HOW DOES SELENIUM FUNCTION AS AN IMMUNONUTRIENT?

• Sponsoring Institution: National Institute of Food and Agriculture
• Project Status: COMPLETE
• Funding Source: NRI COMPETITIVE GRANT
• Reporting Frequency: Annual
• Accession No.: 0215165
• Grant No.: 2008-35204-04624
• Proposal No.: 2008-00813
• Project Start Date: Aug 15, 2008
• Project End Date: Dec 31, 2011
• Grant Year: 2008
• Program Code: [44.0B]- Animal Protection & Biosecurity (B): Animal Well-Being

Recipient Organization
OREGON STATE UNIVERSITY
(N/A)
CORVALLIS,OR 97331

Performing Department
COLLEGE OF VETERINARY MEDICINE

Non Technical Summary
Selenium (Se) has been recognized for years as an essential trace element for animals. In the United States, the Northwest region is among those with the lowest amounts of Se in soils and plants. In general, the majority of livestock raised in low Se regions do not receive sufficient dietary Se to result in optimal health. Selenium affects all components of the immune system. It is known that Se deficiency results in immunosuppression, decreased resistance to bacterial and viral infections, and decreased neutrophil function, antibody production, and cell-mediated immunity. However, the dietary requirements of Se for optimal immune function remain to be determined. Immunoenhancing effects of Se may be achieved at supplementation levels much higher than what the National Research Council currently recommends. We are more interested in supranutritional levels of Se, to determine if supplementing Se at levels above those currently recommended for sheep can decrease the severity and improve recovery from infectious disease such as foot rot. Chronic foot-rot infection remains a constant economic burden for many sheep ranchers by causing lameness, poor wool production and susceptibility to other infectious diseases. Foot rot is caused by bacterial infection. Although morbidity may be high in a flock of sheep, mortality as a result of the disease is rare. Environmental and host factors, including optimal immune function, play an essential role in the initiation and development of the disease. Demonstrating that higher levels of Se intake are beneficial in sheep, and that it decreases susceptibility to infectious diseases such as foot rot, could encourage sheep ranchers to supplement their flocks with additional Se. In a pilot study we showed positive clinical results after injectible Se administration to sheep with foot rot already receiving a mineral salt supplement. Our new goal is to determine whether a more physiologic route (oral), and whether organic Se can be utilized in sheep to maintain more consistently higher-end-of-the-normal-range Se concentrations. This can be accomplished by measuring whole-blood Se concentrations in sheep given Se in an organic (as Se-containing amino acids) vs inorganic (sodium selenite salt) form. We hypothesize that organic Se in sheep results in increased whole-blood Se concentrations compared to those measured in sheep receiving an inorganic Se supplement. We will investigate the mechanisms of Se induced immune responses in sheep, following dietary supplementation with organic versus inorganic Se. We hypothesize that both arms of the immune response i.e., innate immunity of neutrophils and adaptive immunity (both humoral and cell mediated immunity) will be enhanced by supplementation with organic Se. Finally, we will monitor the prevalence and severity of foot rot across time in sheep receiving organic versus inorganic Se. We hypothesize that foot-rot morbidity will be lowest in sheep receiving organic Se. Using foot rot in sheep as a model disease for other ruminants, this specific disease illustrates the potential benefits of Se supplementation for preventing infectious diseases in general.

Animal Health Component

50%

Research Effort Categories

Basic

50%

Applied

50%

Developmental

(N/A)

Classification

Knowledge Area (KA)	Subject of Investigation (SOI)	Field of Science (FOS)	Percent
315	3410	3010	33%
315	3410	3100	33%
315	3410	1060	34%

Knowledge Area
315 - Animal Welfare/Well-Being and Protection;

Subject Of Investigation
3410 - Dairy cattle, live animal;

Field Of Science
1060 - Biology (whole systems); 3010 - Economics; 3100 - Management;

