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A modified dot-blot method of protein determination applied in the tannin-protein precipitation assay to facilitate the evaluation of tannin activity in animal feeds

Published online by Cambridge University Press:  09 March 2007

E. M. Hoffmann
Affiliation:
Institute for Animal Production in the Tropics and Subtropics (480), University of Hohenheim, Fruwirthstr. 12, D-70593 Stuttgart, Germany
S. Muetzel
Affiliation:
Institute for Animal Production in the Tropics and Subtropics (480), University of Hohenheim, Fruwirthstr. 12, D-70593 Stuttgart, Germany
K. Becker*
Affiliation:
Institute for Animal Production in the Tropics and Subtropics (480), University of Hohenheim, Fruwirthstr. 12, D-70593 Stuttgart, Germany
*
*Corresponding author: Professor Dr K. Becker, fax +49 711 459 3702, email [email protected]
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Abstract

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Tannins have received considerable attention from animal nutritionists as potential agents for modifying ruminal fermentation patterns, or for exploring new feed resources. This group of secondary plant compounds is defined by their ability to form complexes with proteins. A widely accepted method for assaying the biological activity of extracted tannins is the precipitation of bovine serum albumin. The protein carries a radioactive label (125I) to allow direct quantification from the precipitate. Tannin–protein complexes dissolve in sodium dodecylsulfate solution. A dot-blot assay for protein determination, which is based on the reversible binding of a fluorochrome, benzoxanthene yellow, to the protein spots and is not disturbed by the presence of detergents, can replace the radioactive method by a fluorimetric measurement. A novel alternative to the last part of the dot-blot assay is to scan the stained protein spots in situ using a video camera and computer image analysis. Several filter sets were tested and, within a concentration range of 0·1–2·0 mg protein/ml, each of them yielded results identical to the original method while the time required was only 30 % of the working time consumed by the original procedure. The modified dot-blot assay should be applicable to the evaluation of tannin activity in all shrub and tree foliages considered as animal feed.

Type
Research Article
Copyright
Copyright © The Nutrition Society 2002

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