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dc.contributor.authorMcLellan, Bradley Johnen_NZ
dc.date.accessioned2008-01-08T16:37:32Z
dc.date.available2008-02-05T14:29:17Z
dc.date.issued2007en_NZ
dc.identifier.citationMcLellan, B. J. (2007). Development of an Intraruminal Controlled-Release Device (Thesis, Doctor of Philosophy (PhD)). The University of Waikato, Hamilton, New Zealand. Retrieved from https://hdl.handle.net/10289/2527en
dc.identifier.urihttps://hdl.handle.net/10289/2527
dc.description.abstractSlow-release devices retained in the rumen, are a simple method for continuous administration of bioactives to ruminant animals. To satisfy regulatory requirements and avoid waste of bioactive due to under- or over-dosing, it is advantageous to have a constant and predictable release rate. Existing intraruminal controlled-release technologies cannot easily be adapted for different bioactives or rates of release and can be influenced by the variable physiological environment in the rumen. Some existing commercial products use the pressure generated by a hydrogen gas-producing cell to extrude fluids from a syringe-like device. This technology may provide advantages for ruminal controlled-release as the gas production rate is unaffected by environment in the rumen and can be easily adjusted using electrical resistance applied to the gas cell. This technology was adapted for use in the rumen in these studies. Initial experiments identified the need for greater understanding of the rate that hydrogen is produced by the gas cell and the rate that gas diffuses through the barrel walls. Gas production rate was found to be inversely proportional to the resistance applied to the gas-producing cell. Factors affecting gas diffusion rate from the device were studied and a polymer was identified that reduced hydrogen diffusion to 5% of that for the initial components used. A relationship was developed to predict the release profile of a device. Controlled-release devices were constructed from selected materials. They released blank formulation at in vitro at a constant rate, which was within experimental variation of predicted values. Release rates from the devices used in vivo were slightly higher than predicted. The presence of rumen gases inside in vivo devices suggested that the difference may be due to inward diffusion of these gases; these may be eliminated by further study of barrel materials. Recommendations on the redesign of this technology for use as a generic intraruminal delivery system are given.en_NZ
dc.format.mimetypeapplication/pdf
dc.language.isoen
dc.publisherThe University of Waikatoen_NZ
dc.rightsAll items in Research Commons are provided for private study and research purposes and are protected by copyright with all rights reserved unless otherwise indicated.
dc.subjectgas-producing cellen_NZ
dc.subjecthydrogen diffusionen_NZ
dc.subjectcarbon dioxide diffusionen_NZ
dc.subjectgas diffusionen_NZ
dc.subjectpolyoxymethyleneen_NZ
dc.subjectnylonen_NZ
dc.subjectmathematical modelen_NZ
dc.subjectsustained release bolusen_NZ
dc.titleDevelopment of an Intraruminal Controlled-Release Deviceen_NZ
dc.typeThesisen_NZ
thesis.degree.disciplineScience and Engineeringen_NZ
thesis.degree.grantorUniversity of Waikatoen_NZ
thesis.degree.levelDoctoral
thesis.degree.nameDoctor of Philosophy (PhD)en_NZ
uow.date.accession2008-01-08T16:37:32Zen_NZ
uow.date.available2008-02-05T14:29:17Zen_NZ
uow.identifier.adthttp://adt.waikato.ac.nz/public/adt-uow20080108.163732en_NZ
uow.date.migrated2009-06-14T21:34:12Zen_NZ
pubs.place-of-publicationHamilton, New Zealanden_NZ


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