Submitted to: Forage Focus
Publication Type: Popular Publication
Publication Acceptance Date: 11/24/2014
Publication Date: 12/15/2014
Citation: Zeller, W.E., Grabber, J.H. December 2014. Researching ways to improve nitrogen-use efficiency on dairies through the use of condensed tannin-containing forages. Forage Focus. p. 10-11.
Technical Abstract: A high proportion of protein in forages can be lost at two major points in the dairy farming nitrogen cycle: during the ensiling process and during rumen digestion. The formation of non-protein nitrogen (NPN) during these processes contributes to a reduction in nitrogen use efficiency (NUE), resulting in lower feed quality and in high nitrogen waste in the excreted manure, respectively. Methods to conserve protein nitrogen during these processes would directly translate to both economic and environmental improvements in the dairy farming nitrogen cycle. Condensed tannins (CT) belong to a class of plant polyphenols that occur in common forages and are distinguished from other polyphenols by their ability to bind protein. Binding of condensed tannins to protein protects the protein from rapid decomposition during the ensiling process and during rumen digestion. Protection of protein during ensiling leads to higher quality silage (higher utilizable protein content). Protein protection during rumen digestion leads to a higher level of utilizable protein escaping into the hindgut where it can be utilized by the dairy cow. It is not well understood how the composition of condensed tannins affects both of these outcomes. This is a brief summary of work being conducted by scientists and collaborators at the U.S. Dairy Forage Research Center related to the analysis and use of condensed tannin-containing forages for improvement of NUE in dairy production systems. Current studies include purification of condensed tannins from a variety of forages for use in laboratory and in vitro studies, development of new methods for analytical determinations of condensed tannin content and composition, identification of CT characteristics of forages which provide optimal level of milk production and nitrogen use efficiency, and the development or improvement of condensed tannin-containing forages.