The copper conundrum: elucidating the modes of copper antagonism in the rumen

Clarkson, A.H. (2020) The copper conundrum: elucidating the modes of copper antagonism in the rumen. PhD thesis, University of Nottingham.

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Copper is an essential trace element. In ruminants interactions occur during digestion which can interfere with copper absorption. Most notably, both iron and molybdenum in combination with sulphur. If there is insufficient copper available, thiomolybdate, formed from molybdenum and sulphur, can be absorbed and subsequently interfere with systemic copper function. It has not yet been established if copper-thiomolybdate is able to persist in the liver, or if the different copper sources participate differently in these interactions. The mode of action of the iron-sulphur pathway has also not been elucidated and very little is known about the nature of this interaction.

The aim of this work was to investigate the interactions of copper and its antagonists for a range of copper sources at different regions of the ruminant digestive tract. To elucidate the mode of iron-sulphur antagonism and to investigate the relationship between antagonist routes. A secondary aim was to assess the understanding of copper-related terminology and problems, across the farming community through a national survey.

The survey demonstrated that copper-related knowledge was not well understood across the farming community and copper supplementation is not as targeted as it could be. Initial in vitro work demonstrated that simulation of rumen conditions was not sufficient for investigation of the iron-sulphur pathway and that the solubility of different copper compounds was similar, but not directly comparable to bioavailability. This lead to in vivo work which demonstrated the potency of thiomolybdate as a copper inhibitor and suggested that iron may have two modes of action; a soluble, un-absorbable compound and an insoluble compound. This work also discovered the omasum as a region of copper accumulation. X-ray absorption studies revealed the ability of the rumen to reduce copper into monovalent and elemental copper, and potentially form a complex with sulphur, iron, oxygen and chloride in the jejunum. Further in vivo work showed that none of the copper sources were able to prevent molybdenum absorption or to replete blood parameters. However, tribasic copper chloride was the most resistant to antagonist challenge, but its solubilisation in the rumen and omasal-flow differed to its hypothesised mode of action. Analysis of bovine and ovine livers using X-ray absorption indicated the presence of copper bound to metallothionein, glutathione and possibility of thiomolybdate presence in high copper status livers.

This work has shown that the iron-sulphur antagonism may be more complex than previously believed and that the rumen, omasum and jejunum are all potential regions where changes can occur to copper complexation. Different copper sources may be able to negate some of the antagonist effects, but not entirely, and require further investigation.

Item Type: Thesis (University of Nottingham only) (PhD)
Supervisors: Kendall, N.R.
Paine, S.
Keywords: copper; antagonism; ruminant
Subjects: Q Science > QP Physiology > QP501 Animal biochemistry
S Agriculture > SF Animal culture
Faculties/Schools: UK Campuses > Faculty of Medicine and Health Sciences > School of Veterinary Medicine and Science
Item ID: 60094
Depositing User: Clarkson, Andrea
Date Deposited: 17 Jul 2020 04:40
Last Modified: 17 Jul 2020 04:40

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