Keywords

selenium supplementation

supranutritional selenium supplementation

sheep

organic se

inorganic se

bioavailability

immune responses

foot rot

Goals / Objectives
Selenium (Se) is an essential trace element; deficiency results in disease, whereas an excess is toxic. It is known that immunity is compromised in Se-deficient hosts, and that supplementation can correct the deficiency. However, the dietary requirements of Se for optimal immune function remain to be determined. Immunoenhancing effects of Se may be achieved at supplementation levels much higher than what the National Research Council currently recommends. In addition, the efficacy of organic vs inorganic sources of Se has not been thoroughly investigated. Our long-term goals are 1) to determine if supplementing Se at levels above those currently recommended for sheep can improve innate and adaptive immune responses, and 2) to determine whether organic Se has increased bioavailability compared to inorganic Se. To achieve these goals we propose two specific objectives. Objective 1: Determine whether supranutritional concentrations of organic or inorganic Se in the diet of sheep enhance Se bioavailability. This can be accomplished by measuring whole-blood, milk, and skeletal-muscle Se concentrations in sheep given supranutritional levels of Se in an organic form (as Se-containing amino acids) vs an inorganic form (sodium selenite salt). We hypothesize that supranutritional concentrations of organic Se in the diet of sheep results in increased whole-blood and milk Se concentrations in the ewes and increased skeletal-muscle Se concentrations in their lambs compared to those measured in sheep receiving an inorganic Se supplement. Objective 2: Investigate the mechanisms of Se-induced immune responses in sheep, both innate and adaptive, following dietary supplementation with supranutritional levels of organic vs inorganic Se. We hypothesize that both arms of the immune response i.e., innate immunity of neutrophils and adaptive immunity (both humoral and cell mediated immunity) will be enhanced by supplementation with supranutritional levels of organic Se. We propose to investigate the two important mechanisms of neutrophil killing, i.e., the ability of neutrophils to phagocytose and kill pathogens, as well as their killing mechanisms associated with neutrophil extracellular traps. We will also measure the relative abundance of selected mRNAs that are specific for neutrophil migration or killing functions (L-selectin, IL-8R, and myeloperoxidase). We will investigate adaptive immunity by measuring an antibody titer response to a novel protein challenge (KLH), which will assess humoral immunity. We will measure CMI using the DTH test to KLH. Finally, we will monitor the prevalence and severity of foot rot across time in sheep receiving varying doses of organic vs inorganic Se. We hypothesize that foot-rot morbidity will be lowest in sheep receiving supranutritional levels of organic Se. Foot rot is an example of an endemic contagious disease that serves as a response criterion to measure immune capacity and complements the other immunological measurements. Using foot rot in sheep as a model disease for other ruminants, this specific disease illustrates the potential benefits of Se supplementation for preventing infectious diseases in general.

