx. Se Content, mg/kg

AS: (NH4)2SO4 36

Urea nil

PR: Phosphate rocks 55

SSP: Single Superphosphate 25

TSP: Triple Superphosphate <4

Replacement of AS by Urea and SSP by TSP

Automatic fertilizer inputs of Se to soils have fallen

Selenium in organic manures from Se-supplemented Livestock (Sager, 2006)

PBA Uncertain, Speciation Unknown

Suspect Selenide form: Unavailable?

Successful Agronomic Biofortification of Se in Pastures and Forages

Country Crop Source (g Se/ha) Reapplication Se-enrichment (mg/kg) Reference

Australia Mixed Pasture Selcote® 5 every year Enriched both in Whelan et al. 1994plant & animal blood

Australia Mixed Pasture Selcote-Two-Year® 10 every 3 years Enriched both inplant & animal blood Whelan et al. 1994

Canada Lucerne Selcote-Ultra® 5 One year study from 67 to 187 Gupta, 1995

Canada Lucerne Selcote-Ultra® 10 One year study from 67 to 220 Gupta, 1995

Canada Ryegrass Selcote-Ultra® 5 One year study from 67 to 232 Gupta, 1995

Canada Ryegrass Selcote-Ultra® 10 One year study from 67 to 292 Gupta, 1995

Florida, USA Fescue Selcote-Ultra® 10 22 weeks study from 30 to 170 Valle et al. 2002

Oregon, USA Alfalfa Selcote-Ultra® 10 One year study from 20-60 to 230-250 Roseberg et al., 2005

Oregon, USA Orchardgrass Selcote-Ultra® 10 One year study from 20 to 170 Roseberg et al., 2005Selcote®: 10 g Se/kg as Na2SeO4

Selcote-Two-Year®: 10 g Se/kg as 1:1 Na2SeO4 :BaSeO4

Selcote-Ultra®: 10 g Se/kg as 1:3 Na2SeO4 :BaSeO4

Note: Na2SeO4 or K2SeO4 is more available for immediate uptake by pasture crops than selenite (Gissel-Nielsen, 1998); BaSeO4 is less-soluble forms of selenate

Se Fertilization

ITEM Se-Fertilized Hay (182 µg Se/kg) + No Se-

Mineral

Se-Unfertilized Hay (15 µg Se/kg) + Se-

Mineral

Hay intake, kg/d 13.1 12.9

Se intake from hay, mg/d 2.39 0.19

Se intake from Mineral Suppl., mg/d

0.00 4.09

Total Se intake, mg/d 2.39 4.28

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.)

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 StudyITEM

Oat Wheat Ann Ryegrass Cereal Rye Milkmaster All

Total Number 12 12 12 12 12 60

%below LOQ 33 25 42 17 42 32

%Deficient 92 100 92 100 100 97

# Marginally Deficient 0 0 1 0 0 1.7

#Optimum 1 0 0 0 0 1.7

Average 18 17 28 21 19 21

Geo-Mean 15 15 17 18 15 16

SD 12 9 33 11 15 18

Forage Se Conc. (µg/kg)

Agronomic Biofortification of Food and Feed Crops

Best Example: FinlandFinnish Ministry of Agriculture and Forestry (1983)Low dietary Se intakes (25-30 µg/head/day)Agronomic biofortification programThe 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/kgFor 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

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

Selenium is a vital micronutrient in animal nutrition

Few National level studies on Se in GA forages and grains:

Deficient or Marginally Deficient in SeMany years oldInadequate to reflect the actual scenario in the stateNo data on soil Se

National level survey of state veterinary diagnostic laboratories:

Categorized Georgia as a state of mild Se deficiency

CONCLUDING REMARKS

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 materialsSoil forming factorsSoil 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 typePlant speciesGrowing season

CONCLUDING REMARKS

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

THANK YOU VERY MUCH!

QUESTIONS?