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
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
Brief History of Selenium Research
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
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
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
1/6000th of S
1/50th 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):
Common selenium concentration in selected materials
(McNeal and Balistrieri,1989; Fordyce et al., 1998; Malisa, 2001)
(World mean: 0.4)
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 Arid/Semiarid Climate Se-Rich Soils
Igneous Rocks Humid Climate/Irrigated
Se-Deficient Soils
Eh-pH diagram of Se in soils (Mayland et al., 1989)
Proton Dissociation Equilibria
0 pK1
H2SeO4
SOIL
pK
1
0
H2SeO3
2.61
Se (+IV): Selenite
Se (+VI): Selenate
0
Se (0): Ground state
Grassland
Paddy Field
Se (-II): Selenides
HSe−
H2Se
pK1
3.90
pK2
HSeO3−
pK2
HSe−
1.70
8.32
pK2
-2
SeO4
-2
SeO3
Se
-2
11.0
pe+pH >15: Selenate
0
H2Se
-3.0
HSeO4−
0
pe+pH = 7.5-15: Selenite
pe+pH: <7.5: Selenide
Redox Equilibria
Contrasting sorption behavior of selenite and selenate
Sorbent
Sorption mechanism
Reference
Selenite
Soils, individual soil •Behaves like
phosphate
components, or
spcimen minerals
•Strongly
sorbed
Selenate
•Behaves like
sulfate
Science 238:783-86, 1987
Am-Fe(OH)3 &
Goethite
•Inner-sphere
Bidentate
SSSAJ 64:101-11, 2000
SSSAJ 51:1161-65, 1987
•Weakly
SSSAJ 52:954-58, 1988
sorbed
SSSAJ 53:70-74, 1989
•Inner-sphere •Outer-sphere J.Soil Sci. 40:17-28, 1989
Bidentate
Env.Sci.Tech. 24:1848-56, 1990
Outer-sphere
Complex
•Inner-sphere
Bidentate
Inner-sphere
Complex
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 Se
Byers et al. (1938)
Hawaiian soils: 6 to 15 ppm total Se
Olsen et al. (1942)
South Dakota Soils: ≥1 ppm total Se
Ravikovitch and Margolin (1975)
Israeli soils: ≥1 ppm total Se
Did not produce seleniferous
vegetation
Did produce Se-toxic
vegetation
Total Se is not a reliable index of plant available Se
Plant-Available Se in Soils
Extractants 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 bioavailable 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
µg/kg
Significant Correlation
with Plant Se Content
Extractant
Procedure
Reference for
Extrac.
Proc.
Reference
Hot Water
10g+50mL, reflux 30 min
Jump and Sabey (1989)
40.1±14.8
Raya, Wheat, Rice, and Maize
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
on boiling water bath
Sequential Extraction Scheme: Various
Operationally Defined Solid Phase Association of
Soil Se (Chao and Sanzolone, 1989)
Contrasting Distribution of Soil Se (Chao and Sanzolone, 1989)
Average Distribution, %
a. 7 Hawaiian Soils
b. 11 California Soils
Average
CaCO3
OM
pH Equivalent
%
6.17
4.24
8.15
2.65
0.59
Fe
%
21.4
3.91
Hawaiian Soils
Mn
Total Se
(mg/kg) (mg/kg)
2621
4.08
513
2.64
California Soils
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-, Acidvolatile Sulfide-, and
Hydrolyzable OM-Bound
4. KClO3 + Conc. HCl:
Sulfides- and Complex
Humified OM-Bound
≈ 0.2 mg/kg
5. HF + HNO3 + HClO4:
Resistant Siliceous MaterialsBound
Fractions
≈ 1.35 mg/kg
Various Operationally Defined Solid Phase Association of
Se in a Soil Profile from Northeastern Wyoming
(Sharmasarkar and Vance, 1994)
Depth
(cm)
0.25 M KCl
(Water Soluble)
Extractant and Phase-Asscociation of Soil Se
1 M KH2PO4
4 N HCl
KClO3 + 12 N HCl HNO3 + HClO4 + HF
(Adsorbed)
(Acid Leachable)
(Organic-bound)
(Siliceous)
SUM
Total
mg/kg
% of Total
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
Humifide Organic Se Fractionation Scheme
(Gustafsson and Johnsson, 1992)
Extract 5g Soil for 1 h twice with 25 mL
0.02 M NaH2PO4
Supernatent: Adsorbed Se
Residue: Extract 16 h with with 50 mL of
0.1 M Na4P2O7+O.1 M NaOH, pH 8
Supernatent: Organic Se
Adust pH of 25 mL pH 1.5 with 6 M HCI