Project Methods
Objective 1: Sheep: Suffolk-Polypay crossbred ewes weighing 160 to 175 lb from the Oregon State University Sheep Center will be provided a free-choice balanced mineral premix that does not contain Se. Study design: Prospective, placebo-controlled clinical trial of 12-month duration. Three variables will be manipulated within sheep using a 2 x 2 x 4 split-split plot factorial study design with disease status, Se source, and supplementation dose as main effects. There will be two types of sheep (healthy and foot rot (FR)-affected), two types of Se supplements (an organic source of Se as selenomethionine and an inorganic source of Se as sodium selenite salt). There will be four dose levels (controls; 0.3 ppm Se--US FDA regulation for ruminant diets; 0.9 ppm Se; and 1.5 ppm Se). There will be 2 groups of control sheep (healthy and FR-affected) that receive no Se supplements. Each of the other three Se dose levels (0.3 ppm, 0.9 ppm, and 1.5 ppm) will have FR-affected sheep that receive organic Se, FR-affected sheep that receive inorganic Se; healthy sheep that receive organic Se; and healthy sheep that receive inorganic Se (n=15 sheep/group). Se treatment will be administered by oral drench once weekly, at an amount equal to the summed weekly intake, for a total of 52 weeks. Control sheep will receive water. As an example of dose calculations, 0.7 mg/d is considered equivalent to 0.3 ppm Se in the diet. This dose is multiplied by 7 for the weekly amount of 4.9 mg. Whole-blood and milk Se concentrations: All ewes will be bled at time 0 and then at 3-month intervals for 1 year to collect whole blood and serum for Se analysis (0, 3, 6, 9, and 12 months). Milk samples will be collected immediately after giving birth, and again at 1 month postnatal. Whole-blood and serum Se concentrations will be assessed in lambs at birth. Se concentrations will be determined using ICP-MS methods. Skeletal-muscle Se concentrations: No Se supplementation will be administered to lambs postnatal for 3 weeks. At that time, an electric docking iron will be used to cut and cauterize the tail simultaneously for tail docking, and 1.5 g of skeletal muscle from docked tails will be collected to assess skeletal-muscle Se content. Specific objective two: Study design: The same sheep groups described above will be used. Assays to assess innate immunity of neutrophils will be performed at time 0 and at the end of the 1-year supplementation period, along with immunology studies for CMI and humoral immunity. Incidence and Severity of FR: Sheep feet will be examined, trimmed, and scored for FR at time 0. At 3-month intervals for 1 year (3, 6, 9, and 12 months) we will reexamine the feet, trim and score for FR. A scoring system based on pathologically defined criteria has been reported. Statistical analyses: In our pilot study, we calculated a power of 80% to detect significance at the P=0.05 and P=0.01 level between groups for FR-affected sheep treated with injectable inorganic Se vs saline once monthly. This correlates with an expected sample size of 10 to 20 animals, respectively, per group to show a significant response to Se supplementation.

Progress 08/15/08 to 12/31/11

Outputs
OUTPUTS: This selenium-supplementation project was conducted using the Oregon State University sheep center flock. One Master's student used this project as his thesis, which was successfully defended on December 2, 2010. His thesis is now available in the Oregon State University library. Three first or second-year professional DVM program veterinary students and many undergraduate students in the Animal Sciences Department were mentored and participated in the project. Results have been presented at the Annual Research Day, College of Veterinary Medicine, Oregon State University, presented September 9, 2009 and September 2, 2010; Corvallis, OR. The results were also presented in part at the 2010 Oregon Sheep Growers Annual Meeting Sunriver, OR on Dec. 2-4, 2010. The results have also been presented at the 2010 American College of Veterinary Internal Medicine Annual Forum, in Anaheim, CA on June 11, 2010. Peer reviewed publications are now available in Journal of Animal Science for dissemination to both national and international audiences, and additional papers have been submitted for peer-review or are in the final preparation stages. The most significant outputs for the entire life of the project are the successful training and graduation of a Masters student, his thesis, and the peer reviewed publications that resulted from this project. PARTICIPANTS: Jean A. Hall, DVM, PhD, Professor, PI/PD. No funding from the agency. William R.Vorachek, PhD, Research Associate. Post-doctoral research associate who was directly responsible for performing laboratory assays. Whit C. Stewart, MS. Masters degree student in the Department of Animal Sciences. Used this project for his thesis, which was successfully defended on December 2, 2010. Michelle L. Heade, Professional DVM Program. (First year Professional DVM Program student funded by the Department of Biomedical Sciences to work on the project during the summer of 2009.) Andrea M. Harwell, Professional DVM Program. (First year Professional DVM Program student funded by the Department of Biomedical Sciences to work on the project during the summer of 2009. No funding from the agency.) Kathryn J. Hooper, Professional DVM Program. (First year Professional DVM Program student funded by the Department of Biomedical Sciences to work on the project during the summer of 2009. No funding from the agency.) Gene Pirelli, Professor and Extension Animal Specialist for Polk County, Oregon and a faculty member of the Oregon State University Extension Service. Provided expertise on the use of selenium supplementation in sheep. No funding from the agency. Wayne Mosher, Professor Emeritus and faculty member of the Oregon State University Extension Service. Participated every week with drenching of the ewes. No funding from the agency. Thomas Nichols, Sheep Center Manager, Oregon State University. Helped with feeding and management of sheep for the project. No funding from the agency. Gerd Bobe, PhD, Assistant Professor, Department of Animal Sciences, Oregon State University. Worked extensively with data analysis and statistics. No funding from the agency. Robert J. VanSaun, DVM, PhD, Professor, Department of Veterinary & Biomedical Sciences, College of Agricultural Sciences, Pennsylvania State University, University Park, PA. Worked extensively with data analysis and statistics. No funding from the agency. Phil Whanger, PhD, Professor Emeritus, Department of Environmental and Molecular Toxicology, Oregon State University. Frequent consultant. No funding from the agency. Neal E. Forsberg, PhD, Professor Emeritus, Department of Animal Sciences, Oregon State University. Consultant. No funding from the agency. James Oldfield, Professor Emeritus, Department of Animal Sciences, Oregon State University. Reference person. No funding from the agency. TARGET AUDIENCES: Target audience includes veterinarians, veterinary students, animal scientists, basic science researchers, commercial sheep producers, and commercial cattle producers. Science-based knowledge has been delivered by oral presentation and abstracts. Peer-reviewed publications are published in journals and in progress. PROJECT MODIFICATIONS: Nothing significant to report during this reporting period.

