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Document Type

Thesis - University Access Only

Award Date


Degree Name

Master of Science (MS)


Animal Science

First Advisor

Rebecca Belt

Second Advisor

Alan Young


Objectives of this study were to elucidate the immune parameters of lineage and activation immune cell surface markers, immunoglobulin production, and tetanus specific immunoglobulin production and fecal egg counts in mares, foals, and adult male horses. The role of yeast supplement, Saccarohmyces cerivisae, on these immune parameters was evaluated. Activation markers CD29, CD44, MHCI, CD11a, CD49d and lineage markers CD4, CD8, and CD21 were analyzed via flow cytometry. In house direct ELISAs were developed to evaluate production of immunoglobulin isotypes IgGb, IgGT, IgGa, IgGc, IgM, IgA, and IgE. Tetanus anti-toxoid ELISAs were developed to determine if yeast supplementation enhances immune response to tetanus booster vaccination. Finally, fecal egg counts were determined through completing fecal floats. Twenty adult male horses were utilized from the South Dakota State University (SDSU) Horse Unit. Ten males served as control (Con Males), while ten received yeast treatment (Trt Males). Blood and fecal samples were collected on days 0, 21, 42, 63, and 84. Yeast supplementation had no effect on percent of lineage and activation markers, immunoglobulin production, tetanus specific immunoglobulins, and fecal egg counts (p>0.05). Six Quarter Horse mares and their foals from the SDSU Horse Unit were utilized over a two year trial. There were four mare/foal pairs per treatment group. Yeast supplementation began 70 days prior to expected foaling date and continued 70 days post foaling. Blood, fecal, and colostrum/milk collections were taken days 0, 0.5, 7, 14, 28, 56 and 70 (foaling = day 0). Yeast supplementation had no effect on percent of lineage and activation markers, colostral immunoglobulins, tetanus-specific immunoglobulins, and fecal egg counts (P>0.05). Treatment had no effect on immunoglobulin production in mares and foals (P>0.05), except IgGb production was greater in FCM compared to FTM (P<0.05). This study provided insight to the phenotype of equine CD4+, CD8+, and CD21+ lymphocytes during development as well as a potential role for dietary yeast regulation of immune function and fecal parasitic eggs. Limited monoclonal antibodies are available for equine immunology research. This experiment discovered additional mAbs to be used within future equine immunology research trials. These mAbs include CD29, CD21, and CD49d.

Library of Congress Subject Headings

Horses -- Immunology
Yeast as feed
Dietary supplements


Includes bibliographical references (pages 114-128)



Number of Pages



South Dakota State University


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