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Document Type

Dissertation - University Access Only

Award Date


Degree Name

Doctor of Philosophy (PhD)

Department / School

Animal Science

First Advisor

George W. Libal


The prevention and treatment of mulberry heart disease (MHD) is based on the premise that the disease results from a deficiency of vitamin E and/or selenium (VESD). Yet, supplementation of growing pig diets with recommended levels of vitamin E and selenium have not slowed the incidence of MHD. Three studies investigated alternatives to VESD in the etiology of MHD. The objective of the first experiment was to investigate an association between MHD and autoimmune antibodies or immune complex deposits. Tissues were collected from pigs submitted to the South Dakota Veterinary Diagnostic Laboratory. A direct fluorescent antibody procedure was used to evaluate the prevalence of immunoglobulin-G (IgG) in myocardial tissue from pigs dying due to MHD (PMHD), pigs dying due to Streptococcus spp. infection (PSPP) and in pigs dying from causes unrelated to the previous two conditions (CONTROL). Liver α-tocopherol concentrations were also determined. Liver α-tocopherol concentrations and the incidence of low a-tocopherol concentrations were similar among MHD, PSPP, and Control pigs (P > .10). No changes in the patterns of fluorescence or level of fluorescence intensity were observed between PMHD, PSPP or CONTROL. The objective of the second experiment was to determine the effects of endotoxin and vitamin Eon in vivo lipid peroxidation and hematological changes in the weaned pig. Lipid peroxidation in plasma or tissues, measured by malondialdehyde (MDA) or thiobarbituric acid-reactive substances, were not affected by endotoxin administration (P > .10) although MDA in myocardial tissue was lower in pigs administered vitamin E (P < .05). Culture filtrates of two Streptococcus suis isolates were administered to weanling pigs in the final experiment in order to evaluate the potential cytotoxic properties of extracellular products of these bacterial isolates. In summary, a direct cause and effect relationship between bacterial products and MHD was not established in these studies, but as initial studies it is this author's opinion that they represent a new and promising direction into the etiology of MHD.

Library of Congress Subject Headings

Swine -- Diseases
Swine -- Feeding and feeds
Heart -- Diseases -- Etiology




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