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Evaluation of dietary fibre as contributing factor in the development of swine dysentery

Durmic, Zorica (2000) Evaluation of dietary fibre as contributing factor in the development of swine dysentery. PhD thesis, Murdoch University.

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Diets that alter fermentation in the hindgut of pigs have been shown to influence the incidence of swine dysentery (SD), an infectious mucohaemorrhagic colitis in pigs caused by infection with the bacterium Serpulina hyodysenteriae. Reducing fermentation can help protect pigs from developing the disease, whilst the fully protective diet, based on cooked white rice, has been described. The aim of this study was to determine links between the diet fed to pigs, hindgut fermentation, and the incidence of SD, and then to develop a commercially applicable diet that would protect pigs against SD.

In this study, the first procedure was to estimate pig performance and the hindgut fermentation that occurred when pigs were fed different diets. This was followed by infection trials to provide information on the incidence of SD when these diets were fed. These results were brought together to provide the required information. Overall 246 weaner pigs were fed one of 20 diets in six experiments. Diets were formulated either to investigate the role of different types and levels of dietary fibre on susceptibility to SD, or to test some dietary treatments (dietary extrusion, addition of exogenous enzymes, application of a protective diet after experimental infection) designed to help prevent or reduce the expression of SD. All pigs were fed the experimental diets for four to eight weeks, and then half of the pigs on each diet were killed and their large intestines collected to assess hindgut fermentation. The remaining pigs on each diet were infected with a virulent strain of S. hyodysenteriae and monitored for SD.

Hindgut fermentation was suppressed in pigs consuming diets with low levels of fermentable fibre (resistant starch, RS, and soluble non-starch polysaccharides, sNSP), and these pigs did not develop SD. The dietary inclusion of either RS, sNSP, or both to an otherwise protective diet based on cooked rice, resulted in increased hindgut fermentation and a high incidence (80 - 100%) of iv SD. Extrusion of wheat reduced hindgut fermentation and the incidence of disease in experimentally infected pigs in one experiment, but not in the other. Dietary addition of an sNSP-degrading enzyme reduced hindgut fermentation and the incidence of SD only when added to a raw wheat diet, or when combined with an RS-degrading enzyme in an extruded wheat diet. Finely ground sorghum-based diets caused a substantial decrease in fermentation, also achieving a considerable reduction in the disease. Further extrusion and/or addition of RS-degrading enzymes did not improve this effect.

The present study confirmed that diets varying in their RS and sNSP content affect several events in the large intestine, with diets having low levels of these ingredients having a capacity to reduce the incidence of SD. This study however failed to identify a diet which would be fully protective as well as commercially applicable and financially viable in farmed pig production. Although protection against SD in pigs by dietary treatments was imperfect, some of these treatments might still be useful if undertaken in combination with other methods for the prevention and control of SD.

Item Type: Thesis (PhD)
Murdoch Affiliation(s): School of Veterinary and Biomedical Sciences
Notes: Note to the author: If you would like to make your thesis openly available on Murdoch University Library's Research Repository, please contact: Thank you.
Supervisor(s): Pethick, David and Hampson, David
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