Supernatent:
Fulvate-bound Se
Residue:
Humate-bound Se
Leach the column with
25 mL 0.1 M NaOH +
25 mL DIW
•Elute through a 14-cm XAD-8
non-ionic resin column
•Elute 25 mL HCI at pH 2 to
collect 50 mL of eluate
Dissolved with 20 mL
0.1 M NaOH
Leachate:
Hydrophobic-Fulvate
bound Se
Elute:
Hydrophilic-Fulvate
bound Se
Solution:
Humate-bound Se
Hydrophobic-Fulvate Fraction: Most Enriched with Se
in A Podzolic Forest Soil (pH 4.0-4.7) of Sweeden (Gustafsson and Johnsson, 1992)
Organic Matter
Humate
Total Se Organic Se
Horizon
µg/kg
Hydrophobic-Fulvate Hydrophilic-Fulvate
ATOMIC RATIO
C : Se
C : Se
C : S : Se
C : S : Se
E
85
148
84
0.632 X 106 : 1
0.704 X 106 : 1
0.434 X 106 : 852 : 1
0.711 X 106 : 2862 : 1
Bs1
576
285
280
0.355X106 : 1
0.395 X 106 : 1
0.336 X 106 : 642 : 1
0.454 X 106 : 1518 : 1
Bs2
727
364
347
0.290 X 10 : 1
Bs3
527
293
280
0.224 X 10 : 1
B/C
327
135
119
0.290 X 10 : 1
C1
144
62
54
0.382 X 10 : 1
6
0.250 X 10 : 1
6
0.250 X 10 : 568 : 1
6
0.257 X 10 : 1
6
0.349 X 10 : 1
6
0.467 X 10 : 1
6
0.342 X 10 : 1271 : 1
6
0.217 X 10 : 531 : 1
6
0.276 X 10 : 617 : 1
6
0.362 X 10 : 666 : 1
6
6
0.336 X 10 : 1443 : 1
6
0.487 X 10 : 1604 : 1
6
0.553 X 10 : 2245 : 1
6
6
6
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).
Organic Selenium Distribution in Selected California Soils
Abrams et al. (1990)
Soils
Total Se
% extr. OC¶
C : Se Ratio §
ppm
Tachi
72
36
6
590
18
0.067 X 10
1020
31
0.067 X 106 : 1
Ciervo wet
700
44
0.067 X 106 : 1
Ciervo clay
1080
32
0.067 X 10
Panoche
1170
25
0.033 X 106 : 1
Lillis
Nahrub
Yolo
290
33
Organic C content: 6-9 g/kg; pH 6.9-8.0
¶
0.714 X 106 : 1
6
Low OM content
:1
:1
0.164 X 106 : 1
%Extracted Organic-C by Alkaline pyrophosphate
§C:Se Atomic ratio in the alkaline pyrophosphate extract
Widely variable
total Se &
Narrower C:Se than
Swedish Forest Soil
Hydrophobic-Fulvate Fraction: Enriched with Se
Se (µg/kg)
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
FUNCTIONS OF SELENIUM IN ANIMALS AND HUMANS
Foods or feeds
Oxidation
CO2 + H2O + Energy
Reduction of O2
ROS:
+ 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)
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
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
General Ranking of Soil Se Level
(Oldfield, 1972)
Soil Se classes
Se content (mg/kg)
Very low
<0.30
Low
0.30-0.50
Average
0.50-0.90
High
0.90-1.50
Very high
>1.50
Selenium Deficient and Seleniferous Soils of US
Se Deficient Soils: 20 States
High Se soils or seleniferous soils:
7 States (2 to 10 mg/kg total Se)
(<0.5 mg/kg total Se)
(Cary et al., 1967; NRC, 1983)
New England
South Dakota
New York
Montana
New Jersey
Wyoming
Delaware
Nebraska
Pennsylvania
Kansas
Maryland
Colorado
West Virginia
New Mexico
Florida
Ohio
Indiana
Illinois
Michigan
Wisconsin
Washington State
Oregon
Montana
Arizona
Coastal regions of Virginia, Carolinas,
and Georgia
Recommended levels Se in various animal diets
(NRC, 1994, 1998, 2000, 2001, 2007, Lewis, 1995)
Animal
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
Note: FDA
regulations (FDA,
1997, 2004, 2005)
allows Se
supplementation:
Immature Laying Chickens
0.10-0.15
Laying Hens
0.05-0.08
up to 0.3 mg/kg
complete diet,
regardless of Forage
Se content
0.15
Not >3mg/head/day
Broiler Chicks
Selenium Contents of Various Forages: US Nationwide Study
Forage Type
Percentage of the analyzed samples under different Se levels*
Deficient
Alfalfa/Alfalfa Mix
Brome
Bermuda
Fescue
Grass
Native grass
Orchard/Orchard grass mix
Sudan
Silage/Silage grass
Cereal
Other
Marginally deficient
Adequate
>MTC**
(<0.100 mg/kg) (0.101-0.199 mg/kg) (0.200-5.000 mg/kg) (>5.0 mg/kg)
24
20
55
1
45
25
30
0
52
28
20
0
78
18
4
0
49
29
23
0
39
27
24
0
68
26
6
0
31
46
23
0
32
23
45
0
20
28
52
0
43
18
43
0
*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.
