ORGANIC & INORGANIC SELENIUM SUPPLEMENTS IN SHEEP: BIOAVAILABILITY & IMMUNITY

• Sponsoring Institution: National Institute of Food and Agriculture
• Project Status: COMPLETE
• Funding Source: ANIMAL HEALTH
• Reporting Frequency: Annual
• Accession No.: 0214657
• Project Start Date: Jun 1, 2008
• Project End Date: Sep 30, 2009
• Program Code: [(N/A)]- (N/A)

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. For example, Se deficiency results in immunosuppression, decreased resistance to bacterial and viral infections, and decreased neutrophil function, antibody production, and cell-mediated immunity. 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 marginal deficiency of Se is immunosuppressive in sheep, and that it contributes to increased susceptibility to infectious diseases such as foot rot, could encourage sheep ranchers to supplement their flocks with additional Se. Having shown positive clinical results with injectible Se treatment in sheep with foot rot, our 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 and selenate) forms. We hypothesize that organic Se in sheep results in increased whole-blood Se concentrations compared to those measured in sheep receiving inorganic Se supplements. 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
302	3610	1010	25%
302	3610	1090	25%
311	3610	1010	25%
311	3610	1090	25%

Knowledge Area
302 - Nutrient Utilization in Animals; 311 - Animal Diseases;

Subject Of Investigation
3610 - Sheep, live animal;

Field Of Science
1090 - Immunology; 1010 - Nutrition and metabolism;

Keywords

selenium supplementation

sheep

organic se

inorganic se

bioavailability

immune responses

foot rot

Goals / Objectives
Objectives: Having shown positive clinical results with injectible Se treatment in sheep with foot rot, our 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. Specific objective one: Determine whether organic vs inorganic Se, given orally to sheep in doses complying with current FDA regulations, enhances Se bioavailability. 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 and selenate) forms. We hypothesize that organic Se in sheep results in increased whole-blood Se concentrations compared to those measured in sheep receiving inorganic Se supplements. Specific objective two: Investigate the mechanisms of Se induced immune responses in sheep, both innate and adaptive, 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. 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 (NETs). 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 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.

Project Methods
Specific objective one: 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 at all times. Study design: Prospective, placebo-controlled clinical trial of 12-month duration. Two variables will be manipulated within sheep using a 2 x 4 study design with disease status and Se source as main effects. There will be 2 types of sheep (healthy and foot rot (FR)-affected) and 4 types of Se supplements (an organic source of Se as selenomethionine, two inorganic source of Se as sodium selenite and sodium selenate, and no supplementation). The current FDA regulations allow ruminant diets to be supplemented with 0.3 ppm Se. Control sheep (15=healthy and 15=FR-affected) will receive water (no Se supplement). The other three groups of sheep, each with 15=healthy and 15=FR-affected sheep/group, will receive organic Se, inorganic selenate, or inorganic selenite. Se treatment will be administered by oral drench once weekly at an amount equal to the summed weekly intake. The Se dose will be suspended in 5 ml water, and administered with a dose syringe as sheep move through a cutting chute. 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. Sheep will be treated once weekly for a total of 52 weeks. Selenium sources: Sources of sodium selenite and sodium selenate are currently available in the lab. A commercial selenized yeast product, containing 600 ppm Se from selenomethionine will be used for the organic Se source. Whole-blood selenium concentrations: All ewes will be bled at the beginning of the study and then at 3-month intervals for 1 year to collect blood for Se analysis (0, 3, 6, 9, and 12 months). Se concentrations will be determined using ICP-MS methods. 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 0, 6, and 12 months. We will perform immunology studies for CMI and humoral immunity at the end of 1-year. Incidence and Severity of FR: Sheep feet will be examined, trimmed, and scored for FR at the beginning of the study, and then ewes will be randomly assigned to study groups. 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. Because sheep in the proposed study do not have access to free-choice mineral mix containing Se as did the sheep in our pilot study, we feel that the dose effects will be more controlled (less variation) in the proposed study.

Progress 06/01/08 to 09/30/09

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: 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 in progress. 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 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. 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.
• 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., and Pirelli, G.J. 2010. Oral bioavailability of organic and inorganic selenium supplements in ewes. J. Ani. Sci., (pending).
• 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., and Hall, J.A. 2010. Transfer efficiency of organic and inorganic selenium supplements from ewes to lambs. J. Ani. Sci. (pending).