Impacts
Publication of the results of this project will increase the knowledge of decision makers in veterinary medicine and of commercial sheep producers and cattle producers. We anticipate that there will be a change in action to increase selenium supplementation in ruminants utilizing organic selenium, as compared to inorganic selenium, the latter which is commonly used in salt-mineral supplements today. In particular, as we gain information about methodologies to deliver increased selenium to ruminants (other collaborators are working on projects to apply selenium to pastures via selenium fertilization to increase forage selenium content), our data will encourage adoption of these new recommendations. It is also recommended that higher levels of organic selenium be administered particularly during the third trimester of pregnancy and early lactation, especially for large framed ewes producing fast growing lambs, and for ewes producing and rearing multiple lambs. The results from our study also may be used to influence future recommendations for increasing whole blood and serum selenium normal reference intervals for sheep during various life cycle stages.

Publications

• Journal Article: Hall, J.A., Van Saun, R.J., Bobe, G., Stewart, W.C., Vorachek, W.R., Mosher, W.D., Nichols, T., Forsberg, N.E., Pirelli, G.J. (2012). Organic and inorganic selenium: I. Oral bioavailability in ewes. J. Animal Science 90(2): 568-76. [Epub ahead of print 2011; Sep 30].
• Journal Article: Stewart, W.C., Bobe, G., Vorachek, W.R., Pirelli, G.J., Mosher, W.D., Nichols, T., Van Saun, R.J., Forsberg, N.E., Hall, J.A. (2012). Organic and inorganic selenium: II. Transfer efficiency from ewes to lambs. J. Animal Science 90(2): 577-84. [Epub ahead of print 2011; Sep 30].
• Journal Article: Stewart, W.C., Bobe, G., Pirelli, G.J., Mosher, W.D., Hall, J.A. (2012) Organic and inorganic selenium: III. Ewe and progeny performance. (Submitted.)
• Journal Article: Stewart, W.C., Bobe, G., Vorachek, W.R., Stang, B.V., Pirelli, G.J., Mosher, W.D., Hall, J.A. (2012) Organic and inorganic selenium: IV. Passive transfer of immunoglobulin from ewe to lamb. (Submitted.)