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
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
Selenium Supplementation
2.0 Organic Supplement:
Organic Se-enriched yeast (e.g., Sel-Plex®, Altech, Inc,
Nicholasville, KY): Cocktail; >50% Selenomethionine
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?
Se is Biologically-active, can form direct Se–C bonds
Se-C bonds: many biomolecules, selenoamino acids and
selenoproteins (25-30 known)
Biotransformation: Replacement of S by Se
For example:
Methionine to Selenomethionine
Cysteine to Selenocysteine
+Se
+Se
Chemical Similarity of S and Se: Presence of
High S Affects the Biological Activity of Se
Size: Se (0.191 nm) and S (0.184 nm)
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
Evaluate the Effectiveness of
Se-Supplementation
Classification of cattle based on blood
selenium content
Dargatznd Ross, 1996: J Anim Sci. 74:2891-2895
Classification
Severely deficient
Whole Blood Se Conc.
g/L
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
Blood Se Level Class
Se-Supplemented
West
(19%)
Not Supplemented
Central
Southeast West
Central
(55%)
(61%)
(81%)
(45%)
% of the Total Animal Examined
Southeast
(39%)
Severely deficient
4.4
0.0
16.7
4.9
7.9
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%
29.1
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 RESULTS
Whole Blood Se Conc of
Calves ( g/L)
Selenium Transfer to Calf from Dam Receiving
Various Se Supplementation (Davis et al., 2005)
Control
220
200
180
160
140
120
100
80
60
40
20
0
Ba-Selenite Injection
(Deposel)
Marginal Deficiency
Sodium selenite
injection (Mu-Se)
Free-choice mineral
mix (sodium selenite)
Severe Deficiency
0
30
60
90
120
150
180
210
Free-choice mineral
mix (Se-Yeast: Sel-Plex)
Biofortification of Se in Pastures and Forages
Genetic Biofortification: Crop varieties with enhanced Seaccumulation characteristics
Agronomic 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
Se Fertilization
Source
(g Se/ha) Reapplication
Country
Crop
Se-enrichment (mg/kg) Reference
Australia
Mixed Pasture
Selcote®
5
every year
Enriched both in
plant & animal blood
Australia
Mixed Pasture
Selcote-Two-Year®
10
every 3 years
Enriched both in
plant & animal blood
Whelan et al. 1994
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
10
One year study
from 20 to 170
Roseberg et al., 2005
Oregon, USA
Orchardgrass
Selcote-Ultra®
Selcote®: 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
Comp. Feeding Trial: Se-Fertilized Hay vs. Se-Mineral Suppl.
with third Trimester Beef Heifers (Pulsipher et al., 2004; Oregon State Univ.)
Se-Fertilized Hay (182
µg Se/kg) + No SeMineral
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
+25.3 kg
+19.0 kg
Initial (beginning of trial, 11/22/2002):
32.3
31.8
Final (at Calving, 01/21/2003):
50.1
45.7
ITEM
Body wt. change (11/22/02-01/21/03)
Blood Serum Se conc. (µg/L)
Calf within 24 h of birth:
88.4 (111 in whole Blood) 39.3 (49.1 in whole blood)
Note: Grass+Alfalfa mixed hay field fertilized with Na-selenite @10g Se/ha
Se Conc. in Some GA Forages (grown
in 2008-09): Our Preliminary Study
ITEM
Forage Se Conc. (µg/kg)
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 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)
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
Estimated Se Intake Finnish Population to Meet Daily Energy
Need of 10MJ or 2400 Kcal/head/d Before and After Se Fert.
Se Added:
@16 mg/kg
and 6 mg/kg
Increased Se
Conc. in 125
Food & Feed
Crops
Se-Rich US Wheat
Import
Before Addition
of Se in Fert.
Reduced Se
Addition by 60%
for food crops
CONCLUDING REMARKS
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
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
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
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?