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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?