Progress 08/15/09 to 08/14/10

Outputs
OUTPUTS: This selenium-supplementation project was conducted using the Oregon State University sheep center flock. One Master's student used this project as his thesis, which was successfully defended on December 2, 2010. His thesis is now available in the Oregon State University library. Three first or second-year professional DVM program veterinary students and many undergraduate students in the Animal Sciences Department were mentored and participated in the project. Results have been presented at the Annual Research Day, College of Veterinary Medicine, Oregon State University, presented September 9, 2009 and September 2, 2010; Corvallis, OR. The results were also presented in part at the 2010 Oregon Sheep Growers Annual Meeting Sunriver, OR on Dec. 2-4, 2010. The results have also been presented at the 2010 American College of Veterinary Internal Medicine Annual Forum, in Anaheim, CA on June 11, 2010. Peer reviewed publications are now available in Journal of Animal Science for dissemination to both national and international audiences. Additional peer-reviewed papers are currently being written, submitted, or under review. PARTICIPANTS: Jean A. Hall, DVM, PhD, Professor, PI/PD. No funding from the agency. William R.Vorachek, PhD, Research Associate. Post-doctoral research associate who was directly responsible for performing laboratory assays. Whit C. Stewart, MS. Masters degree student in the Department of Animal Sciences. Used this project for his thesis, which was successfully defended on December 2, 2010. Michelle L. Heade, Professional DVM Program. (First year Professional DVM Program student funded by the Department of Biomedical Sciences to work on the project during the summer of 2009.) Andrea M. Harwell, Professional DVM Program. (First year Professional DVM Program student funded by the Department of Biomedical Sciences to work on the project during the summer of 2009. No funding from the agency.) Kathryn J. Hooper, Professional DVM Program. (First year Professional DVM Program student funded by the Department of Biomedical Sciences to work on the project during the summer of 2009. No funding from the agency.) Gene Pirelli, Professor and Extension Animal Specialist for Polk County, Oregon and a faculty member of the Oregon State University Extension Service. Provided expertise on the use of selenium supplementation in sheep. No funding from the agency. Wayne Mosher, Professor Emeritus and faculty member of the Oregon State University Extension Service. Participated every week with drenching of the ewes. No funding from the agency. Thomas Nichols, Sheep Center Manager, Oregon State University. Helped with feeding and management of sheep for the project. No funding from the agency. Gerd Bobe, PhD, Assistant Professor, Department of Animal Sciences, Oregon State University. Worked extensively with data analysis and statistics. No funding from the agency. Robert J. VanSaun, DVM, PhD, Professor, Department of Veterinary & Biomedical Sciences, College of Agricultural Sciences, Pennsylvania State University, University Park, PA. Worked extensively with data analysis and statistics. No funding from the agency. Phil Whanger, PhD, Professor Emeritus, Department of Environmental and Molecular Toxicology, Oregon State University. Frequent consultant. No funding from the agency. Neal E. Forsberg, PhD, Professor Emeritus, Department of Animal Sciences, Oregon State University. Consultant. No funding from the agency. James Oldfield, Professor Emeritus, Department of Animal Sciences, Oregon State University. Reference person. No funding from the agency. TARGET AUDIENCES: Target audience includes veterinarians, veterinary students, animal scientists, basic science researchers, commercial sheep producers, and commercial cattle producers. PROJECT MODIFICATIONS: Nothing significant to report during this reporting period.

Impacts
Publication of the results of this project will increase the knowledge of decision makers in veterinary medicine and of commercial sheep producers and cattle producers. We anticipate that there will be a change in action to increase selenium supplementation in ruminants utilizing organic selenium, as compared to inorganic selenium, the latter which is commonly used in salt-mineral supplements today. In particular, as we gain information about methodologies to deliver increased selenium to ruminants (other collaborators are working on projects to apply selenium to pastures via selenium fertilization to increase forage selenium content), our data will encourage adoption of these new recommendations. It is also recommended that higher levels of organic selenium be administered particularly during the third trimester of pregnancy and early lactation, especially for large framed ewes producing fast growing lambs, and for ewes producing and rearing multiple lambs.

