Includes 25 papers previously published in Journals / 114, 16 leaves : / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Thesis (D.Sc.)--University of Adelaide, Dept. of Biochemistry, 1975

Three experiments were conducted to characterize the fate of B-vitamins in the gastrointestinal tract of dairy cows. Experiment 1 was undertaken to verify if differences among published studies could be explained by methods of collection and preparation of ruminal fluid, using four ruminally cannulated non-lactating Holstein cows. Acidification of fresh ruminal fluid, causing the lysis of bacterial cells, yielded higher B-vitamin concentrations than differential centrifugation, while the method of collection used did not have an important impact. Results suggested that most of the vitamins are present in the bacterial fractions, and that only limited amounts are present in the surrounding fluid. Experiment 2 looked at the vitamin concentrations in ruminal bacterial fractions and particle-free fluid as influenced by diet composition. Six lactating ruminally cannulated Holstein cows were used in a cross-over design, and the diets were formulated to have forage to concentrate ratios of 60:40 (high-forage) and 40:60 (low-forage). B-vitamins were present mainly in the bacterial fractions of the rumen, with greater effects of the forage to concentrate ratio on vitamin concentrations in the bacteria associated to the solid fraction than on those present in the liquid portion of the rumen. These results strongly suggested that ruminal B-vitamin synthesis is influenced by the forage to concentrate ratio. Experiment 3 investigated the fate of supplementary B-vitamins, using four cows equipped with cannulae in the rumen, the proximal duodenum and the distal ileum. Extensive losses of dietary supplements appeared prior to the duodenum for all vitamins, but intestinal disappearance rates of most vitamins were increased by supplementation.

Thesis (D.Sc.) -- University of Adelaide, Dept. of Biochemistry, 1975. / Includes 25 papers previously published in Journals.

Thesis (M.S.)--University of Wisconsin--Madison, 1968. / eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.

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