Redesigning forages with condensed tannins

Authors: Zeller, Wayne; Grabber, John

Submitted to: Progressive Forage Grower
Publication Type: Popular Publication
Publication Acceptance Date: 3/1/2015
Publication Date: 3/1/2015
Citation: Zeller, W.E., Grabber, J.H. 2015. Redesigning forages with condensed tannins. Progressive Forage Grower. 16(3):7-8.

Interpretive Summary:

Technical Abstract: Maximizing protein content in forages and minimizing protein loss during silage fermentation and rumen digestion are concerns for livestock and dairy producers. Substantial amounts of forage protein undergo proteolysis (breakdown) during the ensiling process and during rumen fermentation, transformed into non-protein nitrogen (NPN). Some of this NPN can be converted to nutritionally valuable microbial protein, but a large amount fails to be utilized by ruminants and is excreted as urine nitrogen. Identifying methods to increase the proportion of forage protein funneled to and digested in the gastrointestinal tract would improve protein- and nitrogen-use efficiency (NUE), enhance farm profitability and lessen ammonia emissions from farms to the environment. Some forages, like birdsfoot trefoil and sainfoin, contain compounds which naturally bind to proteins called condensed tannins (CTs). Feeding studies with dairy cows using these CT-containing forages or commercial CT products added to total mixed rations result in higher milk production and quality and reduce urine nitrogen levels without affecting animal performance. These results have been rationalized as the CTs binding to forage protein being responsible for increasing the amount of forage protein effectively used by ruminants. This brief summary outlines the ongoing work being conducted at the U.S. Dairy Forage Research Center, along with collaborators, that relates to the analysis and use of CT-containing forages for improvement of NUE in dairy production systems. Current studies include purification of CTs from a variety of forages for use in laboratory and in vitro studies, new method development for analytical determinations of CT content and composition, identifying CT characteristics of forages which provide optimal level of milk production and nitrogen use efficiency, and the development or improvement of CT-containing forages. Best management practices are also identified to help ensure that farmers can reliably grow and feed high quality CT-containing forages to livestock.