Publications

• Abstract: Heade, M.L., and Hall, J.A. 2009. Effects of environmental factors and rumen microbes on Se bioavailability in sheep. Ann. Res. Day, Coll. of Vet. Med., Oregon State Univ., presented September 9, 2009. Corvallis, OR.
• Abstract: Hooper, K.J., and Hall, J.A. 2009. Effects of supranutritional concentrations of organic or inorganic Se in the diet of sheep on Se bioavailability, and foot rot incidence and severity. Ann. Res. Day, Coll. of Vet. Med., Oregon State Univ., presented September 9, 2009. Corvallis, OR.
• Proceedings: Hall, J.A., Van Saun, R.J., Stewart, W.C., Vorachek, W.R., Mosher, W., Pirelli, G.J. 2010. Bioavailability of oral selenium supplements in sheep. Page 271 in Proc. 2010 ACVIM Forum Annual Meeting. Anaheim, CA.
• Thesis: Stewart, W.C. 2010. Effect of selenium source and supplementation rate in ewes on selenium status, passive immunity, and growth performance of their lambs. Master of Science Degree in Animal Sciences, Oregon State Univ., presented December 2, 2010. Corvallis, OR.
• Proceedings: Stewart, W.C., Bobe, G., Vorachek, W.R., Mosher, W.D., Pirelli, G., Hall, J.A. 2011. Effect of selenium source and supplementation rate in ewes on selenium transfer from ewe to lamb and on lamb growth. Abstract 47109. Proc. 2011 Western Section, American Society of Animal Science Conference. Miles City, MT.
• Journal Article: Stewart, W.C., Bobe, G., Vorachek, W.R., Stang, B.V., Pirelli, G.J., Mosher, W.D., Hall, J.A. (2012) Selenium supplementation of Polypay ewes increases immunoglobulin concentrations in colostrum and lamb serum. (Submitted.)
• Journal Article: Hall, J.A., Van Saun, R.J., Bobe, G., Stewart, W.C., Vorachek, W.R., Mosher, W.D., Nichols, T., Forsberg, N.E., Pirelli, G.J. (2011). Oral bioavailability of organic and inorganic selenium supplements in ewes. J Ani Sci. 2011; Sep 30. [Epub ahead of print].
• Journal Article: Stewart, W.C., Bobe, G., Vorachek, W.R., Pirelli, G.J., Mosher, W.D., Nichols, T., Van Saun, R.J., Forsberg, N.E., Hall, J.A. (2011). Transfer efficiency of organic and inorganic selenium from ewes to lambs. J Ani Sci. 2011; Sep 30. [Epub ahead of print].
• Journal Article: Stewart, W.C., Bobe, G., Pirelli, G.J., Mosher, W.D., Hall, J.A. (2012) Organic and inorganic selenium: III. Ewe and progeny performance. (Submitted.)

Progress 08/15/08 to 08/14/09

Outputs
OUTPUTS: This selenium-supplementation project was conducted using the Oregon State University sheep center flock. One Master's student used this project as his thesis, which was successfully defended on December 2, 2010. His thesis is now available in the Oregon State University library. Three first or second-year professional DVM program veterinary students and many undergraduate students in the Animal Sciences Department were mentored and participated in the project. Results have been presented at the Annual Research Day, College of Veterinary Medicine, Oregon State University, presented September 9, 2009 and September 2, 2010; Corvallis, OR. The results were also presented in part at the 2010 Oregon Sheep Growers Annual Meeting Sunriver, OR on Dec. 2-4, 2010. The results have also been presented at the 2010 American College of Veterinary Internal Medicine Annual Forum, in Anaheim, CA on June 11, 2010. Future dissemination to a national audience will take place upon publication of a peer-reviewed papers in Journal of Animal Science and Veterinary Immunology and Immunopathology (pending). PARTICIPANTS: Jean A. Hall, DVM, PhD, Professor, PI/PD. No funding from the agency. William R.Vorachek, PhD, Research Associate. Post-doctoral research associate who was directly responsible for performing laboratory assays. Whit C. Stewart, MS. Masters degree student in the Department of Animal Sciences. Used this project for his thesis, which was successfully defended on December 2, 2010. Michelle L. Heade, Professional DVM Program. (First year Professional DVM Program student funded by the Department of Biomedical Sciences to work on the project during the summer of 2009.) Andrea M. Harwell, Professional DVM Program. (First year Professional DVM Program student funded by the Department of Biomedical Sciences to work on the project during the summer of 2009. No funding from the agency.) Kathryn J. Hooper, Professional DVM Program. (First year Professional DVM Program student funded by the Department of Biomedical Sciences to work on the project during the summer of 2009. No funding from the agency.) Gene Pirelli, Professor and Extension Animal Specialist for Polk County, Oregon and a faculty member of the Oregon State University Extension Service. Provided expertise on the use of selenium supplementation in sheep. No funding from the agency. Wayne Mosher, Professor Emeritus and faculty member of the Oregon State University Extension Service. Participated every week with drenching of the ewes. No funding from the agency. Thomas Nichols, Sheep Center Manager, Oregon State University. Helped with feeding and management of sheep for the project. No funding from the agency. Gerd Bobe, PhD, Assistant Professor, Department of Animal Sciences, Oregon State University. Worked extensively with data analysis and statistics. No funding from the agency. Robert J. VanSaun, DVM, PhD, Professor, Department of Veterinary & Biomedical Sciences, College of Agricultural Sciences, Pennsylvania State University, University Park, PA. Worked extensively with data analysis and statistics. No funding from the agency. Phil Whanger, PhD, Professor Emeritus, Department of Environmental and Molecular Toxicology, Oregon State University. Frequent consultant. No funding from the agency. Neal E. Forsberg, PhD, Professor Emeritus, Department of Animal Sciences, Oregon State University. Consultant. No funding from the agency. James Oldfield, Professor Emeritus, Department of Animal Sciences, Oregon State University. Reference person. No funding from the agency. TARGET AUDIENCES: veterinarians, veterinary students, animal scientists, basic science researchers, commercial sheep producers, and commercial cattle producers PROJECT MODIFICATIONS: Nothing significant to report during this reporting period.

Impacts
Dissemination of the results of this project will increase the knowledge of decision makers in veterinary medicine and of commercial sheep producers. We anticipate that there will be a change in action to increase selenium supplementation in ruminants utilizing organic selenium, as compared to inorganic selenium, the latter which is commonly used in salt-mineral supplements today. In particular, as we gain information about methodologies to deliver increased selenium to ruminants (other collaborators are working on projects to apply selenium to pastures via selenium fertilization to increase forage selenium content), our data will encourage adoption of these new recommendations. It is also recommended that higher levels of organic selenium be administered particularly during the third trimester of pregnancy and early lactation, especially for large framed ewes producing fast growing lambs, and for ewes producing and rearing multiple lambs.

Publications

• Heade, M.L., and Hall, J.A. 2009. Effects of environmental factors and rumen microbes on Se bioavailability in sheep. Ann. Res. Day, Coll. of Vet. Med., Oregon State Univ., presented September 9, 2009. Corvallis, OR.
• Hooper, K.J., and Hall, J.A. 2009. Effects of supranutritional concentrations of organic or inorganic Se in the diet of sheep on Se bioavailability, and foot rot incidence and severity. Ann. Res. Day, Coll. of Vet. Med., Oregon State Univ., presented September 9, 2009. Corvallis, OR.
• Hall, J.A., Van Saun, R.J., Stewart, W.C., Vorachek, W.R., Mosher, W., Pirelli, G.J. 2010. Bioavailability of oral selenium supplements in sheep. Page 271 in Proc. ACVIM Forum Annual Meeting. Anaheim, CA.
• Stewart, W.C. 2010. Effect of selenium source and supplementation rate in ewes on selenium status, passive immunity, and growth performance of their lambs. Master of Science Degree in Animal Sciences, Oregon State Univ., presented December 2, 2010. Corvallis, OR.
• Hall, J.A., Van Saun, R.J., Bobe, G., Stewart, W.C., Vorachek, W.R., Mosher, W.D., Nichols, T., Forsberg, N.E., and Pirelli, G.J. 2010. Oral bioavailability of organic and inorganic selenium supplements in ewes. J. Ani. Sci., (pending).
• Stewart, W.C., Bobe, G., Vorachek, W.R., Pirelli, G.J., Mosher, W.D., Nichols, T., Van Saun, R.J., Forsberg, N.E., and Hall, J.A. 2010. Transfer efficiency of organic and inorganic selenium supplements from ewes to lambs. J. Ani. Sci. (pending).